WAT E R G LO B A L P R AC T I C E WHAT THE A New Paradigm FUTURE HAS for Water IN STORE Storage ABOUT THE WATER GLOBAL PRACTICE Launched in 2014, the World Bank Group's Water Global Practice brings together financing, knowledge, and implementation in one platform. By combining the Bank's global knowledge with country investments, this model generates more firepower for transformational solutions to help countries grow sustainably. Please visit us at www.worldbank.org/water or follow us on Twitter: @WorldBankWater. ABOUT GWSP This publication received the support of the Global Water Security & Sanitation Partnership (GWSP). GWSP is a multidonor trust fund administered by the World Bank's Water Global Practice and supported by Australia's Department of Foreign Affairs and Trade, Austria's Federal Ministry of Finance, the Bill & Melinda Gates Foundation, Denmark's Ministry of Foreign Affairs, the Netherlands' Ministry of Foreign Affairs, Spain's Ministry of Economic Affairs and Digital Transformation (MINECO), the Swedish International Development Cooperation Agency, Switzerland's State Secretariat for Economic Affairs, the Swiss Agency for Development and Cooperation, and the U.S. Agency for International Development. Please visit us at www.worldbank.org/gwsp or follow us on Twitter: @TheGwsp. WHAT THE A New FUTURE HAS Paradigm for Water IN STORE Storage © 2023 International Bank for Reconstruction and Development / The World Bank 1818 H Street NW, Washington, DC 20433 Telephone: 202-473-1000; Internet: www.worldbank.org This work is a product of the staff of The World Bank with external contributions. 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Rights and Permissions The material in this work is subject to copyright. Because The World Bank encourages dissemination of its knowledge, this work may be reproduced, in whole or in part, for noncommercial purposes as long as full attribution to this work is given. Please site the work as follows: World Bank. 2023. “What the Future Has in Store: A New Paradigm for Water Storage.” World Bank, Washington, DC. Any queries on rights and licenses, including subsidiary rights, should be addressed to World Bank Publications, The World Bank Group, 1818 H Street NW, Washington, DC 20433, USA; fax: 202-522- 2625; e-mail: pubrights@ worldbank.org. Report design: Ultra Designs. Cover design: Bill Pragluski, Critical Stages, LLC. CONTENTS Foreword ix Acknowledgments xi Executive Summary xii Abbreviations xxvi PART I. MAIN REPORT 1 1. Introduction: The Importance of Water Storage 2 1.1 Development and Climate Resilience   2 1.1.1 Vital Social, Environmental, and Economic Resource 2 1.1.2 Life Depends on Freshwater Storage 4 1.1.3 Climate Change Upends Our Relationship with Storage 5 1.1.4 Water Security Is More than Storage 5 1.1.5 Services of Storage 6 1.1.6 Needs Differ Around the World 7 1.2 Our Future Under Threat 7 1.2.1 Growing Demand for Freshwater 7 1.2.2 Growing Uncertainty of Supply 9 1.2.3 Decreasing Net Storage 11 1.2.4 A Growing Water Storage Gap 13 1.3 The World Needs Smarter Approaches 15 1.3.1 A Systems Perspective 15 2. Characteristics, Challenges, and Opportunities 17 2.1 Natural, Built, and Hybrid Storage 17 2.2 Natural Freshwater Storage 17 2.2.1 Natural Systems in Decline 17 2.2.2 Nature’s Ability to Meet Demand 23 2.2.3 Harnessing Natural Storage 24 2.3 Built Solutions and Challenges 27 2.3.1 Dams and Reservoirs 27 2.3.2 Sedimentation of Reservoirs 29 2.3.3 Built Storage in Decline 30 2.3.4 Environmental and Social Trade-Offs 31 2.3.5 Hydrological Risks 33 iii 2.3.6 Smaller-Scale, Built Infrastructure 34 2.4 Hybrid Storage 34 2.5 Connections across Physical and Socioeconomic Systems 38 2.5.1 Most Storage Is Interdependent 38 2.5.2 Embedded in Larger Systems 38 2.5.3 Managing Risks at the System Scale 38 2.5.4 Addressing Challenges and Scaling Up 39 3. A New Framework for Integrated Storage Planning 40 3.1 A Problem-Driven, Systems Approach 40 3.1.1 Problem-Driven Approach 41 3.1.2 Systems Approach 41 3.2 The Integrated Storage Planning Framework 42 4. Institutionalizing Integrated Storage Planning 46 4.1 Data and Analysis Gaps 46 4.2 Inter-Sectoral Coordination 49 4.3 Multi-Stakeholder Engagement and Coordination 50 4.4 Regulatory Frameworks 51 4.5 Weak Institutional Capacity 51 4.6 Funding Constraints for Water Management Institutions 52 4.7 Private Sector Participation 52 4.8 Misaligned Incentives and Political Economy Considerations 53 5. Tools for Better Storage Throughout the Project Cycle 55 5.1 Raising or Creating New Storage 55 5.1.1 Preparatory Studies for New Investments 55 5.1.2 Greenhouse Gas Emissions and Climate Resilience 58 5.1.3 Dam Safety During Investment Preparation and Implementation 59 5.1.4 Early Consideration of Sediment Management 62 5.1.5 Funding for Storage Investments 62 5.1.6 Implementation of Storage Solutions 65 5.2 Operating and Maintaining Existing Storage 67 5.3 Reoperating, Retrofitting, and Rehabilitating Existing Assets 68 5.3.1 Reoperating 68 5.3.2 Retrofitting 71 5.3.3 Rehabilitating 72 5.4 Decommissioning Built Storage 73 6. The Future Is Now: A Call to Action 76 6.1 Why Focus on Water Storage? 76 6.2 What do Stakeholders Need to Understand to Develop Smarter Approaches? 76 6.3 Who Needs To Be Involved? 77 6.4 How Can Stakeholders Approach Storage More Strategically? 78 iv WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE PART II. RESOURCES FOR STORAGE PLANNERS 81 7. The Integrated Storage Planning Framework: A Step-by-Step Guide 82 7.1 Stage 1: The Problem: A Needs Assessment 82 7.1.1 Stage 1.A: Defining Development Objectives 82 7.1.2 Stage 1.B: Characterizing Water Service Requirements 84 7.1.3 Stage 1 Outputs 86 7.2 Stage 2: The System: Establishing the Baseline and Understanding Solutions 86 7.2.1 Stage 2.A: Taking Stock of the Current System 87 7.2.2 Stage 2.B: Solutions: Identifying Additional Options 91 7.2.3 Stage 2 Outputs 96 7.3 Stage 3: Bringing It Together: Making Decisions  97 7.3.1 Stage 3.A: Defining Scenarios 97 7.3.2 Stage 3.B: Establishing Decision Criteria 98 7.3.3 Stage 3.C: Comparing and Assessing Scenarios 98 7.3.4 Stage 3 Outputs 106 8. Case Studies 107 Annex 8A. Sri Lanka: Tank Cascades in the Dry Zone and the Rehabilitation of Small-Scale Water Storage 109 Annex 8B. California: Forecast-Informed Reservoir Operation to Enhance Water Storage Efficiency 119 Annex 8C. Cape Town: Resilience through Diversification of Water Sources and Increased Storage 133 Annex 8D. Mexico: Green Water Storage to Adapt to Extreme Hydro-Climatic Events in Monterrey 147 Annex 8E. Indonesia: Getting More from Existing Built Storage: Prioritizing Rehabilitation Investments 155 Annex 8F. Namibia: Conjunctive Surface and Groundwater Management for Drought Resilience in Windhoek 163 Annex 8G. Pakistan: Hydropower Development in the Jhelum-Poonch River Basin 172 9. Water Storage Glossary 183 Bibliography 190 FIGURES Figure ES.1 The Growing Storage Gap xiii Figure ES.2 Water Storage Types, Systems, and Services xiv Figure ES.3 Integrated Storage Planning Framework Stages xviii Figure 1.1 Water Demand vs. Natural Surface Water 5 Figure 1.2 Surface Water Storage Impact 5 Figure 1.3 Response Options to Water Scarcity: Supply and Demand Management 6 Figure 1.4 Water Storage Types and Core Services 6 Figure 1.5 Global Water Demand by 2040 8 Figure 1.6 Flood Occurrence and Economic Damage Over Time 11 Figure 1.7 Net Global Reservoir Storage Volume 12 Contents v Figure 1.8 Changes in Water Storage, by Type, 1970–2020 12 Figure 1.9 Water Storage Gap 13 Figure 1.10 The Growing Storage Gap 13 Figure 2.1 Water Storage Types 18 Figure 2.2 Water Storage Types, Systems, and Services 21 Figure 2.3 Global Freshwater Storage 21 Figure B2.2.1 Examples of Natural Storage 25 Figure 2.4 Development of Dams over Time 31 Figure B2.5.1 Managed Aquifer Recharge in Water Resources Management 35 Figure B2.5.2 Managed Aquifer Recharge Considerations 36 Figure 3.1 Planning and Operating Water Storage 40 Figure 3.2 Integrated Storage Planning Framework Stages 42 Figure B4.1.1 Screenshot of the Decision Support Tool “Water Harvesting Explorer” 48 Figure 4.1 Bangladesh Water Platform 50 Figure 5.1 The 5 R's and the Project Cycle 55 Figure B5.2.1 Decision Tree Framework Phases 60 Figure B5.5.1 Risk Analysis Tools for Dam Safety 69 Figure B5.6.1 Number of Dams Removed on the Rivers of the United States and Europe 73 Figure 7.1 Development Objectives Enabled by Water Storage Services 83 Figure B7.1.1 City-Scale Nature-Based Solutions 88 Figure B7.1.2 Bioretention Areas 89 Figure B7.1.3 Constructed Wetlands 89 Figure 7.2 Complexity for Considering Storage Scenarios 97 Figure B7.6.1 Optimized Environmental Flow Failures Against Flood-Dependent Provisioning Services 103 Figure 8A.1 Cascade Water Course Schematic Diagram 110 Figure 8A.2 Rehabilitation of Tank Cascades Guide 112 Figure 8B.1 Simplified Lake Mendocino Guide Curve 122 Figure 8B.2 Flow Diagram Depicting the FIRO Viability Assessment Process 125 Figure 8B.3 Lake Mendocino FIRO Development Pathway, 2014–20 126 Figure 8B.4 FIRO Decision Support System 127 Figure 8B.5 Release Curve and Modeled Release Curve, 2019–20 128 Figure 8B.6 FIRO Process to Develop an Adaptive Water Control Manual 129 Figure 8C.1 Annual Inflows into the Large Water Supply Dams, Cape Town, 1928–2020 138 Figure 8C.2 Aggregate Dam Levels in WCWSS, Cape Town, 2008–22 139 Figure 8C.3 Cape Town Gross Water Use, 2011–21 139 Figure 8C.4 Water Availability, Anticipated Demand, and the Augmentation Program, Cape Town, 2004–40 141 Figure 8C.5 Cape Town’s Plans to Diversify Water Sources 142 Figure 8E.1 Organogram of the Dam Safety Institutions within the MPWH, Indonesia 159 Figure 8E.2 Modified ICOLD Risk Analysis Method 161 Figure 8F.1 Distribution of Precipitation in Namibia 164 vi WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE Figure 8F.2 Elements of Windhoek’s Water Storage System 169 Figure 8G.1 IFC Guidelines for Conducting Cumulative Impact Assessment 177 Figure 9.1 Aquifer Types 183 Figure 9.2 Polder 185 Figure 9.3 Closed-Loop Pumped Storage Hydropower 186 Figure 9.4 Sand Dam 187 MAPS Map 1.1 Quantity and Distribution of Global Freshwater Resources, by Region 3 Map 1.2 Coefficient of Variation of Mean Monthly Precipitation 7 Map 1.3 Exposure of Hydropower Generation Capacity to Changes in Drought Durations and Intensities 10 Map 1.4 Global Terrestrial Water Trends 12 Map 2.1 Groundwater Stress 23 Map 2.2 Groundwater Table Decline 24 Map 2.3 Distribution of Dams 29 Map 2.4 Large Dams Over 50 Years Old 32 Map 2.5 Prevalence of Sand Dams 37 Map 8B.1 Schematic of the Russian River Watershed and Water Transmission System 120 Map 8C.1 Western Cape Water Supply System 135 Map 8E.1 Distribution of Existing and Planned Dams in Indonesia 157 Map 8F.1 Perennial Rivers of Namibia 164 TABLES Table ES.1 Conceptual Shifts: An Integrated Approach to Thinking about Water Storage xxi Table ES.2 The 5 R’s: Opportunities for Increasing Storage Services xxii Table 1.1 Drivers of Demand and Demand Uncertainty 14 Table 1.2 A Needed Paradigm Shift 15 Table B2.5.1 Managed Aquifer Recharge Typologies 36 Table 3.1 Water Service Attributes 43 Table 3.2 Summary of the Integrated Storage Planning Framework 44 Table 4.1 Changes Required and Recommendations for Integrated Storage Planning 54 Table B5.5.1 Fragility Categories and Factors for Central Water Commission’s Risk Index Scheme 70 Table 7.1 Water Service Attributes 85 Table 7.2 Gaining Additional Storage Services from Current Systems 93 Table 7.3 Identifying Additional Storage Opportunities for Core Storage Services 95 Table 7.4 Illustrative Comparison of Small Catchment Storage Scenarios 101 Table 8.1 Case Study Index 107 Table 8A.1 Recommendations on Tank System Augmentation and Expansion 115 Table 8B.1 Water Control Plan Alternatives and Increases 128 Contents vii Table 8C.1 Summary, Yields, and Allocations of Dams Supplying the WCWSS, 2019 137 Table 8D.1 Criteria Used to Score Threats 151 Table 8F.1 Three-Dam System: Features 167 Table 8G.1 Indicators in DRIFT Model Simulation for the Poonch River 178 Table 8G.2 Scenarios Assessing Ecosystem Integrity 179 BOXES Box 2.1 Four Dimensions of Water Storage 20 Box 2.2 Catalogue of Nature-Based Solutions for Urban Flood Resilience 25 Box 2.3 Dam and Reservoir Inventory Using Remote Sensing and Artificial Intelligence 28 Box 2.4 Dam Safety 33 Box 2.5 Managed Aquifer Recharge 35 Box 3.1 Systems Approaches: Green and Gray Planning 41 Box 4.1 Working in Data-Scarce Environments: Example from the Western Sahel Region 47 Box 5.1 Types of Impact Assessments to Maximize Social and Environmental Development 57 Box 5.2 Confronting Climate Uncertainty in Water Resources Planning and Project Design 60 Box 5.3 A Life-Cycle Approach to Sediment Management 62 Box 5.4 Green Financing 65 Box 5.5 Risk-Informed Dam Safety Management 69 Box 5.6 Dam Removal: A Tale of Too Much Storage? 73 Box 7.1 Urban Flood Management 88 Box 7.2 Water Accounting 90 Box 7.3 Comparing Storage Options Across Storage Types 94 Box 7.4  Storage Decision Criteria 98 Box 7.5  Good Practices and Resources for Economic Evaluation 100 Box 7.6  Multi-Criteria Decision-Making Using Advanced Systems Modeling and Multi-Objective Optimization 103 Box 7.7 An Interactive Platform for Informed Decision-Making 105 Box 8C.1 Hydropower Linked to the Western Cape Water Supply System 136 PHOTOS Photo B7.7.1 Arizona State University Decision Theater 105 PHOTO 8C.1 Cape Town’s Reservoirs 134 viii WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE FOREWORD As climate change impacts escalate, the importance of freshwater storage is rapidly scaling the global agenda. Rising temperatures are scorching already-parched landscapes in some parts of the world, while floods inundate others. Countries from Australia to Zimbabwe are struggling with both water ex- tremes, along with the concurrent threat of forest fires. In the last year alone, Europe, one of the world’s most temperate regions, has seen record temperatures, widespread water shortages, and massive flooding. Worldwide, the toll in human suffering, economic loss and instability, and environmental de- struction is devastating. In some regions, the weather is erasing decades of gains in human develop- ment in a matter of days. It is often said that climate change expresses itself through water. The inevitability of hydrological climate extremes is placing increasing pressure on all water practitioners to manage differently, and nowhere is that more necessary than in storage. Freshwater storage is at the heart of adapting to cli- mate change, most obviously by saving water for drier times and reducing the impact of floods. Many populations are experiencing increasing levels of climate-based turmoil, and for them, any relief that comes with recovery is tempered by anxiety about the future. It is safe to say that going forward, the most stable, durable societies will, in many cases, be anchored in more resilient approaches to water storage. However, as this report illustrates, the world is facing a growing freshwater storage gap. Just as we need more storage, the actual volume of freshwater storage is in decline, primarily due to the loss of natural storage, but buttressed by an underinvestment in the maintenance of built storage that increas- es vulnerability overall. Improving how water storage is planned and managed is about more than climate. Securing reliable water services is also a fundamental part of socioeconomic development, underpinning progress to- wards not just SDG 6—“clean water and sanitation for all”—but also for the multitude of other SDGs that rely on water. The most recent SDG progress reporting (2021) suggests that approximately one-quar- ter of the world’s population lacks access to safely managed drinking water services, and 108 coun- tries are unlikely to have sustainably managed water resources by 2030. Additionally, water storage services are clearly linked to goals in poverty, food security, energy, economic growth, sustainable cities, the environment, and climate. The World Bank has produced this report because we recognize that many of our clients around the world are in unprecedented situations, struggling to cope with water-related disasters and grappling with how to develop, operate, and maintain more—and more resilient—water services. Climate change, twinned with a growing water storage gap, means traditional approaches to water storage must evolve. In developing our understanding of what a twenty-first century approach to freshwater storage could look like, the Bank reflected on its own many decades of experience with natural and built water infrastructure, searched the world for examples of water storage solutions that are not otherwise ix accessible to water practitioners focused on their local regions in isolation, and looked at the variety of new science and tools that could be brought to bear to achieve results. There is no simple path forward; the solutions we need to invest in to meet our common challenge are many and complex. We must harness the power of nature and supplement it, where necessary, with built storage. We must take better care of our existing storage, and use it to meet the needs of multiple sectors, populations, and the environment. Critically, we need to do this while recognizing that all stor- age, big and small, natural and built, underground or on the surface, is part of a bigger water cycle and system that too require understanding and investment. The need for a new water storage paradigm is clear. As this report illustrates, ultimately, true resilience lies at the system level rather than in individual storage facilities—and that requires a change in thinking and approach on the part of water resource innovators across the spectrum. What the Future Has in Store: A New Paradigm for Water Storage proposes the purposeful design of water storage solutions that impact many instead of few. Applying the concepts presented could manifest the kinds of resil- ient, sustainable, even life-saving storage services that both mitigate the impact of climate-related disasters and secure a water future for generations. The ideas, examples, and tools contained here will help a variety of stakeholders begin to put a new approach into action. However, genuinely integrated approaches to storage at scale are still being developed, so the science of the possible is not yet fully known. For the World Bank, this report rep- resents one step in a journey toward a new storage paradigm. It is a journey that will continue for years to come as the intertwined challenges of climate change and development continue to reshape the world around us. Saroj Kumar Jha Global Director, Water Global Practice World Bank Group x WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE ACKNOWLEDGMENTS This report was prepared by a World Bank team led by Eileen Burke and Jacqueline Tront, and included Kimberly Lyon, William Rex, Melissa Castera Errea, Mili Varughese, Joshua Newton, Ayelen Becker, and Allison Vale. Early leadership of the report was provided by Abedalrazq Khalil. We would like to thank the following individuals who contributed to the report, including Esha Zaveri, Lucy Lytton, Kate Lazarus, Winston Yu, Marcus Wishart, Poolad Karimi, Thiruni Liyanage, Nicholas Zmijewski, Sally Zgheib, Bente Brunes, Maria Güell i Pons, Usayd Casewit, Abdulhamid Azad, Virak Chan, Sanjay Pahuja, Zhimin Mao, Anna Cestari, Si Gou, Pravin Karki, Fan Zhang, Amjad Khan, Nagaraja Rao Harshadeep, Defne Osmanoglou, Boris Ton Van Zanten, and Larissa Jenelle Duma. Authors of the case studies presented here include Edoardo Borgomeo, Rolfe Eberhard, Kimberly Lyon, Melissa Castera Errea, and Nimal Gunawardena; case study contributions were also provided by the United States Army Corps of Engineers (USACE). The report also draws on background work by Royal Haskoning DHV, an economics review by Roy Brower and Khusro Mir, and earlier work and suggestions from Rita Cestti. The report benefitted greatly from the strategic direction provided by World Bank management, in- cluding Jennifer Sara (Climate Change Global Director, formerly Water Global Director), Demetrios Papathanasiou (Energy and Extractives Global Director), and Soma Moulik, Practice Manager (Global Solutions Water). The team appreciates the detailed reviews provided by the following World Bank staff: Joop Stoutjesdijk, Satoru Ueda, Ruth Tiffer Sotomayor, Felipe Lazaro, Brenden Jongman, Pierre Lorillou, and Irene Rehberger Bescos. Mathew McCartney of the International Water Management Institute (IWMI) provided peer review, and his analytical work was also used throughout the report. Miki Fernandez and Fiorella Gil provided the layout and design for the report and supported with con- ceptual illustrations. Erin Barrett, Meriem Gray, Sarah Farhat, Zubedah Robinson, Ayse Boybeyi, David Gray, Pascal Saura, and Erika Vargas provided invaluable support for its production and dissemination. We are pleased to recognize the generous funding provided through the Global Water Security and Sanitation Partnership (GWSP) and the support received from colleagues across the Water Global Practice to produce this report. xi EXECUTIVE SUMMARY 1. INTRODUCTION: A NEW PARADIGM FOR WATER STORAGE   The most urgent challenge of our lifetime is water. Worldwide, water crises are taking an astounding toll on people, environments, and economies. At the writing of this report, nearly two-thirds of all municipalities in Mexico are facing a water shortage, leaving desperate people queueing for rations; France is in the grip of the worst drought in its history, forcing 93 regions into restricted water use and trucking water into another 100 municipalities where the pipes have completely run dry; at the other end of the spectrum, four separate flooding events in 11 days—each qualifying as a 1-in-1,000-year rainstorm—have left parts of the United States reeling, washing out roads, swamping city streets, and drowning entire towns. Meanwhile, in Pakistan, flooding has submerged around one-third of the country, killing over 1,200 people and displacing a further 33 million. Water and water-related disasters are rated among the greatest risks facing modern societies (WEF 2022). When water isn’t available at the right time in the right amount, communities large and small can teeter on disaster. For millennia, water storage has helped humans cope with the natural extremes of water availability, meeting freshwater demands by increasing and regulating the volume of accessible water. Today, household wells, reservoirs, dams, tanks, and other built systems work symbiotically with mountain glaciers, coastal floodplains, wetlands, and aquifers to form a web of natural and built freshwater stor- age solutions that people depend on for drinking, sustenance, transportation, recreation, for regulating flows for hydropower, and mitigating the destruction of floods. But we are at a crossroads. The global population has doubled over the last 50 years, and parallel economic growth has translated into a rapidly increasing demand for water—yet the total volume of freshwater storage has declined by around 27,000 billion m³ (McCartney et al. 2022), due to melting glaciers and snowpack and the destruction of wetlands and floodplains. Concurrently, the volume of water stored in built storage is under threat as sediment fills the useful storage space in reservoirs (Annandale, Morris, and Karki 2016), new construction in some large infrastructure solutions have proven far less sustainable than anticipated, and built structures are aging faster than the pace of rehabilitation. In short, we are facing a global water storage gap (GWP and IWMI 2021). Exacerbating the problem is climate change. Nowhere is the impact of climate change more visible than in water. Over the past 20 years, 1.43 billion people have been adversely affected by drought (Browder et al. 2020), leaving human settlements and industries of all sizes without sufficient storage xii to meet growing water demand from people, farms, and industry. Conversely, 1.65 billion were ad- versely affected by floods, with an estimated 290 million people directly affected—an increase of 24 percent over previous decades (Browder et al. 2021; Tellman et al. 2021; CRED and UNDRR 2020). By 2030, projections suggest an additional 180 million people will be directly affected by flooding (Tellman et al. 2021), the poor and disadvantaged primarily among them. What makes this issue progressively more urgent is that the water storage gap—the difference be- tween the amount of water storage needed and the amount of operational storage (natural and built) that exists for a given time and place—is growing and is expected to widen (figure ES.1, McCartney et al. 2022; GWP and IWMI 2021). Closing the water storage gap is our shared challenge. It is an inherently complex mission made expo- nentially more difficult by the fact that current approaches to freshwater storage development and management are inadequate to meet the challenges of the twenty-first century. From decision‐makers at water ministries and ministries that are water-reliant, to engineers, ecologists, and academics, to project teams at the World Bank and other international development agencies, we recognize water storage as a dense web of interdependent natural, built, and hybrid solutions— but rarely is it planned and managed as a system. Most often, water managers approach solutions as separate units, evaluating, designing, developing, and managing storage as independent facilities for a limited set of stakeholders, developing fragmented solutions that are overly reliant on built infrastruc- ture, insufficiently focused on the ultimate service, inadequately maintained and operated, and benefit- ing a finite group without considering the potential to develop service solutions with a broader reach. Intercepting the scale of change to the climate that is underway and achieving a meaningful shift in approaching water storage mean confronting long-standing traditions in planning and development cooperation and coordination. “Business as usual” isn’t an option. FIGURE ES.1 The Growing Storage Gap Present Future Storage needs Flood Environment Storage gap Industrial Municipal Energy Agriculture Operational storage Nature-based Built Hybrid Storage Operational Storage Operational needs storage needs storage Source: Adapted from GWP and IWMI 2021. Note: Amounts of storage needed and operational storage are stylized estimates. Executive Summary xiii What the Future Has in Store: A New Paradigm for Water Storage calls on us to think differently, plan inclusively, and act systematically to address the water storage challenges of the coming age. Grounded in the principles of integrated water resources management (IWRM), it provides a frame- work for accelerating collaboration between sectors and public and private stakeholders globally, set- ting out a strategy for tackling and overcoming the storage gap, and tables an imperative for the whole spectrum of vested water stakeholders to begin championing integrated storage solutions managed as a system to provide long-term, resilient, and sustainable services that benefit many for generations to come. 2. THE CHALLENGE Water is at the center of economic and social development. It influences whether communities are healthy places to live, whether farmers can grow food, or whether cities have reliable clean energy. Water underpins natural ecosystems, drives industry, and creates jobs. It touches every aspect of de- velopment, with a direct link to almost every Sustainable Development Goal (SDG). Over 99 percent of freshwater storage is in nature (McCartney et al. 2022), making it a large part of the solution, but multiple forms of water storage—built and natural—usually combine into storage systems where elements work together to provide the services communities rely on (figure ES.2). For exam- ple, floodplains and wetlands combine with river channels and soil storage, buffering flood water and releasing water in drier periods. Several smaller storage systems may combine into larger systems. The flood vulnerability of a city, for example, will be influenced by surrounding systems of land use, groundwater recharge, and floodplains, as well as local flood mitigation measures. The distribution of water across continents, countries, and basins varies significantly in quantity, qual- ity, and seasonality. Within countries themselves, water is distributed unevenly. Rainfall, surface, and groundwater can all vary considerably within countries; for example, in the United States, the wettest areas can receive roughly 100 times the rainfall that the driest areas receive. Huge variations in rainfall FIGURE ES.2 Water Storage Types, Systems, and Services Natural and built …combine in natural, built, or hybrid …to provide …for multiple Storage Types… Storage Systems… Storage Services… Sectors Snowpack Landscapes and Watersheds Farmer Productivity Increased Water and Resilience Glaciers Floodplains Availability Household Water Lakes and Ponds Supply and Sanitation Wetlands Artificial Urban Retention Manufacturing Systems and Industry Aquifers Flood Soil Moisture Managed Aquifer Recharge Mitigation Hydropower and Systems Renewable Grid Water Harvesting Structures Balancing Water Tanks Other Combined Systems River/Canal Transportation Small Dams and Reservoirs Regulating Cascades of Dams, Flows Environmental Large Dams and Reservoirs Locks, or Weirs Services Natural Hybrid Built Source: Original figure for this publication. xiv WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE exist in many other countries, as varied as India, Colombia, Peru, and Papua New Guinea (Damania, Desbureaux, and Zaveri 2019). Ground and surface water is also geographically dispersed, leaving many countries relying on either natural conveyance systems—including rivers—or built infrastructure to move water from wetter to drier areas. Broadly, water storage provides three main services: (a) improving the availability of water during drier periods, (b) mitigating the impacts of floods, and (c) regulating flows for other purposes, such as hydropower, transportation, or recreation. These services, in turn, underpin everyday water use across most economic sectors, from agriculture to transportation (figure ES.2). Water storage is becoming more important as a vital tool for adapting to, and mitigating, climate change. Climate change can increase variability and water extremes, change the total water available, and increase water needs. Because climate change is bringing less predictable and more variable pre- cipitation, it depresses economic investment and job creation, and it makes farmers less productive and the provision of everyday services, such as reliable urban water supply, more difficult. Water storage provides a mechanism to offset some of the hydrological changes brought about by cli- mate change by improving water availability and reducing the impact of floods. Further, water storage is expected to play an important role in mitigating drivers of climate change; for example, hydropower provides a source of clean energy and is used to incorporate other variable renewable energy sources, such as solar and wind, into the grid, as well as to store energy, using technology such as pumped storage. Careful management is needed to balance these new demands on the storage resource, as well as to minimize greenhouse gas (GHG) production from reservoirs, paddy fields, and other storage types. The Complexity of Storage Planning Addressing the storage gap is inherently challenging, in part because each situation is scale- and context-specific. Measures to fill the storage gap must be fit for purpose, depending on the local con- ditions, as some countries may experience less pressure while others already have significant water storage gaps, which may worsen over time. Some locations may require changes to the operation of existing water storage infrastructure or institutional setup to optimize their existing storage operation. In Lake Mendocino, California, the United States Army Corps of Engineers (USACE) and other stake- holders are piloting new reservoir operating rules that will allow for improved flood management (case study B, chapter 8). Other systems may require a comprehensive intervention to expand the volume of water storage available to provide services. In addition to new built storage, Monterrey, Mexico, has been working to expand natural storage upstream of the city through participatory catchment manage- ment programs to provide flood protection services for the city and its assets (case study D, chapter 8). Ultimately, all water storage gaps are local, measured in simplest terms by supply versus demand. In any system, storage demands occur at varying scales, times, and volumes, with requirements related to reliability, vulnerability, resilience, and control. On the supply side, availability depends on natural, built, and hybrid storage, with combinations offering a variety of advantages in terms of scale, timing, volume, and service. For any given location, the practical responses to addressing storage gaps include considering other water resources management measures, including non-storage measures, as part of a broader ap- proach to water resources. Despite the local nature of water storage gaps, for many, addressing the Executive Summary xv challenge will require working across borders, given that many river basins and groundwater aquifers are transboundary. One of the primary challenges we face is that failure to plan storage as a system often results in overreliance on built storage and overlooking the value of natural storage. Built storage is generally understood to be providing direct services to people, and the fact that natural storage has always been there makes it somewhat invisible and taken for granted. Different types of storage are often developed (frequently, built storage) or degraded (both built and natural storage) in response to various needs or pressures, without full consideration of how natural and built storage can be managed and operated as a system. Siloed approaches to scaling up storage traditionally suffer from other primary challenges, including: » The drive for new storage often eclipses opportunities for making better use of existing systems through rehabilitation, reoperation, and retrofitting actions. » Short-term financial and political incentives often motivate the development of new storage with- out full consideration of options that would increase services provided by existing natural and built storage. » Multiple competing storage systems serve different stakeholders with different services, often separated by borders or boundaries, leading to uncoordinated development or water releases and reduction in benefits overall. » Properly understanding costs, benefits, risks, and uncertainties in advance of investment deci- sions can be time-consuming, expensive, and difficult. They are not always well understood. As a result, negative impacts on people and the environment are not always minimized and mitigated, and solutions are not developed with an eye toward distributional equity. » Insufficient maintenance of existing storage is driven by several factors including inadequate attention to preserving natural storage, sedimentation of built storage, and poor operation and maintenance (O&M). » Storage is unable to meet growing risks of climate change or protect the value of investments. Climate change may mean that storage systems need to meet new performance requirements to provide the same services or need to be altered for safety concerns, such as to handle increased floods. » Policy and institutional measures are often lacking. Without these, water storage runs the risk of limited sustainability, and in some cases, may be counterproductive. Large new storage for urban water supply, for example, might facilitate an increase in water consumption beyond what had been anticipated as new supplies become available. » Overreliance on storage when there may be other more efficient solutions, such as demand man- agement or valuation or pricing of water; supply-side alternatives, such as desalination or treated wastewater; or non-water alternatives to energy and transportation. There is no simple solution to these complex challenges, but focusing on the underlying reasons for them provides a path to better approaches. To measure and model in an integrated way to close the water storage gap is the ultimate objective that begins with the need to think differently about storage planning. xvi WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE 3. A FRAMEWORK FOR INTEGRATED WATER STORAGE PLANNING What the Future Has in Store: A New Paradigm for Water Storage sets out a new framework for inte- grated water storage planning. It presents an approach to systemically address the issues surrounding storage to improve water security and water availability at every level as actioners seek answers to three questions: » What interventions do I need to put in place to meet my water security goals? » How is that accomplished while minimizing negative impacts? » What forms of water storage development and management are part of the solution? The proposed integrated approach to water storage planning fits within broader IWRM, with the river basin as the primary frame of reference. The framework builds on the IWRM planning approach, with a focus on concurrent joint planning around solving specific water-related problems through storage or other management measures. It describes potential approaches to filling the storage gap, starting with the need to consider the full range of choices—including demand management, alternative supply mechanisms, and storage—that may be required at the local level. Whether considering natural or built, surface or sub-surface, small or large, one of the framework’s main purposes is to provide a systemat- ic process for early identification and consideration of potential opportunities and trade-offs that often receive attention after significant sums have been invested in project preparation and some design choices have already been made. A Problem-Driven and Systems Approach Where storage planning often occurs at a project level, the integrated framework moves beyond the status quo, combining a problem-driven approach and a systems approach. Together, they provide a more strategic and robust alternative to conventional planning by considering interconnected water resources management components across storage types, scales, and user needs. A problem-driven approach entails defining the problem and identifying the underlying challenges that require solving. The concept is used across numerous fields where the solution designers (software developers, engineers, biological or pharmaceutical design teams, and social scientists, among others [Fritz, Levy, and Ort 2014]) delve into and define the underlying problem first, rather than beginning from a set of design specifications. Water-related challenges may include impacts of natural disasters, inadequate water supply for household consumption, agricultural or industrial production, reduced electricity generation, potential threats to biodiversity, environmental flows and ecosystem services, reduced transportation for goods and people, and limited recreational opportunities. Targeted devel- opment objectives are formulated from the problems identified.  A systems-driven approach allows for an integrated look at the solutions, stakeholders, impacts, and alternatives. It considers necessary enabling systems and services, the roles played by different parts of the system, and the relationships among those parts with respect to the overall behavior and per- formance of the system, leveraging interconnections to build integrated approaches to development problems that weave together geographic, socioeconomic, and institutional factors. For example, a connected water storage system can support integrated flood and drought management by transfer- ring flood excesses to periods of scarcity through measures such as managed aquifer recharge (MAR) fed by diverted floodwaters, as is being done with the “Underground Taming of Floods for Irrigation” Executive Summary xvii approach in the Ganga Basin. Integrated flood and drought management is also supported by fore- cast-informed reservoir operations as in Lake Mendocino, California. Bringing the problem-driven and systems approaches together into a single framework leads to po- tential solutions not considered by one approach alone. As an options assessment, the framework is intended as an early planning exercise that puts key strategic considerations in a form that helps stakeholders understand and assess the range of options available, how and why they are intercon- nected, the pros and cons of different combinations of measures—including negative impacts—and how non-storage solutions may fit among the options or offer alternatives. Ultimately, it enables a more informed decision about which combinations of storage are worth exploring further and whether they should be implemented in parallel or in series. The framework is organized in three stages: (1) a needs assessment to define the problem; (2) a definition of the system and potential solutions; and (3) a decision-making process that considers a range of scenarios and uncertainties. The first stage includes a definition of the development ob- jectives and the related “water service requirements” to meet those objectives, and then characterizes the current water resources system (including storage) and other systems that may need to be consid- ered (energy, agricultural markets, etc.). The second stage systematically identifies additional potential options (including options other than storage). It includes a range of storage options, from green to gray, small and large, and encourages consideration of many modalities of intervention, from rehabil- itating existing storage, to retrofitting it for different uses, to reoperating storage, raising new storage, or engaging in other sectoral reforms. The final stage models how options, in different combinations or scenarios, would result in changed levels of services, and uses decision criteria to guide the choices for further study (figure ES.3). The framework presented here is not only a technical review but is also ideally an opportunity to shift the conversation on freshwater storage so that it includes the more diverse group of stakeholders crowded in by a broader set of potential solutions. While the process outlined is fundamentally public sector-led, it recognizes the importance of the private sector and civil society in planning, developing, and operating water storage investments and highlights areas where they have specific roles to play. A multi-stakeholder planning process could be at the expense of expedient decisions, but such pro- cesses are proven to increase trust, stakeholder satisfaction, transparency, and performance in the water sector (Fox 2015; Water Witness 2020). These conditions enable greater ownership and buy-in from stakeholders, which could reduce delays in implementation. Each situation should be tailored FIGURE ES.3 Integrated Storage Planning Framework Stages The Problem: The System: Bringing it Together: A Needs Assessment Understanding Making Decisions Solutions • Defining Development • Defining Storage Objectives • Taking Stock of the Scenarios • Characterizing Water Current System • Establishing Decision Service Requirements • Solutions: Identifying Criteria Additional Options • Comparing and Assessing Scenarios Source: Original figure for this publication. xviii WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE appropriately to the needs of the stakeholders to create sustainable and efficient storage capacity for both present and future needs. It is not meant to be exhaustive, but it provides tools and resources to arrive at better storage outcomes. 4. MAKING BETTER DECISIONS NOW In a perfect world, well-developed regulatory and institutional frameworks that clearly lay out roles and responsibilities and set guidelines that support the assessment and implementation of water storage options would already exist. There would be regulatory frameworks that include protections for natu- ral storage as well as for water towers, riparian areas, and critical groundwater infiltration areas, and sufficient quality data available upon which to base basin-level studies that scope options, risks, and opportunities, and sector plans informed by cross-sectoral linkages. But this is not reality. In truth, the challenges in implementing an integrated problem-driven, systems approach to water storage planning are, in many ways, the same as those that encumber the imple- mentation of IWRM. Despite growing awareness of IWRM principles among policy makers and water managers, the implementation of IWRM is progressing at only half the rate that is needed to achieve SDG target 6.5 (UN-Water 2021). The challenges extend to managing water storage in a more integrat- ed way including lack of data, coordination challenges, misaligned incentives, institutional capacity issues, and funding. Many planning and investment decisions are made—indeed, must be made—in the context of financial and human resource constraints and gaps in information. The Integrated Storage Planning Framework will need to be implemented with imperfect information and with finite resources. Water storage planners must strive to make better storage decisions while knowing that perfection is not attainable. The framework is designed to be implementable even in the face of limitations that include: » Multi-Stakeholder Engagement and Coordination ¡ Beyond government, early integration of multi-stakeholder perspectives and knowledge in water storage planning is important—but it is not always hardwired into regulatory and insti- tutional frameworks. As in the case of government agency coordination, ensuring the right composition of stakeholders from early on is vitally important. In many instances, this in- cludes non-governmental stakeholders like civil society organizations (CSOs), private indus- try, and local communities. ¡ The problem-driven, systems approach explicitly includes stakeholder considerations at various levels of the process. Early stages of the framework involve mapping the various stakeholders that may be affected by a set of water storage options and whose behavior will influence the performance of those options. The early mapping of stakeholders is neither costly nor time-consuming and provides a foundation for later stages, where more detailed information needs to be collected about stakeholder interests and capabilities. Having these considerations built in will help to screen out politically, environmentally, and socially infeasi- ble options. » Regulatory Frameworks ¡ Many jurisdictions are missing or have outdated laws and regulations on water resources management and water storage. Existing laws and regulations may not reflect the actual level Executive Summary xix of water resources development or may not be detailed enough to manage the trade-offs that inevitably emerge with ambitious development plans. Regulatory frameworks can support in- tegrated planning if they emphasize the importance of basin-wide approaches, recognize the interdependence of built and natural systems, and include sustainable funding mechanisms for storage planning and management. ¡ The problem-driven, systems approach embeds these kinds of issues into the framework, so that if they are not explicitly provided for in the regulatory framework, they can still be considered in a systematic way. Additionally, deficiencies in the regulatory framework may become apparent through the use of the planning framework and could be reflected in the regulatory reform process. » Private Sector Participation ¡ Private sector participation in water storage planning and management can come in many different forms—from management and operation contracts to the purchase of previously public assets to the provision of equity or loan financing. Private sector players may also have considerable expertise and access to technology that may be difficult to acquire in a fully public venture. Evidence from private sector participation around the world suggests that it increases operational efficiency, leads to higher-quality service provision, and supports the expansion of service delivery to underserved segments (Al-Madfaei n.d.). » Misaligned Incentives and Political Economy ¡ Where institutional arrangements are generally in keeping with international good practice, the political economy situation can lead to a mismatch between policy and implementa- tion, making it harder to action integrated storage planning and management. The specific non-technical drivers of this mismatch will vary from place to place, but they generally reflect a shift to institutional rules that challenge pre-existing norms and behaviors around water management. Integrated storage planning and management, and IWRM, more generally, can be undermined, for example, by local political interference, privileged access of a select few, rent-seeking behavior, and power asymmetries between stakeholders. Problem-driven ap- proaches account for drivers of institutional non-performance by identifying the underly- ing problems as well as different stakeholder interests and capabilities.   Implementing integrated storage planning will take time to be reflected in practice and in institutional frameworks for water management. Nevertheless, the problem-driven, systems approach can guide water managers through a step-by-step process that works around and through some of the institu- tional challenges. For those wanting to understand each phase of the framework in more detail, or to begin using it in practice, chapter 7 of this report elaborates on each stage and includes guiding questions when undertaking an options analysis and examples of technical tools and innovations to help in storage planning. 5. THE OPPORTUNITY: THINKING DIFFERENTLY Across the water management continuum, from policy and key decision-makers in national govern- ments to development and strategic planners in water and water-dependent sectors, to development practitioners who support project- and sector-level interventions, to the research community, our re- sponsibilities and perspectives are manifold. Yet achieving resilient, sustainable storage solutions is xx WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE predicated on a universal shift in thinking, a collective understanding of the new paradigm for water storage, and adoption of the key principles that characterize an integrated approach. Developing an integrated approach requires a systems perspective. The hydrological system is the foundation for integrated storage planning and management, but there are also other environmental, social, and economic systems that need to be understood and addressed. Thinking differently means making conceptual shifts (table ES.1) in how we think about water storage, toward an integrated approach that focuses on outcomes, integrating natural and built as a system, getting more from the current system, and managing risks through diversification. Thinking differently requires not just deciding "What is the next investment to make?" but evaluat- ing which combination of investments and policies offers the most robust and resilient system for long-term storage. This means considering a broad range of options, starting with understanding the current storage system. Being able to model the interactions and performance of the current storage system will help determine whether more storage services can be extracted from the current system, as well as what additional storage opportunities there might be. Critically, it also helps to identify the range of stakeholders that currently depend on the natural and built storage within the system, and who therefore need to be engaged in the process. Additional storage services can be gained from current storage or from adding new storage. Opportunities— known as "the 5 R's"—are outlined in table ES.2. The benefits of a systems approach that includes the 5 R’s—rehabilitating, reoperating, retrofitting, reforming institutions, and raising new—is exponentially more valuable than a siloed approach, culmi- nating in wide-ranging insight into how optimized integrated storage solutions can help. These include managing water extremes, to treat floods as a water surplus that can be captured and stored for drier times (hydrological); saving on infrastructure that could be multipurpose (financial and economic), and serving the needs of several sets of stakeholders, or at least considering their needs in an integrated way (social). It can help reduce correlated risk, by diversifying types and location of water supply. Finally, it can enhance sustainability. TABLE ES.1 Conceptual Shifts: An Integrated Approach to Thinking about Water Storage TOPIC FROM TOWARDS Defining success Storage volumes Storage outcomes—the services enabled by storage Storage approaches Built storage Natural and built storage and their interactions Storage management Facility level System level, working across institutions Storage development New development Getting more from current—through retrofitting, reoperation, and rehabilitation—and developing new Risk management Infrastructure Diversification of storage types across storage systems development Source: Original to this publication. Executive Summary xxi TABLE ES.2 The 5 R’s: Opportunities for Increasing Storage Services Reoperation The modification of storage operations for improved management (efficiency gains), which might include changing the timing of water releases from controllable infrastructure to increased benefits or adding additional benefit streams, such as flood control and minimizing storage losses from evaporation. This may also include managing for synergies between different types of storage or creating new connections between existing storage, so that they may be operated as part of a broader system. Rehabilitation The restoration of current storage—natural or built—to improve storage capacity or performance. Rehabilitation can extend the life of existing storage capacity and defer investment in new storage. Restoration of original capacity or slightly improved capacity could be achieved through addressing structural defects, sediment removal, increasing the flow rates of managed aquifer recharge sites, and environmental restoration of natural storage, among others. Retrofitting The upgrading or augmentation of capacity at existing storage facilities, and or enabling new uses of the facilities. This could be achieved through raising the height of dam walls or adding new hydromechanical or electromechanical equipment to serve different objectives or different customers to make overall gains in the value of storage services. Adding floating solar panels to existing hydroelectric projects or adding hydropower generation to irrigation projects are two examples. Reform: In addition to physical investments in storage, policy makers need to invest in the Investing in institutions that are required to better plan and manage storage. This includes institutional institutions to capacities to: manage storage better • Manage the data, modeling, and planning systems required to develop smarter storage. • Enable and incentivize integrated planning, development, and management at multiple scales across multiple stakeholders. • Mobilize the finance and financial incentives that enable storage to be prioritized, planned, and managed in the broader public interest. Policy and institutional approaches that manage water groundwater, improve the efficiency of services, price water services appropriately, and address social and environmental issues are all necessary complements to appropriate and sustained storage management. Land management, conservation, and protection measures are key requirements for maintaining or restoring natural infrastructure. Raising New: This would involve exploring the full range of available storage types: natural and built; Finding or surface and subsurface; large and small; and centralized and distributed. New storage developing might be built at a variety of scales or created in nature through different landscape additional management practices (e.g., accelerating aquifer recharge). New storage can also be storage designed to leverage or complement other parts of the system to make the whole greater than the sum of the parts. Source: Original to this publication. The concept of the “5 R’s” has been adapted from the Uncommon Dialogue on Hydropower, River Restoration, and Public Safety, Stanford Woods Institute for the Environment 2020. 6.  RISING TO THE CHALLENGE: A CALL TO ACTION This Call to Action summarizes the key conclusions and recommendations of this report around four themes: A. Why focus on water storage? B. What do stakeholders need to understand to develop smarter approaches? C. Who needs to be involved? D. How can stakeholders approach storage more strategically? xxii WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE A. Why focus on water storage? Water insecurity is growing around the world, influenced in some places by increasing demand, in others by degrading quality, and almost everywhere by climate change. Even countries with relatively temperate climates and large infrastructure endowments face increasing water insecurity, such as in Europe at the time of this report. Smarter approaches to water storage will, inevitably, lie at the heart of responses to climate change. Beyond improving the availability of water during drier periods, mitigating the impacts of floods, and regulating flows for other purposes such as hydropower, storage is also a form of hydrological risk management. Families, farmers, businesses, and cities will invest more in their lives and livelihoods when they feel protected from water extremes. As water storage grows in importance, current methods for developing and managing it are more ob- viously inadequate. Many approaches, in general, have been too fragmented and short term. The world today faces growing demand for water, increasing variability, and a growing water storage gap; yet current approaches to storage are no longer fit for purpose and do not add up to the comprehensive, sustainable, and integrated solutions that circumstances increasingly demand. Call to Action Step 1: Focus more, and more strategically, on water storage. B. What do stakeholders need to understand to develop smarter approaches? While humans have been developing water storage systems for several millennia, nature has always provided the vast majority of freshwater storage. The first step, therefore, is identifying what storage we have, particularly the natural systems such as groundwater, wetlands, glaciers, and the soil moisture reserves on which people depend. Systematic mapping of natural and built storage on a basin-by-basin basis (as this is the practical operating scale of most storage systems) is needed, including data on volumes, reliability, and controllability of the water stored. Knowing what we have is the first step toward not taking it for granted and unnecessarily depleting it, as many parts of the world have been doing for several decades. It is also a necessity for informing future planning and investment decisions. The second knowledge challenge is to understand storage as a system. Even very different types of storage are linked as part of a broader water cycle, meaning that they generally need to be developed and managed as an integrated system rather than as stand-alone facilities. Engineers have long under- stood that dams depend on their watersheds, but it is time to go much beyond this and understand not only the hydrological system but the broader social, economic, and environmental systems that inter- act with it, building upon decades of global experience with IWRM. The social and economic systems are the primary drivers of changing demand for storage services, while the broader environmental systems (biological, climatic, etc.) are both major users and shapers of water flows. The third key knowledge challenge is assessing alternatives to storage. Storage challenges usually need to be assessed as part of a broader water resources context, and storage may not be the best solution to the problem at hand. Alternatives to storage could range from demand management to alternative supply measures for reducing scarcity; from zoning regulations to flood insurance for managing floods; and from alternative energy to alternative transport investments to storage’s regulatory services. The important point is to consider alternative ways to deliver the service, not simply volumes of water. Executive Summary xxiii The fourth big knowledge challenge is to develop and manage storage within a context of increasing uncertainty brought about by climate change. Managing storage as a system is a key step in the right direction since a diverse system will be more resilient to weather-related shocks than individual facili- ties. The fact that the past is no longer a reliable guide to the future has several ramifications, including a premium on the rapid collection and analysis of data to guide system understanding and manage- ment. But more broadly, climate change demands smarter approaches and tools to make long-term investments in natural and built infrastructure, and in the institutions to manage it. This report details a number of these tools, from decision-making under uncertainty to integrated modeling techniques, to make our processes “smarter.” Call to Action Step 2: Measure and model storage in an integrated way—natural and built, surface and sub-surface—to understand, develop, and manage storage as a system with long-term, sustainable, and resilient services as the end objective. C. Who needs to be involved? Closing the water storage gap is a shared challenge. Faced with the growing risks of water insecurity around the world, global, national, and regional stakeholders can no longer focus on their own needs in isolation. A conceptual shift in thinking is required. We all have a role to play. Governments and policy makers have a unique opportunity to lead by setting the criteria for suc- cess, advocating for an integrated, systemic approach to storage that begins with a rigorous defini- tion of the water-related problems and prioritizing efficient solutions that benefit the largest range of stakeholders. Utilities, businesses, irrigation schemes, hydroelectric producers, and other bulk users of water ser- vices have a key part in defining the problem through identifying their long-term water needs, including for storage services, as well as potential alternatives to them. The social or environmental implications of different management approaches to built and natural storage (e.g., land-use restrictions) need to be carefully understood. Significant investments in storage may have significant trade-offs associated and different stakeholders with differing views on them. Storage services may be most efficiently provided through multipurpose infrastructure provided to multiple and sometimes competing stakeholders. All stakeholders, including those representing the environment, have a role to play in thinking through the trade-offs, as well as clarifying the value, and therefore the economic and financial sustainability, of future investments, as well as engaging in joint processes that help produce a shared understanding and more resilient, integrated services in the future. Expertise and accountabilities vary significantly across the spectrum of those who work in water. Yet achieving change is predicated on a universal shift in thinking, a collective understanding of the new paradigm for water storage, and adoption of its key principles. Call to Action Step 3: Engage all stakeholders to define the storage services needed (the "problem") and the trade-offs associated with future investments (the "solutions"). xxiv WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE D. How can stakeholders approach storage more strategically? This report proposes an Integrated Storage Planning Framework intended to be helpful in developing more—and more sustainable and resilient—freshwater storage in the future. Together, the framework’s three-step process is designed to build the knowledge and the consensus required for investing in improved long-term water storage services. Critically, the framework includes ways to consider whether storage investments are really the best way to address water-related chal- lenges, or whether alternatives should be considered. At a practical level, this report identifies five major areas for investment in future storage systems (nat- ural and built), summarized as the 5 R’s: rehabilitating, reoperating, retrofitting, reforming institutions, and raising new. Many countries are likely to need to invest in all of these areas, including new institu- tional mechanisms that may be needed to undertake them at aquifer, basin, national, or transboundary levels. It also includes recommendations about how to approach mobilizing finance for storage, as well as to safeguard the economic returns over time through provisions for O&M. Call to Action Step 4: Use an integrated planning methodology to identify and prioritize investments in both natural and built water storage and develop an institutional setup that can maintain and operate storage in the public interest for the long term. Water Storage: The Future Is Now What the Future Has in Store: A New Paradigm for Water Storage is a progressively urgent appeal to multi-sector practitioners at every level, both public and private, to begin championing integrated smart water storage solutions that meet a range of human, economic, and environmental needs. Closing the water storage gap requires a spectrum of economic sectors and stakeholders to develop and drive multi‐sectoral solutions that address solutions holistically, effectively, and efficiently. Done right, a new paradigm for water storage, backed by investment, will create a stronger foundation for sustain- able development, climate action, and resilience, paying dividends for populations, economies, and the planet, through years and generations to come. Executive Summary xxv ABBREVIATIONS 5 R's rehabilitating, retrofitting, reoperating, raising new, reform AMI area of maximum impact ARA active river area CDMU Central Dam Monitoring Unit CGE computable general equilibrium CIA cumulative impact assessment CNFRC California Nevada River Forecast Center CO2 carbon dioxide CONAGUA National Water Commission (Comisión Nacional del Agua) CROPWAT Crop Water and Irrigation Requirements Program CSO civil society organization CW3E Center for Western Weather and Water Extremes CWC Central Water Commission DAD Department of Agrarian Development DGWR Directorate General of Water Resources DMU Dam Monitoring Unit DOISP Dam Operational Improvement and Safety Project DRIFT Downstream Response to Imposed Flow Transformations DRIP Dam Rehabilitation and Improvement Project DSC Dam Safety Commission DSP Dam Safety Project DSS decision support system DSU Dam Safety Unit DTF Decision Tree Framework DWS Department of Water and Sanitation EFA environmental flow assessment EFO ensemble forecast operations ESF Environmental and Social Framework ESIA environmental and social impact assessment ESMP environmental and social management plan ESS Environmental and social standard EU European Union Monterrey Metropolitan Area Water Fund (Fondo de Agua Metropolitano de FAMM Monterrey) xxvi FAO Food and Agriculture Organization of the United Nations FIRO forecast‐informed reservoir operations FVA full viability assessment GCM general circulation models GDP gross domestic product GEF Global Environment Facility GGIS Global Groundwater Information System GHG greenhouse gas GIS geographic information system GRACE Gravity Recovery and Climate Experiment GRanD Global Reservoir and Dam Database HEC Hydrologic Engineering Center HEM hydro‐economic model HMT Hydro‐Meteorological Testbed HPP hydropower plant IBAT Integrated Biodiversity Assessment Tool ICOLD International Commission on Large Dams IDA International Development Association IDB Inter‐American Development Bank IFC International Finance Corporation IGRAC International Groundwater Assessment Center IPCC Intergovernmental Panel on Climate Change IRENA International Renewable Energy Agency IUCN International Union for the Conservation of Nature IWRM integrated water resources management IWRSS Integrated Water Resources Science and Services IWMI International Groundwater Assessment Center IWS investment in watershed services MAR managed aquifer recharge MAWLR Ministry of Agriculture, Water and Land Reform MCDM multi‐criteria decision-making MMA Monterrey Metropolitan Area MPWH Ministry of Public Works and Housing MRV measurement, reporting, and verification NBS nature-based solutions NDC nationally determined contribution NEAP National Environmental Action Plan NGO nongovernmental organization NOAA National Oceanic and Atmospheric Administration NRMC Natural Resources Management Centre O&M operation and maintenance OECD Organisation for Economic Co-operation and Development Abbreviations xxvii PES payment for ecosystem services PPIB Private Power and Infrastructure Board PPP public‐private partnership PVA preliminary viability assessment RCP Representative Concentration Pathway RUSLE Revised Universal Soil Loss Equation SDG Sustainable Development Goal SEA strategic environmental assessment TNC The Nature Conservancy UNU-IWEH United Nations University Institute for Water, Environment and Health USACE United States Army Corps of Engineers USGS United States Geological Survey UTFI Underground Taming of Floods for Irrigation VEC valued ecosystem component WAPDA Water and Power Development Authority WCM water control manual WCP water control plan WCWSS Western Cape Water Supply System WMARS Windhoek Managed Aquifer Recharge Scheme UNITS bm3 billion cubic meter GW gigawatt kl kiloliter km3 cubic kilometer m 3 cubic meter MW megawatt *All dollar amounts are US dollars unless otherwise indicated. xxviii WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE Abbreviations xxix Banten, Indonesia. © Tom Fisk via Pexels.com What the Future Has in Store: A New Paradigm for Water Storage calls on all stakeholders to think differently, plan inclusively, and act systematically to address the water storage challenges of the coming century. xxx WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE MAIN Part I REPORT Introduction: The Importance of Water Storage 1 1 INTRODUCTION: THE IMPORTANCE OF WATER STORAGE 1.1 DEVELOPMENT AND CLIMATE Freshwater ecosystems keep wildlife and vegetation alive; RESILIENCE   provide economically and commercially valuable services, including billions of dollars in water purification and fish 1.1.1 Vital Social, Environmental, and Economic capture (EEA 2021; Funge-Smith 2018), and play an im- Resource portant role in regulating the global climate, sequestering about 25–30 percent of the carbon contained in soils and Freshwater sustains life and livelihoods. As it cours- terrestrial vegetation globally (Russi et al. 2013). es through our bodies, the environment, and our econ- omies, water brings life, removes impurities, and Water challenges are also economic challenges. Water transports everything from nutrients to commerce is not only vital to human and ecosystem health but also from place to place. The central challenges of water— to the health of our economies. There are several ways too much, too little, too variable, and too neglected— in which water quantity has significant economic impact: are central challenges of our time. » Too little: Water is a vital input to most economic Water crises are growing. The combination of growing production systems. Insufficient water could put a demand and climate change are making water crises significant brake on economic growth around the more common and more extreme. Droughts and floods world; as a result of water scarcity, some countries compete for headlines, and the everyday lives of farmers, could experience up to a 6 percent reduction in communities, cities, and countries become more com- growth. This in turn translates into a significant im- plex and uncertain. Water and water-related disasters are pact on jobs and livelihoods (World Bank 2016a). often rated among the greatest risks facing modern soci- » Too much: Floods are the most frequent hydro-cli- eties (WEF 2022). matic hazard, representing nearly half of all natural disasters between the years 2000 and 2019; during The poorest are often most vulnerable to water chal- this period, 1.65 billion people were affected, with lenges. Poor people are often the least connected to re- $651 billion in recorded losses (CRED and UNDRR liable water supply and sanitation services and therefore 2020). are often the first affected by shifts in water availability. » Too variable: The relationship between rainfall and The poor are also often severely affected by floods, living economic growth is particularly clear in agricultural in areas that lack adequate protection and drainage, in- areas where the link between the two is intuitive, but it cluding in degraded landscapes. Finally, to the extent that has also been demonstrated to impact the manufac- the rural poor rely on rainfed agriculture, their livelihoods turing and services sectors (Damania, Desbureaux, are the first affected by rainfall variability and droughts. and Zaveri 2019; Kotz, Levermann, and Wenz 2022). The effects of water scarcity on the poor can last for gen- Farmers, firms, and service providers all need some erations—studies show that drought conditions during a degree of predictability to invest. Unreliable water woman’s early childhood can have a measurable effect on supply also results in disruptions to economic activi- her children a generation later (Damania et al. 2017). ty, including in the informal sector (Islam 2019; Islam and Hyland 2019). The environment is both a provider and user of water. » Too neglected. Poor management of water resourc- Global and local water cycles are shaped by the environment. es hinders, and can even set backward, economic 2 development. Poor water quality impacts econom- water across continents, countries, and basins varies ic growth; for example, the release of pollution up- significantly in quantity, quality, and seasonality. Map 1.1 stream lowers economic growth in downstream ar- summarizes the distribution of global freshwater resourc- eas, reducing gross domestic product (GDP) growth es by continent, demonstrating significant differences. In in downstream regions by up to a third (Damania et addition, water courses do not follow political boundaries, al. 2019). Access to groundwater—especially in deep with nearly half of the rivers in the world spanning at least aquifers and as aquifers are depleted, lowering water two countries, adding complications to managing water quality—can be costly and require large amount of resources. energy for pumping. Water is also distributed unevenly within countries. Water is distributed unevenly around the world. The Rainfall, surface, and groundwater can all vary consider- vast majority of the world’s water is found in the world’s ably within countries. In the United States, for example, oceans—only around 2.5 percent of water is fresh (USGS the wettest areas can receive roughly 100 times the rain- n.d., based on Shiklomanov 1993). The distribution of fall that the driest areas receive. Huge variations in rainfall MAP 1.1 Quantity and Distribution of Global Freshwater Resources, by Region Glaciers and permanent ice caps (km3) Wetlands, large lakes, reservoirs, and rivers (km3) Greenland North America 2,600,000 90,000 Europe Asia 18,216 60,984 Asia North America Europe 30,622 27,003 2,529 Africa 0.2 South America 900 Africa Australia 31,776 South America 180 3,431 Australia Antarctica 221 30,109,800 km3 30,000,000 Groundwater (km3) Asia North America Europe 7,800,000 4,300,000 1,600,000 8,000,000 4,000,000 3,000,000 1,000,000 300,000 50,000 Africa South America 5,500,000 Australia 3,000,000 1,200,000 Source: GRID-Arendal 2009 (Cartographer: Philippe Rekacewicz). Licensed under CC-BY-NC-SA 3.0. Introduction: The Importance of Water Storage 3 exist in many other countries, as varied as India, Colombia, of climate change or anthropogenic interventions, im- Peru, and Papua New Guinea (Damania, Desbureaux, and pacts on downstream nature are very likely. Zaveri 2019). Ground and surface water is also geograph- ically dispersed, leaving many countries relying on either Nature buffers societies against floods, slowing runoff natural systems—including rivers—or built infrastructure and absorbing excess water into soils, vegetation, wet- to move water from wetter to drier areas. More countries lands, and aquifers. The extent of nature’s role in flood are now recognizing, though, that rivers are living ecosys- protection is becoming increasingly clear as we degrade tems—some even with legal rights (Berge 2022)—which it. Between 2000 and 2015, an estimated 255 million to will have to be taken into consideration in the future in 290 million people were directly affected by floods, which those countries when examining moving water within represents a 20 to 24 percent increase in the proportion their borders. of people exposed to flooding. In the future, floods will be- come even more common due to climate change, where 1.1.2 Life Depends on Freshwater Storage projections suggest an additional 180 million people will be directly affected by flooding by 2030 (Tellman et al. Storage increases the amount of water available for 2021). human, environmental, and economic use, reduces the impact of floods, and provides a variety of ancillary ser- Human societies developed around natural storage. vices by regulating water flows. Storage enables vital Reliability of freshwater was so catalytic to the rise of the services such as water supply, sanitation, and irrigation, earliest civilizations that they are often referred to as “river which in turn underpin human health, welfare, and food valley civilizations,” including those that developed on the security. Water stored for hydropower not only produces banks of the Euphrates, Indus, Nile, Tigris, and Yellow riv- clean energy directly but also stores energy for when it ers. Other societies developed around readily accessible is most needed, allowing increased use of variable solar groundwater through springs or shallow wells. Early soci- and wind energy. River or canal transportation also often eties required reliable water supplies not only to drink and relies on water storage to provide year-round accessibility bathe but also to invest in early forms of agriculture and for bulk goods carriers. then manufacturing. Nature has always provided the vast majority of fresh- Humans began to supplement natural storage with water storage. Nature stores water in a variety of ways. dams as early as 3000 BCE. As the needs and ingenui- The rivers we rely on are rapidly filled through rainfall, but ty of early civilizations developed, they began to invest in then also sustained through dry periods by the gradual re- ways to move beyond the constraints of natural storage lease of water stored in the watersheds they flow through. and toward more regulation of the spatial and temporal The groundwater that more than one-third of the world’s variability of water, marking major episodes of develop- population rely on (Richts, Struckmeier, and Zaepke 2011) ment in Asia and Europe. Some 5,000 years later, cities as for daily survival is water stored underground by nature big as Las Vegas have developed in historically arid areas and replenished—or not—by complex ecological process- as large dams brought reliable water services to previous- es. Even today, over 99 percent of freshwater storage on ly parched landscapes. For better or worse, large water earth is in nature (McCartney et al. 2022). The fact that it infrastructure, including dams, has transformed the land- has always been there makes it somewhat invisible, or at scapes most people live in today. the very least, taken for granted. Humans have also invested in storage at much smaller Nature also relies on water storage. The ecosystems scales. Rice paddies, terracing, and other small structures around us have all evolved around the realities of natural have long been used by farmers to boost their productivity storage. Ecosystems downstream of mountain glaciers or and extend their growing season. Rural and urban house- wetlands, for example, have developed as they have be- holds capture water in tanks for domestic use to compen- cause "upstream nature" has stored and released water sate for non-existent or unreliable services, or simply to for "downstream nature" at different times of the year. If take advantage of rainfall. Businesses of all sizes also de- significant changes happen to upstream nature because velop and manage water storage for their needs. 4 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE Time Today, our societies, economies, and the environment FIGURE 1.2 Surface Water Storage Impact depend on a web of natural and built water storage. From the smallest household wells to giant reservoirs, Water demand mountain glaciers to coastal floodplains, water storage Natural water availability Quantity of water improves water availability, mitigates flooding, and other- Water supply gap wise enables a variety of other services—from hydropow- er to water transportation to leisure—that underpin much of modern life. 1.1.3 Climate Change Upends Our Relationship with Time Storage Source: Original figure for this publication. Note: Surface water storage alters the temporal distribution of surface Climate change is bringing profound changes to the flows and makes water available at times and in quantities more closely water cycle, particularly through increasing the vari- matching water demands. ability of precipitation. The Intergovernmental Panel on Climate Change’s (IPCC) Sixth Assessment Report con- firms that significant changes to the world’s water cycle the curves and reduce the gaps in water demand, making are already underway, and that these changes will likely water available over a longer period of time (figure 1.2). grow in the future (IPCC 2021). While regional and local This supports efforts to improve the spatial and tem- impacts will differ, climate change brings several chal- poral distribution of freshwater, including reducing the lenges to storage; for example, as storage becomes more risks associated with floods and droughts, to underpin important to addressing growing variability, current stor- basic service delivery and economic opportunities. It is age becomes less effective as it was designed for histor- important to recognize, however, that flattening the curve ical conditions. Future storage becomes harder to plan. also has the potential to change the availability of water to downstream communities and ecosystems (includ- Storing water is a critical part of the societal response ing wetlands and lakes) that people depend on for their to hydrological variability and mounting water scarci- livelihoods. ty. Water demand is most often not aligned with natural water availability, especially in regions of the world where 1.1.4 Water Security Is More than Storage hydrological availability fluctuates widely between dry and wet seasons (figure 1.1). This creates gaps in water Storage is best understood as one of several elements demand over time when water is either not available that can contribute to long-term water security. Storing when needed or there is too much water proportionate water does not "make" new water but regulates it in ways to demand. By capturing some of the water instead of that shift its prevalence across space and time. Water allowing it to flow naturally, water storage helps flatten storage investments, by making the temporal and spa- tial distribution of water more favorable, can also have FIGURE 1.1 Water Demand vs. Natural Surface Water the unintended effect of creating new water demands or perpetuating perceptions of abundance, which may lead to unsustainable resource exploitation. Investing in and Water demand Natural water availability managing water storage must, therefore, be done in a Quantity of water Water supply gap way that does not undermine the role it plays in improving water security. More storage is not always the answer—and can be part of the problem. While storage is vitally important to cur- rent and future water management, it is only one part of the Time broader integrated water resources management (IWRM) Source: Original figure for this publication. puzzle. Increasing storage may not be the best approach Introduction: The Importance of Water Storage 5 Water demand Natural water availability ater Water supply gap to addressing water resource challenges in many circum- FIGURE 1.4 Water Storage Types and Core Services stances, and the dynamic relationship between demand for water and its easy availability—such as through large Water Storage Three Core Services of Types Water Storage new storage projects—may in fact accelerate the use of water, especially if investments in water storage are made 1. Improving the availability of water during drier periods without having appropriate policies and institutional ar- 2. Mitigating the impacts of floods rangements in place. The right balance between investing 3. Regulating flows for other purposes in storage versus managing demand (including through e.g., hydropower, transportation, better valuation and pricing of water), water trade-offs, or recreation and a variety of other supply-side approaches (figure 1.3) will be dependent on local circumstances, as is explored Source: Original figure for this publication. throughout this report. Improving the availability of water. Storing water is 1.1.5 Services of Storage particularly important where the natural variation in pre- cipitation is high. Most locations on earth experience a Water storage provides three broad services: (a) im- seasonal rainfall pattern, occurring as a single wet and dry proving the availability of water during drier periods, (b) season or multiple wet and dry seasons over the course mitigating the impacts of floods, and (c) regulating flows of a year. In addition to regular dry seasons, there are cy- for other purposes, such as hydropower, transportation, clical droughts that can last months or even years. Over or recreation (figure 1.4). Each of these core services may the last 20 years, droughts affected 1.43 billion people and be derived from multiple forms of storage, and all three cost $128 billion in recorded losses, which is known to be are broadly trying to ensure that water is available in the an underestimate due to incomplete reporting, particular- right amount, in the right place, and at the right time. Each ly in Africa, the region hardest hit by droughts (CRED and of these direct services also provides a more indirect risk UNDRR 2020). Water storage is a mechanism to bridge mitigation or management service. water availability during dry seasons and droughts, mak- ing water services more reliable and increasing water se- curity opportunities for economic development. FIGURE 1.3 Response Options to Water Scarcity: Supply Storage helps manage flood impacts. Storage can cap- and Demand Management ture flood peaks, slowing or even stopping the flow of flood waters and thereby reducing the impacts of floods emand Managem ter D ent downstream. Where flood waters are redirected into Wa Reduce Demand groundwater, reservoirs, or other controllable forms of e.g., awareness campaign; storage, the same water can then be used for times when water pricing; quotas; change rainfall and river flow are lessened (Pavelic 2020). cropping techniques/ calendars, or crop variety Storage is a tool for regulating water levels to suit a e.g., canal lining; e.g., intra or inter specific economic or societal purpose, such as main- ce Losses Reallocation improved dam sectoral Response or river basin to water reallocation taining navigation, recreation, or the ability to produce management, scarcity policy; reduce leakage; hydropower. Upstream storage on a river can be used quotas; water Redu micro-irrigation markets to regulate water levels downstream to allow sufficient e.g., build reservoirs; clearance for passage of vessels. Hydropower can bene- tap groundwater; gate drains fit from storage in several ways: through increased water interbasin transfers; virtual water treatment; desalinisation; availability during dry periods; through higher water levels cloud seeding Sup n for increased power production; and for the regulation of ply A u g m e n t a ti o downstream releases for environmental reasons. Storage can support reservoir or downstream water levels need- Source: Adapted from Molle 2010. ed for boating (including whitewater rafting), fishing, 6 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE swimming, or other recreational purposes. Finally, surface that is practically available, and the status of built storage. water storage can also be used strategically to enhance Current circumstances also include levels of econom- groundwater recharge to curb saline intrusion or for other ic development, and the associated public and private purposes. resources needed to develop storage. Future needs are primarily influenced by changes in variability (i.e., climate Storage is a form of hydrological risk management. The change), growth in demand, and rates of sedimentation, amount of water storage a society needs is influenced by while tolerance for risk pertains to the socially acceptable its tolerance for risk, which is related to the value of the levels of flood, drought, and other related risks. A country goods or services threatened by hydrological extremes in with rainfall that is relatively well-distributed, groundwater the absence of sufficient storage, as well as the non-market that is located close to demand centers, and good infra- value placed on life and health. Floods, for example, can be structure begins in a very different place than a country extremely destructive and can cause damage to property, with highly seasonal rainfall, limited groundwater, and sig- life, and livelihoods. Water storage is, therefore, an invest- nificant infrastructure deficit. ment in risk reduction for drought or floods, and ultimately in resilience to natural disasters and climate change. 1.2 OUR FUTURE UNDER THREAT 1.1.6 Needs Differ Around the World 1.2.1 Growing Demand for Freshwater Water storage needs are influenced primarily by current circumstances, future needs, and tolerance for risk. In the last century, global demand for freshwater use has Current circumstances include the water endowment, increased by a factor of six. This demand continues to variability in precipitation within and across years (map grow at approximately 1 percent per year, roughly match- 1.2) (Fader et al. 2016), the amount of natural storage ing the global population growth rate (UNESCO 2021).1 The MAP 1.2 Coefficient of Variation of Mean Monthly Precipitation Coefficient of Variation 0-50 50-60 60-80 80-100 100-120 120-140 140-200 No data Source: Adapted from Fader et al. 2016. Note: As average for the period 2000–05. Coefficients of variation were calculated by dividing the standard deviation of monthly rainfall by the annual mean of monthly rainfall. Introduction: The Importance of Water Storage 7 global population has grown from 1 billion in 1800 to 7.8 Higher and more concentrated demands for water ser- billion in 2020, and estimates put it at 8.5 billion by 2030, vices will translate into significant increases in fresh- 9.7 billion by 2050, and 10.8 billion by 2100. Until 2100, water needs, as well as a need for water storage (figure more than 60 percent of the world’s population growth 1.5). By 2050, the world will need to grow 60 percent more will be in Sub-Saharan Africa and South Asia; in 2100, food to keep up with population growth, which, under a these regions together are expected to account for 55 per- business-as-usual scenario, is estimated to require a 50 cent of the world's population.2 In member states of the percent increase in irrigated food production while only an Organisation for Economic Co-operation and Development additional 10 percent in water withdrawals is estimated (OECD), where per capita water use rates tend to be high- to be available (He et al. 2021). Expected improvements est in the world, the increase in per capita water use has in water use efficiency and increases in reuse will be im- tapered. However, water use continues to rise in emerging portant in slowing the growth in freshwater withdrawals, economies and middle, and lower-income countries due as will decoupling economic growth from requisite growth to population growth, economic development, and shifting in water use, especially in the agriculture sector, but the consumption patterns. At the current rate of change, by trend toward increased water stress continues. Already, 2050, there will be a 20 to 30 percent increase in water use more than 2 billion people live in countries that are water as compared to today (UNESCO 2021). stressed (United Nations 2018), and an estimated 4 billion people live in areas that experience severe physical water Development is increasing water demand, while rapid scarcity for at least one month per year (Mekonnen and urbanization and shifting demographic patterns are Hoekstra 2016). shifting demand centers. In 2018, about 55 percent of the world’s population lived in urban settlements. By 2050, Climate mitigation efforts mean that demand for energy- this number is expected to grow to 68 percent, concentrat- related water storage is expected to increase. Hydropower ing demand for water services. During that same period, will likely play a key role in climate change mitigation ef- urban water demand is expected to rise between 50 and forts, and demand for water storage for hydropower is 80 percent (Garrick et al. 2019) due to population growth expected to increase. The International Renewable Energy in urban areas, combined with the fact that per capita Agency (IRENA) estimates that 1,300 GW of new capacity water use among urban dwellers is higher because of a is needed to decarbonize the energy sector, meaning that higher standard of living. Compounding the problem, the investment in hydropower production will need to double urban population facing water scarcity is also expected to (IRENA 2021). In addition to generating electricity, hydro- rise from 933 million in 2016 to between 1.7 billion and 2.4 power can provide energy storage and grid-balancing ser- billion in 2050 (He et al. 2021). vices, which are key to enabling the scaling up of other FIGURE 1.5 Global Water Demand by 2040 Withdrawal Consumption Primary energy production* 5,000 2,500 Power generation 4,000 2,000 Industry Municipal 3,000 1,500 km3 km3 Agriculture 2,000 1,000 * Primary energy production includes fossil fuels and biofuels. Water withdrawals and consumption for 1,000 500 crops grown as feedstock for biofuels are included in primary energy production, not in agriculture. 2014 2025 2040 2014 2025 2040 Source: Adapted from United Nations 2018. 8 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE more variable renewable energy sources such as solar and rainfall, river flows, and groundwater recharge. IPCC’s wind. Demand for hydropower pumped storage is also ex- Sixth Assessment Report states that, without significant pected to increase in many markets given its ability to store reductions in GHG emissions, the water cycle will undergo large amounts of surplus or cheap energy and release it substantial changes at global and regional scales (IPCC on demand. Sixty-two percent of the Nationally Determined 2021). This will include increases in hydrological variability Contributions (NDCs), the plans through which countries and extremes in most regions of the world. Many areas disclose their plans to meet the climate commitments are projected to have an increase in evapotranspiration, set at the Paris United Nations Framework Convention on resulting in a decrease in soil moisture, and will be subject Climate Change Conference of the Parties, include water to increasing drought frequency and severity. Precipitation storage as a mitigation measure. As such, energy-related is projected to increase in some parts of the world and de- water consumption could increase by nearly 60 percent crease in others, yet precipitation that comes with extra- between 2014 and 2040 (IEA 2017). Water consumption tropical storms and atmospheric rivers will likely increase related to the transition to clean energy will depend on in most regions. Ultimately, “natural climate variability will which clean energies are employed, as some, such as solar continue to be a major source of uncertainty in near-term photovoltaic (including floating solar panels, wind, and run- (2021-2040) water cycle projections.” (Douville et al. 2021). of-river hydropower), consume relatively smaller amounts of water than biomass and some types of reservoir hy- Climate change will increase hydrological variability, dropower that can have higher water consumption due to shifting “normal” rainfall patterns into new unknowns, evaporation. Water use for each source of energy can vary increasing frequency and intensity of floods and greatly between countries, however, due to different geo- droughts, and increasing the need for storage in some graphic conditions (Jin et al. 2019). areas. A recent study estimated an increase in variation in seasonal precipitation, especially in regions that al- How we operate storage and manage our water may ready experience great seasonal variation in precipitation need to change to minimize greenhouse gas (GHG) (Konapala et al. 2020). Current management tools and emissions, translating into further changes in water coping mechanisms, including our built infrastructure, demand. Our understanding of carbon and methane emis- have been designed around the hydrological reality of the sions from reservoirs is still evolving, and more research past—and may not continue to deliver with the same level and monitoring are needed of storage operated for reduc- of reliability. In some areas of the world, more storage will tion of GHG emissions from drawdown areas (Harrison, be needed to deliver water with the same level of reliabil- Prairie Mercier-Blais, and Soued 2020). Rice uses 40 per- ity provided by current storage systems; this pattern will cent of all irrigation water worldwide (Bouman, Lampayan, hold in locations where climate change will increase the and Tuong 2007). Paddy rice production accounts for 11 variability of rainfall more than the mean annual rainfall percent of all anthropogenic methane emissions and 1.5 will increase (Siam and Eltahir 2017). For hydropower, the percent of global GHG (IPCC 2019). There are ways in projected changes in precipitation and temperature mean which rice production can be altered to decrease meth- greater fluctuations in generation output (map 1.3) (Paltán ane releases, which involve alternating between wetting et al. 2021). Limited local capacity to manage shrinking and drying techniques in rice fields (World Bank 2020), al- reservoirs and lack of adaptation readiness are expected though work is needed to mainstream alternative practic- to exacerbate the situation. es for GHG reduction throughout agriculture. However, this may mean a significant shift in where and when water is Water storage will be a critical adaptation measure to needed for agriculture in certain parts of the world, which combat changes in precipitation and increasing hydro- could also influence other water users, depending on how logical variability. The frequency of severe flood events water storage and supply systems are constructed. and associated economic losses have rapidly increased in recent years (f igure 1.6). The IPCC states in its most 1.2.2 Growing Uncertainty of Supply recent report that continued global warming will “further intensify the global water cycle, including its variability, Climate change is altering the distribution of water global monsoon precipitation and the severity of wet and across space and time, increasing uncertainty around dry events” (IPCC 2021). Hydro and climate variability may Introduction: The Importance of Water Storage 9 10 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE MAP 1.3 Exposure of Hydropower Generation Capacity to Changes in Drought Durations and Intensities a. Current hydropower generation exposed to changes in drought duration b. Planned (future) hydropower generation exposed to changes in drought duration c. Current hydropower generation exposed to changes in drought intensities d. Planned (future) hydropower generation exposed to changes in drought intensities Ratio of change Hydropower capacity (GW) 0–0.2 0.2–0.8 0.8–1 1–5 5–10 10–45 0 >1.75 Source: Adapted from Paltán et al. 2021. Note: Exposed hydropower generation capacity to changes in drought durations and intensities at 1.5ºC, relative to the historical baseline, for current and planned hydropower projects. FIGURE 1.6 Flood Occurrence and Economic Damage Over Time 700 180 600 160 Total flood damage Flood occurrence 140 500 120 ($ billions) 400 100 300 80 60 200 40 100 20 0 0 1976-85 1986-95 1996-2005 2006-15 1976-1985 1986-95 1996-2005 2006-15 High-income countries Lower-middle-income countries Upper-middle-income countries Low-income countries Source: Adapted from UN-Water 2018. Note: Flood occurrence and flood damage figures are based on reported disaster events. cause increases in internal migration of up to 216 million and pollution. Soil moisture is also decreasing through people (Clement et al. 2021). Without additional flood pro- evapotranspiration as temperatures rise and groundwater tection measures, the projected number of people annual- reserves are being depleted through overexploitation and ly affected by river floods could rise to 110 million by 2050 contamination. (Ligtvoet et al. 2018) due to population growth, migration, and climate change. In terms of drought, by 2050, one in Total built storage has increased significantly over the seven people working in agriculture could be exposed to a last century but not necessarily on a per capita basis. severe level of drought (Bowcott et al. 2021). By mid-cen- The rate at which new reservoir storage has been added tury, with increased drought, the global occurrence of for- since about 1980 has declined, and there is increasing est fires could increase by 57 percent (UNEP and GRID loss of storage space to reservoir sedimentation because Arendal 2022). As floods and droughts become more ex- of nonexistent or ineffective reservoir sediment manage- treme and hydrological variability increases due to climate ment. Figure 1.7 shows that total net reservoir storage change, adaptation to maintain and improve water secu- space, after accounting for storage loss due to sedimen- rity becomes more crucial. Water storage plays a key role tation, has decreased since about 2000, while global stor- in alleviating hydrological variability. Areas with the most age space per capita has decreased since about 1980. irrigation coverage experience three times less out-migra- The current per capita net reservoir storage space roughly tion than the areas with the lowest levels of irrigation in equals what it was in 1965 (Kamphuis and Meerse 2017). the time of drought (Zaveri et al. 2021). However, our demands for water storage are higher than they were in 1965. Implementing reservoir sediment man- 1.2.3 Decreasing Net Storage agement techniques to preserve reservoir storage space is critically important. The natural water storage systems people historically rely on—glaciers, wetlands, soil moisture—are in decline Over the last 50 years, natural storage losses are signifi- or being disrupted. From 2002 to 2016, 23 of 34 regions cantly larger than built storage gains, with a net fresh- in a global study demonstrated a negative change in ter- water storage loss of approximately 27,000 bm3, or restrial water storage (map 1.4) (Rodell et al. 2018). That approximately 3 percent of all “operational” freshwater most of these areas are found in ice-covered regions and storage. The volumes and percentage change of storage the mid-latitudes is concordant with the IPCC’s findings by type are summarized in figure 1.8 (McCartney et al. that precipitation will increase in the low and high latitudes 2022). This global pattern may play out very differently at and decrease in the mid-latitudes (IPCC 2013). Glaciers the local level. Ice sheet storage losses, for example, are are shrinking and snow cover is lost due to increased tem- not relevant to most local water storage challenges, and the peratures, and wetlands are disappearing because of cli- major glacier and groundwater storage losses are concen- mate change, land development, agriculture, urbanization, trated in certain areas of the world. However, the breadth Introduction: The Importance of Water Storage 11 MAP 1.4 Global Terrestrial Water Trends 14. Groundwater depletion 2. Ice-sheet loss 15. Groundwater depletion and drought 4. Glacier and ice cap loss 16. Groundwater depletion and drought 5. Precipitation increase 17. Decline of the Aral Sea 3. Glaciers retreating 18. Decline of the Caspian Sea 6. Precipitation increase 11. Glacier melt, surface-water 19. Surface diversion, and irrigated agriculture water drying 10. Precipitation increase 12. Groundwater 20. Progression depletion from dry to wet period 9. Three Gorges and other reservoirs 21. Groundwater filling depletion and 13. Water depletion drought and precipitation 22. Drought decrease 25. Recovery from 8. Precipitation early-period increase and drought groundwater policy change 26. Recent 7. Groundwater drought depletion 24. Progression 33. Progression from wet to from dry to wet dry period period 23. Patagonian 34. Return to normal ice-field melt after wet period 32. Groundwater 1. Ice-sheet loss depletion 28. Increasing lake levels Probable climate change impact and groundwater Possible climate change impact GRACE trend (cm yr-1) 31. Precipitation decrease Probable direct human impact 27. Progression from dry Possible or partial direct human impact to wet period –2.0 –1.0 0.0 1.0 2.0 Probably natural variability 30. Precipitation decrease 29. Precipitation increase Source: Reprinted by permission from Springer Nature Customer Service Centre GmbH: Springer Nature, Rodell, M. et al. “Emerging Trends in Global Fresh- water Availability.” Nature 557, 651–59. ©2018. Note: Data was obtained through GRACE satellite observations from 2002 to 2016 and illustrates water trend changes in centimeters per year. and volume of natural storage losses, and the underlying taking such storage for granted in the future. For those in reasons described in this report, are an important warning areas with groundwater and glacier loss, it presents an im- to water planners around the world that we should not be mediate problem. FIGURE 1.7 Net Global Reservoir Storage Volume FIGURE 1.8 Changes in Water Storage, by Type, 1970–2020 5,000 900 6,000 Change in water storage Per capita net storage volume (m3) 4,500 800 60 Change in storage (%) 4,000 Total net storage volume (bm3) 40 4,000 700 2,000 0 20 3,500 600 (bm3) -2,000 0 3,000 -20 700 -4,000 2,500 -6,000 -40 400 2,000 -8,000 -60 500 -10,000 -80 1,500 300 ds t t ter re rm rs wa t s s We ams yf s 1,000 M nd i shee e ou fros il m Lake Sm dam d ain she Pe acie La istu iel Pa tlan d 100 a 500 nd o nla ice ce gl e all dd rg 0 c Gr So Gr rcti nt 1940 1960 1980 2000 2020 2040 2060 ou ta ee An Net storage volume Per capita net storage volume Change in storage % change Projected net storage Projected per capita net storage volume volume Source: Adapted from McCartney et al. 2022. Source: Annandale, Morris, and Karki 2016. Note: Net global reservoir storage volume, accounting for storage loss from reservoir sedimentation. 12 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE 1.2.4 A Growing Water Storage Gap FIGURE 1.9 Water Storage Gap A water storage gap is defined as the difference between Perceived Storage Storage Available the amount of water storage needed and the amount of Storage Gap Alternatives Storage Needs operational storage (natural and built) that exists for a given time and place (GWP and IWMI 2021). Ultimately, Source: Original figure for this publication. all water storage gaps are local, measured in simplest terms by supply versus demand. However, quantifying Global trends suggest a growing storage gap. Over the the gap for any given location is a complex matrix requir- last 50 years, the global population more than doubled, ing an aggregation of a variety of factors on both the de- water variability grew, and freshwater storage declined mand and supply‐side, as well as an evaluation of supply (McCartney et al. 2022). Regional predictions show that terrestrial water storage will decrease in several parts of alternatives. In any system, storage demands occur at the world under climate change: By the mid- (2030–59) varying scales, times, and volumes, with requirements re- and late (2070–99) twenty-first century, terrestrial water lated to reliability, vulnerability, resilience, and control. On storage is projected to substantially decline in the major- the supply side, availability depends on natural, built, and ity of the Southern Hemisphere, United States, most of hybrid storage, with combinations offering a variety of ad- Europe, and the Mediterranean, but increase in eastern vantages in terms of scale, timing, volume, and service. Africa, South Asia, and northern high latitudes, especially northern Asia (Pokhrel et al. 2021). Figure 1.10 illustrates In designing holistic, strategic responses to a storage how these trends point to a larger gap between global gap, decision-makers must be aware that storage can needs and operational storage in the future (GWP and be supplemented by demand management or supply IWMI 2021). augmentation. As a result, the size of the storage gap may differ significantly over time even if the amount of How the global storage gap will translate in specific storage stays the same. As shown in figure 1.9, perceived locations depends on the country or local conditions. storage needs may be reduced by storage alternatives Some countries may experience less pressure while oth- such as demand reduction measures (leakage reduction ers already have significant water storage gaps that will or demand-control pricing) and alternative supply options likely worsen over time. Some locations may require only (desalination or treated wastewater reuse). slight changes to the operation of existing water storage FIGURE 1.10 The Growing Storage Gap Present Future Storage needs Flood Environment Storage gap Industrial Municipal Energy Agriculture Operational storage Nature-based Built Hybrid Storage Operational Storage Operational needs storage needs storage Source: Adapted from GWP and IWMI 2021. Note: Amounts of storage needed and operational storage are stylized estimates. Introduction: The Importance of Water Storage 13 infrastructure that is already embedded in a solid, holistic two-thirds do not have institutional structures governing water resources management institutional setup to opti- their planning and use, making joint coordination difficult mize their operation. Others may require a more compre- (United Nations 2018). This institutional issue is even hensive intervention to expand the scale of water storage more protracted for transboundary groundwater systems available, necessitating more storage or more efficient where only five transboundary aquifers had a cooperative use and management of storage, as well as other water management framework in place (Burchi 2018). Within resources management measures. countries, public responsibility for storage planning and management is usually divided across sectoral ministries Demand for additional storage may be direct or indirect, (from agriculture, energy, environment, water supply and have varying levels of predictability, and stem from the water resources) and administrative levels of government, variety of services that storage supports. Direct users of with responsibility also resting with dam owners and water storage services, such as water utilities or irrigators, operators. have the incentive to plan for their future needs. Indirect users, such as urban households or businesses, have less While storage gaps are likely common in many parts incentive (and less control). Significant uncertainties can of the world, their distribution and severity are large- also make planning for storage more complex, including ly unmeasured. The lack of systematic data on storage environmental and climate change, and societal shifts ranging from changing diets to migration, displacement, gaps is likely partly related to a more general lack of spe- and economic change. Table 1.1 provides some examples cific water data in many places but is also likely because of demand drivers and sources of uncertainty for freshwa- many stakeholders do not yet see the value of measur- ter storage demand. ing their storage gap at an aggregate level, which in turn is related to the way that storage development has been The storage gap is further complicated by the trans- approached in the past. As the next section outlines, it is boundary nature of water, as well as institutional di- time to think differently and develop smarter approaches visions. Of the world’s transboundary rivers, around to water storage. TABLE 1.1 Drivers of Demand and Demand Uncertainty SERVICE DIRECT DEMAND SOURCES OF UNCERTAINTY Increasing water • Bulk water planning for urban utilities • Sudden demographic shifts or population movement, such as availability • Expanding irrigation needs through conflict • Small-scale rural water supply • Changes in consumer sentiment, including willingness to • Industrial water user needs such as energy reduce consumption, changes in diets, or resistance to utilities, mines, manufacturing, etc. infrastructure development • Technologies that significantly improve water use efficiency • Upstream investments that change downstream water flows, including transboundary impacts • Climate change Flood protection • Residents and investors in areas of known • Climate change impacts on flood extent and duration flood risk • Accuracy of flood risk maps based on historical hydrology • Governments, including urban or national • Willingness to pay for flood mitigation measures planners • Changes to upstream land use, land cover • Insurance providers and financial sector • Urban subsidence more broadly Water-level • Hydropower and pumped storage systems • Demand shocks for water-based transportation regulation developers • Extent to which climate change accelerates hydropower • Shipping/logistics managers, passengers investment as a complement to other renewables or reduces benefitting from inland water transport hydropower investment due to water availability risks • Tourism and leisure service providers • Changes to water quality affects demand for leisure services Source: Original to this publication. 14 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE 1.3 THE WORLD NEEDS SMARTER We need a diagnostic process to measure the gap in APPROACHES water services, and to work out whether it’s best filled through demand—side measures, alternative supply, or Current approaches to freshwater storage development storage—and if storage, what type(s) and developed in and management are inadequate for the twenty-first- what sequence. If additional storage is needed, the gap century challenges we face. The problem with fresh- might be closed through rehabilitating, reoperating, or water storage today is not only that storage gaps are repurposing current storage, "raising" new storage, and growing but also that the current paradigm for closing through reforming institutional management practices, the gap is no longer fit-for-purpose, and in some cases, what from here on are referred to as the “5 R’s” of water is counterproductive. Current approaches are often storage.3 fragmented, overly reliant on built infrastructure, insuffi- ciently focused on the ultimate service, and inadequate- 1.3.1 A Systems Perspective ly maintained and operated, among other challenges. Table 1.2 outlines dimensions of a paradigm shift that A systems approach to planning and managing storage will be required for effective freshwater storage in the is needed to integrate the hydrology, socioeconomic fac- coming decades. tors, and institutional framework of a geographic area. A proper understanding of the hydrological system is the Within the shifts described, principles for better stor- starting point for a systems approach, and, in particular, to age planning can be applied. For example, the paradigm allow an integrated perspective on natural and built infra- shift allows for more efficiency in obtaining services from structure. A systems approach moves beyond the current storage, recognizing that funding and investment resourc- fragmented approach to water storage development and es are limited for meeting the storage gap. Further, the management. There is a tendency to approach develop- paradigm shift will need to allow us to look at equity and ment and management of water storage—whether natural distributional impacts of storage, or lack thereof, including or built, surface or sub-surface, small or large—as sepa- on marginalized populations, the environment, and future rate units rather than an integrated system, leading to a generations. variety of negative consequences. TABLE 1.2 A Needed Paradigm Shift RELATED TO FROM TOWARD Defining success Success measured by storage volumes Success measured by storage outcomes: the services enabled by storage Storage A focus on built storage (and, more recently, A focus on natural and built storage and their technologies advocacy for nature-based services) interdependencies on a hydrological system of storage Planning and A focus on the next investment for the A focus on long-term aggregate system development for development stakeholder with the presenting problem all relevant stakeholders, including alternative supply and approach demand management. This includes a basin perspective in siting new infrastructure, considering hydrological, environmental, and social factors, to minimize and mitigate impacts Life-cycle A focus on storage development, with mixed Emphasis on maintaining and extending the life of natural approach performance on long-term maintenance, and built systems—from wetland protection to sediment rehabilitation, etc. management—in addition to new development designed for long-term, sustainable use Operations Managing storage on a facility-by-facility Managing storage as an integrated system, including both approach basis, with some examples of multiple facility natural and built storage, to achieve system optimization coordination Source: Original to this publication. Introduction: The Importance of Water Storage 15 Storing water and managing storage are key elements management of water storage to better equip water man- of water security but must be part of broader integrated agers and policy makers in developing and operating water management, service planning, and implemen- water storage in the twenty-first century and beyond. This tation. Storage is one of several elements that can con- study proposes a step-by-step approach, using a prob- tribute to long-term water security, including managing lem-oriented lens, to guide the planning and operation water demand—for example, through better valuation and of a resilient water storage management system. Finally, pricing of water—and decoupling economic development this report provides examples of water storage solutions from requisite increases in water demand, and with broad- from around the world to help shed light on and support er natural resource depletion. Where water storage is part the scale up of successful experiences (see case studies, of the solution, it is essential to look at a holistic range chapter 8). of options, including non-water-dependent options where appropriate. . ENDNOTES These challenges, as well as examples of opportuni- 1 World Bank Database. Population growth (annual percent- ties to address them, are further explored in this report. age). Accessed October 18, 2021. https://data.worldbank.org/ Understanding the current status of the world’s water indicator. stores and adopting more integrated, systems-based 2 United Nations, Department of Economic and Social Affairs, approaches will help us make better decisions around Population Division (2019) database. World Population managing existing storage and investing in new storage. Prospects 2019. Accessed October 17, 2021. https://popula- tion.un.org/wpp/. These combined resources are intended to help advance 3 The concept of the “5 R’s” has been adapted from the sustainable development and management of water stor- Uncommon Dialogue on Hydropower, River Restoration, and age worldwide in order to build water security. Toward Public Safety, Stanford Woods Institute for the Environment, this, this study seeks to outline a framework for integrated 2020. 16 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE CHARACTERISTICS, 2 CHALLENGES, AND OPPORTUNITIES quarter in groundwater. The remaining forms—lakes, soil 2.1 NATURAL, BUILT, AND HYBRID STORAGE moisture, mountain glaciers, reservoirs, wetlands, etc.— collectively make up only around 1 percent of terrestrial Natural, built and hybrid forms of water storage offer a freshwater storage. vast array of water storage options (figure 2.1). Large amounts of freshwater are stored naturally in ice, em- The relative value of this storage for people depends on bedded in soils and vegetation, underground in aquifers, its location as well as its form. The Antarctic ice shelf, for or on the surface in lakes and wetlands. Strategically sig- example, is by far the world’s biggest store of freshwater, nificant water is also stored in or behind built structures such as dams, tanks, and retention ponds. Storage may and while it has huge environmental value for the world, also be a combination of natural and built (sometimes given its location, it provides little to no direct storage ser- also called green and gray solutions) offering hybrid solu- vices to people. Similarly, estimates suggest that less than tions. Managed aquifer recharge (MAR), for example, is an 5 percent of groundwater is practically (physically and approach that uses built structures to accelerate the re- economically) available to people. charge of natural underground storage. While categorized for simplicity in figure 2.1, all of these storage types and While globally insignificant compared to huge natural systems are interconnected and part of and dependent on water stores, built storage can be highly significant at the overall water cycle, making all water storage hybrid to the local level, and has usually been located and de- different degrees. For example, large dams and reservoirs signed to provide direct services to people. Built storage depend on several natural elements, including the natural varies from small household rainwater harvesting tanks topography of land that forms the reservoir, and the provi- to large reservoirs; for example, Kariba, the world’s largest sioning services provided by the catchment above it. reservoir, stores over 180 bm3 of water. The various types of built storage, as well as their pros and cons, are dis- Several types of storage and natural dynamics can cussed later in this chapter. work in conjunction with one another to create stor- age systems (box 2.1). For instance, sponge cities are an approach to urban design that is intended to absorb 2.2 NATURAL FRESHWATER STORAGE and store water in an urban environment. A cascade of reservoirs may be operated jointly to form a storage sys- 2.2.1 Natural Systems in Decline tem. If properly managed and maintained, some natural systems—like certain wetlands, landscapes, watersheds, All forms of natural water storage are in decline. and floodplains—can also provide water storage. Figure Worldwide, anthropogenic activity is undermining natural 2.2 provides an overview of freshwater storage types, sys- systems and threatening nature’s capacity for freshwater tems, and services. storage. From glaciers to wetlands to groundwater, all the ways in which nature stores water are diminishing at On the global scale, natural storage accounts for the vast the global level. Glaciers are in retreat, the area covered majority of freshwater storage. As illustrated in figure 2.3, by wetlands is being reduced, and usable groundwater more than 70 percent of terrestrial freshwater storage is is being depleted through overexploitation and contami- in the Antarctic and Greenland ice sheets, and about a nation. Built storage is also under pressure as inefficient 17 FIGURE 2.1 Water Storage Types GLACIERS SNOWPACK RESERVOIR TANKS DAM WETLANDS PADDY FIELDS RIVERS PONDS SAND DAM FLOODPLAINS URBAN SPONGE POLDER FLOOD CHANNELS LAKES FORESTS AQUIFERS SUBSURFACE DAM Natural Storage Types Hybrid Storage Types Built Storage Types Source: Original to this publication. 18 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE Characteristics, Challenges, and Opportunities 19 BOX 2.1 Four Dimensions of Water Storage 1. Natural, Built, and Hybrid. Natural water storage: All spaces in the water and soil system for (temporary) storage of surface water, rainwater, and/or groundwater. This includes snowpack, glaciers, lakes, aquifers, soil moisture, in-stream storage, wetlands, landscapes and watersheds, and floodplains. Built water storage: Infrastructure that retains water for a determined period of time that cannot be found in nature and has been constructed artificially. This includes dams, reservoirs, in-field storage, and tanks. Built infrastructure has been instrumental to better manage seasonal water variability, and to bridge the water supply-demand gap temporally and spa- tially. The size of this type of storage can vary dramatically, from small water harvesting tanks to small retention dams to large-scale dams, such as the Three Gorges Dam on the Yangtze River. Hybrid water storage: Natural and built storage can often be combined into hybrid storage systems. 2. Surface and Sub-Surface. Surface water storage: This includes water storage options, natural and built, that exist above ground, such as dams/reser- voirs, tanks, and wetlands. Sub-surface water storage: This includes water storage options, natural and built, that exist underground, such as aquifers, underground tanks, soil, and underground dams, among others. They often require a mechanism for water abstraction (pumps), and depending on the level of technology employed, can have higher construction, operation and maintenance costs than surface options, though are less susceptible to evaporation than surface water resources (van der Gun 2012). Managed aquifer recharge is a common method to replenish or maintain aquifer storage levels. 3. Small and Large. "Small water storage" refers to small-scale options to serve the water demand of small user communities. When built, they are usually located close to the water demand. "Large water storage" refers to large-scale options that can respond to the needs of large water users, such as urban set- tlements, irrigation, hydropower, and industrial, or a combination of these. Because of their size, when built, they may be located far away from water users so additional infrastructure and energy may be needed for water conveyance. 4. Distributed and Centralized. Distributed water storage: Decentralized and distributed in the users’ locations (e.g., storing rainwater in the soil of non- tilled fields or on terraced fields, and “harvesting” runoff water by storing it in small farm tanks), and at the scale of the micro-watershed and village (micro-dams and aquifers). Generally, management requirements are at the individual level, and downstream impacts on others or the environment depend on their cumulative scale. Centralized water storage: A (small, medium or large) reservoir collects surface water, and users connected to the canal or pipe system have access to water. The management requirements of the centralized options are significantly more com- plex compared with the distributed approach, as solutions are more sophisticated technologically, there are more actors involved, and regulations on water allocation, operation, safety, and environmental and social impact need to be in place. 20 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE FIGURE 2.2 Water Storage Types, Systems, and Services Natural and built …combine in natural, built, or hybrid …to provide …for multiple Storage Types… Storage Systems… Storage Services… Sectors Snowpack Landscapes and Watersheds Farmer Productivity Increased Water and Resilience Glaciers Floodplains Availability Household Water Lakes and Ponds Supply and Sanitation Wetlands Artificial Urban Retention Manufacturing Systems and Industry Aquifers Flood Soil Moisture Managed Aquifer Recharge Mitigation Hydropower and Systems Renewable Grid Water Harvesting Structures Balancing Water Tanks Other Combined Systems River/Canal Transportation Small Dams and Reservoirs Regulating Cascades of Dams, Flows Environmental Large Dams and Reservoirs Locks, or Weirs Services Natural Hybrid Built Source: Original figure for this publication. FIGURE 2.3 Global Freshwater Storage in Nepal from 2000 to 2015 due to glacier retreat poses the threat of future glacier lake outburst floods (Rounce, Watson, and McKinney 2017), which can cause massive Groundwater Permafrost 300,000 erosion and flooding, and threaten life and infrastruc- 10,396,000 Mountain glaciers 158,000 Lakes 102,424 ture downstream. Huss and Hock (2018) indicate that 26% Soil moisture 54,100 1% approximately half of 56 glaciated watersheds globally Wetlands 11,200 Ice sheets Large dams 9,025 have already passed peak glacier runoff, putting at risk 29,350,000 Small dams 1,873 Paddy fields 334 entire regions dependent on that water. With changing or 73% diminished flows from snow cover and glaciers, ground- water reservoirs are being overexploited for irrigation and Source: Adapted from McCartney et al. 2022. human domestic use. Overall, such variability and reduced Note: Amounts in bm³. flows provide a significant challenge to water managers to be able to sustainably manage water resources. sediment management is reducing reservoir capacity. Reversing this trend is key to water security. Wetlands—natural systems that provide flexible ter- restrial water storage—are in decline because of land- Glacial retreat and loss of snow cover, highly visible use change, pollution, and sea-level rise due to climate indicators of climate change in many regions, are dra- change. Wetlands provide several vital services such as matically decreasing and changing water storage. flood protection, carbon sequestration, groundwater re- Widespread retreat of glaciers and snow cover loss affect plenishment, pollution prevention, and biodiversity ser- human society by changing seasonal stream runoff and vices. Globally, wetlands are among the most degraded increasing geohazards (Huss et al. 2017). Historically, ecosystems (Ramsar Convention on Wetlands 2018). melt from glaciers has provided water during dry months, Approximately 87 percent of global wetlands have been which is important for agriculture and environmental degraded during the last 300 years, and 50 percent since flows. Changes in these hydrological flows due to glacier the beginning of the twentieth century (Davidson 2018). It retreat and snow cover loss put agricultural production, is estimated that over 50 percent of “wetlands of interna- energy production, and freshwater ecosystems at risk. tional importance” have been degraded due to pressures Geohazards are also a risk to glacier retreat and snow from agriculture, including livestock/farming, agricultur- cover loss. The widespread expansion of glacier lakes al/forestry effluents, and/or land clearing (Convention Characteristics, Challenges, and Opportunities 21 on Wetlands 2021). Furthermore, wetland ecosystems going from 312 km3 in 1960 to 968 km3 in 2010 (UNESCO are vulnerable to climate change, including sea level rise, 2012). More than half of the world’s 37 largest aquifers because they normally adapt slowly to keep pace with are being depleted, according to NASA data (Richey et changing environmental conditions (Erwin 2009). al. 2015). Much of this increased level of extraction has come from arid and semiarid parts of the world, with ir- Groundwater—an unseen, vital, yet often undervalued rigation as the largest driver of groundwater depletion store of water—is difficult to regulate and often poor- worldwide (UNESCO 2022). Groundwater overuse also ly regulated, leading to overexploitation and massive occurs because of high population density, heavy reliance water security sustainability challenges in some parts on groundwater, little or highly variable rainfall, and low of the world. Even though surface water provides a larg- rates of natural recharge (Fienen and Muhammad 2016). er proportion of freshwater supply that meets human While global trends have been trending in one direction, water demand globally, the groundwater component is local circumstances differ widely around the world, with significant. The world’s dependence on it has increased some areas overexploiting their groundwater resources over time as surface supplies become less reliable and and others underexploiting them (map 2.1). predictable, and demand increases for freshwater from growing populations. Groundwater currently provides half Contamination of groundwater, either from pollu- of the global domestic water needs (Rodell et al. 2018; tion or from mismanagement, severely diminishes UNESCO 2022), while around 40 percent of the irrigation the world’s ability to harness water stored in aquifers. water used to grow the world’s food is supplied from un- Overexploitation of groundwater is not the only threat derground sources. The exchange between surface water to this type of natural water storage. Contamination of and groundwater means there is an overlap of resources groundwater limits the amount of water that is available (where the same volume of water flows between surface to both humans and nature. While natural contamination and groundwater). This overlap is often not recognized, exists (e.g., from arsenic, fluoride, and salinity) that may leading to "double counting," an overestimation of avail- be exacerbated by overextraction, contamination intro- able water and the depletion of groundwater resources duced by humans is increasing and is usually preventable. that have increased during the last decades. This increase Agricultural contaminants (such as pesticides and fertiliz- is likely to continue (Rodell et al. 2018). The magnitude of ers), industrial and domestic waste disposal, wastewater global groundwater depletion has been estimated through treatment plant discharges, seepage from petrol filling Gravity Recovery and Climate Experiment (GRACE) satel- stations and sanitation systems, and industrial discharg- lite measurements (Famiglietti 2014; Rodell et al. 2018). es all threaten the quality of groundwater. Given the im- Because of its wide distribution and accessibility, ground- portance of groundwater, especially with the increase of water is difficult to manage where regulation is weak, and water scarcity, maintaining and increasing water security usage is not measured. Ignorance about the overlap be- will invariably depend on sustainably managing ground- tween groundwater and surface waters, and of the long- water and activities that affect its quality. term impacts of allowing it to become contaminated, add to the physical pressures on groundwater availability. Groundwater misuse and mismanagement can have The difficulty of regulating its use is a challenge that has compounding effects and can destroy the possibility of huge implications for future water security. The problem using aquifers for storage in the future—further deplet- is often exacerbated by a lack of information and data ing our storage capacity. Groundwater withdrawal and on the status of aquifers, resulting in a large element of depletion can cause several issues, including exacerba- uncertainty in determining when unsustainable levels of tion of hydrological droughts (e.g., reduced summer flow abstraction have been reached. due to decreasing groundwater), cause declining water tables, springs to dry up, seawater intrusion, shrinkage of Groundwater extraction rates differ significantly across wetlands, water pollution, and negatively impact ground- the world, with some areas, including parts of Sub- water-dependent ecosystems. All these impacts translate Saharan Africa, still underexploiting groundwater rel- into a reduction of water availability—both in quantity and ative to its potential sustainable yields. From 1960 to quality—and can in turn further increase groundwater de- 2010, groundwater extraction worldwide more than tripled, pletion as other water sources become scarcer. Further, 22 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE MAP 2.1 Groundwater Stress Groundwater Stress Low (0-20%) Medium (20-50%) High (50-100%) Very high (>100%) No data Source: Based on IGRAC 2022. Note: Groundwater stress is defined as the ratio percentage of mean annual groundwater withdrawals over the mean annual groundwater recharge (IG- RAC 2022). This map is based on a global dataset. Countries may have more detailed maps depicting groundwater stress/depletion nationally that is not reflected here. if aquifer overdraft and land subsidence are inelastic in widespread decreases in soil wetness, with no regions nature, this can prevent using the aquifer for any future displaying significant increases (Berg and Sheffield 2018), storage, even from natural replenishment. The areas ex- supporting projections of increased land drying, although periencing the highest levels of decline are shown in map there are large uncertainties. Models indicate a slight de- 2.2. Although essential to regional irrigated agricultural crease in mean soil moisture levels, with the more signifi- economies, continuing groundwater overexploitation in cant changes in soil moisture projected in regions of lower such regions is unsustainable. Aquifer contamination may precipitation. This corresponds to an increase in drought not affect its storage capacity, but the economic viability conditions (area, duration, and frequency) (Berg and of aquifer storage reduces if the groundwater stored in Sheffield 2018). In terms of soil moisture, continuing de- such an environment requires extensive treatment to be clines can increase the need for irrigation in agriculture or usable. lead to smaller yields and even desertification, with poten- tially significant impacts on food production (EEA 2019). Soil moisture—a critical water store for agricultural pro- duction and ecosystem health—is expected to continue 2.2.2 Nature’s Ability to Meet Demand to decline as temperatures rise. The rising of tempera- ture due to climate change is expected to increase land Large amounts of natural storage are inaccessible to surface evapotranspiration, in turn reducing soil moisture, which can lead to agricultural and ecological drought, re- humans. At the global scale, the largest stores of fresh- ducing agricultural production and ecosystem services, are largely water—the Antarctic and Greenland ice sheets—­ respectively. At the same time, climate change also may inaccessible to large-scale human use. Similarly, some of affect soil characteristics, which in turn may affect soil the largest aquifers are under major deserts or are at depths moisture storage properties. Most existing analyses of that make their use uneconomical or inadvisable due to the future surface soil moisture with climate change show permanent geological deformation that would result. Characteristics, Challenges, and Opportunities 23 MAP 2.2 Groundwater Table Decline Groundwater Table Decline Low (<0 cm/yr) Low – medium (0–2 cm/yr) Medium (2–4 cm/yr) High (4–8 cm/yr) Extremely high (>8 cm/yr) Insignificant trend Source: Based on WRI 2022. Note: Groundwater table decline measures the average decline of the groundwater table as the average change for the period of study (1990–2014). The result is expressed in centimeters per year. Higher values indicate higher levels of unsustainable groundwater withdrawals (WRI 2022). This map is based on a global dataset. Countries may have more detailed maps depicting groundwater stress/depletion nationally that is not reflected here. Natural storage may not meet water demand. At the the next century (Dippenaar 2015)—some with large more local scale, while early human settlements were ecological impacts. heavily influenced by the local availability of water, larg- er and more concentrated populations have sometimes 2.2.3 Harnessing Natural Storage meant that use of water has outstripped supply: in some places, built water storage is needed in addition to nat- Natural storage mitigates floods, increases water avail- ability, and regulates downstream water levels. Many ural, and water is transferred from other basins to meet forms of natural storage can provide effective flood mit- demands. In addition, human development patterns are igation services by absorbing and slowing the flow of influenced by many factors beyond water, including the water. Indeed, many downstream communities have availability of land, location of minerals, strategic loca- discovered how effective natural storage was in mitigat- tions for trade, and political decisions, among others. ing floods in retrospect as upstream land-use changes This means that cities and other centers of demand resulted in a very different precipitation runoff response may be located far away from adequate water sup- and worsening floods from the same amount of precipita- plies, or natural storage systems. The Gauteng region tion (see box 2.2 for examples of urban flood resilience). in South Africa, for example, has long struggled with Natural storage can also enhance dry season water avail- ensuring adequate water security as demand for water ability through the slow release of water, such as moun- outstripped local availability to serve its growing econ- tain glaciers and snowpacks in parts of Asia, Europe, and omy and population. Early settlements used local rivers South America have been shown to significantly improve and groundwater, but the discovery of gold in the 1880s downstream flows during the dry season. Depending on led to demand rapidly outstripping the volumes of water their absorptive capacity, large wetlands can also act as naturally available, and a series of investments in built sponges, absorbing wet season flows and releasing the water storage and inter-basins transfers followed over water over the dry season. 24 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE BOX 2.2  Catalogue of Nature-Based Solutions for Urban Flood Resilience The World Bank Catalogue of Nature-Based Solutions for Urban Resilience (World Bank 2021a) is a flagship report that was jointly launched by the Global Program on Nature-Based Solutions (NBS) for Climate Resilience and the City Resilience Program, both housed in the Global Facility for Disaster Reduction and Recovery. The catalogue lays out the 14 main typol- ogies of nature-based interventions for climate resilience in cities found in figure B2.2.1, and provides illustrative designs, examples, information on costs, benefits, implementation considerations, and generic principles for integrating NBS into urban environments. Detailed examples of landscape architecture designs at various scales have been developed to help visualize how the solutions fit in the urban context. The catalogue was created as a resource for those aiming to shape urban resilience with nature by enabling an initial iden- tification of potential investments in NBS. Many urban resilience building professionals who make planning, financing, and technical decisions have limited knowledge of how and when to build with nature. The catalogue supports policy makers, project developers, development professionals, urban planners, and engineers with the identification of potential NBS in- vestments and provides the tools to start a policy dialogue on NBS in cities. FIGURE B2.2.1 Examples of Natural Storage TERRACES AND RIVER AND STREAM BUILDING URBAN FORESTS OPEN GREEN SPACES SLOPES RENATURATION SOLUTIONS BIORETENTION NATURAL INLAND CONSTRUCTED GREEN CORRIDORS URBAN FARMING AREAS WETLANDS INLAND WETLANDS RIVER FLOODPLAINS MANGROVE FORESTS SALT MARSHES SANDY SHORES Source: World Bank 2021a. (box continues next page) Characteristics, Challenges, and Opportunities 25 BOX 2.2  Catalogue of Nature-Based Solutions for Urban Flood Resilience (cont.) Project: Chulalongkorn Centenary Park, 2012–17. Location: Bangkok, Thailand Description: The Chulalongkorn Centenary Park is the first crucial piece of green infrastructure in Bangkok. Designed to mitigate detrimental ecological issues, it has added a much-needed outdoor public space to the gray city in 2017. The green roof is the largest in Thailand; the filtration system treats water from neighboring areas. The park water treatment system is built around constructed wetlands with detention lawns and retention ponds. The constructed wetlands follow the slope of an inclined plane and step down through a series of weirs and ponds. Passing through a weir, water cascades, flows through a plant-filled pond below, passes through another weir, and flows through another pond. Water is cleaned every time it passes through plants until it reaches the retention pond, where children and adults can safely play and enjoy the water. Chulalongkorn Centenary Park has become a showpiece for ecological and social impacts of landscape architec- ture in dense urban areas. The site area spans 48,000 m² and is 1.3 kilometers in length, and it sits in the campus area of Chulalongkorn University. Sources: LandProcess, Kotchakorn Voraakhom (http://www.landprocess.co.th/); Holmes 2019. Project: Araucárias Square: Rain Garden and Pocket Forest, 2017–18. Location: São Paulo, Brazil Description: This is one of the first rain gardens implemented in a Brazilian city with the active involvement of residents. The garden collects runoff across a surface of 900 m² that would otherwise go directly into the drainage system, and which used to flood lower areas of the city. After the garden's implementation, the vegetation thrived, and runoff was reduced. Residents and leaders of the grassroots movements actively participated to transform this remnant derelict piece of land. In an effort to plant pocket forests in small plots of land, social media was employed to invite and challenge volunteers. This social experience, with people of all ages coming from various districts to actively contribute to nature’s reconstruction in the park, has also led to private funding contributions to maintain and protect the new pocket park. Source: CARDIM Arquitetura Paisagística. https://oppla.eu/casestudy/20079; http://www.cardimpaisagismo.com.br/portfolio/largo-dasaraucarias/ Project: St. Kjeld’s neighborhood: Tåsinge Plads, 2013–15. Location: Copenhagen, Denmark Description: The bioretention project is part of The Climate Neighborhood project, in the St. Kjeld’s neighborhood, launched as a neighborhood renewal program. The bioretention area was sloped to collect rainwater at the bottom where it seeps into the ground, instead of being directed to the drains. Water from the streets collects in waterbeds, which are filled with mold that filters the water. This climate adaption creates capacity in the drains to prevent flooding. The entire St. Kjeld’s neighborhood is a showcase for ground-breaking climate adaptation solutions. Source: City of Copenhagen, HOFOR, GHB Landskabsarkitekter. https://urban-waters.org/sites/default/files/uploads/docs/tasinge_Plads.pdf Project: Usaquén Urban Wetland, Completed in 2016. Location: Bogotá, Colombia Description: The 8,500 m² landscape project, completed in 2016, aims to transform and revitalize an emblematic public space in northeastern Bogotá. Its design concept is based on the wetlands of the Bogotá Savannah, a neighboring rocky area, and the typical plant species. The project re-creates the geometry of the half-aquatic, half-terrestrial ecosystem, its colors, and textures. A rainwater garden in the main square uses recycled water and creates a native urban wetland that blends with its surroundings and the Andean hill backdrop, and preserves the native vegetation in its natural habitat. Underpinned by a clear, rationalized structure and construction style within its spatial composition, the urban design’s as- pects are seemingly wild, natural, and freeform. Source: Obraestudio. https://www.archdaily.com/912462/usaquen-urban-wetland-cesb-obraestudio 26 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE Natural storage cannot always be translated into con- and micro-dams, among others. Small water retention trollable bulk water supply. With the exception of ground- structures can serve the small, immediate water needs water, most natural storage cannot readily be tapped for of different water users, and can be built closer to where bulk water supply of the sort needed for household water the water is needed. Large built structures can ensure supply, industrial use, or irrigation. It also cannot be turned long-term availability, be designed and operated as mul- on or off in the short term. From a societal perspective, tipurpose facilities, and support nearby smaller dams the value of natural storage depends on the services that (Blanc and Strobl 2014). Large dams provide substantially people require. Soil moisture, for example, is directly use- greater storage capacity, operate at a lower per unit cost ful for farmers but only indirectly beneficial to cities or hy- (though with higher total investment and operation costs), dropower operators. and lose less water owing to evapotranspiration when compared to small dams (Blanc and Strobl 2014). They Natural storage may need more time than built storage can also be operated as a form of battery when config- to retain flows. For instance, the dynamics of natural ured as a pumped storage hydropower scheme by pump- groundwater storage may mean that more time is need- ing water to a higher-level storage when energy costs are ed to capture water—and only some of the flow is collect- low and releasing the water at a time when hydropower ed. Because water enters aquifers through infiltration (or generation is needed. The relative weight of the advantag- sometimes through artificial injection wells), time may be es and disadvantages of large versus small built solutions needed to transfer the water into the aquifer. As such, nat- depends upon various factors involved, such as climatic ural storage such as aquifers may not be as effective in and geophysical conditions, water demand to be supplied, capturing the entirety of large volumes of flow over a short longevity, and costs (box 2.3). period of time, such as seasonal snow melt. However, they can be used to capture flows over a longer period of time 2.3.1 Dams and Reservoirs and may be able to simultaneously improve water quality through the infiltration process. Dams, and the reservoirs behind them, are the most significant form of built storage. According to the Global Reservoir and Dam Database (GRanD) database, which 2.3 BUILT SOLUTIONS AND CHALLENGES contains data for 7,320 dams greater than 15 meters in height or with a reservoir of more than 0.1 km3, there is Built storage infrastructure provides societies with the an estimated 6,863.5 km3 of storage capacity from large flexibility to locate storage where they need it and im- manmade reservoirs. Smaller reservoirs are estimated to proves controllability for provision of storage services. Water stored in human-built systems,1 from household represent an additional 1,873 km3 of storage (Lehner et tanks to large dams, represents less than 1 percent of al. 2011). Map 2.3 shows the spatial distribution of dams accessible freshwater storage on earth. However, built worldwide. storage is developed in response to specific needs, and is therefore generally in locations and forms that provide di- The location of built storage is, to some extent, based on rect services to users. Built water storage has been instru- human choices, but the location of dams and reservoirs mental in increasing and securing water availability during is highly dependent on the opportunities provided by droughts, in supplementing water for irrigation when rain local topography, hydrology, geology, accessibility, and is insufficient, for hydropower, and for the regulation and proximity to demand centers. From a purely hydrological control of floods. perspective, good sites for dams require a place where na- ture can trap water (such as a valley) and the required flow Besides large reservoirs and dams, other types of built of water through that space, and where the downstream storage include small reservoirs and dams and a va- impacts of changing river flows can be adequately miti- riety of forms of ponds and tanks.2 Small water reten- gated. In practice, good dam sites are naturally occurring tion structures, such as small dams, ponds, and tanks, and scarce, and in many parts of the world have already can be found around the world, where they are known been utilized. The expansion of dam-based storage is under multiple names: johads, açudes, small reservoirs, therefore not simply a matter of what can be built but also Characteristics, Challenges, and Opportunities 27 BOX 2.3  Dam and Reservoir Inventory Using Remote Sensing and Artificial Intelligence Problem Dams and reservoirs account for the majority of built storage capacity around the world and are used as an important water management measure to augment supplies and protect from floods, as well as specific economic purposes such as power generation. Understanding the existing portfolio of dams is an essential step in characterizing the water management space. Preparing an inventory of dams is essential from an integrated storage management perspective as it provides a basis for siting new storage, connecting reservoirs to other hydrological features, conjunctive use planning, and informing flood risk management. Establishing a dam inventory is also the first step in dam safety assurance so that an appropriate dam safety management system can be put in place. Despite their economic importance, associated risks, and numbers, it can be very difficult to complete an inventory of all existing dams. Dams, large and small, can be constructed and operated by a range of government authorities at the national or local level, or by private owners for irrigation, hydropower, mining, or other purposes, sometimes without centralized gov- ernment knowledge or oversight. In the absence of a complete inventory, it is difficult to assess the total storage volume and impact of available storage on the larger hydrological system and plan for flood risk prediction and protection. Approach Improvements in remote sensing technologies and pattern recognition and machine learning algorithms are creating new opportunities for quick and cost-effective identification and mapping of dams and reservoirs. Open-source semi-automated algorithms can be developed to locate and identify basic reservoir properties including geometry, size, and type of dam, as well as delineate the dam bodies attached to the reservoirs. The process includes preparation of training data, including preparation of preliminary analytical algorithm, calibration of the algorithm using training data, and full implementation in the geography of interest. Possible methods to distinguish artificial reservoirs from natural water bodies include (a) use of surface reflectance characteristics of the reservoirs; (b) pattern recognition (geometric patterns are unique to artificial reservoirs); (c) seasonal fluctuation of reservoir areas caused by dam operation; and (d) relative altitudinal gap between the reservoir surface and downstream area. Possible methods to delineate the dam bodies attached to the reservoirs include (a) use of surface reflectance characteristics of dam bodies; and (b) pattern recognition of high-resolution visual imagery. Incremental development across national portfolios can help deliver a geo-referenced global inventory of dams, which can in turn be used in tandem with online global forecasting systems to improve dam safety and safety of life and property downstream. In Zambia, using remote sensing techniques, 1,022 reservoirs were identified in the Southern Province alone in 2011 (Wishart et al. 2020). Based on physical verification efforts being carried out by the government, the official estimate of dams in the country currently stands at 1,700 dams, situated mostly in the drought-prone, semi-arid areas of the Eastern, Lusaka, Central, and Southern provinces. Good Practices Under maximum assurance, preparation of an inventory requires that all dams be registered and classified based on size or a combination of size and hazard, ideally shared publicly in a well-maintained database. Classification can be used for proportioning dam safety mandates such that higher requirements on surveillance and design standards are applied to higher-hazard dams, and lower requirements to lower-hazard dams, thereby allowing optimal allocation of available finan- cial and human resources. At minimum, local authorities should maintain a register of dams in their jurisdictions, with assigned hazard ratings. This can help monitor the density of hazardous dams and continually update assessments of potential risks to downstream areas as they develop. 28 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE MAP 2.3 Distribution of Dams a. Number of dams per country Number of Dams per Country 10 50 100 500 1,000 No data Dams b. Location of dams Source: Based on Mulligan, van Soesbergen, and Saenz 2020. the range of opportunities that local hydrological systems water and sediment as they flow from source to sea. and other factors provide. When undisturbed by human activity, the quantity of sed- iments transported by a river is determined by hydrologi- 2.3.2 Sedimentation of Reservoirs cal processes, topography, and natural soil erosivity in its watershed. Floods and tectonic forces can change the While the extent depends on the specific dam and river equilibrium between river and landscape temporarily. This conditions, it is broadly true that rivers transport sed- equilibrium sustains the geomorphic and aquatic health iment and dams trap sediment. Rivers transport both of river systems. When reservoirs are built, a barrier is Characteristics, Challenges, and Opportunities 29 created, which can trap large amounts of sediments car- There is an acute need for better planning and opera- ried by the river. tional approaches to improve sustainable sediment management in existing and new reservoirs. Sediment In the absence of sediment management, the capture of management approaches range from those that avoid sediments by reservoirs can create many problems for trapping sediment in the first place, such as reducing wa- dams and reservoirs. For sand dams, the trapping of sed- tershed erosion and routing sediment through or around iment is a design feature and core to the way they operate the reservoir, to approaches such as flushing and dredging, to store water in ephemeral rivers. For traditional dams aimed at the removal of sediment and recovery of usable and reservoirs, sedimentation is a threat to the available storage volume, to creating “dead storage,” and dedicated storage volume. As available storage volumes decline, space in a reservoir for sediment (although this is a lim- so does the capacity to provide reliable water supply and ited solution that must include wider sediment manage- generate power. Reduction in storage volumes also reduc- ment). Sustainable sediment management should be an es the capacity to hold flood waters, increasing flood risk early planning consideration and reflected into the design and dam safety risks. Sediment can damage electrome- of storage facilities. Awareness of the importance of sus- chanical equipment, hydraulic machinery, and civil struc- tainable sediment management is increasing with time tures that are important for the safe operation of dams; it and as more data and tools emerge for water managers also speeds up the wear and tear on parts and equipment and planners; still, there are a large number of facilities de- such as turbine runners, necessitating their replacement signed without proper sediment management strategies, before the expected end of their operational life. contributing to a gradual loss of built storage capacity. Overall, a shift in approach is needed for sediment man- Sedimentation of current dams is reducing built storage agement. Instead of viewing reservoirs as limited resourc- volumes around the world. Loss of existing water storage es that are to be abandoned due to sedimentation over due to reservoir sedimentation is estimated to be between time, reservoir and storage assets should be managed 0.8 and 1 percent per year, contributing to a decrease in per and viewed as renewable resources. capita water storage to 1960s levels (Annandale, Morris, and Karki 2016). Once lost, it is very expensive to replace 2.3.3 Built Storage in Decline storage volume—either through new storage investments or by recovering storage by removing sediment. In 2003, New dam construction continues but at a slower pace. it was estimated that $13 billion would be required to re- For a variety of reasons, the number of new large dams place storage volumes lost annually (Palmieri et al. 2003). being constructed is much lower compared to the 1950s Globally, sedimentation causes hydropower production through 1970s (f igure 2.4). Large dams have been the losses of 1 percent annually (HydroSedi.Net 2022), due to subject of criticism by some civil society organizations loss of storage and damage to equipment. (CSOs) and local communities due to the negative im- pacts of some projects on people and nature, which has Trapping sediment in dams also increases erosion down- led to increased awareness globally of the social and envi- stream and threatens aquatic ecosystems. The water re- ronmental impacts of dams. In addition, many of the dam leased downstream of a dam, without effective sediment sites with better natural conditions have been already management, is starved of sediment. As these flows have developed in many countries, particularly high-income greater capacity for transporting sediment, this leads to ero- countries—especially as many older sector plans ranked sion of the riverbed and riverbanks downstream. Reservoir investments by least cost. Meanwhile, the high capital sedimentation can also contribute to coastal erosion by costs of large dam projects constrain their development, starving delta areas of important sediment deposits, which, particularly in low- and middle-income countries where when combined with groundwater over-abstraction, can con- there is generally less fiscal space and technical capacity, tribute to subsidence and increased salinity (Basson 2005). and where risk—and in some cases, creditworthiness— Reductions in sediment transport downstream of dams also can deter investors. means reduction in nutrient transport, which can affect total availability of nutrients and lead to a decline in aquatic eco- The stock of dams is aging, standards are changing, and systems and fish stocks. some dams are becoming obsolete. There are a number 30 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE FIGURE 2.4 Development of Dams over Time 16 Number of dams built (thousands) 14 12 10 8 6 4 2 0 Pre-1900 1900-09 1910-19 1920-29 1930-39 1940-49 1950-59 1960-69 1970-79 1980-89 1990-99 2000-09 2010-16 Source: Wishart et al., 2020 based on ICOLD World Register of Dams. of dams operating around the world today that are well major maintenance projects. Between fiscal years 2002 over a century old. Given the global dam-building boom and 2021, the Bank approved more than 140 projects from the 1950s to 1970s, many others are between 50 related to dam rehabilitation or upgrading, including na- and 100 years old (map 2.4). Age alone is not necessar- tional-scale or similarly large rehabilitation projects. While ily a problem for a dam if it was well constructed, appro- approximately 40 percent of World Bank-financed projects priately maintained, and periodically rehabilitated when involving dams included dam rehabilitation, more than 70 Water palette needed. However, for many dams, both the physical and regulatory environment has changed since they were de- percent of the actual dams supported were the subject of rehabilitation. A significant proportion of this work, partic- signed and constructed. With climate change increasing ularly in South and Southeast Asia, is addressing safety variability and the occurrence of extreme events, some improvements and deteriorated conditions from deferred dams no longer have sufficient flood-handling capacity and need to be upgraded. Also, as engineering standards maintenance across a country’s portfolio of dams. and environmental regulations evolve to reflect new un- derstanding W1 W2 W3 2.3.4 Environmental and Social Trade-Offs Water 2some dams need Water 1 and changing attitudes, Water 3 major upgrades to remain in or 206R/84G/64B 1a68a3 regain compliance. In 101R/67G/60B 539932 125R/191G/66B ffff00 some cases, these rising maintenance and rehabilitation If not well planned, dams can create significant environ- costs for older dams may tip the scale for considering mental, social, and economic impacts that need to be their decommissioning. carefully considered, mitigated, and compensated for, where appropriate. Some negative impacts of dams are Decades of deferred maintenance pose challenges that well documented. Construction of a dam may involve land range from sub-optimal performance to risks of cata- acquisition or involuntary resettlement; this physical and strophic failure. Maintenance of W1B existing water storage W2B W3B W4B 116R/215G/237B 255R/203G/88B economic 244R/130G/44B displacement of communities can weaken 101R/166G/68B BLACKso- 80% infrastructure 74d7ed is often a low priority, ffca58 and insufficiently f4822c 65a644c cial networks, diminish cultural identity, disrupt livelihoods, funding maintenance generally results in a lower level and even lead to impoverishment. Physical cultural heri- of service provision. This is due to a range of factors, tage can be lost to reservoir impoundment or damaged including competition for funding with other urgent na- during construction. Dams also reduce the connectivity of tional or regional priorities, lack of expertise, inadequate rivers, change their flow regimes, and degrade their water consideration of operation and maintenance (O&M) costs quality, which can affect aquatic and other species that at an early stage, and a possible bias by water manag- ers toward realizing new investments to overcome a ser- inhabit freshwater ecosystems. This is of particular con- vices deficit. More severe impacts of poor maintenance cern for migratory fish species that traverse the lengths and/or operation can lead to increased risk of flooding of rivers for feeding and breeding. Dams can also lead to and even dam failure. The World Bank, for example, has waterborne diseases, biodiversity loss, and colonization seen an increase over the years in dam rehabilitation and of exotic species. Characteristics, Challenges, and Opportunities 31 MAP 2.4 Large Dams Over 50 Years Old Large Dams Over 50 Years Old 1 40 200 800 12,739 No data Middle East and North Africa Others Sub-Saharan Africa Latin America and the Caribbean South Asia East Asia and Pacific 0 500 1,000 1,500 2,000 12,801 Number of dams per region Source: Based on ICOLD World Register of Dams. Note: Number of large dams over 50 years old by country and region. The extent of these impacts differs significantly by boundaries. While important to consider, the distributional the nature, location, and operating regime of the dam. consequences of dams are difficult to measure due to the Large dams in relatively flat landscapes will inundate long time horizon over which the costs and benefits ma- much larger areas than dams constructed in deep valleys. terialize. Selection bias is also a challenge as hydrological Hydropower schemes operating as baseload are generally investments are placed in favorable geographies, and the better able to mimic natural downstream flows than those distribution of costs and benefits may be influenced by di- operating as peaking facilities. Several small dams in a alogue between project planners and local communities, basin could potentially have greater cumulative impacts which have their own complex political economies (Dillon than a single large dam, while a new dam on a free-flowing and Fishman 2019). river stretch could have significantly greater impacts than a new dam in a heavily regulated branch of a river (Ledec Informed planning is vitally important to avoiding and and Quintero 2003). Hydrological investments can also reducing the negative impacts of storage projects, in- have uneven distributions of costs and benefits for up- cluding dams. Not every dam that is technically feasible stream groups compared to groups downstream, as well is economically, socially, and environmentally feasible. as between those who do and do not directly benefit from By constructing a barrier across a river, dams, by defini- the regulation of the water. This is true in shared water- tion, alter the landscape in which they are placed and courses as well, where the construction of dam infrastruc- create trade-offs against other development goals. The ture creates distributional impacts across international impacts of a dam and the potential for their mitigation are, 32 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE therefore, largely determined by the decision of where to risks” framework that has inspired many other actors to site a dam. By avoiding sites that are of high conservation develop implementable tools, guidelines, and system plan- value, while involving project-affected communities as real ning approaches to operationalize these principles (ADB, stakeholders from early on, storage planners and develop- MRC, and WWF 2013; IHA 2021; Opperman et al. 2015; ers can reduce environmental and social risks, improve the Skinner and Haas 2014), including the World Bank’s own acceptability of storage investments, and avoid high costs Environmental and Social Framework (World Bank 2019c), of mitigation and compensation. Building these consider- the Performance Standards of the International Finance ations and constraints early into storage planning produc- Corporation (IFC 2012), and the Multilateral Investment es a more realistic picture of storage options that reflect Guarantee Agency (MIGA 2013). The World Bank has also the full social costs and benefits of potential investments developed a number of resources on dam safety (box 2.4). (Meng, Devernay, and Lyon 2014; Opperman et al. 2015). This report recognizes that immense body of work, and while chapter 5 summarizes good practices at different Several international initiatives have outlined ways to stages of a storage project’s life cycle, the main focus of approach dams so as to maximize benefits and mini- the report is on the early planning phase and assessment mize negative impacts. The World Commission on Dams, of storage options through a more integrated lens. launched in 1997, ushered in an era of multi-stakeholder, evidence-based approaches to improving the sustain- 2.3.5 Hydrological Risks ability of dams (Bird and Wallace 2001). While often cri- tiqued as difficult to implement, the Commission’s report Dams are long-lived structures and should be designed contains principles and guidelines based on a “rights and to withstand hydrological extremes; as a result, they are BOX 2.4  Dam Safety Dam safety is defined in various ways, often depending on the country context, but it can be considered “the art and science of ensuring the integrity and viability of dams such that they do not present unacceptable risks to the public, property, and the environment” (FEMA 2019). The main pillars of a dam safety program are (a) adequate engineering design and construc- tion, (b) regular surveillance (monitoring and inspections), (c) adequate operation and maintenance (O&M), and (d) plans for dealing with emergencies. The basis for an effective dam safety management system is a fit-for-purpose regulatory framework, the foundation of which is an enabling legislative framework that establishes minimum standards as well as duties, roles, and responsibilities for assuring the safe development and operation of dams. Also essential is a well-defined institutional framework that is clear on the responsibilities for ownership and operation of dams as well as oversight of dam safety assurance. The techni- cal content of the regulatory regime will contain mandates for how to define which dams are regulated, how such mandates are proportioned according to size or hazard, standards and criteria for dam design, requirements for surveillance and O&M, technical guidelines, education, training, and, lastly, compliance enforcement. Regulatory frameworks for dam safety, while largely defined by the type of legal system and the constitutional basis for lawmaking and administration, should be informed by the size of a country’s portfolio of dams, their geometric dimensions, their hazard potential and vulnerability, and the degree to which there is public or private ownership. These factors will determine where along a continuum from minimum to maximum safety assurance the most appropriate framework for that jurisdiction lies, considering that moving along the continuum from minimum to maximum assurance has cost and capacity implications. Sources: Wishart et al. 2020; World Bank 2020a, 2021b. Characteristics, Challenges, and Opportunities 33 costly endeavors. Before even breaking ground on a new trying to select the most probable climate futures; instead, dam, significant studies should be undertaken, including it identifies those investment options that perform most geological investigations, feasibility studies, environmen- optimally under a range of scenarios (Hallegate et al. 2012; tal and social assessments, and detailed engineering Rodríguez et al. 2021). designs. The costs of construction vary greatly, and not only according to size but also according to the geological 2.3.6 Smaller-Scale, Built Infrastructure conditions, ease of access, method of construction, costs of environmental and social risk management, costs of Beyond traditional dams, large and small, societies have financing, and many other factors. engineered a diversity of water retention structures to suit their needs. The ancient tank system of Sri Lanka Cost and schedule estimation for built infrastructure is (see annex 8A) is one example, whereby small artificial not an exact science. Uncertainty around the develop- reservoirs, or tanks, were built in cascades according ment cost gradually narrows the more study has been to the natural topography of the land. Connected to one done and the closer the project is to a final design, but it another and to larger reservoirs by canals, they support is never eliminated. Cost and schedule overruns are a per- irrigation and other water supply needs of the communi- sistent challenge in large infrastructure, and large dams ties around them. Similar tank structures can be found in are no exception. Data from large hydropower projects India, some of which are fed by natural springs. They serve developed after the year 2000 have an average cost over- a variety of purposes, such as irrigation, water supply, run of 33 percent and an average schedule overrun of 18 and religious and cultural purposes. In other parts of the percent. While schedule overruns appear to have reduced world, smaller-scale water storage might take the form of compared to previous decades, there has been no signif- elevated storage reservoirs, forming part of the potable icant reduction in cost overruns (Plummer Braeckman, water supply system in cities and towns. Like dams, these Disselhoff, and Kirchherr 2019). Dam projects also tend storage solutions tend to be public or community-scale to suffer from so-called geological surprises, where un- facilities, whereas in private homes and businesses, it is derground conditions, especially for projects involving increasingly common to find lightweight manufactured extensive tunneling, are much less favorable than investi- tanks, sometimes deployed in modular systems. These gations suggested they would be. more decentralized forms of water storage can avoid some of the negative externalities of larger, centralized Future hydrological uncertainty is a major challenge for storage reservoirs, but they may provide limited storage the design and operation of dams as well. While an oppor- and, in some cases, can have higher per-unit costs (van tunity for some regions, given the expectation of more run- der Zaag and Gupta 2008). off, climate change is increasing the hydrological risk for new and existing dams. This can include projected chang- es in hydropower production or risks to the infrastructure 2.4 HYBRID STORAGE and downstream communities posed by large floods, as noted in chapter 1. In designing new water infrastructure, Hybrid storage combines both natural and built storage the approach of relying on the historical hydrological record options and contains built elements that interact with under the assumption of hydrologic stationarity is no longer natural features that seek to enhance their water-related adequate. Whether it is greater flood risks or the possibility ecosystem services (WWAP 2018). Hybrid storage op- of lower inflows, climate uncertainty should factor into the tions include MAR (box 2.5), urban sponges, paddy fields, design and reoperation of any dam or water storage facility. flood channels, sand and subsurface dams, ponds and This can be achieved through climate sensitivity screening haffirs, and polders and dry dams. Like purely green or in the planning phase, possibly followed by robust climate gray storage, hybrid storage is often multifunctional and risk analysis during preparation. Climate risk analysis to find can provide co-benefits outside of the primary sector ben- the most robust investments involves stress-testing proj- eficiaries (e.g., flood control, sediment control, water pu- ect designs and alternatives against a multitude of possible rification, and recreation). This type of solution has been climate futures. Referred to as “decision-making under un- increasingly implemented to enhance water availability certainty” or “robust decision-making,” this process avoids under various climatic, geographic, and socioeconomic 34 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE BOX 2.5  Managed Aquifer Recharge Managed aquifer recharge (MAR)a is a useful water management tool in a variety of areas to enhance the quality and in- crease the quantity of water supply. It is a nature-inspired solution that intentionally recharges aquifers with surface water for later use or environmental benefits (figure B2.5.1). MAR can be a less expensive and less environmentally damaging option to boost water supplies in a region compared to constructing large surface storage. FIGURE B2.5.1 Managed Aquifer Recharge in Water Resources Management Evapotranspiration Reservoir Runoff Treatment Municipal/ Plant Industrial Vegetation Use Stream Treatment River Plant Lake Irrigated Recharge Basin Municipal/ Agriculture Industrial Supply Well Infiltration Well Natural Monitoring Groundwater Wells Managed Aquifer Recharge Recharge Agricultural Well Source: INOWAS n.d. Apart from direct benefits of increasing the availability of water in an aquifer, reducing evaporation, and helping to improve or maintain the water balance, MAR can provide other community and environmental benefits. For example, MAR projects that utilize stormwater in urban areas can help mitigate floods and improve water quality of local streams and coastal water bodies. MAR can also be used to improve groundwater quality by controlling saltwater intrusion or by helping in diluting existing groundwater of higher salinity and thus making it slightly better for irrigating crops. MAR can also help in providing extra water for environmental flow and groundwater-dependent ecosystems. However, if not managed properly, MAR can cause groundwater pollution due to recharge with low-quality surface water. Depending upon the local hydrogeology, needs, and other factors, a variety of methods and configurations can be used to recharge aquifers. For example, open infiltration ponds can be used to recharge unconfined aquifers, while injection well techniques like aquifer storage and recovery (ASR) can recharge aquifers that are more deeply confined (CSIRO n.d.). Site selection for MAR activity is important to ensure that there is a sufficient supply of water, and that the soil and aquifer are sufficiently permeable. Table B2.5.1 lists the different typologies of MAR systems. a MAR is also known by other terms such as artificial recharge, water banking, and groundwater replenishment. (box continues next page) Characteristics, Challenges, and Opportunities 35 BOX 2.5  Managed Aquifer Recharge (cont.) TABLE B2.5.1 Managed Aquifer Recharge Typologies MAR METHODS SPECIFIC MAR METHODS Techniques referring Spreading methods Infiltration ponds (soil aquifer treatment) primarily to getting water Flooding infiltrated Ditches and furrows Excess irrigation Induced bank infiltration River/lake bank infiltration Dune filtration Well, shaft, and Deep well injection: aquifer storage and recovery and aquifer borehole recharge storage, transfer, and recovery. Shallow well, shaft, pit infiltration Techniques referring In-channel Recharge dams primarily to intercepting the modifications Subsurface dams water Sand dams Channel spreading Runoff harvesting Rooftop rainwater harvesting Barriers and bunds Trenches Source: INOWAS n.d. adapted from IGRAC 2007. Note: A thorough description of each one of the MAR typologies can be found at INOWAS n.d. The sound technical design of a MAR system is crucial to ensure the system will operate effectively in the long term. Five main, site-specific questions to consider at the project planning and design stage are (a) What is the source of water? (b) How will water be transferred and stored in the aquifer? (c) How will the aquifer properties affect the stored water? (d) How will water be recovered from the aquifer for subsequent use? and (e) How will the end use of recovered water be managed? (NRC 2008) (figure B2.5.2). The consideration of these questions requires a detailed field investigation and stakeholder consultations. It is also important to ensure there is adequate capacity to operate the MAR system, especially with more advanced MAR technologies that use injection wells. FIGURE B2.5.2 Managed Aquifer Recharge Considerations Water Recharge Aquifer Recovery Use source method storage of water management Quantity, quality, Land availability, Capacity of aquifer Volume and Quantity, quality, duration, and aquifer geology, and and changes in flow rate duration, and reliability location of water quality of stored reliability source water Source: Adapted from NRC 2008. ater palette 36 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE conditions. For example, spurred by nongovernmental space for hybrid infrastructure and river restoration, many organization (NGO) support, sand dams have been used cities are considering or even implementing major infra- in many locations over the past 25+ years (map 2.5) structure projects and removing key assets like major high- (Ritchie, Eisma, and Parker 2021). ways or housing developments (Sutton-Grier, Wowk, and Bamford 2015). Such is the case in the Cheonggyecheon Hybrid storage can increase the reliability and produc- stream restoration in Seoul, Korea, which involved demol- tivity of natural storage. Ecosystem restoration or newly ishing an elevated freeway and uncovering a section of constructed natural infrastructure can take time to reach the stream within the built environment. This greening of its full potential. As organisms need to take hold, these the infrastructure added storage capacity and provided ecosystems will grow stronger as they mature. A hybrid protection from a 200-year storm event during the rainy storage solution can help communities to use built infra- season, as well as providing recreational opportunities structure to provide benefits in the interim while natural during the dry season. As a result, land values increased infrastructure is established. Built infrastructure has the in the surrounding area by 30–50 percent (Landscape potential to be protected by natural infrastructure (Sutton- Architecture Foundation 2014). Grier, Wowk, and Bamford 2015). For instance, vegetation and temporary storage in urban areas can contribute to However, hybrid solutions can pose some inherent the protection of stormwater systems from collapse and challenges to be considered by planners and design- overflows, mitigating floods in dwellings. This helps cities ers. The life cycles of green and gray infrastructure are to release less flood water through the gray infrastructure distinctly different (Andersson et al. 2022). Another drainage system that can overburden wastewater treat- central difference is that societal functions of green in- ment plants (Busayo et al. 2022). frastructure are characterized by  regenerative process- es—yet they need to be protected to allow this to occur; Hybrid storage has the potential to be implemented in gray infrastructure needs substantial financial invest- areas where natural storage alone would not be viable ment to stave off material decay in order to uphold its (Sutton-Grier, Wowk, and Bamford 2015). To create the functions (Andersson et al. 2022). The knowledge and MAP 2.5 Prevalence of Sand Dams Record of sand dams No sand dams known Source: Adapted from Ritchie, Eisma, and Parker 2021. Characteristics, Challenges, and Opportunities 37 resources needed to work with them are often embed- 2.5.2 Embedded in Larger Systems ded in different, disconnected sectors. These differenc- es present a challenge, but at the same time, they are A hydrological system of storage is often embedded in a source of diversity that can be used to build layers of broader social, environmental, and economic systems. resilience (Andersson et al. 2022). The storage system in any given place is part of a broad- er hydrological system, including precipitation and flows of water, which in turn is part of broader environmental 2.5 CONNECTIONS ACROSS PHYSICAL AND systems that rely on the water and influence its behavior. SOCIOECONOMIC SYSTEMS The fact that humans are constantly using and consuming water, and usually relying on stored water when they do so, 2.5.1 Most Storage Is Interdependent also means storage systems are part of broader social and economic systems that shape and are shaped by them. Freshwater storage facilities—whether natural, built, or Not all water storage solutions will work in all settings and hybrid—generally rely on the same water, which often will depend on geography, population density, hydrology, flows between them over time. The concept of how water and network connectivity, among other factors. moves constantly through the whole water cycle applies to storage. For example, the same drop of water might Social and economic preferences shape water storage first be stored in a mountain glacier, then in a downstream needs, including the nature of the service required, wetland, then in an aquifer, before emerging into a river willingness to pay, necessary levels of reliability, and and being stored in a dam, then in urban water tanks, and risk tolerance. For example, farmers practicing rainfed so forth. irrigation will focus on rainwater harvesting to increase soil moisture, while those practicing irrigation will want Storing water impacts the hydrological system, and it storage that enables controllable flows of water to their is necessary to understand the dynamics of the system farms; urban consumers want relatively small amounts to ensure that investments in storage achieve the de- of water literally on tap, while hydropower operators want sired goals. For example, investments aimed at increased large volumes of water stored for future needs. Different rainwater harvesting via terracing will increase local soil types of users need different levels of reliability in their moisture storage but reduce runoff, thereby potentially re- service and have different tolerances for risk. Industries ducing downstream wetland or reservoir storage. Similarly, that require 100 percent reliability will have a different installing a dam upstream of aquifer recharge zones may level of willingness to pay for storage services and a very reduce downstream groundwater, or change the timing of limited tolerance for risk. The Integrated Storage Planning water availability across seasons. These consequences Framework introduced in chapter 3 includes consider- may be desirable or undesirable depending on the local ation of the water service requirements of users, which context but need to be understood and planned for. can help to differentiate what types of water storage or broader water management measures may be needed to Storage investments and management must be coor- meet their requirements. dinated across the hydrological system to achieve ag- gregate goals. Since the development and management 2.5.3 Managing Risks at the System Scale of one storage facility may impact other storage facilities, it becomes necessary to plan and coordinate at the rele- Each type of storage is subject to performance risks. vant system scale, often the basin level. Similarly, it may Risks to the reliability of water storage services may take be necessary to build connections between storage types several forms, including water quantity, quality, location, to allow for more deliberate control of the storage system. and timing. Landscapes may become degraded, reduc- Integrated planning and management is not only a tech- ing soil moisture and slowing aquifer recharge. Droughts nical process, but, given the likelihood of multiple stake- will impact small surface storage more rapidly than holders seeking multiple outcomes, it becomes a social, large groundwater deposits. Public multipurpose reser- political, and economic one as well. voirs may be subject to more stakeholder conflict than 38 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE privately owned single-purpose reservoirs. Water quality development and risk management point of view—partic- may be more easily controllable in local reservoirs than ularly given that storage can take a long time to develop. aquifers. However, there is a consequential risk that new activi- ties will arise to take advantage of this storage surplus, Multiple and different types of storage are likely to pro- which may or may not be economically justifiable from a vide more reliable storage services than individual fa- longer-term perspective. Several cases around the world cilities. The types of risks are numerous, and while they have illustrated this two-way relationship between storage may be connected by large events like floods or droughts, demand and supply: Demand creates supply, but supply they are not necessarily immediately correlated. Droughts can also create demand (Damania 2020). From a policy will impact different types of storage over very different perspective, it’s always important to focus on how storage timescales, for example. Many storage risks are therefore use will be regulated and efficiencies incentivized, rather best managed at the system scale. For hydropower in par- than simply on storage supply supplementation. This can ticular, system-scale planning can help stakeholders find include valuation and pricing of water, as well as of the better-balanced solutions with lower impacts and con- storage services themselves. flicts and can help governments avoid burdens or delays, thereby delivering better development outcomes (TNC et If additional storage services are needed, they may be al. 2016). addressed through rehabilitating, reoperating, or retro- fitting existing storage, as well as through raising new 2.5.4 Addressing Challenges and Scaling Up storage. These measures are not simply about physical construction but also around the policy and institutional Storage gaps need to be addressed—but not always with environments that shape storage services and the behav- more storage. The two chapters so far have described ior of storage users—including reform. Chapter 3 outlines the importance of freshwater storage, the risk of growing an approach to addressing these issues in a systematic storage gaps, the variety of storage that exists, and why it way. needs to be managed as a system. Chapter 3 describes potential approaches to filling the storage gap, starting with the need to consider the full range of choices—in- ENDNOTES cluding demand management, alternative supply mecha- nisms, and storage—that may be required to fill identified 1 Built, or gray, infrastructures are "built up, engineered and phys- storage gaps at the local level. ical structure[s], often made of concrete or other long-lasting materials, that mediate between the human, built up system and the variability of the meteorological and climatic system” A supply-side only approach to storage risks encourag- (Depietri and McPhearson 2017). ing an unsustainable demand-side response. Some sur- 2 For further details about these solutions, please refer to the pluses in storage may be very desirable from a long-term Glossary. Characteristics, Challenges, and Opportunities 39 3 A NEW FRAMEWORK FOR INTEGRATED STORAGE PLANNING The new Integrated Storage Planning Framework pre- » What interventions do I need to put in place to meet sented in this report aims to begin to address the stor- my water security goals—while minimizing negative age gap in a way that is efficient while being cognizant impacts? of the environmental and social risks that are inherent in » What forms of water storage development and man- water resources planning and development. One of the agement are part of the solution? main purposes of the framework is to provide a system- atic process for early identification and consideration of Moving beyond the status quo, where storage planning potential opportunities and trade-offs that are often only often occurs mostly at a project level, this integrated given attention after significant sums have been invested framework combines two approaches: a problem-driv- in project preparation and some design choices have al- en approach and a systems approach (figure 3.1). A ready been made. Given that storage needs and dynamics combined problem-driven, systems approach to planning vary greatly by location, this framework acts as a guide and operation of storage is a more strategic and robust and will need to be adapted to each individual setting, de- alternative to conventional planning, as it considers inter- pending on needs, data availability, and how much storage connected water resources management components planning has already taken place. across storage types, scales, and user needs. This framework—introduced in this chapter and elabo- This combined approach to water storage planning fits rated on with step-by-step instructions in part II of this within broader integrated water resources management report—is primarily targeted at government officials and (IWRM), with the river basin as the primary frame of refer- others involved in policy development and strategic plan- ence. However, this approach builds on IWRM, with focus ning in water-dependent sectors, as well as the develop- on concurrent joint planning around specific water-related ment practitioners who support project- and sector-level interventions to improve water security and water storage FIGURE 3.1 Planning and Operating Water Storage availability. It can be used flexibly to suit specific challeng- es: Water managers can conduct a quick desk review or guide a longer, iterative planning process with engage- Problem-driven ment of stakeholders across sectors.1 approach Problem-driven, 3.1 A PROBLEM-DRIVEN, SYSTEMS systems approach to planning and APPROACH operating water storage Integrating multiple approaches offers additional solu- Integrated tions to address the water storage gap. The storage plan- systems ning framework supports decision-makers as they strive approach to answer the questions: Source: Original figure for this publication. 40 problems to be solved, thorough storage or other manage- like zoning or insurance, as well as management options ment measures. such as reoperation of existing infrastructure. The most effective response may well be a combination of storage, 3.1.1 Problem-Driven Approach non-storage, and non-water measures. A problem-driven approach entails defining the chal- 3.1.2 Systems Approach lenge and identifying the underlying problems that re- quire a solution. The concept is used across numerous A systems approach takes into account necessary en- fields, where the solution designer (software developers, abling systems and services, the roles played by different engineers, biological or pharmaceutical design teams, so- parts of the system, and the relationships between those cial scientists, among others) (Fritz, Levy, and Ort 2014) parts with respect to the overall behavior and perfor- delve into and define the underlying problem that must mance of the system (box 3.1). A water resources man- be solved rather than starting from a set of design spec- agement system is usually defined at the basin scale and ifications, for example, impacts from disasters such as can include the (a) natural sub-system, including hydrolo- floods and droughts, inadequate water supply for house- gy and relevant water management infrastructure, (b) the hold consumption, agricultural or industrial production, socioeconomic sub-system, including all water-related reduced electricity generation, potential threats to biodi- human activities (including energy, irrigation, etc.), and versity, environmental flows and ecosystem services, re- (c) the administrative and institutional sub-system that duced transportation for goods and people, and limiting plans, builds, operates, and governs water management recreational opportunities. From these identified prob- systems (Loucks et al. 2017). lems, targeted development objectives can be formulated. A systems approach can leverage interconnections to The underlying problems to be addressed, the constraints build integrated approaches to development problems, and challenges to address them, and their potential neg- integrating geographic, socioeconomic, and institutional ative consequences should be carefully defined to iden- factors. For example, a connected water storage system tify the most appropriate solutions in the given context. can support integrated flood and drought management This allows for the comparison of a range of possible by transferring flood excesses to periods of scarcity solutions that may be evaluated to identify the most fea- through measures such as managed aquifer recharge sible path to achieving the stated development objectives. fed by diverted floodwaters, as is being done with the Applying this process to the example of reducing the im- Underground Taming of Floods for Irrigation (UTFI) ap- pacts of floods, the solutions could range from built water proach in the Ganga Basin. Integrated flood and drought storage measures such as reservoirs, to nature-based management is also supported by forecast-informed res- storage solutions such as upstream wetlands restoration, ervoir operations (FIRO) as in Lake Mendocino, California to non-storage solutions like drains, to non-water solutions (see case study, chapter 8). BOX 3.1  Systems Approaches: Green and Gray Planning The City of Cape Town experienced a 1-in-a-590-year drought from 2015 to 2018, which demonstrated its limited capacity to access other sources of water outside of water storage. After solving the short-term water scarcity issue through reducing water demand and reallocation of water in storage (which required underlying water rights and robust water management systems), Cape Town developed a new water strategy that will add other sources of storage and water to its portfolio to relieve overdependence on its current systems. This includes both built infrastructure in the form of desalination plants and wastewater reuse facilities as well as green storage through the increased use of groundwater and groundwater storage. This will be combined with increasing the resilience of the regional water storage system to create an integrated, multiple water source approach to mitigate future drought impacts. (For details, see case study, chapter 8.) A New Framework for Integrated Storage Planning 41 3.2 THE INTEGRATED STORAGE PLANNING rehabilitating existing storage, to retrofitting it for differ- FRAMEWORK ent uses, to reoperating storage, to raising new storage or engaging in other sectoral reforms. The last major step Bringing together both the problem-driven and systems in the framework is to use decision criteria to guide the approaches into a single framework leads to potential choices for further study. solutions not considered by one approach alone. As an options assessment, the framework proposed is intend- Underlying problems in the system can be translated into ed to be an early planning exercise that puts key strategic development objectives, and these objectives can be bet- considerations in a form that helps stakeholders under- ter defined by understanding the water service require- stand and assess the range of options available, how and ments that are needed to achieve them. The term water why they are interconnected, the pros and cons of differ- service requirements is used as a broad term, describing ent combinations of measures, including negative im- the supply and control of water needed to support the de- pacts, and how non-storage solutions may fit among the velopment objectives and outcomes identified during the available options or offer alternatives. It enables a more needs assessment stage. These could include: informed decision about which combinations of storage are worth further exploration and whether they should be » Water supply for drinking and domestic use, crops implemented in parallel or in a phased manner.2 and livestock, industry, etc., expressed as an amount » Flood protection and attenuation of excess flows for The framework is organized in three stages: (1) a needs disaster risk reduction assessment to define the problem; (2) a definition of the » Control of flow and level for navigation, hydropower system and potential solutions; and (3) a decision-mak- generation, or recreation and cultural services ing process considering a range of scenarios and un- » Environmental flows for ecosystem preservation and certainties (figure 3.2). The first stage includes defining restoration (including prevention of saline intrusion) the development objectives, such as access to safe and affordable drinking water, and the related water service re- The volumetric, temporal (when and how often), and geo- quirements to meet those objectives. It then characteriz- graphic dimensions of the requirements should also be es the current water resources system (including storage) considered. and other systems that may need to be considered (en- ergy, agricultural markets, etc.). Following that, it system- Water service requirements can be more specifically atically identifies additional potential options and models described with key parameters that provide for compar- how those options, in different combinations or scenarios, ison of different water management options, including would result in changed levels of service. This includes storage, in terms of quality of service. These parame- options other than storage, as well as a range of storage ters, referred to as water service attributes in this frame- options, from green to gray, small and large. It encourag- work, are (a) reliability; (b) controllability; (c) adaptability; es consideration of many modalities of intervention, from (d) vulnerability; and (e) quality (table 3.1). FIGURE 3.2 Integrated Storage Planning Framework Stages The Problem: The System: Bringing it Together: A Needs Assessment Understanding Making Decisions Solutions • Defining Development • Defining Storage Objectives • Taking Stock of the Scenarios • Characterizing Water Current System • Establishing Decision Service Requirements • Solutions: Identifying Criteria Additional Options • Comparing and Assessing Scenarios Source: Original figure for this publication. 42 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE TABLE 3.1 Water Service Attributes WATER SERVICE DEFINITION PERFORMANCE INDICATOR UNIT (EXAMPLES) ATTRIBUTE 1. Reliability Degree to which water management — — options consistently succeed in serving all intended purposes 1a. Assurance Performance reliability of the water Average time between consecutive Years, months, days levels management option performance failures (predicted probability or historic) 1b. Impact of Magnitude of performance failure Size of impact if option fails to Hectares of crop lost, unreliability if underlying option fails to support deliver on intended purpose (can be financial/economic cost service delivery graded by percentage of failure) 2. Controllability Degree to which water management — — may be controlled or operated for intended purposes 2a. Volumetric Degree to which volume of water Least amount of water that may be Cubic meters control can be controlled released 2b. Geographic Geographic area that can be Service area that can be supported Square kilometers control serviced by underlying water by the option management option 2c. Temporal Frequency with which underlying Average time needed between Years, months, days control water management option can be consecutive operations or for re-mobilized for service delivery recharge 3. Adaptability Ability to adjust or modify water Number of other uses or conditions Number management option to new the water resources management conditions, uses, or purposes​ option could be modified for 4. Vulnerability Susceptibility to and magnitude — — of potential damage from hydroclimatic hazards 4a. Physical Susceptibility to flood and drought Likelihood of significant damage or Low, moderate, substantial, vulnerability hazards (influenced by design total system failure high parameters, location, and operating condition) 4b. Magnitude of Magnitude of consequences of Extent of potential impact Hectares of crop lost, kilowatt- vulnerability significant damage or total system hour of hydropower foregone, failure potential loss of life, financial or economic cost 5. Quality Degree to which freshwater is free — — of contaminants that negatively affect its uses 5a. Salinity Amount of dissolved salts in the Concentration of dissolved salts Conductivity values water body or source 5b. Pollution Presence of pollutants from point Concentration of pollutants such as pH values, total dissolved and nonpoint sources heavy metals, harmful chemicals, solids levels, biological oxygen bacteria, nutrients, and oxygen- demand, quantitative mass depleting substances measurements 5c. Turbidity The relative clarity of freshwater Concentration of suspended Quantitative mass sediment measurements Source: Original to this publication. Note: — = not applicable. A New Framework for Integrated Storage Planning 43 TABLE 3.2 Summary of the Integrated Storage Planning Framework DIMENSIONS TECHNICAL CHARACTERIZATION  STAKEHOLDER AND IMPACT ANALYSIS  THE PROBLEM: A Needs Assessment. Characterize the problem, stakeholders, and water service requirements 1.A Defining • What are the development objectives for the • Who has the problem and who may be part of the development system? solution?   objectives • Are the right priorities set in pursuit of sustainable • How will the solutions to the various problems development and inclusive growth? identified be agreed and advanced?   STAGE 1 1.B Characterizing • What are the water service requirements for • Which stakeholders’ water service requirements are water service meeting development objectives in the system? not met? requirements • What are the priority service attributes desired for • What are their vulnerabilities and opportunities if water the water service requirements?  service requirements are met?  Stage 1 Outputs: A needs assessment that specifies the water service requirements for the system developed through decision criteria and characterization of stakeholder interests, capabilities, enabling environment, and alternatives THE SYSTEM: Understanding Solutions. What are the current water management and storage measures in the system? What additional measures are possible in the system? 2.A Taking stock of • What are the water security measures, storage and • To what extent does the existing water management the current system non-storage, in place in the current system? system engage and benefit stakeholders?  • What is the performance against relevant criteria, • What are stakeholder incentives, capabilities, and including the ability to meet the system’s water institutional systems to determine feasibility of options service requirement attributes, infrastructure to improve existing water management systems?  functionality, sustainability and condition, and • How are existing water security and storage systems benefits that will be quantified and compared used/not used for their intended purpose or how they during the analysis of options in Stage 3? may serve alternative purposes?  • How do existing storage systems positively or adversely impact (or exacerbate vulnerabilities for) STAGE 2 stakeholders?  • How do existing storage systems and their operations contribute to environmental sustainability? 2.B Solutions: • What are the additional options for meeting the • What are stakeholder interests related to additional Identifying water service requirements of the system? options considering how they relate to interests in the additional options • How can you get enhanced performance from the current system and as they may relate to other new current system and what are the opportunities for options? developing new options? • Are there non-water alternatives to problems identified in the system? • How do the options contribute to the desired water service requirement attributes? Stage 2 Output: A model of the system, a set of potential solutions, and a stakeholder map BRINGING IT TOGETHER: Making decisions. Storage planning, management, development, and operations  3.A Defining What are the different storage scenarios? storage scenarios STAGE 3 3.B Establishing What are the different decision criteria that should be Engage stakeholders in a structured decision-making decision criteria in place to assist with the decision-making process? process 3.C Comparing What is the best solution to address the water and assessing security issue? scenarios Stage 3 Output: Ranked list of storage solutions for further study and preparation Source: Original to this publication. Note: Feasibility study, ESIA, and/or further preparation and design of selected storage measures, as needed. 44 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE The framework presented here is not only a technical The framework ties together the three stages of es- review but is ideally an opportunity to shift the conver- tablishing the problem, information gathering, and sation on freshwater storage so that it includes a more decision-making, while incorporating stakeholder en- diverse group of stakeholders, thereby allowing for a gagement and key questions to address and develop broader set of potential solutions. The needs of and po- integrated solutions at the system scale (table 3.2). tential impacts on different stakeholders, including the en- For those wishing to better understand each phase of vironment, are explicitly taken into account at each stage the framework, or apply the framework, chapter 7 of this of the framework. Starting in the first stage, the identifica- report elaborates each stage of the framework, including tion and mapping of different stakeholders is an essential key questions each stage should ask and answer, and task. In the second stage, the framework includes charac- provides some guiding questions for use when undertak- terization of how different stakeholders may benefit or be ing an options analysis using this framework as a tool. disadvantaged by potential changes to the system as well Additionally, examples are provided to spotlight technical as identification of potential risks and opportunities. In the tools and innovation that may help in storage planning. third stage, during the comparison of different scenarios, stakeholder interests and environmental considerations become more specific, and ideally quantified, as they be- ENDNOTES come part of the decision-making criteria used to deter- mine the way forward. 1 This framework is not intended to replace normal project preparation studies, nor serve as an additional step that While the process outlined in the framework is funda- must be undertaken before any storage intervention can be mentally public sector-led, it recognizes the importance designed. Rather, it provides a planning exercise that can be of the private sector and civil society in planning, de- undertaken to identify opportunities for improved storage planning and management. The framework is presented as veloping, and operating water storage investments, and an opportunity for stronger development outcomes, as a new highlights areas where they have specific roles to play. good practice, but is not a World Bank requirement for project While a multi-stakeholder planning process would be at identification or preparation. the expense of expedient decisions, such processes are 2 The framework deliberately casts a wider net than a typical proven to increase trust, stakeholder satisfaction, trans- options assessment—which is often already focused on dif- ferent permutations of the same technology— to ensure more parency, and performance in the water sector (Fox 2015; potential solutions and counteract the natural biases planners Water Witness 2020). These conditions enable greater may have for one kind of approach over another. An earlier ownership and buy-in from stakeholders, which could re- attempt by the Dams and Development Project (UNEP 2011) duce delays in implementation. Each situation should be to introduce a Comprehensive Options Assessment on Dams tailored appropriately to the needs of the stakeholders to and Their Alternatives shared many of the same principles as create sustainable and efficient storage capacity for both the framework put forward in this chapter, but this framework is borne from a technology- and sector-neutral perspective present and future needs. It is not meant to be exhaustive, on water storage with greater emphasis on the potential of but it provides tools and resources to arrive at better stor- nature-based solutions to be used conjunctively with built age outcomes. infrastructure. A New Framework for Integrated Storage Planning 45 4 INSTITUTIONALIZING INTEGRATED STORAGE PLANNING This chapter highlights institutional issues that will need among policy makers and water managers, the implemen- to be addressed to undertake a problem-driven, systems tation of IWRM is progressing at only half the rate that is approach to water storage planning and management. needed to achieve Sustainable Development Goal (SDG) As the services provided by water storage and the prob- target 6.5 on IWRM implementation. According to the 2021 lems water storage addresses can involve a range of sec- progress update, 107 countries were not on track to have tors and institutions, new institutional arrangements and sustainably managed water resources by 2030 (UN-Water mandates may be needed to engage in more effective 2021). There are many challenges for IWRM implementa- storage operation and management. This is the fifth "R" tion, which also extend to managing water storage in a more in storage management—reform. In other cases, existing integrated way. Among these are lack of data, coordination mechanisms such as basin planning processes may be challenges, misaligned incentives, institutional capacity is- activated and adapted. sues, and funding. The problem-driven, systems approach is designed with some of these challenges in mind. In most places, an integrated framework will need to be implemented with imperfect information and in the While institutional barriers constrain the use of inte- face of resource constraints. In an ideal situation, there grated planning approaches, taking a problem-driven, would already be a well-developed regulatory and institu- systems approach to storage can offer better outcomes tional framework that clearly lays out roles and responsi- compared to siloed development approaches. Water bilities and sets guidelines that support the assessment storage planners must strive to make better storage de- and implementation of water storage options. Ideally, the cisions while knowing that perfection is not attainable. regulatory framework would include protections for nat- The following section explores many of the institutional ural storage like wetlands, rivers, and forests, as well as challenges and considers lessons learned on how to best for water towers, riparian areas, and critical groundwater manage them. infiltration areas. There would be sufficient data of good quality upon which to base basin-level studies that scope options and potential risks and opportunities; sector plans 4.1 DATA AND ANALYSIS GAPS would be informed by cross-sectoral linkages; and ade- quate resources would be available for detailed investiga- Hydrological, geological, and socioeconomic data as tions and project-specific analyses. However, the reality is well as analytical tools for interpretation are key ingre- that many planning and investment decisions are made— dients to developing a good understanding of the current and indeed have to be made—in the context of financial water storage system and what additional options may and human resource constraints, as well as gaps in infor- be feasible to meet storage needs. Traditionally, much of mation. This chapter focuses on how to apply the storage this data is collected by in situ instruments and field sur- framework given these challenges. veys, which require adequate physical infrastructure and a skilled workforce. In low- and middle-income countries, The challenges in implementing this problem-driven, there are often significant gaps in hydrometeorological systems approach to water storage planning will, in many networks and technical skills. Similar challenges exist in ways, be the same as those that encumber the imple- wealthier countries due to difficult-to-traverse terrain or mentation of integrated water resources management where lack of investment has led to the degradation of (IWRM). Despite growing awareness of IWRM principles older systems. 46 Where data exists, there may be analytical gaps that hin- is a fast-growing field. Remote sensing can provide spa- der its use in decision-making. Data must be collected, tially distributed and timely observations, and very large stored, analyzed, and interpreted to provide useful input amounts of this data is freely available and open to the into decision-making processes. Models and other analyt- public; however, processing and interpretation of data is ical and visualization tools transform raw data collected required to ensure proper monitoring and reporting (García into actionable information that can be communicated to et al. 2016). Validation and calibration with field-level data those with the power to act on it. Due to the complexity is usually needed. For operational purposes, services of the natural and socioeconomic systems implicated in can be developed to automate and process images, pre- water storage decision-making, these tools are often high- senting an approach to observe water storage dynamics ly customized and require extensive training to use, and if (World Bank 2021d). developed with proprietary software, can be expensive to maintain, especially in low-income environments. Remote sensing plays an important role in providing the information needed to meet water challenges. García et In the current information age, the rise of earth observa- al. (2016) present available data by remote sensing that tion data, machine learning, and advances in computing can be used to fill the gap where ground data is scarce. have resulted in a proliferation of free and low-cost data- It includes a guide for determining the data needs and an sets, and open-source analytical platforms and modeling overview of relevant variables provided by earth observa- tools that are helping in closing information gaps. Today, tion for each water challenge, indicating the most suitable some of these resources are robust enough to support sensors rearranged to focus on spatial and temporal res- improved decision-making as stopgap measures while olution. For instance, for identifying and monitoring water investments are being made in higher resolution on-the- storage, spatial resolution is usually the most important ground data collection—though they still require validation factor and high resolution may be required, whereas slow and calibration with ground data. Increasingly, however, water dynamics mean that a moderate frequency is likely they offer complements to—or even lower cost alterna- to be required. High-resolution sensors1—either optical or tives to—traditional data collection methods (box 4.1). radar—can be used to identify the surface area of a small dam (World Bank 2021d). Measuring surface water eleva- Satellite images can be a powerful tool in facilitating tion using earth observation technology can provide esti- the process of closing information gaps. The use of re- mates of changes in total water volume in reservoirs and mote sensing for operational purposes (planning, design, other water storage systems such as wetlands (García et monitoring, or operating) in water resources management al. 2016).2 BOX 4.1  Working in Data-Scarce Environments: Example from the Western Sahel Region How do you plan water storage in regions where data is scarce and capacity is constrained? How do you identify appropriate small-scale water storage solutions, at scale, for communities dispersed across the landscape? With Africa's population growing at the highest rate in the world, the availability of water resources is decreasing, not only in relative (per capita) terms but also in absolute terms. The actual storage capacity in large dams in most Sub-Saharan basins decreased by 5–10 percent in the 20-year period from 1990–2010 (Wisser et al. 2013). Therefore, it is critically important to look at other modes of reliable water storage, especially small-scale and nature-based solutions. To this end, the World Bank, in collaboration with a consortium of international partners, has supported the development of the Water Harvesting Explorer, a decision-support tool for small-scale water storage interventions planning. The tool was developed initially for the Western Sahel region to provide field-level agency staff and local communities with a starting list of interventions that are “water-appropriate” for any given location. (box continues next page) A New Framework for Integrated Storage Planning 47 BOX 4.1  Working in Data-Scarce Environments: Example from the Western Sahel Region (cont.) The Water Harvesting Explorer (figure B4.1.1) provides potential options for water harvesting at any location of inter- est, based on the local biophysical conditions, including annual precipitation, slope, and land cover. The tool uses global datasets and draws on the World Overview of Conservation Approaches and Technologies Repertory of Sustainable Land Management to suggest a long-list of intervention options, which can then be narrowed down through community consul- tations and local ground-truthing. The user can click on a desired point on the map and then is shown an illustrated list of potential water harvesting technologies that have been successfully implemented in similar bio-physical conditions. It also provides important information for each of the options, such as technical specifications, specific benefits and limitations, and costs. Information on local socioeconomic conditions can be added by the users to guide the choice of appropriate water harvesting methodologies. In addition, warnings and notifications inform users about any conditions (such as loca- tions in protected areas, erosive settings, etc.) that could change or complicate the intervention. The menu of options identified by the tool can facilitate the dialog with the local communities, by serving as a starting point for exploring the range of potential solutions to address their water needs. The tool is currently being piloted in a World Bank-supported intervention in Niger, and is being expanded in similar settings in Nigeria, Ethiopia, and Somalia. The tool is available at https://sahel.acaciadata.com. New features are expected to be added in the future. FIGURE B4.1.1 Screenshot of the Decision Support Tool “Water Harvesting Explorer” Source: Water Harvesting Explorer: https://sahel.acaciadata.com. The problem-driven, systems approach to storage plan- that facilitate early scoping of options and their associat- ning is designed to be implementable even in the face ed risks and opportunities. It values local knowledge and of data limitations. It can be used as a desktop exercise, robust decision-making approaches that are useful in the relying on the use of publicly available datasets and tools face of climate-related changes and other uncertainties. 48 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE The phased approach of the framework enables water of floods and droughts. Several aspects are relevant to managers to prioritize the options deserving of more de- integrated storage planning—including coordination over tailed study. data and forecasts, strategic investments such as those to promote healthy watersheds and green-gray water re- sources infrastructure, as well as conjunctive groundwa- 4.2 INTER-SECTORAL COORDINATION ter management, among others. Inter-agency coordination within the water sector is Effective water storage planning necessitates the often difficult, even where significant investment has breaking of sectoral silos and managing the power been made in the institutional framework for water re- asymmetries that may exist between water manage- sources management. This may be due to overlapping ment authorities and those of other sectors. Siloed or lack of clarity of institutional mandates at different planning approaches have led to suboptimal storage in- planning scales, or where a process of decentralization vestments, including single-purpose facilities that can or devolution of responsibilities to the river basin level is foreclose future opportunities or negatively affect other underway. Thus, it is important to clarify from the outset components in the system. There are, however, effective who is responsible for leading the water storage planning ways of strengthening inter-sectoral coordination that process and the roles of other key stakeholders. In some can produce better outcomes for water storage planning jurisdictions, groundwater is governed differently than sur- and operation, including the establishment of interagency face water, with legal regimes often making a distinction fora, ensuring appropriate and representative stakehold- between entitlements for flowing water versus for water er composition, and establishing procedures to increase use on land. This legal or institutional separation does not engagement and measure progress. In Tanzania, for ex- account for the complex interconnectivity between sur- ample, even though the institutional framework legally face and groundwater systems and can make integrated separates issues of water resources management from planning less effective. Moreover, the tendency to treat water supply and irrigation, the Ministry of Water has a different water resources and storage projects as isolated legal mandate for multi-sectoral coordination, and laws endeavors—especially if they are funded through different and policies governing water-intensive sectors encourage sources—can lead to duplication, interface challenges, or or require coordination with the water sector. Specifically, even set project objectives against one another. the powers given to the Minister of Water in Tanzania’s Water Resources Management Act include, among oth- Coordination between the water sector and other sectors ers, the authority to “(b) appoint members of the National may also present a challenge as several different parts Water Board; (c) establish basin water boards; . . . [and] of government may be responsible for collecting infor- (e) facilitate sectoral coordination and coordinated plan- mation and administering policy that affect or depend ning on aspects that may impact on water resources . . . ,” on water storage. For example, it is common for climato- and the National Water Board, established under the act, logical data to be collected and stored by a meteorological advises the minister “on matters related to multi-sec- service while information on land use and ownership may toral coordination in integrated water resources planning be housed within a dedicated land agency. Similarly, data and management . . .” (Government of Tanzania 2009). collection and policy implementation related to irrigation, Implementation challenges remain, but the foundations hydropower, or aquatic ecosystems may be the respon- are built into the legal and institutional framework and sibility of an agriculture, energy, or environment ministry, guide government stakeholders toward more inter-sec- respectively. While it is possible to achieve some degree toral governance (World Bank 2017a). In Bangladesh, a of rationalization by trying to house the various aspects multi-sectoral water platform has been formed that brings of water management under the same ministry or agency, together government agencies, donors, and other partners it is impossible to do so completely. The EPIC Response to assist in the implementation of its multi-sectoral delta Framework (Browder et al. 2021) outlines opportunities plan (figure 4.1). The platform provides a forum to coordi- that national governments can explore to holistically man- nate fundraising, investment, and management around a age floods and droughts risks with the aim of efficiently multi-sectoral plan, while addressing cross-cutting issues reducing the economic, social, and environmental costs like climate change and water stress. A New Framework for Integrated Storage Planning 49 FIGURE 4.1 Bangladesh Water Platform COUNTRY PRIORITIES Water and Economy Focus Area Focus Area Focus Area Climate Change 1 2 3 Water Stress Growth and Social Climate and Competitiveness Inclusion Environmental Inadequate and Poor Services Management Urbanization Instruments Sustain Water Deliver Build Resources Services Resilience • Support the DP2100 enabling setup • 2030 WRG Multi-Stakeholder Partnership • Water Sector PER WATER PLATFORM • Sanitation Full Area Convergence Development • MFD-Water & Wastewater PPPs Partners • Three-layer water-risk management & climate insurance Communicate Cooperate Coordinate Collaborate • Water Data Plataform Government World Bank • GPs Collaboration Continuum & IFC • Disruptive Technology & Agility Source: World Bank internal document. Note: DP = Delta Plan; GP = Global Practice; IFC = International Finance Corporation; MFD = maximizing finance for development; PER = public expenditure review; PPP = public-private partnership; WRG = Water Resources Group. Even with institutional enhancements to support nature-based, have the potential to affect diverse stake- multi-sector coordination, there often remain political holder groups, in both positive and negative ways. In recent challenges to successful functioning. Applied political decades, there have been greater efforts to study and ad- economy analysis during integrated storage planning can dress the various environmental, social, and distributional help identify both the non-technical barriers to success impacts of water storage investments, especially for large Water palette and which policy measures and strategies will be most ef- built infrastructure; regulators that permit infrastructure fective in unlocking technically preferred opportunities. It developments increasingly have more rigorous standards may be that the solutions identified will need to be adapt- around public consultation and disclosure. However, these ed to fit prevailing realities, or there may be room to begin regulatory requirements often come during the investment altering the relative influence of different stakeholders to preparation phase where a preferred storage intervention create space for an improved approach (Fritz, Levy, and has already been selected and has likely already secured Ort 2014). W1 W2 W3 funding to go forward. In the absence of earlier stakehold- Water 1 Water 2 Water er3 engagement efforts, the potential for stakeholder oppo- 206R/84G/64B 101R/67G/60B 125R/191G/66B 1a68a3 539932 ffff00 sition at this late stage is much higher. 4.3 MULTI-STAKEHOLDER ENGAGEMENT AND COORDINATION Multi-stakeholder engagement is, thus, important from the earliest planning stages. This includes in the develop- Early integration of multi-stakeholder (including ment of sectoral plans and basin-level/strategic studies, non-government) perspectives and knowledge in water such as strategic environmental assessments (SEAs). As storage planning is beneficial and important, but it is not in the case of government agency coordination, ensuring W1B always hardwired into the 255R/203G/88B W2B regulatory and institutional W3B W4B the right composition of stakeholders from early on is also 116R/215G/237B 244R/130G/44B 101R/166G/68B BLACK 80% framework. Water storage interventions, 74d7ed ffca58 whether built or many instances, this would include f4822c vitally important. In 65a644c 50 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE non-governmental stakeholders like civil society organi- planning and management. For example, in Costa Rica, zations (CSOs), private industry, and local communities. dedicated legislation (Law Nº 8023) was enacted in 2000 In the case of indigenous and historically marginalized for the Upper Reventazón river basin, one of the most crit- groups, securing their full and continuous engagement ical basins in the country for hydropower generation, for may require special effort, including through language better management of the basin. Through this law, the interpretation and translation as well as working through Commission for the Planning and Management of the the institutional structures of those groups. Still, this may Upper Basin of the Reventazón River was established with be difficult to do in the early, public sector-led phases of a mandate for multi-sectoral coordination toward basin water storage planning because of lack of funding or ap- development and conservation (Porras Peñaranda 2012). propriate skillsets, especially in low- and middle-income The problem-driven, systems approach embeds these is- countries. sues into the framework, so that if they are not explicitly provided for in the regulatory framework, they can still be The problem-driven, systems approach explicitly in- considered in a systematic way. Some deficiencies in the cludes stakeholder considerations at various levels of regulatory framework may become apparent through the the process. Early stages of the framework involve map- use of the planning framework and could be reflected in ping of the various stakeholders that may be affected by the regulatory reform process. a set of water storage options and whose behavior will in- fluence the performance of those options. This early map- ping is neither costly nor time-consuming and provides 4.5 WEAK INSTITUTIONAL CAPACITY a foundation for later stages where more detailed infor- mation needs to be collected about stakeholder interests Institutional clarity alone is not sufficient for integrat- and capabilities. Having these considerations built in will ed planning; responsible institutions must also possess help to screen out politically, environmentally, and socially the capabilities to carry out the mandates. As discussed, infeasible options. By the time detailed stakeholder con- integrated water storage planning and operation require sultations need to be carried out for specific interventions many parties to act. The operating environment is highly that have advanced for further study, some potential is- contextual; a given technology or approach that works in sues will have already been identified and ideally fed back one situation is not guaranteed to work in another, how- into the project concept.3 ever similar. This creates a heavy institutional burden for water managers. It can be difficult to build and retain the institutional capabilities needed for effective implementa- 4.4 REGULATORY FRAMEWORKS tion, especially in countries that suffer from high rates of outward migration of their skilled professionals. Many jurisdictions are missing or have outdated laws and regulations on water resources management and Long-term institutional strengthening is a critical as- water storage. Existing laws and regulations may not re- pect of integrated storage planning and operation. This flect the actual level of water resources development or includes the legal foundations that define the existence of may not be detailed enough to manage the trade-offs that relevant institutions, along with their roles and responsi- inevitably emerge with ambitious development plans. In bilities and the obligations of other actors in the system. addition to clarifying mandates and supporting multi-sec- It also includes more detailed institutional arrangements, toral coordination, legal and regulatory frameworks will such as how different entities coordinate with one anoth- better facilitate integrated storage planning if they include er, how they are staffed, and how they are funded. While protections for natural storage and areas that play a criti- legal and institutional frameworks are not static and must cal role in the provisioning of water. evolve over time to reflect the changing realities in a juris- diction, it is much more effective and less costly to get the Frameworks will support integrated planning if they em- fundamentals right from early on. At this moment, many phasize the importance of basin-wide approaches, rec- countries are going through a process of legal and insti- ognize the interdependence of built and natural systems, tutional reform, especially as they introduce dedicated and include sustainable funding mechanisms for storage water management laws or policies for the first time or A New Framework for Integrated Storage Planning 51 update their frameworks to reflect IWRM principles. This planning and policy development, to project preparation presents an opportunity to address the key elements that and/or implementation, to asset management. Regulatory are needed for tackling water storage challenges through oversight might also be performed by agencies involved in a problem-driven and systemic lens. sector planning or project development, or it may be the responsibility of an independent body. Depending on the functions, one or more of the basic funding sources could 4.6 FUNDING CONSTRAINTS FOR WATER be more sustainable and appropriate, especially where in- MANAGEMENT INSTITUTIONS dependence is important. Financial sustainability of water management institu- tions is a well-documented challenge and a key barrier 4.7 PRIVATE SECTOR PARTICIPATION to holistic early planning of water storage interventions. Many water institutions suffer from chronic funding gaps Though this framework is fundamentally a public sec- driven by insufficient budget allocations from government, tor-led approach, it recognizes the important role of inadequate collections, or low tariffs that have been set the private sector as a partner in integrated planning. below cost recovery for political or economic reasons. Private sector participation in water storage planning This can lead to understaffing, lack of data, and lack of and management can come in many different forms, resources to carry out sufficient early scoping, modeling from management and operation contracts, to pur- work, and technical, social, and environmental due dili- chase of previously public assets, to the provision of gence. In low- and middle-income environments, studies equity or loan financing. Private sector players may also that occur before the emergence of specific bankable have considerable expertise and access to technology projects are often funded by bilateral and multilateral that may be difficult to acquire in a fully public venture. partners or CSOs, often with grant funding. The extent to Evidence from private sector participation around the which resources are a challenge will be influenced by sec- world suggests that it may increase operational effi- toral differences in revenue generating potential and the ciency, leads to higher-quality service provision, and degree of private sector participation. supports expansion of service delivery to underserved segments (Al-Madfaei n.d.). Lack of funding is also a problem for optimal manage- ment of existing water storage assets. This can lead to However, the desire to attract private investment in deferred maintenance of equipment and facilities, which water storage can lead to investments that maximize pri- not only affects their efficiency and quality of service de- vate benefits rather than net social benefits, resulting in livery but also their safety. In a recent study of dam safety slower progress in underlying development objectives. regulatory frameworks, which included case studies from Private investors favor interventions that they perceive to 51 countries, only 14 percent of the case study countries be less complex, less risky, and faster to implement. In the were found to have a well-funded dam safety assurance case of hydropower, this has manifested as a preference program (Wishart et al. 2020). for single-purpose run-of-river facilities, which have fewer stringent regulatory requirements in some jurisdictions Water management institutions are typically resourced (Venus et al. 2020). It has also manifested in a preference by one of three basic sources: (a) tariffs or fees, (b) gov- for smaller projects. According to the World Bank’s Private ernment budget allocations from tax revenue, or (c) trans- Participation in Infrastructure database, 954 private in- fers of monies or in-kind assistance from external sources vestments in hydropower over the last century were for such as development assistance. They may also have ac- plants with installed capacity ranging from 0.4 MW to cess to financing in the form of loans or bonds, which will 11,565 MW, but 71 percent of those were for plants under ultimately be repaid to creditors using monies obtained 250 MW. Similarly, greenfield projects are preferable to through one of the three basic sources above. brownfield projects. According to the same database, less than a quarter of private hydropower investments were The funding needs of institutions will vary according brownfield investments, including for rehabilitation (World to their mandates, which may range from upstream Bank 2022). While it is expected that private investors will 52 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE prefer certain types of projects over others, if these prefer- Among the issues common to infrastructure planning ences drive the selection process, it will limit the range of globally is the misalignment of political cycles and solutions and could lead to suboptimal choices. incentives with the timeframes needed to apply an in- tegrated approach to storage development and opera- Thus, during the early stakeholder mapping and analy- tion. The path of least resistance is to implement what sis as well as later in the assessment of options against is already conceptualized, rather than taking a step back the agreed decision criteria, it is important to consider to undertake a wider planning effort. On top of this, elec- when and how it is most appropriate for private com- toral cycles typically last between two and six years, panies and investors to become involved in the project which is usually not enough time to take a water storage development process. It is also an opportunity for early investment from the early scoping phase through to op- thinking on what types of risk-sharing arrangements or erationalization. For the largest and most complex en- incentives may be needed to crowd in private finance for gagements, it takes upward of a decade to bring them the options under consideration, including nature-based to fruition. While in office and seeking re-election, public solutions (NBS) for which investor confidence is gen- officials are also under pressure to solve the most urgent erally lower. It is also important to consider what water crises and may opt for expedient, even if partial, solu- rights—which may be closely tied to land tenure in some tions that can show results in the shortest time possible. jurisdictions—are vested to private partners according to Broadening the range of possible solutions by taking a the various modalities of private sector participation and problem-driven, systems approach to storage planning how those decisions may affect the water rights of other and management may yield some fast-to-implement users in the basin. solutions, but in most cases, the right combination of op- tions to deliver sustainable and robust performance will include longer-term measures. Notwithstanding, water 4.8 MISALIGNED INCENTIVES AND managers can leverage urgent crises like droughts and POLITICAL ECONOMY CONSIDERATIONS floods to spur action, including more resources for inte- grated planning. In addition, pragmatic approaches, such Where institutional arrangements are generally in as implementing “no-regret” actions to show progress, keeping with international good practice, the political may give more space to planners to undertake longer economy situation can lead to a mismatch between planning processes. policy and implementation, making it harder to facili- tate integrated storage planning and management. The Implementing integrated storage planning will require specific non-technical drivers of this mismatch will vary some conceptual and attitudinal changes that will from place to place, but they generally reflect a shift to take time to be reflected in practice and in institutional institutional rules that challenge pre-existing norms and frameworks for water management. Nevertheless, the behaviors around water management. Integrated storage problem-driven, systems approach can guide water man- planning and management, and IWRM more generally, agers through a step-by-step process that works around can be undermined, for example, by local political inter- and through some of the institutional challenges. Table ference, privileged access of a select few, rent-seeking 4.1 summarizes some of the main areas where change behavior, and power asymmetries between stakeholders. is needed as well as some recommendations for how to Problem-driven approaches account for such drivers of manage them in the short term while longer-term solu- institutional non-performance by interrogating the under- tions can be implemented in parallel. lying problems as well as different stakeholder interests and capabilities. A New Framework for Integrated Storage Planning 53 TABLE 4.1 Changes Required and Recommendations for Integrated Storage Planning WHERE WE NEED CHANGE RECOMMENDATIONS Hydrometeorological networks are insufficient Earth observations can be a stopgap and are quickly becoming alternatives to in situ data collection Complexity of water systems often yields highly technical and Free and low-cost analytical platforms are available and can be customized analytical tools that are expensive to maintain and used to improve baseline understanding of existing systems and require significant training model possible changes Unclear institutional mandates and outdated legal and regulatory Establishment of inter-agency platforms can support fundraising frameworks make it difficult for agencies to coordinate and multi-sectoral planning around cross-cutting issues and integrated planning and development problems while institutional reform is in progress Power asymmetries exist among different government Applied political economy analysis while planning water storage ministries or other stakeholders; political interference of specific investments can help identify the non-technical barriers to actors may undermine a rational decision-making process success and find opportunities to advance technically preferred solutions Multi-stakeholder engagements are not always hardwired into Stakeholder mapping in the early phases of the investment the institutional framework planning helps to clarify stakeholder interests and capabilities and flag potential issues early In funding-constrained environments, private investor It is important to recognize the private sector as a key player in preferences may drive project selection, yielding suboptimal storage development and management, but investor interests investments from a socioeconomic perspective and capabilities should be mapped as with other stakeholders to detect where de-risking may be necessary to reduce mismatch between public and private interests Politicians may be incentivized to implement politically expedient “No-regret” actions can provide space to undertake a more solutions even if they are not the technically preferred solution informed planning process, and crises can be useful levers to generate support for technically preferred solutions Source: Original to this publication. ikonos-satellite/; QuickBird Satellite, available at: https://earth. ENDNOTES esa.int/eogateway/catalog/quickbird-full-archive. 2 More resources about geospatial information can be found in 1 Some of the high-resolution space-based global optical imagery https://www.spatialagent.org/HydroInformatics/ and more in- records can be found here: The NASA/USGS Landsat Program, formation on World Bank Global Reach Spatial Agent Portal for available at: https://landsat.gsfc.nasa.gov/; ASTER (Advanced Water: http://www.appsolutelydigital.com/GlobalReach/map. Spaceborne Thermal Emission and Reflection Radiometer), html. available at: https://terra.nasa.gov/about/terra-instruments/ 3 For further resources, see Dye, Hulme, and FutureDAMS- aster; SPOT, available at: https://earth.esa.int/eogateway/mis- Consortium n.d. sions/spot; Ikonos, available at: https://gisgeography.com/ 54 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE TOOLS FOR BETTER 5 STORAGE THROUGHOUT THE PROJECT CYCLE Integrated water storage management does not end at 5.1 RAISING OR CREATING NEW STORAGE the planning phase outlined in chapter 3. Closing the water storage gap sustainably and efficiently requires After the initial planning phase, specific water storage a life-cycle approach to managing storage assets from investments, whether natural or built, need to be pre- planning, investment preparation, and implementation, pared in more detail and then implemented. For new through to operation, and in some instances, eventual investments, this usually involves more steps than invest- decommissioning (figure 5.1). This chapter draws from ments involving existing storage assets. guides and tools that have been developed on the techni- cal, environmental, social, and institutional good practices 5.1.1 Preparatory Studies for New Investments in water storage development and management. While it cannot give full treatment to the breadth of relevant is- More detailed investigations are needed to examine the sues, it highlights some specific areas that are important feasibility of the potential investments prioritized via the to consider from a system perspective for both new and options assessment process. Feasibility studies, defined existing storage assets. broadly, investigate the technical, financial, economic, FIGURE 5.1 The 5 R's and the Project Cycle Reform Assess Opportunities to Raise New Storage Project Project Project Planning Preparation Implementation Operation (using the Integrated Storage Planning (and maintenance) Framework) Assess Opportunities to Rehabilitate, Retrofit, If extension of life is no longer Reoperate Existing Storage feasible or beneficial, assess opportunities to decommission Source: Original figure for this publication. 55 environmental, social, and governance aspects of a pro- World Bank Environmental and Social Standards (ESS) posed investment. They are important for understanding 1 on Assessment and Management of Environmental the various trade-offs involved in developing or, in the and Social Risks and Impacts for specific World Bank case of nature-based solutions (NBS), tapping into water requirements. stores to support water service delivery, accelerate the clean energy transition, and strengthen resilience to cli- At the investment preparation stage, assessing the mate change and natural variability. Linked environmental sustainability of a specific storage project will be eas- and social impact assessments (ESIAs) scope potential ier if strategic/basin-level analyses are completed. If a impacts and look at mitigation options, informed by the strategic environmental assessment (SEA) or cumulative mitigation hierarchy. Specific measures can be explored impact assessment (CIA) has been carried out, many envi- as needed, including the establishment of environmental ronmental, social, and governance risks and opportunities flows. Capitalizing on opportunities for greening of areas will already have been scoped and provide important input surrounding reservoirs can also enhance the aesthetic into the project-specific environmental and social impact and ecological value of artificial reservoirs, creating hab- assessments and management plans. Project ESIAs and itats for biodiversity and attracting eco-tourism. ESMPs can be tools for building local acceptance and identifying opportunities to exceed legal requirements. There are many types of assessments that can be useful For example, community benefit sharing is considered for assessing and minimizing impacts of potential water good international industry practice for storage invest- storage projects. At the project level, project ESIAs and ments since the communities bearing most of the cost environmental and social management plans (ESMPs) of the project, such as livelihood disruption or physical re- are focused on the potential positive and adverse impacts location, may not be the same communities that are the of the specific project and are usually required as part of direct beneficiaries of the investment. Thus, it is important the project permitting process by national or subnational for both equity and social acceptability of the project that authorities. Though normally required, they do not have to the local communities directly share in the benefits. be solely compliance-oriented; on the contrary, they can be useful tools for building local acceptance of a proj- Depending on the nature of the storage facilities being ect and identifying opportunities where said project can investigated, there may be a need to revisit the needs of go beyond the satisfaction of legal requirements. Within the system. This ensures continued alignment between these tools, the Mitigation Hierarchy provides guidance the different options being considered, both at the proj- on designing projects to avoid risks and impacts, to min- ect level as well as in larger system planning, in addition imize or reduce residual risk, to mitigate remaining im- to ensuring that resources are not wasted along the way. pact, and compensate where necessary. See box 5.1 for Depending on the nature of the potential investments, an overview of environmental and social tools. Refer to there may be a need for more detailed study of the sys- tem, through SEA (if not already done during the options assessment) and/or CIA. Re-examining the needs of the The Mitigation Hierarchy system is also a way to achieve greater operational link- (ESS 1: Assessment and Management of ages among different water storage types that may be Environmental and Social Risks and Impacts) operating in isolation. » Anticipate and avoid risks and impacts For instance, many governments hold master plans or » Where avoidance is not possible, minimize or other planning documents that are decades old, and the reduce risks and impacts to acceptable levels status quo in the basin may be drastically different from » Once risks and impacts have been minimized when new dam projects were first identified and as- or reduced, mitigate; and sessed. In this case, a CIA may prove a useful tool to evalu- » Where significant residual impacts remain, ate the cumulative impacts of the interventions across the compensate for or offset them, where techni- basin to determine whether the proposed intervention will cally and financially feasible. provide adequate benefits to offset costs of the intervention and consider how to minimize those costs. In the case of 56 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE BOX 5.1  Types of Impact Assessments to Maximize Social and Environmental Development Strategic environmental assessments (SEAs),a also called strategic environmental and social assessments, are defined by the World Bank’s Environmental and Social Framework (ESF) as a systematic examination of environmental and social risks, impacts, and issues associated with a policy, plan, or program, typically at the national level but also in smaller areas or in a specific sector. SEAs are typically not location specific; rather, they are prepared in conjunction with project and site-specific studies that assess project risks and impacts (World Bank 2016b). For water storage, an SEA is likely to be applicable to (or part of) a water storage master plan or a river basin management plan that incorporates water storage. Because SEAs are applied at an early stage, they have meaningful input on key choices in the design of the water storage system. They serve to facilitate multi-stakeholder decision-making at a high level. SEAs are increasingly required by national regulators and financiers as part of the ESIA process. Alternative assessments, also known as option assessments, identify alternatives to a planned project that achieve the same goal while generating higher environmental and social benefits. They should be an integral part of any impact assess- ment study, but in some cases they can be used as a stand-alone analysis. Alternative assessments look at a system from a cross-disciplinary perspective and, as such, are especially suitable to support the decision process related to water storage development by bringing environmental, social, and economic considerations into early decision-making. A serious analysis of alternatives can also reduce the project cost, assist in gaining greater public support for the project, and improve the likelihood of project approval by the various stakeholders. In most instances, if this opportunity is not acted upon, the best that can be achieved is damage limitation during project implementation (ADB 2012). Cumulative impact assessments (CIAs) are done to determine the summative impacts of past, present, and reasonably foreseeable future developments on valued ecosystem components (VECs). VECs can range from wildlife population to ecosystem services and social development. A CIA can be an integral part of an impact assessment study or can be a stand-alone study. CIAs are frequently used to assess the impacts of multiple hydropower developments within one river network. In this case, the VECs identified will mostly be associated with the river network that the hydropower projects have in common, such as endemic or endangered species, types of habitats, or cultural heritage. When looking at water storage in a broader perspective, CIAs can be used to assess the impacts of multiple water storage projects (e.g., simultaneous im- plementation of multipurpose dams, rural water storage, and managed aquifer recharge) in one basin. CIAs are increasingly required by national regulators and financiers as part of the ESIA process. Environmental flow assessments (EFAs) provide information on how the physical characteristics of a river could change with planned developments, how ecosystem services and biodiversity could be impacted, and how all these changes could affect people and local and wider economies. There are many different methods (IFC 2018) to determine environmental flows, which range from using hydrological and hydraulic data to determine a minimum flow in a river to holistic methodol- ogies addressing the condition of the whole river ecosystem. To be most effective, EFAs should also be an integral part of a wider body of environmental planning and assessment tools, such as an SEA, CIA, or EIA. Biodiversity assessments analyze specific risks and impacts of projects on biodiversity and natural habitats, including through the identification of the types of habitats, species, and ecosystem services potentially affected and consideration of potential risks to and impacts on the ecological function of the habitats, especially those ecosystems that have protected status (national, local, international). Also analyzed is whether the project will pose threats to species that are of significant local interest for livelihoods or nutrition or are of global or national conservation interest (endangered, Red List, etc.) (World Bank 2018a). Following the assessment, a biodiversity management plan may need to be prepared. a For more information, see World Bank 2013. (box continues next page) Tools for Better Storage Throughout the Project Cycle 57 BOX 5.1  Types of Impact Assessments to Maximize Social and Environmental Development (cont.) Project-specific environmental and social impact assessments (ESIAs) are done to determine the potential positive and adverse impacts of a specific project and are frequently required by national legislation or international financiers. An ESIA is often carried out in parallel with the (pre-) feasibility stage of project design and follows a few distinct steps: screening, scoping, baseline study, impact assessment, and mitigation and enhancement measures. Many ESIAs also include an alter- native assessment, but as this is carried out at a stage where most of the strategic decisions on project design (technology used, location) are already taken, this alternative assessment usually takes the form of a description of earlier high-level considerations or focusses on lower-level alternative considerations that can still be influenced. ESIAs are an essential tool to incorporate opportunities for social and environmental enhancement in the project design and are important in building local acceptance and ownership of projects. ESMPs also known as Environmental and Social Management and Monitoring Plans, are the outcome of an ESIA process and provide an overview of all mitigation and enhancement measures that have been identified, who is responsible for the implementation, information on their costs and planning, and who is responsible for monitoring the implementation and effect of the mitigation and enhancement measures. The ESMP is an essential document in which required follow-up of the environmental and social process for a project is made specific. Environmental and social audits are an instrument to determine the actual impacts of existing projects or activities and to what extent mitigation and enhancement measures are effective and adhered. The outcomes of an environmental and social audit may lead to changes in the ESMP or the project as a whole. the Poonch River in the Upper Indus River Basin, the gov- managing environmental, social, and governance issues.1 ernment in collaboration with the International Union for Though the tools are hydropower-specific, many of the is- the Conservation of Nature (IUCN) carried out an SEA in the sues are relevant to other projects related to dams, and the wider Mahaseer National Park, and subsequently conducted organizing framework is relevant to other technologies as a CIA and EFA of a specific hydropower project to determine well (Lyon 2020). the best way to meet development objectives across sec- tors, including hydropower, fisheries, and the environment. It 5.1.2 Greenhouse Gas Emissions and Climate also provided information for an EFA to determine the water Resilience requirements to maintain downstream ecosystems. The methodology employed for those studies provides a useful Given the climate crisis, due diligence of storage invest- model for others in similar situations. (See Jhelem-Poonch ments—large ones, especially—should also include eval- River Basin case study, chapter 8.) uation of the project’s expected greenhouse gas (GHG) footprint. Rivers are major conveyors of carbon from Sustainability audits are useful in verifying the sustainabil- terrestrial areas to lakes and the sea; terrestrial areas are ity performance of a potential storage project and helping generally net carbon sinks, and aquatic systems are net to identify gaps to be addressed before proceeding. In the carbon emitters (World Bank 2017b). The construction case of hydropower, the Hydropower Sustainability Tools, of a dam and impoundment of a reservoir alters the GHG produced by the Hydropower Sustainability Council, offer cycle, resulting in a change in flux of GHGs to the atmo- a comprehensive assessment of project sustainability at sphere compared with the situation before the reservoir different stages of the project cycle, including preparation. was created. Some of the GHGs will be displaced from They include more than 20 topics, including project-affected one part of the river system to another, while additional people, biodiversity, environmental flow regimes, Indigenous GHGs could be released depending on the availability of people, climate change mitigation, and overall systems for carbon and characteristics of the air and water (Liden 58 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE 2017). Research on GHG emissions from reservoirs is a on the project, as compared to other variables, such as relatively new scientific activity, and most studies have population growth, technology, and demand, that remain been conducted during the last 25 years. However, tools difficult to estimate and mitigate. As such, it is necessary have been developed to estimate the potential GHG emis- to employ tools like the Decision Tree Framework (DTF) sions from a planned dam based on a range of environ- in box 5.2. mental and design factors (IHA 2017). Depending on the services the project is being developed to deliver, a dam 5.1.3 Dam Safety During Investment Preparation that is a net emitter of GHGs may still turn out to be a and Implementation climate change mitigation project, depending on the coun- terfactual situation. For dam projects, the management of safety risks be- gins in the investigation and design stage. A dam needs Storage projects may provide opportunities to store GHG. to be designed by experienced and competent profession- For example, as mentioned previously, altering operation als, and certain safety measures should be included in of existing reservoirs or using a wetting/drying method in the design. The International Commission on Large Dams paddy fields can reduce methane emission. In addition, as ICOLD (2005) says, “the traditional approach to dams en- the largest terrestrial carbon pool, soils have a key role to gineering is that in which risks are controlled by following play in climate change mitigation. Soil carbon comprises established conservative rules as to design events and 9 percent of the mitigation potential of forests, 72 percent loads, structural capacity, safety coefficients and defensive for wetlands, and 47 percent for agriculture and grass- design measures.” Based on preliminary assessment, new lands (Bossio et al. 2020). Sustainable soil management dams should be classified based on size and/or poten- practices could increase soil carbon and overall soil health tial hazard. This will inform the design criteria, including while reducing soil carbon losses by promoting reduction the inflow design flood and the maximum earthquake for of soil disturbance, maintaining or regenerating soil cover, which the dam should be designed. For large dams and and maximizing plant and soil biodiversity. Similarly, forest dams that could cause safety risks, irrespective of size, it management (e.g., land preservation, reduced harvest) is good international industry practice (and a requirement can contribute to climate change mitigation by promoting for World Bank financing under ESS4) to establish an inde- forest carbon sequestration. Water storage projects that pendent panel of experts. A panel of experts provides re- include these activities, such as those including sediment view from as early as the investigation phase and through management to prevent erosion, watershed/landscape detailed design, construction, and the start of operations management practices to promote NBS or sustainable (World Bank 2020). The articulation of dam safety plans is agriculture practices, such as climate-smart agriculture, also a critical aspect of securing a new dam for the com- could generate climate benefits, in addition to financial, munities downstream. Dam safety plans that should be environmental, and social benefits. assembled during project preparation are (a) a construc- tion supervision and quality assurance plan; (b) an instru- Given the uncertainty of hydrological flows because of mentation plan; (c) an outline for the eventual operation climate change, it is important to also evaluate whether and maintenance plan; and (d) a framework emergency investments are robust and can withstand a range of cli- preparedness plan (World Bank 2020). mate futures. There exist few tools to inform investment decisions that include an assessment of the climate risks As in the design phase, experienced and competent faced by water resources management projects. Past hy- professionals are needed during dam construction. drology may not be an accurate reflection of future hydrol- According to ICOLD, 50 percent of dam failures occur ogy because of climate change. Downscaling of climate during construction, first impoundment, or the first five projections from time series of general circulation models years of operation (ICOLD n.d.). Dam safety measures for (GCM) may also not be accurate, because of (a) their ir- the implementation period should be built into the bid ten- reducibility to scales relevant to water resource projects, dering process with a detailed and clear scope of work. for example, GCM models are unable to accurately pre- Depending on the complexity and risk involved, it may dict local hydrological variability and extremes, and (b) be necessary to pre-qualify bidders to ensure that only the relative magnitude of the impacts of climate change those with proven expertise can be selected. Review by Tools for Better Storage Throughout the Project Cycle 59 BOX 5.2  Confronting Climate Uncertainty in Water Resources Planning and Project Design Approach. How do you know if a new potential storage project is resilient to climate change? In 2015, the World Bank introduced a Decision Tree Framework (DTF) to help identify and manage climate risks in water resourc- es projects (figure B5.2.1). It takes into consideration local realities and sensitivities and builds bottom-up through a four-phase hierarchical process to prepare a Climate Risk Management Plan and Climate Risk Report for the project under evaluation. In the first phase, Project Screening, the decision-maker explores climate sensitivities in context of the four C’s: choices, consequences, connections, and uncertainties. In phase 2, Initial Analysis, a rapid project scoping exercise is conduct- ed using a simplified water resources system model that compares climate impacts with existing variability, population growth, and other variables to see if climate is a dominant factor. Phase 3, Climate Stress Test, combines historical data, global climate model projections, a hydrologic-economic water system model, and other elements to determine the plausi- ble climate risk. And finally, in Phase 4, the decision-maker tests for robustness—returning to phase 3 if adjustments can ensure robustness, or to phase 1 if there is a need to redesign the process. FIGURE B5.2.1 Decision Tree Framework Phases IDENTIFYING AND MANAGING CLIMATE RISKS CLIMATE RISK MANAGEMENT PLAN THE CLIMATE CHANGE & CLIMATE RISK REPORT DECISION TREE Ensure project robustness is documented * A scientifically defensible, flexible, cost-efficient tool on climate risks * A bottom-up approach that takes into YES account local realities and climate sensitivity If project robustness is Can the project cope not achievable, the project PHASE 4 with potential climate is adjusted and put CLIMATE RISK changes in the system NO through Phase 3 again, MANAGEMENT ("robustness")? or a redesigned project starts at Phase 1. YES Exhaustive climate risks analysis: PHASE 3 Combines historical data, global climate CLIMATE RISK What is the plausible Climate LOW Risk Report model projections, a hydrologic-economic STRESS TEST climate risk? water system model, and other elements YES A rapid project scoping exercise, using a simplified water resources system PHASE 2 Is climate Climate NO Risk Statement model that compares climate impacts INITIAL a dominant factor? with others such as existing variability, ANALYSIS population growth, and other variables YES Climate sensitivity PHASE 1 Climate screening for all Is the proposed project PROJECT NO Screening Bank projects: climate sensitive? SCREENING Worksheet Is climate a factor to take into account? Source: Ray and Brown 2015. (box continues next page) 60 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE BOX 5.2  Confronting Climate Uncertainty in Water Resources Planning and Project Design (cont.) For projects exiting the decision tree at Phase 3, cost-benefit analyses must include safety margins and sensitivity analyses, given that these projects were identified in Phase 2 as having significant potential sensitivities to climate change, though current climate change projections do not indicate a high likelihood of resulting system failure (relative to performance threshold). Four descriptors that might be used to characterize the robustness of a project in Phase 4 are (a) climate sensitive, that is, whether its performance is affected by climate at all; (b) reliable over a wide range of climate risks, that is, though it might be sensitive to climate change, its performance thresholds might not be violated; (c) vulnerable to very costly failures, that is, though it might resist failure, if it does fail, it might fail catastrophically; and (d) resilient, that is, able to recover quickly from failure to previous levels of performance. The DTF provides a scientifically defensible, flexible, cost-efficient tool for assessing climate risks. In the Chancay- Lambayeque watershed in Peru, the DTF was applied to assess the robustness and resiliency of the system to climate risks and inform prioritization of infrastructure interventions to address inadequate water supply, flood risk, and environmental degradation. Good Practices. When evaluating risks faced by a proposed water project, it is important to include climate risks alongside economic, politi- cal, and other natural risks. When evaluating the relative importance of climate and non-climate factors, one might consider initial water stress conditions, recent local climate and demographic trends, and length of project life. One must use outputs from all available GCMs to ensure that the largest available subset of possible climate futures is applied. Stakeholder consultation is fundamental to the bottom-up approach and must be used for characterizing historical system performance, desired future performance thresholds, and vulnerabilities to change. an independent panel of experts throughout the procure- considerable. Most likely the period of diverting the river ment and construction process of complex and high-risk discharges will be selected to coincide with a dry season, projects offers significant value as members can suggest and any delay in construction progress of a dam closing cost-saving design alternatives and identify project risks section may threaten timely completion as well as the from an early stage. Preparation of dam safety plans for quality of the dam. Completing a closing section of a dam the construction period is critical. Monitoring against the in a hurry because of time pressure may lead to compro- construction supervision and quality assurance plan and mised construction and be a safety risk. The dam safety implementation of other dam safety plans are also crucial, panel and authorities responsible for supervision should as is the selection and use of the right construction mate- carefully review the proposed method of execution and rials to ensure the dam’s structural integrity under design make sure that the contractor has a viable plan B in case stresses. of a delay or another accident. Critical conditions during construction that require care- Another critical point will be the time of first filling of a ful analysis include the flood discharge that will be ad- reservoir. Often that will be allowed to commence when opted for the temporary river diversion. The recurrence a dam body has reached a certain elevation. The pace of period of such flood may be adopted rather low in order to raising the reservoir level often should not exceed a certain limit the capacity as well as the cost of a diversion. When prescribed speed. However, in case of an extreme inflow, a diversion tunnel needs to be constructed, its cost can be the pace of raising could be higher and require immediate Tools for Better Storage Throughout the Project Cycle 61 release of the excess inflow. In that case, a flood release exhaustible resource, constructed for use over a predict- structure with sufficient capacity should be operational. ed design life calculated based on sedimentation rate and Another period with higher risk occurs during and just trap efficiency. At the end of this life, the infrastructure is after first filling of the reservoir when the underground and decommissioned. This attaches with it certain issues of the dam abutments are being saturated. During this peri- generational equity (with costs borne by future genera- od the performance of the dam should be carefully mon- tions), which are heavily discounted in the initial economic itored visually and by piezometers and surface beacons, analysis. Decommissioning also creates a need for new and any leakage discharges should be recorded in order reservoirs—a costly and inefficient cycle. Instead, proper to be able to make decisions on how to proceed in case planning for sediment management can ensure that the of unexpected behavior. The stage of first filling is a period lifetime of a storage option is properly estimated and can in which the occurrence of dam breaches is higher than in realistically be attained. Box 5.3 provides further informa- other periods. tion on the life-cycle approach to sediment management in storage planning. 5.1.4 Early Consideration of Sediment Management 5.1.5 Funding for Storage Investments Planning for sediment management must begin during project conceptualization. Traditionally, dam reservoirs Funding can be a critical constraint to storage develop- and other forms of storage have been treated as an ment. Especially for large investments with high capital BOX 5.3  A Life-Cycle Approach to Sediment Management Approach. A life-cycle approach to infrastructure planning means reservoir storage is actively planned to perform as a renewable resource and sustained through the incorporation of sediment management technologies from the beginning of the project. The World Bank first introduced the life-cycle approach in the reservoir conservation approach, or RESCON model, in 2003 to identify technically and economically optimized reservoir sediment management strategies. The Bank has since upgraded the approach and added further guidance on practices for hydro and water supply projects. Sediment management integrates one or more of the following three options: (a) reducing sediment yield from upstream, typically using reforestation and construction of sediment retention structures, (b) sediment routing (managing flows during high yield to minimize trapping), typically through sluicing, bypassing, and density current venting, and (c) redistri- bution from active to dead storage zones or removal of deposits through flushing, hydraulic, or mechanical dredging. In addition to using these methods to manage sediments at headworks, in a run-of-river project one must consider removal of sands from water diverted for power generation. Common challenges relate to flow imbalances, hydraulic short-circuiting, and excessive hydraulic loading. An example is the Dasu Hydropower Project, a 4,320-MW run-of-river facility to be constructed on the Indus River. To preserve reservoir volume and protect hydraulic machinery, the project is designed to be equipped with outlets and flush- ing tunnels that can jointly be used to discharge 4,400 cubic meters of water per second to remove deposited sediment (Annandale, Morris, and Karki 2016). Finally, adaptive strategies can be taken up where, instead of handling deposited sediments, storage volumes and equip- ment are modified. Examples include raising dam walls, applying protective coatings on equipment, and providing sacrificial civil structures. (box continues next page) 62 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE BOX 5.3 Box .  A Life-Cycle Approach to Sediment Management (cont.) 5.3  When choosing between options, one must consider technical as well as economic feasibility. Consider for example the case of hydrologically large reservoirs holding 0.5 times mean annual inflows. Flushing and dredging become unfeasible both from a cost and technical effectiveness perspective. Monitoring and management must therefore commence as early as possible, and sediment inflows restricted to the extent possible. Planning considerations must include hydrologic data, suspended sediment data, long-term sediment yield and variability calculations, hazards posed by extreme events, sedi- mentation modeling, and a careful consideration of upstream and downstream impacts. Resources: Annandale, Morris, and Karki 2016; Palmieri et al. 2003; HydroSediNet: https://www.hydrosedi.net/ Hydropower Sediment Management Knowledge Hub: https://www.hydropower.org/sediment-management outlays, loan or additional equity financing may be needed small number of buyers. This independent power producer to supplement internal budgets of the entity developing model has few parallels in bulk water supply and none for the project. Funding may come from private and/or public other water storage services like flood protection. sources, including development assistance in the form of loans or grants. Because of their revenue-generating po- Publicly financed storage projects can more easily be tential, some types of storage projects may be more likely developed to meet development goals. When govern- to obtain private repayable financing; other investments, ments are the primary or only shareholder of a storage because of their development importance and contribu- project, they can exercise a greater degree of control tion to other related development goals, may be higher over how those facilities are designed and operated, in- priority for limited government-backed funding through cluding whether to design them as multipurpose facilities budget allocations or earmarked sources. Large, trans- and which sectors are prioritized for use. They also have formational storage projects also need “patient” financing more control over the tariffs that will be paid for the ser- (long-term financing, with a grace period and low interest vices provided by those facilities (Plummer Braeckman, rates) as the risks owing to technical uncertainties are Markkanen, and Souvannaseng 2020), which may be in- highest at the start of the project and diminish with time. fluenced by factors other than cost recovery and profit maximization, such as affordability and impacts on pover- Storage assets, such as hydropower facilities or facil- ty reduction goals. In some sectors, like hydropower, fully ities supporting agricultural production, have benefit publicly funded projects are, however, becoming less com- streams that can be monetized to secure the loan or mon. Since 2000, fewer hydropower projects in low- and equity financing that is needed for their development. middle-income countries were funded exclusively from Water stored in hydropower reservoirs, for example, gener- public sources. China is the exception. Projects there have ates revenues tied to electricity tariffs, which tend to better been developed largely with public sector money, much reflect the real cost and value of energy services compared of it provided by domestic development banks (Plummer to water tariffs, which are typically well below the real value, Braeckman, Markkanen, and Souvannaseng 2020). and sometimes the cost of providing water. Reservoir and pumped storage hydropower facilities generate ancillary In low- and middle-income countries, public funding services, including voltage and frequency control, for the for water storage investments often involves develop- electrical grid that can be monetized; while markets for ment assistance. This may come either from develop- ancillary services are underdeveloped, this function of res- ment banks such as the World Bank or regional banks ervoirs for energy storage is increasingly recognized and like the Asian, African, and Inter-American Development being remunerated (IEA 2021). Privately funded hydropow- Banks, or from bilateral aid agencies. For hydropower, de- er schemes also have long-term off-taker arrangements velopment financing institutions have provided most of that provide for the sale of power to a single buyer or a the public investment, which for the period 2013 to 2017, Tools for Better Storage Throughout the Project Cycle 63 amounted to more than $37 billion on average each year to the table, multilateral institutions can offer partial risk (IRENA and CPI 2020). From fiscal years 2000 to 2017, guarantees and political risk insurance. These PPP ar- the World Bank committed over $8 billion in financing for rangements are more common for hydropower facilities, hydropower projects, which is more than one-third of the though they exist in other subsectors, such as municipal financing it provided for all renewable energy technolo- water supply. There are few examples, if any, of PPPs in gies during that period (IEG 2020). Projects supported a classic sense in smaller, distributed water storage or by multilateral development banks are reputed to take for nature-based storage, but there are many examples longer, but there is limited evidence on how those de- of non-government interest and funding arising from lays compare to public-private partnership (PPP) proj- community or civil society sources. Further, the pricing ects, and some research points to delays being more of ancillary services provided by hydropower, including closely related to country context (Plummer Braeckman, for ramp-up of production for grid stability—a form of Markkanen, and Souvannaseng 2020). Climate financ- reliability that has opened the possibility for more cost ing, much of which is administered through development recovery—is providing greater incentive for private sector financing institutions, is another source of funding for financing of hydropower. While a relatively new concept, storage projects, but the amounts committed have been the exploration of pricing of ancillary services of storage relatively limited. Funding for mitigation projects far ex- to increase reliability beyond hydropower in other water ceeds the funding available for adaptation from climate sectors, may yield better cost recovery from reservoirs funds. In terms of water storage, hydropower projects, (IEA 2021). which can generate certified emission reduction credits (carbon credits), have received some limited mitigation Financing innovative NBS with few immediate/direct- financing ($693 million between 2003 and 2018), while ly monetizable benefits through traditional means can adaptation funding for water storage has been focused pose an impediment to their adoption, but in recent on small-scale interventions such as water harvesting, years, investment has been increasing. In 2015, an esti- small-irrigation, micro-dams, and landscape-related in- mated $25 billion was invested in nature-based infrastruc- vestments (CFU database 2022). ture for water worldwide and increased annually by more than 11 percent between 2013 and 2015 (Bennett and Private involvement in storage investments can take Ruef 2016). Historically, there have not been many spe- many forms. There are several different models of pri- cific financing mechanisms for investment in NBS (Davis, vate sector participation when it comes to storage proj- Krüger, and Hinzmann 2015). In the water sector, these ects, ranging from fully private endeavors by private investments have been dominated by government-subsi- utilities or captive projects developed by industry for their dized efforts at the local scale (WWAP 2018), concession- own use, to PPPs with varying degrees of private inter- al financing, and grants allocated by governments, which est and control. For larger, centralized storage projects may be motivated by potential social and environmental with higher capital costs, private sector actors may be co-benefits, private finance pursuing opportunities for involved as equity partners; in such cases, there might green investing, and development finance incentivized to be split ownership of facilities or the creation of special maximize resilience, sustainability, and poverty reduction. purpose vehicles with multiple shareholders, including For example, in Monterrey, Mexico, where urbanization on public and private investors. Private operators can be the floodplain of the San Juan River Basin has left it sus- brought in for publicly owned facilities through a conces- ceptible to both floods and droughts, stakeholders have sion agreement or an operation and maintenance con- worked together to develop the Monterrey Metropolitan tract after commissioning. Alternatively, a PPP can be Area Water Fund. This fund, which aims primarily to re- extended through construction and operations by way duce the impacts of floods and maintain safe access to of build-operate-transfer or build-own-operate-transfer affordable drinking water, focuses on the rehabilitation arrangements, where private partners source their own of the watershed to improve green storage capacity. This financing for project construction and retain control (and has been done through reforestation and land and soil in some cases ownership) of the asset for some time conservation in areas of the watershed that produce 60 before handing it over to the government. To reduce the percent of Monterrey’s water supply. See the case study in risks of such investments and attract private partners chapter 8 for more information. 64 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE Other sources of private finance are emerging for both positive tangible and intangible effects due to the project. NBS and built storage options that meet high environ- The guidelines issued by environmental protection agen- mental, social, and governance standards. Green bonds cies or the concerned ministries for impact analysis gen- and other sources of green financing are on the rise and erally refer to the impacts of development projects during have the potential to mobilize much more financing for the life cycle of the project, positive and adverse, and miti- sustainable water storage projects. The demand for green gation/compensation measures, in addition to monitoring bonds actually outstrips the ability of green bond issuers activities to implement corrective measures. Construction to identify and validate eligible projects (OECD 2022). This of projects might involve temporary structures, which also fast-growing asset class has increased the amount and need to be safe and minimize their disruption on natural diversity of financing options available to water storage systems. Also, special consideration should be given to projects (box 5.4). the interaction of the new project with the existing envi- ronment and infrastructure base. For instance, in the case 5.1.6 Implementation of Storage Solutions of cascade systems, the impacts of the project on existing facilities should be examined. Any water storage project involving construction of new infrastructure must fulfill the requirements of tech- Along with population growth and higher awareness of no-economic viability, environmental safeguards, and environmental damage from construction of water stor- social acceptability. Detailed project reports are prepared age projects, more stringent laws and procedures for according to the guidelines and standards, which need to protection of environment and ecology have been en- be progressively revisited to account for technological ad- acted in recent decades. In addition to feasibility studies, vancements, new issues, and safety concerns. Reports of environmental impact assessments have been made for impact assessments on environment and social aspects the guidance of state agencies. Necessary safeguards are expected to give a complete picture of the overall are an essential part of decision-making and evaluation BOX 5.4  Green Financing Problem. Financing available through traditional public sources, such as tariffs, taxes, and transfers, are often insufficient to finance infrastructure owing to tight public budgets and low tariffs driven by affordability and political constraints. Against this backdrop, financing innovative nature-based solutions with few immediate/directly monetizable benefits through traditional means can pose an impediment to their adoption. Alternative financing opportunities exist in the form of concessional financing and grants allocated by governments motivated by potential social and environmental co-benefits, private finance pursuing opportunities for green investing, and development finance incentivized to maximize resilience, sustainability, and poverty reduction. Approach. Instruments used for leveraging private sector funds for green financing include: Water funds: Downstream water users, including private sector companies, agricultural producers, and hydropower plant managers, may join forces with upstream communities, water utilities, and conservation nongovernmental organizations (NGOs), to create water trust funds for investing in catchment restoration upstream. This is a type of payment for ecosys- tem services (PES). In many cases, a multi-stakeholder governance board monitors project impacts and selects/identifies new investment opportunities. This model is seen in the Greater Cape Town Region, where catchment restoration through the elimination of invasive plants was assessed to deliver greatest gains in water supply at the lowest unit cost. Highly replicable, there are 24 such water funds known in Latin America and two in Africa. (box continues next page) Tools for Better Storage Throughout the Project Cycle 65 BOX 5.4  Green Financing (cont.) Green bonds: Issued to raise funds for investments that generate environmental or climate co-benefits alongside a finan- cial return. Proceeds from the bond issue are used for eligible investments defined upfront together with evaluation and selection criteria for such investments. They help finance green infrastructure by spreading the costs of the project over its useful life in the form of periodic fixed income payments. An example is the 2017 issuance of £250 million Green Bonds by Anglian Water Pvt. Ltd. for 60 green projects, including construction of wetlands in the river Ingol watershed with the poten- tial to generate £10.4 million in cost savings related to water treatment, as well as 53 percent water consumption savings, 89 percent reduction in CO2 emissions (lower energy use and lower levels of dissolved organic carbon), adaptation benefits (flood risk reduction), and biodiversity co-benefits. Environmental impact bonds: Impact bonds use proceeds for a particular green investment and links payouts to the per- formance of the investment in order to share risk with investors who are encouraged by the model to conduct own due-dili- gence and may earn reputational benefits from investing in these projects. A golden example is the 30-year, tax-exempt $25 million bond issued by DC Water to two private investors, for financing installations to reduce stormwater runoff and thereby reduce dumping of combined sewer overflow into its rivers, thereby protecting the city’s watershed and ecosystem. Similar models are now being replicated in cities around the United States. Other instruments: Include tax increment financing, business improvement districts, stormwater retention, and credit trad- ing, stormwater purchase agreements, insurance payments for risk reduction, corporate stewardship to protect own source waters, and traditional public-private partnerships (PPPs). On the public side, there are general transfers, earmarking of revenue, dedicated service fees, issuance of municipal bonds, and environmental mitigation/compensation funds into which payments must be made for causing unavoidable impacts on ecosys- tems. Meanwhile development finance institutions can contribute through direct lending or pay-for-success financing models. Climate Finance. Water storage projects can generate payments for emission reductions or increases in carbon sequestration. Restoration of forests, through afforestation or reforestation, peatland, and wetland restoration, in addition to agricultural practices that promote sustainable soil management, could generate carbon benefits. Such emission reductions or enhanced carbon storage may allow land managers to leverage finance from entities in the private sector, civil society, multilateral funders, or buyers in the carbon market seeking to offset emission, as well as potentially contributing to Nationally Determined Contributions (NDCs) and other existing measurement, reporting, and verification (MRV) frameworks (World Bank 2021c). The Ethiopia Humbo Assisted Natural Regeneration project is an example of tapping into climate financing instruments to improve land degradation, in addition to other environmental and economic benefits. Supported by the World Bank’s BioCarbon Fund, the project has taken a community-based approach to land restoration in the Humbo region, a drought-prone area where around 85 percent of the population live in poverty (Donaldson 2009). Poverty, hunger, and increasing demand for agricultural land have driven local communities to over-exploit forest resources, which threatens groundwater reserves that people depend on for potable water. Soil erosion is also a severe problem in the Humbo region, which is exacerbated by heavy rain events. Among the results and achievements of the project (World Bank 2015), in less than four years, the project has restored 2,700 hectares of previously degraded land in Ethiopia and boosted crop yields. The project’s community-based approach has made a lasting environmental impact and generated emission reductions that provide revenue that is invested back into local communities (e.g., carbon payments are made to the community to invest in grain mills, storage, and com- munity infrastructure). (box continues next page) 66 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE BOX 5.4  Green Financing (cont.) Good Practices. In situations where affordability and/or collectability of revenue streams associated with benefits of green storage are low, and long-term-income guarantees are absent, such as urban sponges for flood management, public instruments and concessional funding must be used to leverage private funds. Countries must develop policies and institutional and regulatory frameworks to support the leveraging of private finance for green investments. Measures can include tax incentive programs, performance-based subsidies or conditional transfers, promoting market-based approaches, clarifying risk-sharing mechanisms for PPPs, and setting up dedicated offices for guiding and planning investments. Resources: Browder et al. 2019; Dougherty, Hammer, and Valderrama 2016; and Wishart et al. 2021. The Nature Conservancy. Water Funds Toolbox. Accessed March 10, 2022. Available at: https://waterfundstoolbox.org/project-cycle Donaldson, K. 2009. Humbo Community Managed Forestry Project, Ethiopia. Climate Change, Community Forestry and Development, Climate Change Case Studies, World Vision Australia, Farmer Managed Natural Regeneration (FMNR). Accessed March 10, 2022. Available at: http://fmnrhub.com.water storage. processes, and in almost all countries, new projects are information throughout the project life cycle. Involving now subjected to environmental impact assessments communities in the implementation of small-scale stor- (ICID 2004). Any assessment needs to be generated ac- age and NBS is important, particularly for those solutions cording to the legislative framework applicable to the that require their action to ensure sustainability and main- project. In some cases, there is a law on environmental tenance during operation. assessments that provides for the procedure and matters related to environmental assessment of projects in which the government is involved either directly in implemen- 5.2 OPERATING AND MAINTAINING tation or indirectly by providing approval or permission EXISTING STORAGE for implementation. Other policies to consider are those potentially covering water resources, environmental pro- Beyond the planning phase, utilizing best practices in tection, prevention and control of water pollution, forest operating and maintaining water storage can not only conservation, and resettlement and compensation mea- extend the life of water storage assets, but make them sures, among others. operate more efficiently as well. Each storage type, whether built or natural, is connected through the larg- The implementation of water storage solutions requires er hydrological system and, thus, should be managed an inclusive approach across all sectors and all gov- as such. For example, operational rules of built storage ernment levels. National agencies provide leadership in should consider ecological flow regimes in the wet and dry the definition of the water storage solutions being imple- seasons. Monitoring the water resource, in addition to the mented, but considering the multifaceted nature of these storage type, is also important, so that adjustments can solutions, cross-sectoral collaboration is necessary to be made to storage operations to adapt for changing hy- ensure sound optimization of outcomes across the coun- drological conditions. In terms of maintenance, the needs try’s development objectives. In addition, the decisions of natural and built infrastructure may look very different, and actions of society will determine the ultimate effec- but maintenance is critical for optimal operation, extend- tiveness of government efforts. Water storage projects ing the life of the storage type and ensuring its safety. need to equally prioritize technical expertise with social Water storage facilities that are properly maintained can engagement through dedicated programs to promote deliver services for decades without the need for major stakeholder participation, social inclusion, communica- refurbishment; in contrast, facilities that are improperly tion, education, research, and ensuring public access to operated and neglect routine maintenance will be prone to Tools for Better Storage Throughout the Project Cycle 67 defects and will frequently need to be refurbished. In the sediment cores, and characterization of suspended sed- worst cases, poorly operated and maintained storage as- iment concentration and particle size distribution in water sets may undermine their very objective and even become delivered to turbines and outlet works. the danger themselves; this is especially true for reser- voirs that have become filled with sediment and offer little Continued monitoring and adaptation of outcomes to no flood control for the communities that have settled to meet environmental flow targets are also needed. downstream of them. Operational rules will need to be implemented to main- tain the agreed ecological flow across days or seasons. It is good international practice to begin preparation of Additional changes may be needed to meet water quality an operation and maintenance strategy during the fea- targets, for example (Linnansaari et al. 2012; Williams et sibility stage of water storage project preparation. Early al. 2019). consideration of how a facility will be operated and main- tained can have many benefits, including improving inves- Dam safety is also a critical consideration in operation tor confidence. It may also influence the final design of and maintenance. Currently, there are more than 58,000 major components. A well-developed operation and main- large dams registered with ICOLD with several million tenance strategy will include (a) a diagnosis of the asset smaller dams estimated to exist globally. Dam failures fleet and operational environment; (b) objectives with key are rare events, but the consequences of failure can be performance indicators; (c) a set of activities and plan for significant, with major failures resulting in loss of life and their implementation; (d) contractual arrangements; (e) a damage to infrastructure, communities, and the ecosys- human resources plan; and (f) cost estimates and funding tems located downstream. While dams are generally plan (World Bank 2020b). becoming safer thanks to improvements in design, con- struction methods, and surveillance, other factors have Operation and maintenance of water storage includes led to increased risk associated with dams, including preventative and corrective maintenance that is nec- changing hydroclimatic variables from climate change essary for the smooth functioning of the assets and and shifting settlement patterns with more people mov- to detect inefficiencies and defects that might lead to ing into the areas downstream of dams. The global stock a failure. Operation and maintenance of water storage of dams is also aging, which is increasing the needs for assets includes regular safety inspections, assessing the major maintenance and refurbishment. About a third of condition of assets, purchase and installation of spare the current stock of large dams have been operating for parts, repairs, and monitoring of instrumentation. In many 50 years or more (Wishart et al. 2020). For hydropower, instances, routine maintenance is delayed due to budget nearly half of global capacity is more than 30 years old constraints. It cannot always be avoided, but deferred (Morgado et al. 2020). It is extremely important to ensure maintenance can accelerate deterioration and increase that dams are structurally sound and have essential dam the costs of corrective measures. safety management measures in place due to the fact that so many people and economic sectors depend on For dams and reservoirs, a life cycle or sustainable use dams functioning safely (Ueda, Pons, and Lyon 2021). See approach to sediment management can be applied both box 5.5 on risk-informed dam safety management in India to new and old projects. In the case of old projects, this and the case study on dam safety in Indonesia (chapter 8) means modifying initial operations configurations to im- for further details. prove the balance between sediment in- and out-flows, while continuing to generate significant benefits. In the face of significantly reduced storage volumes, hydropow- 5.3 REOPERATING, RETROFITTING, AND er projects may be forced to transition to run-of-river or REHABILITATING EXISTING ASSETS power peaking operations with operational and structur- al modifications. This option is unavailable to reservoirs 5.3.1 Reoperating meant for water supply, irrigation, and other consumptive uses. Monitoring is critical to sediment management and Large gains in water storage services, such as enhanced must include periodic bathymetric surveys, analysis of flood mitigation, improved hydropower generation, or 68 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE BOX 5.5  Risk-Informed Dam Safety Management Increasingly, risk-informed approaches to dam safety are being employed due to recognition that some dam safety inci- dents caused by non-structural issues may not be well-captured by the traditional standards-based approach. Risk-informed approaches can range from relatively simple qualitative analysis to rigorous, quantitative methodologies based on the prob- ability of failure (figure B5.5.1). These approaches require more institutional capacity, but they can lead to more efficient allocation of financial resources and prioritization of measures and monitoring activities. FIGURE B5.5.1 Risk Analysis Tools for Dam Safety Dynamic simulation HIGH model for EPP Preliminary consequence assessment study, and consequence Dam break, inundation Preliminary risk classification Semi/full quantitative risk analysis assessment Essential level MODERATE Full PFMA Risk level Simplified PFMA Risk index matrix LOW Insufficient, inadequate Adequate Knowledge level Source: World Bank 2020a. Note: EPP = emergency preparedness plan; PFMA = potential failure mode analysis. For countries or companies with a large portfolio of dams, portfolio risk assessment techniques that can provide a com- parative estimation of risks overall are being used with more frequency. The Risk Index Method is a basic, qualitative portfolio risk assessment tool, relying mostly on visual inspection of dams, that enables screening across a portfolio of existing dams using color-coded risk matrices or additive scoring methods to characterize the likelihood of failure. It is not a measure of risk based on the estimation of failure probability for individual dams but provides a relative indication of potential risk within the portfolio and, as such, is helpful for evaluating and prioritizing safety issues in a systematic way. Several countries have developed risk index (or similar) tools, including Australia, Canada, the Czech Republic, New Zealand, Poland, the Republic of Korea, and South Africa. In India, the Central Water Commission (CWC) is developing a risk index scheme, which it intends to apply to over 5,000 large dams. Under CWC’s Risk Index, risk is defined as the product of fragility of the dam and the potential hazard associated with the dam with fragility scored according to three subcategories: (a) technical characteristics of the dam; (b) existing conditions of the dam; and (c) safety plan for dam safety (table B5.5.1). Good Practices. Portfolio risk assessment, using risk indexing, can be supplemented by more advanced risk assessment methods for higher risk dams. Some critical failure modes could be missed or underestimated because risk indexing approaches largely rely on visual inspection of the condition of dams (World Bank 2021e). Refer to the Technical Note on Portfolio Risk Assessment Using Risk Index (World Bank 2021b) for methods of developing a risk index considering potential failure modes of dams. (box continues next page) Tools for Better Storage Throughout the Project Cycle 69 BOX 5.5  Risk-Informed Dam Safety Management (cont.) TABLE B5.5.1 Fragility Categories and Factors for Central Water Commission’s Risk Index Scheme TECHNICAL CHARACTERISTICS EXISTING CONDITIONS SAFETY PLAN 1 Dam age 1 Seismic design 1 Design documentation 2 Inflow design flood 2 Installed flow control equipment 2 Operation and maintenance manual 3 Seismic zone 3 Flow control equipment condition 3 Emergency preparedness plan 4 Landslide, glacier lake 4 Presence of backup power 4 Organization, staff number, capacity, outburst flow, landslide dam qualification outburst flow, debris flow 5 Length 5 Access to site 5 Safety inspection, monitoring, and reporting 6 Conduits 6 System operation 6 Dam safety reports, analysis, and interpretation 7 Filters 7 Concrete gravity structure 7 Follow-up actions 8 Foundation and abutments 8 Spillway structure 9 Masonry structure 10 Embankment, foundation, and abutments Source: World Bank 2020a. A first step in portfolio risk assessment is establishing the portfolio. In India, the World Bank supported development of a web-based system for dam-related asset inventory and management under the first Dam Rehabilitation and Improvement Project (DRIP I, 2010–2021) by bringing together stakeholders across the federal government. The system now contains a basic inventory of 5,000 large dams and comprehensive records for about 1,485. Several thousand small dams are not included in the inventory at present. It will be further developed under the DRIP II project to include automatic monitoring, data acquisition, and operational systems. Resources: Wishart et al. 2020; World Bank 2020a, 2021b. the minimization of water loss from evaporation, can inform dam operators how to make decisions on releases come from reoperating current water storage. Dam op- in a systematic way that balance coexisting water uses erating rules are often determined at the time of dam de- and protection of the ecology. Some DSS are general- sign and are often not updated to reflect changing water ly supported by a hydrodynamic model and can include availability and patterns of water use downstream. In forecast of flows and of climate as well as optimization other cases, dams may be designed to provide a range of for cascade systems. Such is the case of the multipur- services (from hydropower to irrigation to flood control) pose Tres Marias dam in the São Francisco River, in the but, for various technical and non-technical reasons, are Brazilian state of Minas Gerais, which provides hydropow- only ever operated to meet the demands of the primary er generation, flood control, navigation, municipal and service. There are many examples of large gains obtained industrial water supply, and irrigation. It is one of several through the reoperation of existing systems. Decision large multipurpose reservoirs located in the São Francisco support systems (DSS)2 have been widely used to better River and its tributaries. An operational forecasting and 70 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE DSS were developed that integrate different sources of world’s large dams are used for hydroelectric generation ground information, remote sensing data, and numerical (Yuguda et al. 2020), offering an opportunity to consider weather predictions with hydrological and hydrodynamic retrofitting those dams to enhance their capabilities. In the models to generate short-term flow forecasts for up to 15 United States alone, there are more than 50,000 suitable days ahead for each of the reservoirs (Miltenburg n.d.). non-power dams with the technical potential to add about 12 GW (31 TWh/year) of hydropower capacity through Given advancements in inflow forecasting, it is possi- retrofitting (United States Department of Energy 2018). ble to increase the value of services provided by dams Compared to the construction of a new dam, and under through the employment of forecast-informed reservoir certain conditions, retrofitting can provide a cost-effective operation (FIRO). By altering reservoir levels based on way to increase and enhance/optimize water production. short- or long-term forecasts (to increase storage capac- Impact on the environment can be less severe as most ity in advance of a flood event or to conserve storage if substantial impacts have already been caused through a dry spell is predicted), additional storage services can the initial project construction (Energypedia 2015). With be delivered through better deployment of existing infra- around 30 percent of dams worldwide being multipur- structure. The FIRO case study provides a methodology to pose (OECD 2017) and increasing demand for storage assess the feasibility of and to pilot FIRO in two reservoirs services in some areas, it is crucial for policy makers to in California (see case study, chapter 8). Good hydromete- comprehend and plan for growing trade-offs between key orological monitoring capability is an essential ingredient functions by allowing provision for multipurpose use in for implementing FIRO; increasingly, machine-learning as- law and policy, as well as through developing capacity for sisted tools are proving effective for probabilistic forecast- such multi-sector work to occur. ing, using both in situ and satellite-based observations. Retrofitting involves different options and can serve Reoperating dams can provide drought relief in the different purposes. To meet base or peak electricity de- short term, in dire situations of water shortage. From mands, reservoirs that are already in existence for other 2015–18, the City of Cape Town experienced a 1-in-590- purposes can be fitted with hydropower generators year drought, and water storage was critical to managing (Yuguda et al. 2020). Existing non-power dams can be ret- water supplies during it. In addition to demand manage- rofitted for hydropower generation without the costs and ment measures, short-term water exchanges or transfers impacts of additional dam construction. Similarly, existing (e.g., from agriculture to urban use) proved important. hydropower dams may be retrofitted with more efficient Cape Town arranged a transfer of water from a group variable-speed turbines and higher capacity generating of irrigators in an area that had a surplus. In order to be equipment. Retrofitting can also be used to facilitate sed- able to manage storage in this fashion, clear water alloca- iment sluicing (Sumi et al. 2015) and improve sediment tion mechanisms and policies were necessary. The Cape management (Kondolf et al. 2014), modifying dams to Town experience illustrated that water allocations (and accommodate probable maximum flood (Graham 2000), associated water rights) from the integrated system need earthquake retrofitting to improve reliability and safety, to be regularly updated to ensure that these rights fall and returning the reservoir to its original storage capaci- within the available yield for a given assurance of supply. ty (Santa Clara Valley Water District 2021). Operators can In the absence of this, the system will be less secure and have more operating flexibility, which can be translated into the impacts of droughts more severe. potential cost savings, if facility equipment is retrofitted to adjust to changing operating conditions. Instrumentation 5.3.2 Retrofitting retrofitting could also be used for continuous monitoring and inspection of dams to identify timely rehabilitation and Retrofitting existing storage can provide new services for dam safety purposes (Melih Yanmaz and Ari 2011). As without building an entirely new project. Retrofitting mentioned above for reoperations, hydrometeorological refers to the addition or expansion of the production ca- monitoring and forecasting data is critical; without this in- pabilities of an existing water storage facility, including formation, reservoir operation is less flexible and may not electric power generation or water supply services or flood be able to capture the potential benefits of increased water control.3 According to ICOLD, fewer than 20 percent of the supply, hydropower generation, and flood control. Tools for Better Storage Throughout the Project Cycle 71 Retrofitting with floating solar panels, or incorporation infrastructure in the Gorno Badakshan Autonomous Oblast of solar panels into facets of storage facilities such as region, Tajikistan. Pamir Energy Company was formed irrigation channels, can create synergies with the elec- through a PPP with the Government of Tajikistan act- trical sector by reducing investment in electrical grid ing as regulator, and the Aga Khan Fund for Economic infrastructure or by providing electric supply for onsite Development, a private NGO, which has a controlling 70 consumption. Many reservoirs, especially those of hydro- percent share of the company. The International Finance power plants, have nearby grid connections to which the Corporation (IFC, whose debt was converted into equity in floating solar panels could connect. Usually, dry seasons 2007) has a 30 percent share. Pamir Energy Company has with less water flow correspond to periods of high solar a 25-year concession agreement, allowing a long-term ap- potential and vice versa. Combining the two technologies proach and flexibility with respect to returns. Through WB- in some areas can reduce seasonal variations in power IDA and IFC financing and a Swiss grant for subsidies for production. Also, a hybrid system can optimize the diurnal poor consumers, the power supply in the region improved cycle by leveraging more solar power during the day and hy- from only around 3 hours per day to around 24 hours of dropower at night. In the case of large irrigation reservoirs, power supply per day in winter to customers of the main water treatment plants, cooling ponds for industrial use, or grid (over 70 percent of the total customers) (Jumaev n.d.). other energy-intensive infrastructure, the onsite self-con- Experiences like this one can be promoted or further ex- sumption of the electricity produced by the installed float- panded through adequate policy reforms. In the United ing solar panel could further decrease costs and energy States, the recent Twenty-First Century Dams Act intends losses. This offers great potential worldwide for the com- to incentivize retrofitting, in addition to rehabilitation and bined and integrated operation of dams and floating solar decommissioning of dams, while conserving waterways panels (World Bank Group, ESMAP, and SERIS 2019). to build stronger, more resilient water infrastructure and hydropower systems in the United States (Landers 2021). Even though retrofitting can be an attractive alternative to building greenfield storage projects, some financial 5.3.3 Rehabilitating barriers remain. Inexistent, unclear policies and regu- lations about retrofitting that translate into lengthy per- If not adequately maintained, water storage infrastruc- mitting and licensing process, prolonged development ture may fall into disrepair and need rehabilitation to timelines from inception to operation, lack of investor function effectively; even if well-maintained, equipment knowledge, and other project development risks are just wears out after a period of time and needs to be replaced. some financial barriers for retrofitting projects (Patel, Through development or even misuse, natural ecosystems Shakya, and Rai 2020). In addition, investors remain hesi- may lose their storage capacity as land is denuded, soils tant to finance non-power dam electrification projects due are depleted, and floodplains are built over. Rehabilitation to a lack of financial standards or analysis on their project of the storage alone may not be sufficient to fill a water valuation and economics, a lengthy and complex regula- storage deficit, but when compared with the cost of new tory process that leads to project uncertainty, and mini- infrastructure, the restoration of existing assets and get- mal state and federal support to stimulate development ting them fully operational again may be the lowest cost and financing (Guerrero 2021). Another concern is relat- option for increasing water storage availability in a system. ed to schemes of revenue allocation and who will bene- One example is Sri Lanka, where ancient tanks are being fit, in addition to the priority setting for water allocation rehabilitated to provide water for irrigation, household use, (Energypedia 2015). Also, it is harder to make the case for industry, and the environment. The case of tank cascade rehabilitating and retrofitting existing hydropower plants rehabilitation in Sri Lanka illustrates the importance of to access climate financing (Patel, Shakya, and Rai 2020). evaluating rehabilitation of small-scale water storage at the level of a sub-basin tank cascade, providing examples However, private finance mobilization for retrofits is pos- of a methodology that can be used to evaluate the value of sible, and there are examples of policy reforms to pro- linked small-scale storage, as well as a process to priori- mote retrofit and rehabilitation. One example of private tize investments in storage rehabilitation. Further, the case financing is the Pamir Private Power Project, aimed at retro- study on dam safety in Indonesia provides examples of fitting and rehabilitating hydropower plants and associated how dams were assessed and prioritized for rehabilitation. 72 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE Finally, natural ecosystems can be rehabilitated, and natu- In the case of dam decommissioning, if the dam has al- ral storage capacity restored, as is the case in Monterrey, tered the ecological status of the river through changing Mexico (see case studies, chapter 8). the flow regime, and the ecosystem has been altered and has adjusted around these changes; an assessment may be needed to understand how a decommissioning could 5.4 DECOMMISSIONING BUILT STORAGE help—or harm—the downstream system. Aspects to con- sider in decommissioning include distribution of benefits Even if the decommissioning of water storage is the last and costs across owners and other stakeholders and the stage of its lifespan, it remains important to use good related ways to finance the decommissioning, public safe- practices through this phase. When it is decided that ty, fish passage, river restoration, sediment management, water storage will no longer be rehabilitated, reoperated, and other environmental impacts (USSD 2015). At this or retrofitted to extend its lifetime, it should be decommis- stage, the Mitigation Hierarchy may again be a useful tool. sioned (box 5.6). This is often not simply a task of stop- Several references exist to help dam owners and stake- ping utilizing the storage but taking into consideration holders investigate and evaluate the possibility of dam what impacts decommissioning could have on stakehold- decommissioning, including those from the United States ers, including social and environmental considerations. Society on Dams and the Government of Australia. BOX 5.6  Dam Removal: A Tale of Too Much Storage? What Is Dam Decommissioning?. ICOLD defines dam decommissioning (or dam removal) as ranging from a partial breach of the dam to full removal of the dam and appurtenant facilities (ICOLD 2018). The United States Society on Dams uses the term retirement to refer to the discontinued use of a dam (USSD 2015). Trends in Dam Removal. In the United States, an estimated 1,654 dams were removed between 1968 and 2019, and thousands more could be removed by 2050 (figure B5.6.1). Of the dams removed, 99 percent were below 15 meters in height. Since the 1980s, an FIGURE B5.6.1 Number of Dams Removed on the Rivers of the United States and Europe 90 90 A B 80 80 < 2.5 m 2.5–7.4 m 70 70 7.5–14.9 m 15.0–29.9 m Number of barriers Number of barriers 60 60 30.0–45.0 m 50 50 > 45.0 m Total 40 40 30 30 20 20 First data 10 10 0 0 1968 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 2018 1968 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 2018 Source: Habel et al. 2020. Note: Number of dams removed in the United States (panel A) and Europe (panel B). Data for Europe exclude Sweden, Russia, Wales, and Scotland. Water palette (box continues next page) Tools for Better Storage Throughout the Project Cycle 73 BOX 5.6  Dam Removal: A Tale of Too Much Storage? (cont.) increasing trend is observable with the number of dams removed growing each decade. In Europe, some 342 dams were removed between 1996 and 2019, and as in the United States, the vast majority—98 percent—were low-height dams (Habel et al. 2020). Globally, some 3,869 dams are estimated to have been removed over the last half century, with dam removal starting to gain momentum in the Republic of Korea and Japan (Ding et al. 2019). Most of the dams being removed are older dams. In the United States, 78 percent of dams that have been removed were built before 1940, with dams built as far back as 1750 included (Habel et al. 2020). Research shows a clear upward trend in the median age of dams that have been removed (Ding et al. 2019). Drivers of Dam Removal. A public debate around the issue of dam decommissioning was launched by a report by the United Nations University Institute for Water, Environment and Health (UNU-INWEH) in 2021, which discussed the risks posed by a “mass ageing” of dams and removal as an option to address the emerging threat of obsolescence (Perera et al. 2021). The aging of the world’s fleet of dams is, indeed, a concern due to rising maintenance costs, sedimentation, loss of efficiency, and others, as noted in the UNU-INWEH study (Perera et al. 2021), though statistics on dam failures suggest the highest probability of dam failure is in the early years of a dam’s life (ICOLD n.d.). Based on evidence assembled to date, safety concerns do factor into decisions around dam removal, including both public safety and concerns around high-hazard dams or dams with structural deficiencies. Overall, the reasons behind the increase in dam decommissioning and removal are complex and varied, includ- ing not just safety-related considerations but environmental, cultural, economic, and legal as well. In the United Kingdom, safety is considered the primary reason for dam removal, with many dams located near to densely populated areas, and this is also a major factor in the United States for small dams as more than 280 public safety incidents related to persons crossing small or low-head dams have been recorded between 2000 and 2015 (Habel et al. 2020). Ecological restoration, which is closely linked to changing values around the environment, is also a major driver of dam removal. In the United States, dam removal is concentrated in Western states and northern Midwestern states (Bellmore et al. 2017), with some of the most famous examples relating to the restoration of salmon habitat. The Glines Canyon and Elwha dams, for example, were simultaneously removed from the Elwha River in Washington State between 2011 and 2014—the largest dam removal project to date in the United States (NOAA n.d.). Dam removal in Europe is closely related to the implementation of the Water Framework Directive in 2006, compliance with which is driving river restoration projects in France, Spain, Sweden, and other countries in the European Union (Habel et al. 2020). Similarly, in China, which has the largest number of dams of any country, its vision of shifting to an “ecological civilization” and restoring degraded rivers may lead to future removal of smaller, aging, and low-efficiency dams (Liu, Zhou, and Winn 2020). Another driver is regulatory change. It is said that “standards age faster than dams.” Across the world, changes to environ- mental and safety regulations related to dams have led many dams, particularly small and privately owned dams, to fall out of compliance. It is, sometimes, more costly to rehabilitate or reoperate the infrastructure to meet new standards than to decommission. In the State of Massachusetts, for example, a cost comparison of alternatives for three dams that did not meet state regulations concluded that removal was on average 60 percent less expensive than repair and maintenance over 30 years (IEc 2015). Dam owners may opt to decommission their dams rather than be saddled with the potential legal liabilities of having non-compliant dams, in addition to the costs of repairs. (box continues next page) 74 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE BOX 5.6  Dam Removal: A Tale of Too Much Storage? (cont.) Notwithstanding these considerations, decommissioning of dams can be controversial as the future benefits of well-main- tained infrastructure need to be weighed against the benefits of removal, which implicitly involve societal and cultural values around water. Lessons. After multiple extension-of-life investments, some dams will eventually need to be decommissioned or removed due to various reasons. Even though decommissioning may be less costly than alternatives, the up-front costs of removal are still a barrier and are usually not accounted for during project development and operation. Changing societal values influence decisions around dam removal directly as well as through updated environmental and safety regulations. Multi-stakeholder engagement in the planning phase helps ensure that selected investments are more societally acceptable, and selecting investments that are robust to a range of different future scenarios may result in infra- structure that is more adaptable in the long run. 3 In this study, the definition of retrofitting includes upgrade, ENDNOTES which can consider a project in which existing generation ca- pacity is augmented and is more encompassing than those 1 http://hydrosustainability.org. definitions of retrofitting found in some literature that refer 2 Any tool that facilitates decision-making processes and sup- only to the construction of generation facilities at non-hydro- ports more rational decisions. power dams. Tools for Better Storage Throughout the Project Cycle 75 6 THE FUTURE IS NOW: A CALL TO ACTION The Call to Action summarizes the key conclusions and as hydropower, transportation, or recreation. Storage not recommendations of this report around four themes: only provides these direct services but is also a form of hy- drological risk management: families, farmers, business- 1. Why focus on water storage? es, and cities will invest more in their lives and livelihoods 2. What do stakeholders need to understand to de- when they feel protected from water extremes. velop smarter approaches? 3. Who needs to be involved? As water storage grows in importance, current methods 4. How can stakeholders approach storage more for developing and managing it are more obviously inade- strategically? quate. Total volumes of freshwater storage have declined over the last 50 years, some large infrastructure solutions have proved far less resilient—and far more damaging— 6.1 WHY FOCUS ON WATER STORAGE? than had been initially understood, and many approaches in general have been too fragmented and short term to Water is fundamental to life. It’s at the center of economic add up to the more comprehensive, sustainable, and inte- and social development and influences whether commu- grated solutions that circumstances increasingly demand. nities are healthy places to live, farmers can grow food, or cities have reliable clean energy. Water underpins natural The result is that the world today faces growing demand ecosystems, drives industry, and creates jobs. It touches for water, increasing variability, and a growing water stor- every aspect of development, with a direct link to almost age gap—and current approaches to filling the storage every Sustainable Development Goal (SDG). gap—are no longer fit for purpose. Water insecurity is growing around the world, influenced in some places by increasing demand, in others by degrad- Call to Action Step 1: Focus more—and more ing quality, and almost everywhere by climate change. strategically—on water storage. Addressing water security is much broader than water storage, but water storage is a key part of building water security, particularly to manage the increasing variability 6.2 WHAT DO STAKEHOLDERS NEED TO and growing extremes being brought about by climate UNDERSTAND TO DEVELOP SMARTER change. Climate change means that even countries with APPROACHES? relatively temperate climates and large infrastructure en- dowments face increasing water insecurity, such as in Freshwater storage takes place in a wide array of forms: Europe at the time this report is being published. For much built and natural; large and small; underground and on of the world, "business as usual" is not a viable strategy. the surface. While humans have been developing water storage systems for several millennia, nature has always Smarter approaches to water storage will, inevitably, lie at provided the vast majority of freshwater storage on which the heart of responses to climate change. Water storage humans depend—whether knowingly or not. The first provides three broad services: (a) improving the availabili- thing necessary to know, therefore, is what storage is al- ty of water during drier periods, (b) mitigating the impacts ready being utilized, particularly the natural systems such of floods, and (c) regulating flows for other purposes, such as groundwater, wetlands, glaciers, and soil moisture 76 reserves. Systematic mapping of natural and built storage approaches and tools to make long-term investments in on a basin-by-basin basis (as this is the practical operat- natural and built infrastructure and in the institutions to ing scale of most storage systems) is needed, including manage it. This report details a number of these tools, data about volumes, reliability, and controllability of the from decision-making under uncertainty to integrated water stored. Understanding current storage systems is modeling techniques, to make processes “smarter.” the first step toward not taking storage for granted and un- necessarily depleting it, as many parts of the world have Call to Action Step 2: Measure and model storage in been doing for several decades. It is also a necessity for an integrated way—natural and built, surface and sub- informing future planning and investment decisions. surface—to understand, develop, and manage storage as a system with long-term, sustainable, and resilient The second knowledge challenge is to understand stor- services as the end objective. age as a system. Even very different types of storage are linked as part of a broader water cycle, meaning that they generally need to be developed and managed as an 6.3 WHO NEEDS TO BE INVOLVED? integrated system rather than as stand-alone facilities. Engineers have long understood that dams depend on Closing the water storage gap is a shared challenge. their watersheds, but it is time to go much beyond this Faced with the growing risks of water insecurity around and understand not only the hydrological system but also the world—particularly in the face of the climate crisis— the broader social, economic, and environmental systems global, national, and regional stakeholders can no longer that interact with it, building upon decades of global ex- focus on their own needs in isolation. If we are to achieve perience with integrated water resources management sustainable, climate‐resilient water storage solutions that (IWRM). The social and economic systems are drivers of sustain generations, a conceptual shift in thinking—an- changing demand for storage services, while the broader chored in an integrated, systemic approach to planning environmental systems (biological, climatic, etc.) are both and managing water storage—is required. major users and shapers of water flows. Governments and policy makers have a unique opportuni- The third key knowledge challenge is assessing potential ty to lead by setting the criteria for success, advocating for alternatives to storage. Storage challenges usually need to an integrated, systemic approach to storage that begins be addressed as part of a broader water resource context, with a rigorous definition of the water-related problems to and storage may not be the best solution to the problem be solved, and prioritizing efficient solutions that benefit at hand. Alternatives to storage could range from demand the largest range of stakeholders. But we all have a role management to alternative supply measures for reducing to play. scarcity; from zoning regulations to flood insurance for managing floods; and from alternative energy to alter- Utilities, businesses, irrigation schemes, hydroelectric native transport investments to storage’s regulatory ser- producers, and other bulk users of water services have vices. The important point is to consider alternative ways key roles in defining the problem through identifying their to deliver the service, not simply volumes of water. long-term water needs, including for storage services, as well as potential alternatives to them. The fourth big knowledge challenge is to develop and manage storage within a context of increasing uncertainty Significant investments in storage may have significant brought about by climate change. Managing storage as a trade-offs associated with them, which different stake- system is a key step in the right direction since a diverse holders may have differing views on. The social or environ- system will be more resilient to weather-related shocks mental implications of different management approaches than individual facilities. The fact that the past is no lon- to built or natural storage (e.g., land-use restrictions) also ger a reliable guide to the future has several ramifications, need to be carefully understood. Similarly, storage ser- including a premium on the rapid collection and analysis vices may be most efficiently provided through multipur- of data to guide system understanding and management. pose infrastructure provided to multiple and sometimes But more broadly, climate change demands smarter competing stakeholders. All stakeholders, including those The Future is Now: A Call to Action 77 representing the environment, have a part to play in think- 1. Rehabilitating current storage, including restor- ing through these trade-offs, as well as clarifying the value, ing natural systems, to improve the effectiveness and therefore the economic and financial sustainability, of and sustainability of current storage services future investments for them, through joint processes that 2. Retrofitting existing storage to increase or im- help produce a shared understanding and more resilient prove storage services and integrated services in the future. 3. Reoperating existing storage to change the na- ture of the storage service being provided by cur- From decision‐makers at water ministries and ministries rent natural or built infrastructure that are water-reliant, to engineers, ecologists, and ac- 4. Raising new storage if improvements to current ademics, to project teams at the World Bank and other storage systems are insufficient to meet current international development agencies, expertise and ac- or future needs countabilities vary significantly. Yet achieving resilient, 5. Reforming institutions so as to enable the more sustainable storage solutions is predicated on a universal integrated planning and operation of storage shift in thinking, a collective understanding of the new par- systems into the future adigm for water storage, and adoption of the key princi- ples that characterize an integrated approach. Many countries are likely to need to invest in all these areas, and the report also includes recommendations about how to approach mobilizing finance for storage, as Call to Action Step 3: Engage all stakeholders to well as how to safeguard the economic returns over time define the storage services needed (the “problem”) and through provisions for operation and maintenance costs the trade-offs associated with future investments (the and a life-cycle approach. “solutions”). Call to Action Step 4: Use an integrated planning 6.4 HOW CAN STAKEHOLDERS APPROACH methodology to identify and prioritize investments STORAGE MORE STRATEGICALLY? in both natural and built water storage and develop an institutional setup that can maintain and operate This report suggests an Integrated Storage Planning storage in the public interest for the long term. Framework that could be helpful for developing more— and more sustainable and resilient—freshwater storage in the future. The framework covers three stages: (1) a In short, What the Future Has in Store: A New Paradigm for needs assessment to define the problem; (2) definition Water Storage calls on all stakeholders to think different- of the system and potential solutions; and (3) a deci- ly, plan inclusively, and act systematically to address the sion-making process considering a range of scenarios water storage challenges of the coming century. It pres- and uncertainties. ents a progressively urgent appeal for multi-sector prac- titioners at every level, both public and private, to begin Together, these steps are designed to build the knowledge championing integrated smart water storage solutions and the consensus required for investing in improved that meet a range of human, economic, and environmen- water storage services for the long term, including in the tal needs. Closing storage gaps will require a spectrum of face of a changing climate. Critically, the framework in- economic sectors and stakeholders to develop and drive cludes ways to consider whether storage investments are multi‐sectoral solutions that address the water storage really the best way to address water-related challenges, or gap holistically, effectively, and efficiently. Done right, a whether alternatives should be considered. new paradigm for water storage, backed by investment, will create a stronger foundation for sustainable develop- At a practical level, this report identifies five major areas ment and climate action and resilience, paying dividends for investment in future storage systems (both natural for populations, economies, and the planet through years and built), which it summarizes as the “5 R’s”: and generations to come. 78 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE Itaipú dam from above. © Mykola Gomeniuk | shutterstock.com The Future is Now: A Call to Action 79 A new paradigm for water storage, backed by investment, will create a stronger foundation for sustainable development and climate action and resilience, paying dividends for populations, economies, and the planet through years and generations to come. RESOURCES FOR STORAGE Part II PLANNERS 7 THE INTEGRATED STORAGE PLANNING FRAMEWORK: A STEP-BY-STEP GUIDE This chapter provides a step-by-step explanation of how » Access to safe and affordable water and sanitation to apply the Integrated Storage Planning Framework pre- services for current and future populations sented in chapter 3 of What the Future Has in Store: A » Food security (access to safe, nutritious, and suffi- New Paradigm for Water Storage, for those who want to cient food now and into the future​) and sustainable apply some or all of its principles in their storage planning. agricultural livelihoods Please see table 3.2, "Summary of the Integrated Storage » Inclusive and sustainable industrialization Planning Framework," for a synopsis of the process elab- » Mitigating the impacts of and strengthening resil- orated in this chapter. ience to floods » Economic and efficient means of transporting goods and peoples 7.1 STAGE 1: THE PROBLEM: A NEEDS » Affordable, reliable, and modern energy services ASSESSMENT » Increase share of renewable energy in the total en- ergy mix The first stage comprises a needs assessment of two » Access to recreation and cultural services steps: (A) defining the development objectives related to » Retention and upkeep of the health of natural sys- the problems that need to be solved, and (B) characteriz- tems for inherent value ing the water service requirements needed to achieve the development objectives. By first identifying development objectives (figure 7.1), rather than specific engineering or management solutions, 7.1.1 Stage 1.A: Defining Development Objectives it may be possible to identify other objectives to pursue in parallel, creating greater efficiencies. At this stage, it is also possible to identify the different systems that are involved, directly or indirectly. For example, pursuing sustainable ag- KEY QUESTIONS TO ANSWER IN STAGE 1.A ricultural livelihoods in a district will, at a minimum, involve › What are the development objectives for the the agronomic system and agricultural supply chain for the system? area and touch one or more hydrological basins. › Who experiences the problems and who may be part of the solution? Tools Some development objectives may already be well known; in some cases, a recent or ongoing crisis such as a flood or drought may be driving the planning process. To iden- Technical Characterization tify other, co-existing needs, existing multi-stakeholder The first step entails defining the problems in the sys- planning processes such as a national or subnational tem and the development objectives linked to them. For development plan or strategy are a logical starting point. example, if the underlying problem includes flooding, the Often, such plans have already been narrowed down main development objective may be to reduce the impacts to an actionable scope with spatial boundaries in time- of floods in a specific geography. Typically, development bound agency business plans or sectoral plans, such as objectives that involve action in the water sector include integrated water resources management (IWRM) man- versions of the following high-level objectives: agement plans, power system master plans, disaster risk 82 FIGURE 7.1 Development Objectives Enabled by Water Storage Services Reduce the impacts Retention of natural Inclusive and Recreation of and strengthen systems for their sustainable and cultural resilience to intrinsic and industrialization services flood related ecosystem disaster value Access to safe Access to safe, Access to Increase the share of and affordable nutritious, and affordable, reliable, renewable energy in drinking water sufficient food modern energy the global services energy mix Source: Original figure for this publication. management plans, or city-level plans. In the absence of private spheres whose actions either advance or con- plans, or to identify objectives that may not yet be includ- strain the development objective being pursued. The en- ed in them, contact with professionals in other water-us- vironment should also be considered a stakeholder at ing sectors may help identify objectives. this stage as elements of the environment, such as cer- tain species, may be the intended beneficiaries of water Stakeholder and Impact Analysis resources management interventions (noting that risks and impacts to the environment are introduced in Stage 2.A, which aims to build understanding of the existing sys- KEY QUESTIONS FOR EACH IDENTIFIED tem). It is important to identify and map the stakehold- STAKEHOLDER ers, how they interact with the system, and whether they would benefit or be disadvantaged by possible changes. › Where in the geography of concern are they Depending on the level of study/analysis, direct contact located? with stakeholders will likely be needed early in the process › To what extent do they use, restore, pollute, or to ensure that hypothesized needs and preferences are rely on the hydrology of the system? true to reality (while balancing the need to control expec- › Is this interaction sustainable or at risk? tations with affected communities). › How do their actions impact other stakeholders? › How do other actors impact this stakeholder? Communities and local government have an important › What tools are available to modify the role to play at this stage. Local experiences are critical to stakeholder’s behavior or environment, if needed? filling gaps in official statistics during the needs assess- › For this stakeholder, what are some of the ment, and local knowledge around the performance and related development objectives that potentially interlinkages of existing systems is crucial to problem support or conflict with the objective in focus? definition. Civil society organizations (CSOs) may also have technical expertise that can help communities ar- ticulate the challenges faced and even serve a brokering Characterize stakeholder needs, interests, and impacts function to bring different stakeholders together to ad- for each development objective. Options for address- dress the issue. For example, in the creation of the Upper ing the development objective at hand will affect a set Tana-Nairobi Water Fund in Kenya, CSO partners and of stakeholders throughout the system, including direct foundations were integral in bringing to reality a project beneficiaries as well as stakeholders further upstream to incentivize upstream smallholder farmers to conserve or downstream who influence the status quo or who and restore the natural water storage capabilities of the will be affected by changes introduced in the system. catchment (wetlands and forests), which supplies bulk Stakeholders also include other actors in the public or water, including for industrial use, to the city of Nairobi The Integrated Storage Planning Framework: A Step-by-Step Guide 83 downstream, as well as flows to several hydropower sta- » Control of flow and level for navigation, hydropower tions in the basin. A comprehensive analysis of benefits generation, or recreation and cultural services and costs to the various private and public sector stake- » Environmental flows for ecosystem preservation and holders was also a critical part of creating a business case restoration (including prevention of saline intrusion) for the project and establishing its viability (TNC 2015). These requirements should be expressed in volumetric, tem- Tools poral (when and how often), and geographic dimensions. Stakeholder analysis can be carried out with the aid of a stakeholder map, which enables identification and pri- Identifying parameters that can assist with decision- oritization of stakeholders and their perspectives and is making. Considering the questions above, water service helpful to inform communication and consultation plans, requirements can be more specifically described with key which will be useful while advancing through the stages of the framework. Depending on the complexity of relation- KEY QUESTIONS TO ANSWER IN STAGE 1.B ships and power dynamics, a political economy analysis may also be a useful and informative part of the stake- › What are the water service requirements holder analysis at this stage. In subsequent stages of the for meeting development objectives in the framework, we consider environmental risks, impacts, and system (present and future)? opportunities in the areas of concern, but at this stage, › What are the service attributes of the water it is important to remember the environment is also a requirements?  water user that will be affected by the preferences and › How do these water requirements relate to actions of other stakeholders in the system. Resources different stakeholders? such as the “Engaging Stakeholders in Water-Energy- Food-Environment Systems Assessment and Planning: A Future DAMS Guide” can assist with these analyses (Dye, MORE SPECIFIC GUIDING QUESTIONS USEFUL IN UNDERSTANDING THE NATURE Hulme, and FutureDAMS-Consortium, n.d.). OF THE REQUIREMENT › Is the problem one of too much water or too 7.1.2 Stage 1.B: Characterizing Water Service little? Requirements › If too little, then what is the additional volume of water needed? Technical Characterization › Is the water that is needed going to be After identifying the underlying problem and mapping consumed (removed from the water resources the stakeholders, the next step is to determine the water system after being used) or is it a non- service requirements for meeting the specified develop- consumptive use (water returned to the water ment objectives now and into the future. Water service re- resources system after being used)? quirements is used as a broad term describing the supply › When and how often (inter-annual, seasonal, and control of water needed to support the development periodic) is additional water needed? objectives and outcomes identified in Stage 1.A. At Stage › Where geographically is the water required? 1.B, thinking about water service requirements instead of › Is it a temporary need or will the water be technical interventions or infrastructure facilities enables required in perpetuity? holistic, system-wide planning for getting desired benefits › If too much water, what is the volume of excess? to intended beneficiaries. Water service requirements for › When and how often does this excess occur? the development objectives listed above could include: › What spatial area experiences excess water? How is the need for more water or the impacts » Water supply for drinking and domestic use, crops › of excess water likely to evolve in the future and livestock, industry, and so on expressed as an given climate change, urbanization, and any new amount economic aspirations? » Flood protection and attenuation of excess flows for disaster risk reduction 84 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE TABLE 7.1 Water Service Attributes WATER SERVICE DEFINITION PERFORMANCE INDICATOR UNIT (EXAMPLES) ATTRIBUTE 1. Reliability Degree to which water management — — options consistently succeed in serving all intended purposes 1a. Assurance Performance reliability of the water Average time between consecutive Years, months, days levels management option performance failures (predicted probability or historic) 1b. Impact of Magnitude of performance failure Size of impact if option fails to Hectares of crop lost, unreliability if underlying option fails to support deliver on intended purpose (can be financial/economic cost service delivery graded by percentage of failure) 2. Controllability Degree to which water management — — may be controlled or operated for intended purposes 2a. Volumetric Degree to which volume of water Least amount of water that may be Cubic meters control can be controlled released 2b. Geographic Geographic area that can be Service area that can be supported Square kilometers control serviced by underlying water by the option management option 2c. Temporal Frequency with which underlying Average time needed between Years, months, days control water management option can be consecutive operations or for re-mobilized for service delivery recharge 3. Adaptability Ability to adjust or modify water Number of other uses or conditions Number management option to new the water resources management conditions, uses, or purposes​ option could be modified for 4. Vulnerability Susceptibility to and magnitude — — of potential damage from hydroclimatic hazards 4a. Physical Susceptibility to flood and drought Likelihood of significant damage or Low, moderate, substantial, vulnerability hazards (influenced by design total system failure high parameters, location, and operating condition) 4b. Magnitude of Magnitude of consequences of Extent of potential impact Hectares of crop lost, kilowatt- vulnerability significant damage or total system hour of hydropower foregone, failure potential loss of life, financial or economic cost 5. Quality Degree to which freshwater is free — — of contaminants that negatively affect its uses 5a. Salinity Amount of dissolved salts in the Concentration of dissolved salts Conductivity values water body or source 5b. Pollution Presence of pollutants from point Concentration of pollutants such as pH values, total dissolved and nonpoint sources heavy metals, harmful chemicals, solids levels, biological oxygen bacteria, nutrients, and oxygen- demand, quantitative mass depleting substances measurements 5c. Turbidity The relative clarity of freshwater Concentration of suspended Quantitative mass sediment measurements Source: Original to this publication. Note: — = not applicable. The Integrated Storage Planning Framework: A Step-by-Step Guide 85 addressed, stakeholders that would potentially impact or KEY QUESTIONS be impacted by the actions taken were identified. Having ascertained the water service requirements for achieving › Which of the stakeholders identified in Stage the specified development objective and the desirable 1.A have the water service requirement, and water service attributes that correspond to those require- how would it affect their socioeconomic and ments, it is important to then consider how those affect environmental well-being? the different stakeholders. › What are the opportunities available to them once the water service requirement is met, and In a full-scale options assessment, this would entail ad- how can these potential benefits be measured? ditional consultations to verify assumptions with stake- › What are the trade-offs created by serving this holders. As in Stage 1.A, local knowledge and experience set of stakeholders versus another? brought by communities, local government, and CSOs are › Is it possible to disaggregate the stakeholders valuable during this process. It is also important to consid- at this stage by gender, occupation, income er the full range of public and private stakeholders identi- level, or other characteristics to understand how fied in Stage 1.A, including vulnerable groups whose views meeting the water service requirements could and needs may be underrepresented. serve to narrow inequalities? › What are the water service requirements that 7.1.3 Stage 1 Outputs support biodiversity and ecosystem functioning? Clearly defined development objectives and the water service requirement(s) to meet those objectives to de- parameters that will enable later comparison of different liver present and desired future uses of water. This initial water management options, including storage, in terms of characterization of needs supports decision-makers in quality of service. In the framework, these parameters are identifying which enabling services of storage (described referred to as water service attributes (table 7.1). In many in chapter 1) possess desirable service attributes and are, cases, water storage, both natural and built, enhances thus, able to meet the water service requirements. these attributes: A needs assessment: Stage 1 concludes with an assess- » Reliability, which measures the degree to which ment that specifies water service requirements for the water management options consistently succeed in system, characterization of stakeholder interests and ca- pabilities, and the enabling environment. It provides an ini- serving all intended purposes tial characterization of the various services of storage that » Controllability, which measures the degree to which will support achievement of water security goals. water management may be controlled (volumetric, spatial, and temporal) over service delivery for in- tended purposes 7.2 STAGE 2: THE SYSTEM: ESTABLISHING » Adaptability, which measures the ability to adjust or THE BASELINE AND UNDERSTANDING modify a water management option to new condi- SOLUTIONS tions, uses, or purposes​(GWP and IWMI 2021) » Vulnerability, which measures the susceptibility to The second stage of the framework relates to estab- and degree of potential damage from hydroclimatic lishing the baseline by characterizing the current sys- hazards tem and the potential for additional water management » Quality, which measures the degree to which water options or other solutions. This is an important step is free of contaminants that negatively affect its uses after characterizing water service requirements but be- fore beginning to evaluate different investment or man- Stakeholder and Impact Analysis agement options. This characterization of the system Clarify water service requirements. In Stage 1.A and enables better understanding of existing supply-side and the identification of the development objective to be demand-side water management measures, the extent to 86 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE which existing measures engage and benefit stakehold- Supply-side characterization: Identifying the supply-side ers, and what alternative or complementary water man- water management measures in place in the system and agement actions may feasibly be scaled up to contribute services they provide, including all forms of infrastruc- to meeting development objectives. While this frame- ture and interventions that contribute to the collection, work focuses primarily on storage-related measures, it retention, conveyance, treatment, desalination, storage, recognizes the need to characterize and evaluate stor- and distribution of water as well as monitoring of the re- age-related measures alongside a broader suite of water source. These measures aim to (a) increase the quantity management measures, including demand control, quo- of freshwater supply (e.g., desalination and treatment); (b) tas and enforcement, non-traditional water sources, and provide access to bulk water (e.g., water distribution infra- more, as well as to consider measures outside the water structure); and/or (c) manage and alter water availability sector (e.g., alternative sources of energy generation). through space and time (e.g., storage and flood retention measures). This should include the level of functionality of 7.2.1 Stage 2.A: Taking Stock of the Current System the existing system. KEY QUESTIONS TO ANSWER IN STAGE 2.A Demand-side characterization: Examining current and future water demands as well as measures in place to › What water security measures, storage and non- manage water demand. Water demand is the volume of storage, are in place in the current hydrological water that is needed to satisfy all water service require- system? ments in a system. This includes all different forms of › What are the systems that need to be water demand by different sectors, such as water de- considered, beyond the water system? mand for irrigation, industry, navigation, and environ- › To what extent do the existing water mental flows. An assessment of water demand includes management systems engage and benefit or current needs and projected future needs, taking into con- harm different stakeholders? sideration population growth, economic growth, industri- alization and other sectoral shifts, and improvements in technology and efficiency. It is important to distinguish Technical Characterization between consumptive and non-consumptive water de- Characterizing the current hydrological system starts mand as the latter does not necessarily diminish the with understanding the physical system as well as the amount of water available for other uses. Water demand water service requirements supported by the compo- varies across space and time and, in many cases, follows nents of that system. This assessment provides data on a seasonal pattern, especially where demand for irrigation how the current freshwater system works, including avail- water exists. Measures to control water demand and con- ability of water, demand for water, a model of how water strain its growth include pricing, quotas, and loss reduc- is stored in the system, how it is managed, and how other tion measures, among others. elements of the system interact. Existing built and natural infrastructure are considered here, as well as the contri- Identifying other systems. Water resource management butions from the system to achieving the desired water involves several systems beyond the physical hydrology, service requirements (using comparable measures of per- including other natural resource systems, socioeconom- formance such as those in table 7.1). This should not only ic systems, and administrative and institutional systems cover infrastructure owned or operated by the public sec- (Loucks et al. 2017). At this stage, a brief screening is nec- tor but also, to the extent possible, all the infrastructure essary for other elements that may need to be considered, in the basin regardless of ownership. This is sometimes for example, power transmission and trade, agricultural referred to as a “baseline.” The characterization should management systems, or other institutional systems, include consideration of future trends, including climate such as authorities involved in disaster risk management. change. Box 7.1 provides an example of determining the Relevant information on these systems can be gathered, scale of the system for urban flood management. and stakeholder assessments updated accordingly. The Integrated Storage Planning Framework: A Step-by-Step Guide 87 BOX 7.1  Urban Flood Management How do you know which scale to address in system planning? The scale of storage planning itself is determined by the development objective being pursued and the stakeholders and jurisdictions involved. In pursuing objectives, the system of concern should encompass (a) intended beneficiaries and the location of their service needs, (b) upstream and downstream actors who influence the service delivery challenge, (c) a uniform administrative/ policy jurisdiction, and (d) parts of the watershed that make implementation of solutions institutionally and technically feasible. In the case of dams, areas of planning may include the catchment area (where water is impounded), the command area (which is irrigated), and downstream of the irrigated area. In the case of urban flood protection, measures can be pursued across three scales to maximize disaster risk reduction: river basin, city, and neighborhood. At the river basin scale, it is important to recognize the interconnectedness of communities and the importance of in- tegrated catchment management approaches to address flooding and water resource challenges. Basin scales can be used to tackle the problem near the source, outside of the city where a problem may be felt and before it reaches the city (e.g., upstream forests to intercept and slow floodwater, and river floodplains to enhance storage and reduce flood risk downstream). At the city scale, solutions include measures that seek to complement and strengthen urban land-use planning and support disaster risk management. The landscape and ecological structure of the city, together with the unique challenges faced by city residents, determine the suitability and potential of solutions (figure B7.1.1), such as constructed wetlands to collect and store water runoff and open green spaces or parks throughout the city to add infiltration capacities. FIGURE B7.1.1 City-Scale Nature-Based Solutions Source: World Bank 2021a. At the neighborhood scale, solutions can help address resilience challenges, including measures in buildings, streets, and open public spaces. For example, smaller-scale interventions can build resilience by increasing stormwater retention ca- pacities and reducing the "heat island" effect. These solutions can be very effective for local rainwater collection, to mit- igate impacts of air, water, and soil contamination, and to reduce heat levels in cities by providing shade. Working at the 88 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE BOX 7.1  Urban Flood Management (cont.) neighborhood level can relieve pressure on existing local infrastructure such as stormwater drains. Examples of solutions at the neighborhood scale include green roofs, green facades, private gardens in combination with green streets; retention basins, rainwater retention ponds, or green water squares to store water; and small-scale rainwater catchment and drainage interventions such as bioswales (e.g., bioretention areas [figure B7.1.2] and constructed wetlands [figure B7.1.3]). FIGURE B7.1.2 Bioretention Areas Source: World Bank 2021a. FIGURE B7.1.3 Constructed Wetlands Source: World Bank 2021a. The Integrated Storage Planning Framework: A Step-by-Step Guide 89 Tools and Data Stakeholder and Impact Analysis Water accounting is a useful way to approach the charac- Characterize the extent to which existing water manage- terization of a current situation, where a proper accounting ment systems engage and benefit stakeholders.  With of both supply and demand within the system is needed to greater understanding of the water management sys- understand how much water is required to meet the sys- tem, it is possible to refine the mapping of stakeholders tem’s requirements, where, and why (box 7.2). However, as and their needs. Initiated under Stage 1, this includes a the framework is intended to be an upstream and largely broad range of stakeholders, including those dependent desktop phase, planners will need to rely on data and tools on water for lives and livelihoods, those with spiritual and that can be gathered relatively easily. This could include (a) cultural ties, and those that can represent environmental existing storage mapping and quantification literature and interests. If relevant, the private sector could also be con- datasets (outlined in the previous chapters); (b) existing sidered during this exercise to ensure that privately owned planning documents from river basin authorities, cities, and assets that are part of the storage and hydrological sys- industries (c) existing global or regional datasets on precip- tem are accounted for and that industrial water demands itation, streamflow, and land cover, and (d) new high-level are quantified, including where the potential exists for data collection from remote sensing or similar methods. new industries to enter, or existing industries to expand in BOX 7.2  Water Accounting Water accounting is the “systemic study of the current status and trends in water supply, demand, accessibility and use in domains that have been specified” (FAO 2012). It allows for the systematically acquiring, quality controlling, and analyzing of water-related information and evidence, which in most cases will come from diverse independent sources that can be used for (FAO 2017): n Situational analysis n Social and institutional learning n Evidence-informed planning n Development and updating a common information base n Water allocation, regulation, and conflict resolution n Challenging factual errors or biased views n Evaluating anecdotal evidence, expert opinion, and folklore n Awareness-raising Water accounting can help with the understanding of the impacts of water use in a basin by multiple sectors and the natural environment, and can evaluate the way changes—natural or human caused—in one part of the hydrologic cycle may affect other elements of the cycle in natural, disturbed, or engineered environments (World Bank 2020d). This is especially import- ant when considering options for water storage, as this tool considers not only the impacts on the water itself but also the capacity, condition, and operations and maintenance (O&M) of the water storage in the basin. Very much a mechanism that can support the proposed framework, water accounting helps answers questions such as: n What are the underlying causes of imbalances in water supply (quantity and quality) and demand of different water users and uses? n Is the current level of consumptive water use sustainable? n What opportunities exist for making water use more equitable or sustainable? Source: FAO 2017. 90 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE potential future challenges facing delivery of water service KEY QUESTIONS requirements and achievement of objectives. Constraints may be natural (external variables relating to hydrology › To what extent do existing water management and geography), technical (engineering or ecological or measures and infrastructure engage and benefit nature-based human interventions to control nature), po- stakeholders? litical/institutional (governing interactions between the › What are the stakeholder incentives, capabilities, natural and socioeconomic systems), financial (resources and institutional systems that exist to improve available, public and private), behavioral (incentives and functionality of existing water management cultural norms), or relating to capacity (institutional and systems? workforce). › How are existing storage measures used/not used for their intended purpose, or how may they Tools and data. This characterization of the existing sys- serve alternative/additional purposes?  tem can be aided by a broad analysis of the benefits and › To what extent do existing storage measures costs to the different users of water-related services fa- positively or adversely impact (or exacerbate cilitated by water management measures. Economic and vulnerabilities for) certain stakeholders?  environmental aspects could be considered as well as ex- isting and potential distributional impacts. These impacts GUIDING QUESTIONS TO CHARACTERIZE IMPACTS may also be felt beyond intended beneficiaries of the mea- OF EXISTING SYSTEMS ON THE ENVIRONMENT sures. If strategic/basin-level studies such as strategic environmental assessments (SEAs) or cumulative impact › To what extent is the natural environment assessments (CIAs) have been carried out in the area, surrounding the area of interest altered or these may have identified valued ecosystem components degraded? (VECs), which may have included preliminary screenings › Does the area of interest have protected status of environmental and social risks. Where such detailed or is it considered to be of high conservation studies do not yet exist, public datasets and geospatial value? platforms from CSOs and international organizations may › Does the area form part of the habitat for be useful, such as the Integrated Biodiversity Assessment endangered or endemic species? Tool (IBAT), the Map of Life, Global Biodiversity Information › To what extent are surface water flows regulated Facility, Protected Planet (World Database on Protected by existing infrastructure? Areas), the Key Biodiversity Areas platform, and the Global Invasive Species Database, among others. response to better water management in the area of study. For example, private irrigation canals or fallow fields can Accurate assessment of supply and demand (Stage 2.A) serve as conduits of intentional groundwater recharge, if and characterization of how these factors may be altered managed as part of the system. (Stage 2.B) are crucial to inform whether the system is in need of “new” infrastructure, or if there are opportuni- Characterize impacts of existing water management ties with interventions and policies that focus on demand systems on the environment. This is an opportunity to management (in the case of a water supply gap) or other identify those elements of the environment in the area of non-structural measures. interest that have scientific, economic, social, or cultural significance, as well as the beneficial or detrimental im- 7.2.2 Stage 2.B: Solutions: Identifying Additional pacts of current water management infrastructure and Options measures on them. This will enable early identification of environmental risks to the system and how potential mea- Technical Characterization sures may remediate, exacerbate, or create them. Identify other potential options to meet development ob- jectives—through water and beyond. After identifying the Characterize existing challenges in the water manage- development objectives, prioritizing water service require- ment system. It is important to consider ongoing and ments, and looking at the current system, it is possible to The Integrated Storage Planning Framework: A Step-by-Step Guide 91 gains), which might include changing the timing KEY QUESTIONS TO ANSWER IN STAGE 2.B: of water releases from controllable infrastruc- ture, managing for synergies between different › What are the additional options for meeting the types of storage, or minimizing storage losses water requirements of the system, including from evaporation. This may also include creating enhanced performance and the options for new new connections between existing storage so development? that they may be operated as part of a broader › Who will benefit or be harmed by each option? system. 2. Rehabilitation: The restoration of current stor- age to improve storage capacity or performance. see where supply-demand gaps exist and whether there Rehabilitation can extend the life of existing stor- are needs for additional options—through water manage- age capacity and defer investment in new stor- ment or more broadly—to support achievement of objec- age. Restoration of original capacity or slightly tives. Some development objectives, such as access to improved capacity could be achieved through water supply or reducing flood risks, are often inextricably addressing structural defects, sediment remov- water-dependent and require water-related solutions. In al, increasing the flow rates of managed aquifer other cases, water storage may be needed to meet water recharge (MAR) sites, and environmental resto- service requirements; what is perceived to be a water sup- ration of natural storage, among others. ply gap may really be a water storage gap. 3. Retrofitting: The upgrading or augmentation of capacity at existing storage facilities or enabling Identification of alternative water management solu- new uses of the facilities. This could be achieved tions can be informed by the water service requirements through raising the height of dam walls or add- and may not involve water or water storage. Alternative ing new hydromechanical or electromechanical solutions may exist outside of the water sector for many equipment to serve different objectives or differ- water-related development objectives. For example, power ent customers to make overall gains in the value generation or transportation of goods and people may be of storage services. met by non-water alternatives, depending on the circum- stances, where solar or wind power may be competitive Exploring these potential gains could be guided by the with run-of-river hydropower or where rail transportation types of questions and examples included in table 7.2. may be as effective as restoring or improving river navi- gability. The details of the alternatives, however, must be This type of analysis establishes "first order" estimates explored to verify the needed alignment between scale, of potential increases in storage services from cur- scope, and timing of the water-dependent choice and the rent storage systems. Some of these options may be alternative. For instance, while solar power or wind may low-hanging fruit and therefore worth pursuing immedi- be able to generate the same amount of electricity, they ately, whereas others might require further consideration. may not meet requirements for reliability and grid integra- This could include deeper investigation (e.g., more techni- tion. In other cases, water management options can meet cal studies on the potential for expanding groundwater ex- water service requirements without the need for storage. traction and recharge) and/or initial data in the modeling For example, run-of-river hydropower may enable the gen- and scenario stage to compare these options with new eration of electricity at acceptable levels of reliability with- storage development options (box 7.3). out water storage. Finding or Developing Additional Storage Getting More from Current Storage In Stage 2.B, it is important to not only include previ- Opportunities to gain more storage services from the stor- ously identified storage options that exist in master age that already exists may include: plans or other sector planning documents but also to look beyond at the full range of available storage types: 1. Reoperation: The modification of storage op- natural and built; surface and subsurface; large and erations for improved management (efficiency small; and centralized and distributed. Depending on the 92 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE TABLE 7.2 Gaining Additional Storage Services from Current Systems TOPIC ISSUES "CITY X" EXAMPLES Rehabilitation of Does the current storage system City X has its storage system that it controls but does not yet consider Natural and Built include all the (significant) actual the amount of water stored within the natural landscape or private Storage freshwater storage in the service area agricultural dams within its watershed. If there is, in fact, significantly of interest? If not, it would ideally be more storage in these other places, the question is whether, and under added to the picture. If it does, could what conditions, City X can leverage these other water stores to deliver better management, repurposing, or services. rehabilitating current storage meet the projected water storage gap? City X has access to some groundwater. Is it possible to increase sustainable yields, either permanently or temporarily, during dry seasons or years? Has the full potential of managed aquifer recharge been exploited yet? Retrofitting or Could retrofitting or reoperating current Farmers control a significant volume of storage upstream of City X Reoperating storage produce additional gains, and use it to irrigate crops. In an average year, the returns to crops are Existing Storage and could related costs be suitably greater than the marginal cost of city water supply, but in particularly compensated for? Would physically dry years, it may be considerably cheaper for the city to buy stored connecting existing storage provide water from farmers than invest in other alternatives. greater resilience? Upstream hydropower facilities are being optimized for energy production. Under what circumstances would it be economic to optimize from a water storage/flood protection perspective as well? Reoperation How is this storage operated now, City X’s upstream natural landscape storage is being impacted by by whom, and what gains could be alien vegetation that is accelerating evapotranspiration. Control over affected from its reoperation? this landscape is shared between private and public parties. Can City X influence governance structures to reduce the negative impacts of alien vegetation on natural storage and flows? Environmental Can any environmental and social If changed behavior by farmers or landholders in watershed areas and Social impacts or distributional effects be is required, which results in lost livelihoods, can this be effectively impacts (across suitably mitigated or compensated compensated for? all solutions) for? Have land rights, private ownership, and applicable regulations in the region been considered? Source: Original to this publication. services desired, a combination of options may be worth feasible options; it does not promote an exhaustive examining. Table 7.3 outlines some of the key resources consideration of options. Guided by the water service re- that could be considered in identifying additional storage quirements and performance indicators outlined in Stage opportunities. 1.B (table 7.1), options that are obviously unable to meet the needs at hand or are indicated as having unaccept- For most forms of natural storage, "new storage" assess- able risks or impacts may be discarded to focus on those ments would involve understanding the potential of the options that are promising, even if further study is needed natural environment to retain and release freshwater in a before an informed decision can be made. somewhat predictable (if not actually controllable) way. If natural storage options are not already included in formal Stakeholder and Impact Analyses planning documents, broad scoping studies may need to Characterize the extent to which additional water secu- be undertaken. rity and storage  options positively or  adversely impact stakeholders: Similar to the stakeholder mapping exercise The process outlined in this stage aims to encourage conducted to characterize stakeholder interests related water planners to consider the full range of potentially to the current system, stakeholder interests for additional The Integrated Storage Planning Framework: A Step-by-Step Guide 93 BOX 7.3  Comparing Storage Options Across Storage Types Denver, Colorado, and surrounding cities draw water supply from the South Platte River, a tributary of the Colorado River. With the growth of the population in the Front Range, the Colorado General Assembly, in coordination with the Colorado Water Conservation Board, the Colorado Division of Water Resources, and the South Platte Basin and Metro Roundtables, commissioned a study to look at opportunities to increase water storage. The resulting South Platte water storage study compared a range of water storage options, including groundwater recharge, expansion of existing reservoirs, and new reservoirs. One aspect of the study was to quantify the amount of “available water for storage” at various locations, considering both the hydrological supply, demands, and the legal obligations of the state to comply with the Law of the Colorado River, given its position as an upstream state. The study then compared storage options, as well as packages of storage options, including mainstream dam versus upper basin storage and mid-basin stor- age versus packages of aquifer storage. For each of these packages, the study then rated performance across a range of indicators, including whether the package met firm yield requirements, whether they enhanced stream flows overall, and at times of low flows at the border (to meet legal water sharing requirements), the potential for flood attenuation, environmen- tal factors, and recreational provisions, among others. By comparing types of storage across each other, several important conclusions were reached, including: n “Combinations of storage options working conjunctively can provide significantly more benefit than individual options. A combination of upper basin and lower basin storage concepts rivals the large mainstem dam option for firm yield benefits. However, there will be a reduction in efficiency as the number of projects goes up.” n “Aquifer storage projects are more limited by recharge and recovery rates rather than storage volume. Typical aquifer storage projects are designed as supplemental supply sources, not as projects to recharge large volumes of water diverted during peak spring snowmelt periods. This results in lower firm yield and does not attempt maximize use of potential storage capacity as occurs with surface reservoirs. However, a related benefit is that aquifer storage projects are relatively low cost and can be scaled up over time (not constructed all at once). These unique characteristics make aquifer storage projects difficult to compare to surface water storage projects.” n “Storage options lower in the basin tend to be more efficient (better storage yield ratio) because there is more water available. However, they are further from the main demand centers." n “Using existing irrigation canals to fill storage sites could significantly reduce infrastructure costs for some concepts. Partnerships with irrigation companies and available canal capacities should be investigated further.” While these findings are basin and context specific, they illustrate the value of considering and comparing a range of storage options in various combinations, to better understand how various storage options can be used to best meet the needs of populations. Further, some of the findings related to comparing surface and groundwater storage may hold across basins. The tools and methodologies used in the study may be of use to others undertaking similar studies, including the selection of attributes (or indicators) used to evaluate storage options. Sources: LRE Water 2017; C. Nobel, LRE Water, interview with World Bank, January 19, 2019. storage options should also be assessed. This character- those related to the water service requirements and attri- ization should be conducted for both retrofitting current butes in particular. It should also examine existing water systems as well as for any new elements of the system allocations and rights, the incentives and perceptions of that are identified. This mapping exercise should charac- stakeholder groups, and the benefits received by specific terize the main benefits for the primary interest groups, groups. Distributional impacts of proposed options should 94 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE TABLE 7.3 Identifying Additional Storage Opportunities for Core Storage Services STORAGE CORE STORAGE POTENTIAL DATA SOURCES METHODOLOGICAL REFERENCES OPPORTUNITY SERVICES New l Previous studies of groundwater Resources on groundwater assessments groundwater from IGRAC: https://www.un-igrac.org/areas- Regional and global datasets expertise/groundwater-assessment The Global Groundwater Information System (GGIS) maintained by the International Groundwater Assessment Center (IGRAC), available at: https://www.un-igrac.org/global- groundwater-information-system-ggis Managed aquifer ll Some wide-area assessments of MAR or MAR: https://gripp.iwmi.org/natural- recharge (MAR) Underground Taming of Floods for Irrigation infrastructure/water-storage/ (UTFI) potential have been developed based on geological maps and remote sensing UTFI: https://gripp.iwmi.org/natural- approaches infrastructure/water-retention-3/ underground-taming-of-floods-for-irrigation- utfi-2/ Sand dams l Local knowledge and physical surveys For Africa, the World Agroforestry Centre and subsurface developed an atlas of possible water dams At the sub-catchment level, desktop feasibility harvesting opportunities, including sand can be established with the help of GIS and dams and subsurface dams: "Mapping remote sensing the Potential of Rainwater Harvesting Technologies in Africa: A GIS Overview on Development Domains for the Continent and Nine Selected Countries" Excellent Development maintains a knowledge hub on sand dams and has published a manual on sand dams Flood channels, l Global high-resolution data on floodplains by Guidance on Floodway Analysis and floodplain GFPLAIN Mapping by US Federal Emergency storage, and Management Agency (FEMA) polders Room for the River Programme in the Netherlands European Union (EU) resources on environmental options for flood risk management Constructed l Land-use maps A Catalogue of Nature-Based Solutions for wetlands and Urban Resilience urban sponges Estimates on the source and volume of water to be stored (stormwater, wastewater) A Manual for Integrated Urban Flood Management in China, featuring China’s Sponge City Initiative Watershed lll Local knowledge and physical surveys Global Database on Sustainable Land management Management with documented practices and sustainable At the sub-catchment level, desktop feasibility from all over the world land can be established with the help of GIS and management remote sensing WOCAT database and Sahel Water Harvesting Tool -https://sahel.acaciadata. com/ (table continues next page) The Integrated Storage Planning Framework: A Step-by-Step Guide 95 TABLE 7.3 Identifying Additional Storage Opportunities for Core Storage Services (cont.) STORAGE CORE STORAGE POTENTIAL DATA SOURCES METHODOLOGICAL REFERENCES OPPORTUNITY SERVICES Dams and lll National and regional water resources The Food and Agriculture Organization of the reservoirs development plans United Nations (FAO) Manual on small earth dams Dam safety inspection reports World Bank Good Practice Note on Dam Systematic high-resolution assessment of Safety and associated technical notes global hydropower potential by the Delft University of Technology Hydropower Sustainability Guidelines and Assessment Tools Global pumped hydro atlas by the Australian National University l Improving the availability of water during drier periods l Mitigating the impacts of floods l Regulating flows for other purposes: such as hydropower, transportation, or recreation Source: Original to this publication. be analyzed, as well as opportunities for affected stake- or detrimental impacts of additional water management holders to share in the benefits of the options under con- infrastructure and measures on the environment and will sideration. Impacts on stakeholders should be considered enable early identification of cumulative impacts from the across a range of geographies, as projects can have var- options identified, allowing planners to understand how ied impacts across geographic areas. It is also valuable introducing those changes may remediate, exacerbate, or to identify the different time frames of interest for each create environmental risks. stakeholder and the potential differences in access to in- formation and technology. It is important to identify these 7.2.3 Stage 2 Outputs variables that will determine the practical capacities and interest of stakeholders to contribute to solutions, includ- A model (or linked models) of the current system: The ing the willingness and capabilities of private sector actors model will include current availability of water across to contribute with financing, knowledge, and technology. sources, current and expected changes in water demands, Stakeholder mapping should be conducted in consider- and an understanding of how well the existing system is ation of the full system, taking into account not only the serving and can serve those requirements. Resulting from interests of individual actors in the current system and this is an indication of whether there are gaps between the additional options but also how those interests would in- supply and demand of water services to meet existing and teract with various permutations of additional water secu- future requirements, and whether additional water storage rity and storage options. The stakeholder mapping could is needed in the system. also include identification of the degree to which differ- ent stakeholders will be involved in the planning process. A set of potential solutions: In considering additional Levels of interaction can vary from informing stakeholders water management options, including storage options, to consulting with them to collaborating with them or em- following the two-part scoping exercise should yield a powering them to do the planning directly. broad set of solutions, including options to get more out of existing storage and options for new, additional storage Characterize the potential impacts of additional water across the range of available storage types. security and storage options on the environment: As with the stakeholder mapping exercise, a preliminary A stakeholder map and environmental screening: Stage screening of environmental impacts should be carried out. 2 ends with a stakeholder map and environmental screen- This is an opportunity to pre-emptively identify beneficial ing, which are further developed and may begin to reveal 96 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE some options as feasible or infeasible from a social, en- The focus is on examining combinations of options vironmental, economic, or technical capacity perspective. rather than each individual option sequentially, because Outputs from Stage 2 form the foundation of the devel- it is important to understand the interactions among the opment of more detailed scenarios in Stage 3, whereby current and planned forms of storage as part of hydro- actual decisions can be made around funding further in- logical, economic, and governance systems. Each poten- vestigations of promising options. tial combination could be considered a storage scenario, which can then be compared with other storage scenarios until the "best" scenario(s) for further study and potential 7.3 STAGE 3: BRINGING IT TOGETHER: investment are identified. MAKING DECISIONS  The level of detail in each scenario and the sophistica- tion of the analytic techniques used to compare them KEY QUESTIONS TO ANSWER IN STAGE 3 could vary significantly. This is because each scenario is based on the data, analytic tools, and modeling capacity › What are the combinations of options— management and new investment—that best available to the sponsors, as well as the time and resourc- meet the development objectives of the range of es available. These approaches could be conceived of as stakeholders? existing on a continuum, such as is suggested by f igure › What new investments or management 7.2. While there are likely significant benefits to more so- measures should be taken forward for further phisticated approaches, the important thing is to consider study and/or preparation? the full range of issues, even if only in a relatively simple or manual way. Utilizing the process to make decisions: Having identified 7.3.1 Stage 3.A: Defining Scenarios the problems to be solved and the needs of stakeholders (Stage 1), the parameters of the system and the range of In order to compare costs and benefits of ranges of in- specific options that could be pursued (Stage 2), the focus terventions at the system scale, scenarios need to be of Stage 3 is on how to make choices about the combina- defined. A scenario is a grouping of interventions—a set of tions of options that make the most sense to carry out, specific potential investments and management changes including complementary non-storage measures. in a particular combination. The scenario includes specific FIGURE 7.2 Complexity for Considering Storage Scenarios Simple Complex APPROACH Manual comparison of most promising Multi-objective optimization approach involving scenarios computerized simulation of multiple scenarios DATA Previously existing early-stage studies Previously existing feasibility studies Professional estimates Remote sensing data Multidimensional modeling, including simulation across MODELING Basic hydrological model systems, potentially linked with optimization Can be done in-house or using relatively Likely requires contracting external expertise, including COST & TIME short-term and inexpensive consulting sophisticated modeling capacity expertise Source: Original figure for this publication. The Integrated Storage Planning Framework: A Step-by-Step Guide 97 details about each potential investment’s size, location, financial, economic, social, environmental, and gover- storage performance, as well as the hydrological linkages nance parameters most relevant to stakeholders (box 7.4). to other storage or water flows in the area of study. Information to guide the development of criteria and ac- companying metrics will have been collected and refined The amount of detailed data available for each scenario using the framework, beginning with Stage 1 with the defi- will depend on the existence of previous studies. Where nition of service attributes, and will continue to be useful previous studies do not exist, data will need to be estimat- for establishing scope of detailed studies once potential ed based on techniques such as professional estimates or investments have been identified. Engagement of stake- remote sensing. Since at this stage the purpose is to sim- holders in the selection of decision criteria is a critical ply compare options for further investigation, very specific component of participatory decision-making. and detailed data—such as that needed for detailed de- signs— is not yet necessary. 7.3.3 Stage 3.C: Comparing and Assessing Scenarios 7.3.2 Stage 3.B: Establishing Decision Criteria How to evaluate the options and make decisions: The Options should be evaluated against a broad set of approach to understanding the pros and cons of each criteria to measure the performance of the options. scenario—including how they might be adjusted to im- Regardless of the complexity of scenario modeling re- prove benefits and reduce costs—will vary significantly by quired, these criteria would ideally cover the technical, the complexity of the need and the capacity of the entity BOX 7.4  Storage Decision Criteria Key considerations to define decision criteria for integrated storage planning include: n Technical: Hydrological and other factors that affect the technical performance of the storage system, including vol- umes of water stored, levels of reliability and redundancy, physical location of storage solutions, seasonality, and in- teractions between different parts of the system. These factors broadly address whether a particular solution will do the job. Technical criteria need to be explicit around the nature of the service or services required and their attributes, including increasing water availability, reducing flood impact, and regulating water for other purposes. n Financial: Likely financial costs, including investment costs and long-term maintenance costs, and any potential cost recovery or income that would flow from the form of storage being considered. n Economic: Non-financial costs and benefits that are associated with the storage solution, such as the value of services not being charged for (e.g., public health benefits, reduced flood impacts) or the lost livelihoods associated with land- use changes. While environmental and social costs should be considered within an economic analysis, they are also broken out separately below for completeness. n Environmental: Environmental impacts (gains or losses) that are associated with the storage investments (e.g., changed flows, fragmentation of river systems, increases in natural wetlands water levels, and impacts on biodiversity). n Social: Impacts on people, both positive and negative, of new storage investments or different operating protocols (e.g., changes in livelihoods necessitated by new approaches to natural storage, impacts of new infrastructure, resettlement estimates). This should include an analysis of the distributional impacts of storage and possible measures for benefit sharing, as well as the potential engagement of stakeholders in the governance of new storage. n Governance: Different types of storage will require different forms of governance, which may significantly impact on the likely performance and sustainability of the desired services. Consideration should be given to who will own, operate, and maintain the investment and how they will be held accountable for the performance of the investment. Source: Original to this publication. 98 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE exploring the scenarios. There is likely a continuum of comparable investments, local labor, and materials options for the overall approach to developing and com- costs. These should include: paring scenarios that could be adapted to meet the cost, ¡ Financial costs of storage development and any time, and capacity constraints of the sponsoring institu- potential financial returns (e.g., will any user be tion/s. This section explores some of these approaches prepared to pay for the service?). ranging from relatively simple to potentially cutting-edge ¡ Recurrent financial costs associated with stor- approaches. age system management and maintenance as well as period rehabilitation and who would be Less-Detailed Stakeholder-Focused Approach responsible for these. Where the storage problem is relatively clear and con- ¡ Economic costs and benefits of the investments tained, it should be possible to pursue a straightforward (in other words, costs or benefits that are not approach that is based primarily on local consulta- directly monetized). For example, an economic tions, building on local experiences, and where compar- cost may be the loss of productive land to a MAR isons between scenarios are done as a series of local zone or small dams, while an economic benefit interactions. may be the improved household health due to more reliable local water supply. (Further details Local storage investments can be combined in different are provided in box 7.5.) ways to produce different storage scenarios, which can » Environmental and social impacts: Some of these then be compared. The different elements that could be may also be captured in the economic cost-benefits, considered are: but it is important to identify and quantify these as part of the stakeholder engagement process. Issues » Potential investments: Each of the potential invest- to be identified include direct local impacts (lost land ments is mapped and its storage service contribu- or lost livelihoods) as well as potential downstream tions estimated over time and space (service area). impacts caused by reduction in or the shifting timing Different sizes, locations, and combinations of these of downstream flows (these may be environmental, potential investments (including associated "soft" such as on downstream wetlands or fisheries, or measures such as management approaches) rep- social, such as through reduced fish catch or water resent different storage scenarios for investigation. available for downstream irrigation). » Hydrological system perspective: How these dif- » Governance requirements: Each investment will ferent storage nodes interact under each scenario is require someone or a group of stakeholders to take mapped and estimated (either manually sketched or responsibility for the development, operation, main- modelled by computer) to help estimate: tenance, and occasional rehabilitation of the storage ¡ Hydrological interactions, such as the extent to investment. Governance arrangements need to clar- which the different investments may be addition- ify who this will be, where they obtain their authority al to one another in terms of water storage or and resources, what performance incentives they may reduce one another’s performance. are subject to, how they will need to cooperate with ¡ Aggregate storage system performance com- others, and who holds them accountable. pared to the previously identified needs, as well as for comparison across scenarios. The data on storage scenarios developed can be present- ¡ Potential ancillary services could also be ed in simple side-by-side forms that would facilitate easy identified. understanding and comparison by a variety of stakehold- ¡ Robustness to climate extremes should be es- ers. Table 7.4 is an illustrative example of this approach timated. For a small catchment, this may be with two scenarios, but additional scenarios could be pre- as simple as extending previously recorded ex- sented in this format. tremes by a certain percentage. » Financial and economic costs and benefits: Tables like this, or other simple presentations that are ap- Approximate costs of each of the interventions propriate to the local context, could be used to facilitate in each scenario could be estimated based on community discussions about which storage scenarios The Integrated Storage Planning Framework: A Step-by-Step Guide 99 BOX 7.5  Good Practices and Resources for Economic Evaluation Good Practices. n Understanding the distribution of costs and benefits across different stakeholders must be an essential exercise in economic evaluation of storage options—built, nature-based, or hybrid. As such, costs and benefits of all stakeholders impacted by the project must be included in the evaluation. This is especially relevant in transboundary watercourses, where interventions in one jurisdiction can have positive or adverse impacts in another. n Systematic biases are observed in planners’ estimation of potential delays, cost-overruns, and expected benefits, as well as in the study of social impacts of dams (Jeuland 2020). Analysts must be cognizant of these and attempt to identify and remove these throughout the valuation process. n Attention must be paid to non-efficiency objectives and institutional constraints faced by planners, social and cultural evolution of attitudes of different stakeholders, as well as risk perceptions which place different weights on potential gains and losses. Resources: Valuation of dams and built infrastructure: Khusro M. and B. Roy. Re-Thinking the Economic Evaluation of Water Storage. Department of Economics and the Water Institute, University of Waterloo, Ontario, Canada. (unpublished). Whittington and Smith 2020; Jeuland 2020; Baker and Ruting 2014. United States Federal Interagency River Basin Committee’s Proposed Practices for Economic Analysis of River Basin Projects (Subcommittee on Evaluation Standards 1958). FutureDAMS, Research Themes: Economic Analyses: Ex-post Economic Analysis of Dams. Accessed March 10, 2022. Available at: https://www.futuredams. org/research-themes/economic-analyses/ex-post-economic-analysis/. FutureDAMS, Research Themes: Economic Analyses: CGE Economic Modelling. Accessed March 10, 2022. Available at: https://www.futuredams.org/ research-themes/economic-analyses/cge-modelling/ FutureDAMS, Research Themes: Economic Analyses: Agriculture and Livelihoods. Accessed March 10, 2022. Available at: https://www.futuredams.org/re- search-themes/economic-analyses/agriculture-and-livelihoods/ NBS valuation: Browder et al. 2019; Wishart et al. 2021; Kalra et al. 2014; World Bank 2019b. For a rapid screening of costs and benefits associated with a range of green infrastructure, readers may use the Earth Economics’ Green Infrastructure Benefits Valuation Tool (Earth Economics 2018) as a starting point. InVEST (Integrated Valuation of Ecosystem Services and Trade-offs). Accessed March 10, 2022. Available at: https://naturalcapitalproject.stanford.edu/software/invest. Lette and de Boo 2002. GI-Val is the Mersey Forest’s Green Infrastructure Valuation Toolkit. Accessed March 10, 2022. Available at: https://www.merseyfor- est.org.uk/services/gi-val/. would be most appropriate to meet their needs. Such an consideration. Cost-benefit analysis uses market values approach has the advantage of not only facilitating a deci- where possible and adjusted or estimated monetary val- sion but also increasing stakeholder ownership and there- ues as needed (Subcommittee on Evaluation Standards fore commitment to the next stages. 1958). Traditional cost-benefit analysis has routinely been carried out for built storage projects and can trace Economic Analysis of Storage Investments its origins to water infrastructure investments (Jeuland Economic analysis is an important tool for policy mak- 2020; Whittington and Smith 2020). On the other hand, ers deciding on the allocation of scarce public resources the benefits of nature-based solutions (NBS) may not across competing investment needs. Ex-ante analysis have market values that can be used for economic evaluates the anticipated benefits and costs—tangible evaluation, and such analyses may rely on non-market and intangible—of a proposed intervention, considering a valuation techniques such as contingent valuation (will- with-project and without-project scenario as well as proj- ingness to pay and willingness to accept) and revealed ect alternatives. A well-defined counterfactual situation preference methods, which estimate values based on the is important for comparing scenarios to determine the actual choices that people make, such as what a family benefits and costs attributable to the intervention under spends to travel to a scenic reservoir area for recreation. 100 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE TABLE 7.4 Illustrative Comparison of Small Catchment Storage Scenarios SCENARIO 1 SCENARIO 2 Storage investments 15 kilometers of terracing in X area; 3 small 10 kilometers of terracing in X area and soil micro dams in locations a, b, and c; 1 km2 MAR regeneration in Y area. Sand dams in 2 small settlement area ephemeral rivers. Hydrological performance Extends growing season by 43 days in average Extends growing season by 35 days in average year year If 20-year drought, extends growing period by 21 If 20-year drought, extends growing period by 25 days days If twice as bad as previous worst drought, Reduced evaporative losses by an estimated extends growing period by 3 days 10,000 cubic meters per year compared to surface reservoirs The potential for oversaturation of terraced lands during the wet season Financial and economic $720,000 estimated construction costs plus $700,000 estimated construction and materials costs and benefits some voluntary community labor on terracing. cost plus voluntary community labor for Compensation to 3 families who give up a terracing and construction of sand dams. An portion of their land to be inundated by the international expert to advise on sand dams. small check dams. Extended growing season Extended growing season estimated to increase estimated to increase farmer income by 15 farmer income by 12 percent. Minimal O&M for percent, but they will have to pay $1,300 annually sand dams, but more time inputs required to for O&M of new infrastructure. maintain reduced tillage cropland. Social and environmental Some community members end up with reduced Crop diversification improves soil quality but costs and benefits land holdings, but no one needs to be resettled. reduced disturbance increases the need for Small dams provide water for drinking as well as pest management. No resettlement or land for irrigation, but downstream villages may end acquisition needed. up with less water during the dry season. MAR settlement area provides habitat for ecologically important birds. Governance considerations Lack of history of paying for water in the area Controls over water abstraction will need to be poses a potential challenge to the collection of agreed on to avoid exhaustion of the water held tariffs needed to operate, maintain and assure in the sand dams during the dry season. the safety of the small dams. Source: Original to this publication. Note: This table intends to introduce the estimates of additional storage associated with each option and then translating it into a service, such as additional water for crops. For instance, to estimate crop water requirements see CropWat, a decision support tool developed by the Land and Water Development Division of FAO, available at: www.fao.org/land-water/databases-and-software/cropwat/en/. O&M = operation and maintenance. Such approaches are also used for built infrastructure management options and economic values” and are used projects, which also often have non-market benefits and to simulate behavior of the system, including its response costs associated with them. to the addition (or removal) of storage infrastructure (Harou et al 2009; Jeuland 2020). CGE models simulate Given the complexity of the water resources system and economy-wide impacts of large interventions, specifically the broader knock-on effects of large investments such their impacts on equilibrium prices and demand for goods as large dams, there are two tools that offer greater un- and services. Both tools offer the advantage of situating derstanding of proposed investments: (a) the use of the evaluation of economic costs and benefits within the hydro-economic models (HEMs), and (b) the use of com- context of broader system performance, which is essen- putable general equilibrium (CGE) models (Jeuland 2020). tial to applying an integrated approach to water storage HEMs integrate “water resources systems, infrastructure, planning. However, despite the potential power of these The Integrated Storage Planning Framework: A Step-by-Step Guide 101 tools for integrated planning, they are not widely used in water elsewhere in the system (i.e., reducing oth- ex-ante economic analysis of dams or other water stor- er storage—and water availability—in a similar age investments. This is, in part, due to significant data amount). requirements, and in the case of CGE models, the lack of ¡ Their combined service delivery characteris- market prices for water and environmental services and tics, for example, estimated contributions to in- the need to correctly characterize water uses and their creased water availability or flood protection at substitutability (Jeuland 2020). particular times of the year (including for particu- larly dry or wet years) in particular places, as well While ex-ante economic analysis is used to predict how a as, for example, the system’s collective resilience storage project or investment will do in terms of expected or redundancy. benefits and costs, ex-post analysis of real-world impacts » Incorporate the hydrological behavior of non-storage enables the derivation of conclusions about the actual solutions, if desired, to test how non-storage invest- performance of different storage interventions. Ex-post ments might contribute to meeting the decision-cri- analysis can be done for individual investments or as sys- teria in an integrated way. tematic (“Large-N”) studies using datasets covering large numbers of interventions, from which it is possible to infer In addition to this hydrological modeling, storage scenari- causal relationships. os would need to include estimated information about the other key types of parameters—financial, economic, envi- Other types of analysis that are highly relevant for inte- ronmental, social, and governance aspects. grated water storage planning include analysis of the dis- tributional impacts of storage interventions, considering Such modeling approaches are complex but increasing- upstream and downstream users, as well as analysis on ly possible due to advances in modeling approaches and the cost-effectiveness and fiscal impacts of large invest- cloud computing. Box 7.6 includes examples of modeling ments being implemented with public funding. approaches that are designed to test the robustness of different combinations of infrastructure with multiple de- Sophisticated Large-Area Optimization Approach cision criteria. A more sophisticated modeling approach to adequate- ly expose inter-linkages and trade-offs among dif- Decision-Making ferent options will be required in some cases. These Multi-criteria decision-making (MCDM) (or multi-cri- can include a storage gap that is severe, covers a large teria analysis) techniques are widely used in water re- geographic area, and includes multiple systems beyond sources management for the selection of infrastructure, hydrology or multiple stakeholder groups. For example, nature-based, and non-structural solutions to water examining storage scenarios in a large basin with multi- management challenges. The typical steps involved (Yoe ple cities, industrial interests, agriculture, significant ener- 2002) are similar to those employed in the problem-driven, gy needs, as well as multiple existing storage systems is system approach to water storage planning described in better carried out with the help of multi-criteria optimiza- this paper, specifically: tion modeling. » Define the multi-criteria problem and objectives The modeling approach would need to: (Stage 1.A) » List and describe alternatives for meeting objectives » Be able to create different storage facilities, along or goals (Stage 2.B) with their key parameters, as nodes within a spatially » Define criteria, attributes, or performance indicators disaggregated network, and be able to model the in- for alternatives (Stages 1.B) teractions among them to derive conclusions about » Gather data to evaluate criteria (Stages 2.A and 2.B) the overall system performance. This would include: » Arrange the alternatives against the criteria (Stages ¡ The likely interactions of different storage nodes, 3.A and 3.B) including whether they are likely to provide genu- » Assign weights to criteria (Stage 3.C) inely additional storage or simply store the same » Rank alternatives and get results (Stage 3.C) 102 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE BOX 7.6  Multi-Criteria Decision-Making Using Advanced Systems Modeling and Multi-Objective Optimization Multi-criteria decision-making (MCDM) encompasses a broad class of techniques used by decision-makers faced with com- peting options. They can be used to identify the most preferred option, to rank different options, to shortlist a select few, or to distinguish between acceptable and unacceptable alternatives (DCLG 2009). Unlike cost-benefit analysis, where all op- tions are evaluated on their economic merit by converting costs and benefits into monetary streams, MCDM methods allow inclusion of a variety of criteria to reflect competing economic, ecological, and socio-cultural objectives. These criteria can further be assigned different weights using stakeholder preferences. When undertaken in a participatory setting, MCDM can empower all stakeholders with an understanding of the trade-offs involved in selecting different options. MCDM can be used in situations where a discrete number of alternatives or an infinite continuum of them exist. They range from simple methods involving pairwise comparison of alternatives to using advancements in computational power to co-optimize up to 10 objectives at the same time. The latter allows development of multi-dimensional possibility frontiers that can be represented in simplified terms using multi-dimensional visualization techniques to enable discussion of com- plex trade-offs among different stakeholders. A multi-criteria systems modeling approach is employed in the Tana River Basin in Kenya (Hurford et al. 2020) to inform how controlled releases from multiple reservoirs on the river can be optimized to maximize the services delivered through the combination of built and natural assets of the river (figure B7.6.1). These sometimes-competing services include provision FIGURE B7.6.1 Optimized Environmental Flow Failures Against Flood-Dependent Provisioning Services ure ion re on w f me l tch ain al l nn p ca ual fai men l n a atc plai ual griall rec ual es tch l –) (–) ure ntal lur tal nn h ne h flo viron nnua ag od re nnua flo ) viron nnua (to imp nnua ) ) es tch ha (ha (to fis s ) s) h ultu ssi ca odpl nnu allcult ess es s( n fi nn c od nn od nn es ( e nn ca en an a a flo n a sh an a na flo an a flo an a sh an a c all (ton –)) ean ) ) ail a all ea llim Me Me Me e e Me h aM M M M c ar r n n n e ((h on w n ff ll n ffi ll h h o n ua a ri a a h h h so al ll s ( ll ua ua u a)) a)) ch at ch e (( iio siio nttal –) ua s s s)) s)) ec a ua nu u fl me ua me ua s s ato e ntta (– s ((– u plla nu u n ha s)) ttc ha s)) tc i i u nu es es nn nn i irron nu ss ss nn plla nn n n h a nn nn urre n n ne ne nn nn an an es es onmnn ca ca n ( an es es h (( aiin h ((t aiin 0 1,450 10,370 87 0 1,450 10,370 87 aiil me aiillu e nn nn an od an a na e ullttu ce an pc pc na urre od a na urre urre na on on na ulltt c c an vi n a viirro a A B hrrii n shr an mp p e 87 tto to grrii rre grriic d rre an an lu 87 n m 0.0 u es es an an w f on w ff n ea ea an p dp m ((to hriim 10,350 0.0 ea ea ne ne 10,350 a ea ffllo ea Me Me a ea attc d d Me d Me od fa a nn nn Me o M Me M Me cu cu e ch Me ch oo oo M M oo oo on ton sh M M c nv nv M M attc ffllo ffllo ffllo ow ow ((tto s s en en ca ca 86 e e ag ag ffllo ffllo 1,400 10,300 86 c c 0 0 1,450 1,450 10,370 87 0 1,450 1,450 10,370 1,400 10,370 10,30087 87 a a 0.5 0.5 A AAA 10,250 85 B 10,250 85 1,350 1,350 1.0 10,200 1.0 84 10,200 84 1.5 1,300 10,150 83 1.5 1,300 10,150 83 Director of preference of preference preference of preference preference 10,100 82 10,100 1,250 1,250 82 2.0 2.0 10,050 10,050 81 81 Direction of of 1,200 1,200 10,000 10,000 Direction 2.5 Direction Direction 80 2.5 80 1,150 9,950 9,950 79 1,150 3.0 3.0 79 9,900 9,900 1,100 78 1,100 78 3.5 9,850 3.5 9,850 77 77 1,050 9,800 1,050 9,800 4.0 4.0 4.0 4.0 4.0 4.0 1,025 1,025 1,025 1,025 9,770 9,770 76 76 76 4.0 4.0 1,025 1,025 1,025 1,025 9,770 9,770 9,770 9,770 76 76 76 76 76 4.0 1,025 9,770 76 4.0 1,025 9,770 76 OptimizedOptimized system system (highlighted) (highlighted) operation operation Optimised (highlighted) Optimised (highlighted) Natural system Natural system system (no operation system operation built infrastructure) (no built infrastructure) (not highlighted) OptimizedOptimized system system (not highlighted) operation Optimised Current Current operation (not highlighted) system system system operation operation operation Optimised (not highlighted) system operation Natural system Natural (no built system (no built infrastructure) infrastructure) Source: Hurford et al. 2020. Current system Current system operation operation Resources: Amorocho-Daza et al. 2019; Huskova et al. 2016. (box continues next page) The Integrated Storage Planning Framework: A Step-by-Step Guide 103 BOX 7.6  Multi-Criteria Decision-Making Using Advanced Systems Modeling and Multi-Objective Optimization (cont.) of water for hydropower generation, reservoir fisheries, flood control, irrigation, and environmental reserve flows offered by the built infrastructures, as well as floodplain grazing and fisheries, riverplain gardens, beach nourishment, and marine and estuarine fisheries offered by natural infrastructure and flows to the sea. A subset of 10 performance metrics representing these services were used to define the optimization objective function. The optimization exercise delivered Pareto optimal operating rule sets for the system—each with different trade-offs and synergies between the different services offered by the built and natural systems, among them the finding that “mainte- nance of environmental minimum flows traded off against the flood dependent provisioning services,” leading the authors to believe that the existing regime of environmental reserve flows at discrete locations may not be suitable for protecting distributed environmental services. Meanwhile, low flow regime alteration correlated negatively with consistency of hydro- power generation and positively with provisioning services. If following the framework, the building blocks to carry out introduced in Stage 1.B, which can be refined into appro- the arranging of alternatives with weighting for their com- priate criteria for the area of concern. parison and ranking are laid in Stages 1 and 2. The selection of criteria used to compare water storage As described in box 7.7, there are various methods for scenarios, and the weighting given to the criteria as ap- MCDM, ranging in complexity and differing in accuracy plicable, would ideally involve stakeholders and experts and ease of use by participants. Among the most utilized who can speak to the different technical, environmen- methods are pairwise comparisons, ranking methods, tal, social, economic, and governance aspects that need and weighted summation. Pairwise comparison involves to be included. Depending on the nature of the storage listing the selected criteria, comparing them in pairs of challenge being addressed, the resources available, and alternatives, and indicating a preference for one alterna- the range of concerned stakeholders, the process for con- tive over another until an overall preference is revealed. sidering the outputs from this phase may range from a Ranking typically makes use of expert opinions to inform relatively simple and technocratic process to one involv- a scale (numerical or non-numerical) based on relative ing significant multi-stakeholder consultations. Criteria performance. Weighted summation involves allocating and their weighting can come from expert input or broad- standardized points to different criteria, assigning prefer- er stakeholder engagement, directly or indirectly, and any ence weights, and multiplying the weights by the points use must be carefully calibrated to make sure it is aiding to arrive at a total weighted score for each alternative rather than obfuscating decision-making. Expert and (Zardari et al. 2015). In water resources management and stakeholder preferences can be obtained directly through infrastructure selection, it is common for criteria to be cat- workshops and consultations. In addition to government egorized and given sub-weighting if the weighting sum- agencies and local governments that are charged with mation method is used. For example, in its prioritization of leading the planning process, outside experts from the new hydropower developments, the Royal Government of sector and representatives of beneficiary and other af- Bhutan used five categories (technical, economic, social, fected stakeholder groups may strengthen the quality of environmental, and balanced regional development) with the outputs with global and local knowledge and improve a total of 21 individual criteria to arrive at a final ranking the political acceptability of the ranked solutions. Criteria of projects (World Bank 2016c). The problem-driven, sys- and weights can also be collected more indirectly through tems approach lays out potential categories of criteria to surveys or by reviewing literature and databases. Deciding consider in Stage 3.B, utilizing comparable parameters on the criteria and their weights may take multiple rounds 104 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE BOX 7.7  An Interactive Platform for Informed Decision-Making Planning and operating water storage systems are generally multifaceted, requiring the consideration of multiple stakeholders and needs over space and time. Novel approaches are being developed, which employ both decision-support systems and visu- alization, to facilitate collaborative working sessions to understand and compare trade-offs between different alternatives and scenarios, and to better help stakeholders understand each other’s needs, values, and viewpoints. Finding ways to use models to inform and enable more productive stakeholder dialogue is a challenge: a promising example is the Decision Theater developed by Arizona State University (photo B7.7.1). The Decision Theater combines a variety of sciences and technical capabilities to allow for better understanding of complex problems while enabling technical and policy decision-makers to forecast the consequences of decisions before they’re made. The Decision Theater relies on a three-phased methodology: integrate models and data databases; conduct data and predictive analytics; and visualize the integrated models and data to convene engagements. The Decision Theater offers the ability to make decisions in a range of disciplines and with multiple streams of real-time information. The core physical component, called “the Drum,” is a meeting space with a dashboard that provides a simultaneous view of multiple, integrated models to show how changes in one area affect outcomes in others. This dashboard allows users to toggle back and forth between the visualizations and display different models or data results based on user preferences. Economic policy, emergency preparedness, disaster response, water sustainability, and food, energy and water supply chains are some of the policy areas where the Decision Theater has been used. PHOTO B7.7.1 Arizona State University Decision Theater Source: Arizona State University Decision Theater website. Accessed March 10, 2022. Available at: https://dt.asu.edu/ The Decision Theater has been used to help water decision-makers to better understand how water security is affected by pop- ulation growth, drought, climate change impacts, and water management policies, as well as to inform investment and policy changes around these factors. Coupled with various rainfall-runoff simulation models, the Decision Theater has encouraged viewers to manipulate assumptions and hypotheses about the future and to discuss policy options under different scenar- ios. It was used in Monterrey, Mexico to help stakeholders understand how the siting of upstream watershed management (box continues next page) The Integrated Storage Planning Framework: A Step-by-Step Guide 105 BOX 7.7  An Interactive Platform for Informed Decision-Making (cont.) interventions could influence downstream water flows, including flood attenuation. It has been used by decision-makers in Arizona to understand how different supply- and demand-side measures can be combined to create different water-related outcomes across different points in the system. Water decision-makers have used the Decision Theater to narrow the gap between scientific and political uncertainty by reflecting a shared understanding among researchers and decision-makers. The Decision Theater is one of many ways that modeling and visualization can be used to inform stakeholder dialogue and decision-making for water storage planning and operations. Given the significant difficulties associated with water storage planning, new approaches to decision support systems and visualizations like the Decision Theater can help to support decision-making under a systems approach. of discussion and may need to be done as an iterative environmental, social), and can therefore proceed to im- process. plementation. These might include, for example, certain landscape management approaches. However, for more Not all MCDM approaches are equal, and different ap- significant interventions that involve greater costs, risks, proaches have different qualities that may make one and impacts, additional investigations will be required. approach more appropriate than another, depending on the circumstances. Weighted summation, for example, is 7.3.4 Stage 3 Outputs considered computationally simple and highly transpar- ent if done properly, while pairwise ranking can become A short list of potential storage options: The options as- very complex and challenging the greater the number of sessment phase should have resulted in a short-list of po- alternatives being considered. One of the main criticisms tential storage options that, in combination, are most likely of MCDM is the potential for manipulation by omission or to meet stakeholder needs and that, based on preliminary addition of relevant criteria or alternatives, which can lead examination, are likely to be economically, technically, so- to a misplaced sense of accuracy of the results (Zardari cially, and environmentally feasible. Another factor to be et al. 2015). considered is the timing of need versus timing offered by the solution—digging boreholes and withdrawing ground- The results of MCDM or another multi-objective op- water, constructing and filling up a dam, and implement- timization exercise provide a framework for decisions ing watershed management are all measures to augment about which investments are worth investigating in supply. However, all three offer very different timelines on more detail, including through detailed feasibility stud- when the service will be delivered. In areas of acute stress, ies. Depending on the nature of the storage interventions it might become more important to deliver the service. (or alternatives) being considered, some of the storage options could be considered low-hanging fruit that do The investment preparation phase that follows is de- not require much further feasibility or other preparatory signed to support more detailed studies that establish the work. This may be true for relatively simple and cheap feasibility of the various investments being considered, interventions that were tested within the modeling exer- both individually, and in combination. cise to estimate unintended consequences (hydrological, 106 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE CASE 8 STUDIES The case studies featured in this chapter provide exam- storage have been tried with success and offer lessons ples of water storage solutions that have been implement- and insight for more holistic planning using the frame- ed in different parts of the world—built and natural storage work. Each case provides the relevant development and types—that serve a range of different purposes across institutional context and describes the evolutionary pro- diverse geographies (table 8.1). They are not applications cess through which more informed decisions were made of the Integrated Storage Planning Framework laid out in about storage investments and system operation in that chapters 3 and 7, but they are examples of where more particular basin or region. integrated approaches to planning and operating water TABLE 8.1 Case Study Index CASE TYPE(S) OF WATER SER- WATER REQUIREMENT(S) OF 5 R’S RURAL/ STORAGE USED VICE(S) PROVIDED STORAGE MET URBAN A Sri Lanka: Tank • Small • Increased water • Water provision for ecosystem • Rehabilitation • Rural Cascades in the reservoirs/ availability preservation and restoration Dry Zone and the retention • Flow regulation • Water provision for domestic Rehabilitation of structures needs and industrial Small-Scale Water processes Storage • Water provision to meet crop/ livestock requirements in seasons/locations without precipitation B California: • Large • Flood mitigation • Prediction and attenuation of • Reoperate • Rural Forecast-Informed reservoirs • Increased water excess water for risk reduction • Reform • Urban Reservoir availability • Water provision for ecosystem Operation to • Flow regulation preservation and restoration Enhance Water • Water provision for domestic Storage Efficiency needs and industrial processes • Water provision to meet crop/ livestock requirements in seasons/locations without precipitation C Cape Town: • Large • Increased water • Water provision for domestic • Raise • Urban Resilience through reservoirs availability needs and industrial • Reform Diversification of • Aquifers • Flow regulation processes Water Sources and • Water provision to meet crop/ Increased Storage livestock requirements in seasons/locations without precipitation • Water controlled for electricity generation (table continues next page) 107 TABLE 8.1 Case Study Index (cont.) CASE TYPE(S) OF WATER SER- WATER REQUIREMENT(S) OF 5 R’S RURAL/ STORAGE USED VICE(S) PROVIDED STORAGE MET URBAN D Mexico: Green • Landscapes • Flood mitigation • Water provision for domestic • Rehabilitate • Rural Water Storage and • Increased water needs and industrial • Reform • Urban to Adapt to watersheds availability processes Extreme Hydro- • Soil moisture • Prediction and attenuation of Climatic Events in • Aquifers excess water for risk reduction Monterrey • Water provision for ecosystem preservation and restoration E Indonesia: Getting • Large • Increased water • Water provision for domestic • Reform • Rural More from Existing reservoirs availability needs and industrial • Rehabilitate • Urban Built Storage: • Small • Flood mitigation processes Prioritizing reservoir/ • Flows • Water provision to meet crop/ Rehabilitation retention regulation livestock requirements in Investments structures seasons/locations without precipitation • Water provision to meet crop/livestock requirements throughout growing season • Water controlled for electricity generation • Prediction and attenuation of excess water for risk reduction F Namibia: • Aquifers • Increased water • Water provision for domestic • Raise • Urban Conjunctive • Large availability needs and industrial • Reform Surface and reservoirs processes • Rehabilitate Groundwater Management for Drought Resilience in Windhoek G Pakistan: • Large • Flow regulation • Water controlled for electricity • Raise • Rural Hydropower reservoirs generation • Reform • Urban Development • Small • Water provision for ecosystem in the Jhelum- reservoirs/ preservation and restoration Poonch River retention Basin structures 108 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE ANNEX 8A. SRI LANKA: TANK CASCADES IN THE DRY ZONE AND THE REHABILITATION OF SMALL-SCALE WATER STORAGE CASE STUDY BRIEF Summary Small-scale water storage is a key source of resilience for rural communities in many parts of the world. This case study describes an approach to plan the rehabilitation of small-scale water storage in the dry zone of Sri Lanka, where this storage solution, locally known as tanks, has been used for centuries to harvest surface runoff and rainfall. There are more than 15,000 small tanks1 in Sri Lanka, arranged in cascades, whereby tanks are hydrologically connected in a series. Tank cascades function as multipurpose water storage facilities for villages, providing a range of enabling services for irrigation, aquaculture, groundwater recharge, domestic drinking water use, and habitat conservation. The approach described in this case study—considering the rehabilitation of tanks within a cascade rather than as individual projects—was designed to help planners assess and understand the entire hydrology of the cascade before implementing interventions on any specific tank in the cascade. Hence, the approach helps to maximize the enabling services of each individual tank, especially to improve irrigation, while ensuring that rehabilitation of any one tank does not cause problems for other water users in the cascade or the surrounding ecology. The approach is based on multilevel participatory planning, computer simulations, and multi- criteria prioritization. The flexibility of the approach and its reliance on local knowledge mean that it can also be applied in situations where detailed hydrological databases for the tank cascade are lacking. Type(s) of water storage used › Small reservoirs/retention structures Water service(s) of storage provided › Increased water availability › Flow regulation Water requirement(s) of storage met › Water provision for ecosystem preservation and restoration › Water provision for domestic needs and industrial processes › Water provision to meet crop/livestock requirements in seasons/locations without precipitation Case Study | Sri Lanka 109 BACKGROUND FIGURE 8A.1 Cascade Water Course Schematic Diagram Built water storage has been critical to human settle- Main axis of cascade ments in Sri Lanka’s dry regions for centuries. This case Micro-catchment boundary study describes the development and application of a system-wide approach to the rehabilitation of small water storage in Sri Lanka’s dry zone. In this area, annual aver- age evaporation (between 1,700 mm and 1,900 mm) con- sistently exceeds the average annual rainfall (1,250 mm), resulting in the area being water constrained. The high- ly variable nature of rainfall, high evaporation rates for a greater part of the year, and the low availability of ground- water mean that stable human settlements were only Micro-catchment y ar area rshed bound possible thanks to water storage. Small tanks or village tank systems have been constructed since ancient times, mostly during the medieval period, and were the centers Wate of ancient village settlements (Panabokke, Sakthivadivel, Sid and Weerasinghe 2002). ev alle y Small tank cascades have been a key water storage method utilized to meet water requirements. A tank cas- cade is a connected series of tanks organized within the meso-catchment of the dry zone landscape (Madduma Bandara 1985). It drains to a common reference point of a Main valley natural drainage course, thereby defining a sub-watershed unit with a definite watershed boundary (f igure 8A.1). It stores, conveys, and utilizes water from first- or second- Small tank/retention area Flow order ephemeral streams. In these small valleys or me- River/Stream Paddy so-catchments, the surface water flows are intercepted by small, constructed earthen bunds to create reservoirs that Source: Based on Panabokke 2009. generally increase in size as one moves down the valley. Each small tank has its own catchment area. When farm- make a vital contribution to both food security and liveli- ers draw water from one tank to irrigate land, the irrigation hoods (FAO n.d.). return flows are captured in the next downstream tank (Madduma Bandara 1985). Nowadays there are 1,162 cascades with a total of 15,958 small tanks (Witharana Small tank cascades go beyond serving agriculture and 2020). Out of these, 90 percent of the cascades are lo- are multipurpose in function. Small tank cascades play cated within the north, north-central, south, northwestern, a dominant role in supporting irrigated agriculture (pri- and eastern provinces of Sri Lanka. marily paddy cultivation). However, they provide enabling services well beyond irrigation. Tank cascades function as Tank cascades have been globally recognized as im- multipurpose water storage facilities for villages in rural portant agricultural heritage systems. Tank cascade Sri Lanka, providing enabling services such as: systems are characterized by remarkable agrobiodiver- sity, traditional knowledge, and landscapes. In 2017, the » Water provision for perennial crops: Seepage wa- Food and Agricultural Organization (FAO) designated the ter that flows laterally from the tank sidewalls and cascade systems of Sri Lanka as “Globally Important tank bed sustains perennial crops like fruit (e.g., Agricultural Heritage Systems”; for farmers, tank cascades mango, wood apple) and food trees (e.g., breadfruit, 110 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE jackfruit). This also includes a variety of medicinal Farming communities and local water management in- plants and annual food crops. stitutions typically respond to these impacts by trying » Water provision for domestic needs: Many domes- to augment water supplies and improve water-use effi- tic water requirements, such as bathing, washing, ciency. Therefore, small tank rehabilitation and improve- and cleaning utensils, are met with water from the ment projects generally aim to (a) repair the distribution tanks. network to reduce conveyance losses and eventually » Water provision for ecosystem services: Tank cas- expand irrigated areas, and (b) increase water availabil- cades provide a range of ecosystem services includ- ity by raising or extending the tank bund, or both, and ing keeping the water table stable in nearby domes- by increasing direct withdrawals from streams or other tic wells. tanks. » Water provision for fisheries: Aquaculture in tanks is an important source of animal protein. While these standard measures tend to improve water availability in the short term and around a specific tank These enabling services strengthen the resilience of rural along the cascade, they can also alter the cascade’s hy- communities against shocks. A study conducted in one drology, causing impacts upstream and downstream. of the cascades (Mahakanumulla) in the Anuradhapura Altering the hydrology of one or more tanks by increasing District during the COVID-19 pandemic in the first half storage capacity, expanding the irrigated command area, of 2020 showed that the cascade community was able or diverting water from elsewhere in the cascade chang- to meet its food security needs despite a country-wide es the cascade hydrology. If the cascade has more water lockdown (Dayananda et al. 2020). This shows that the than demand, the effect of altering the cascade hydrology services provided by tank cascades can be an important may not have significant downstream impacts. However, source of resilience for rural communities. if water is limited in relation to total demand, there may be a serious effect on the water available to downstream users. Improvements to one tank can also affect other PROBLEM DEFINITION water users by inundating lands in the command area of the tank immediately upstream. Finally, because tank The enabling services that tank cascades have been pro- hydrology strongly influences groundwater levels, wells viding for centuries are now threatened by several pres- below tanks consistently have more groundwater than sures. These include climate change and related floods other wells, even in the driest parts of the year. Changes and droughts, outdated hydro-meteorological information in water availability in tank cascades can thus affect the systems, growing socioeconomic demands, lack of water- availability of groundwater for irrigation and other purpos- shed management, and water governance issues (MMDE es. For these reasons, rehabilitation of tank cascades re- 2017). The combined impacts of these pressures are (a) quires assessing and understanding the entire hydrology decreasing agricultural production due to water shortages of the cascade before intervention to any tank in the cas- resulting from increasing hydrological variability; (b) silt- cade is contemplated. ation of tanks as a result of soil erosion associated with deforestation of tank catchment areas and high-intensity While the hydrological assessment is considered key rainfall events leading to reduced storage capacity; (c) to guide rehabilitation planning, there has been no sys- decreased availability of year-round water supplies due tematic attempt to collect and organize the hydrologic to longer droughts and declining water quality, worsened data on the tank cascades for any portion of Sri Lanka’s by inadequate knowledge of seasonal weather patterns; dry zone. It is reported that the disappointing record of and (d) loss and damage of livelihood assets, including past small tank rehabilitation efforts stems from poor livestock and community infrastructure (such as village ir- understanding of tank hydrology, lack of data, and the rigation canals), due to very heavy rainfall events and flash variability of water supplies in the dry zone (Sakthivadivel, floods. In the floods of 2012, 982 village irrigation reser- Fernando, and Brewer 1997). This case study synthesiz- voirs and diversion canals were destroyed; 967 similar es existing methods developed in Sri Lanka to carry out a structures were destroyed during the 2014 floods (MI&WR system-wide hydrological assessment of tank cascades 2018). and guide rehabilitation interventions. Case Study | Sri Lanka 111 implementing this program with the support of the provin- INSTITUTIONAL FRAMEWORK cial irrigation departments in each province. Rehabilitation of tank cascades has become a top pri- ority to adapt to climate change. Sri Lanka has prepared a Strategic Action Plan for Adaptation of Irrigation and THE EVOLUTIONARY PROCESS: A SYSTEMS Water Resources Sector to Climate Change 2019–25 APPROACH and beyond to provide adaptation actions for the sector. A four-step hydrological assessment was developed to The recently updated Nationally Determined Contribution guide the rehabilitation of tank cascades in Sri Lanka’s (NDCs) 2020–30 has identified activities to “prioritize dry zone (f igure 8A.2). The assessment takes a systems abandoned tanks (including small tank cascade systems) approach to screen and evaluate proposals for tank cas- and canals to be rehabilitated in the most critical areas of cade rehabilitation that benefit the entire cascade, rather climate change vulnerability, paying attention to productivi- than a single tank. This approach was initially developed ty gains in restoration.” The National Environmental Action specifically for small tank rehabilitation projects in the Plan (NEAP) 2020–30 also recognizes the importance of Anuradhapura District of the North Central Province in cascade systems. The NEAP identifies ecosystem-based Sri Lanka (Sakthivadivel, Fernando, and Brewer 1997). cascade improvement programs as a key pillar to help en- The approach was subsequently refined for application in sure the country’s water security. other parts of the country and with new data sources and computer models. The Sri Lankan government has shown interest in maintaining the momentum of rehabilitating tank cas- 1. Cascade Screening cades. Cascade-based development was also agreed to as a national policy in 2016 (Tennakoon 2017). A major The first step consists of screening cascades using sec- national program called “Wari Suwubagya” was initiat- ondary data sources and field visits, followed by mul- ed in 2020 to rehabilitate 5,000 small tanks within two tilevel participatory planning and mapping of selected years, though progress has not met anticipated levels. In sites. Published topographic maps and reports provide in- view of this enormous task, the Department of Agrarian formation to identify cascades for a given area (1:50,000 Development under the Ministry of Agriculture and the topographic maps in the case of Sri Lanka). For each Irrigation Department under the Ministry of Irrigation is FIGURE 8A.2 Rehabilitation of Tank Cascades Guide Desk-based study of secondary sources (topographic maps) and field visits to screen cascades based CASCADE on total command area and total tank and cascade surface areas SCREENING Multilevel participatory planning to further identify priorities and build a comprehensive picture of water use along the cascade 1 CASCADE OUTFLOW Computer simulation to determine cascade outflow and runoff from individual tanks ESTIMATION CASCADE WATER Evaluate cascade water surplus as (WSc) = cascade outflow per unit area (Re)/mean annual rainfall SURPLUS (R50). If ratio is less than 5 percent, then rehabilitation may not be hydrologically feasible EVALUATION HYDROLOGICAL Tank water availability, as effective runoff, R 0/Irrigation requirement for Maha season (It) > 1 EVAUATION OF Tank storage capacity (S t)/Irrigation requirement for Maha season (It) > 0.3 TANKS Cropping intensity in Maha season (CIm) > 60 percent Source: Original figure for this publication. 112 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE cascade, key measurements such as total surface area, cascades being considered, and then guide the selection total tank surface area boundaries, and the total com- of sites for the multilevel participatory planning and map- mand area are recorded.2 ping exercise. In the tank cascade rehabilitation project in Sri Lanka’s Anuradhapura District, this initial screening Field visits are carried out to further screen the cascades. was helpful to narrow down the selected cascades from The data to be collected include information on water re- 76 to 50. sources, agricultural land (currently cultivated, potential for expansion), cropping patterns, seasonal cropping intensi- For the selected cascades, multilevel participatory ap- ties, population details (number of farmers for each tank), praisal and planning techniques are applied to investi- tank details (number of tanks in a village, spilling details, gate and plan the rehabilitation work with farmers. This physical condition, year of last rehabilitation), tank manage- multilevel participatory planning involves getting farmers ment (responsibility for tank management), and ground- in each village to propose work needed on their tank sys- water use (numbers of wells, water quality). For the tank tems and then getting representatives from all the villages cascade rehabilitation project in Sri Lanka’s Anuradhapura together to analyze the cascade hydrology and agricul- District, this information was collected by interviewing tural systems as the basis for formulating development small groups of knowledgeable farmers in each village. plans for the cascade. Participatory mapping is the main technique used for data analysis and planning in the case Following the field visits, each cascade is scored to as- of Sri Lanka (Jinapala, Brewer, and Sakthivadivel 1996). sess its land, water, and labor resources potential. The cri- teria include (a) potential beneficiary families; (b) average Farmers generally know the situations only for their own family holding; (c) Maha3 season cropping intensity; (d) tanks and not for the cascades as a whole. By getting yields; (e) frequency of tank spilling; (f) duration of spill; them together, multilevel participatory planning helps to (g) spill at the bottom of the cascade; (h) physical condi- build a comprehensive picture of water resources and tion; (i) conjunctive use of water; (j) potential new land for water use within each cascade. This multi-village partic- development, and any other special factors. The individual ipatory planning allows farmers to consider the develop- items in this list correspond to key dimensions of the cas- ment of water resources in the cascade. This is important cade screening as listed below (Sakthivadivel, Fernando, for two reasons: First, it allows farmers to make the best and Brewer 1997): use of the potential water supply, and second, it avoids conflicts that might arise from improvements made with- » The greater the number of beneficiaries, the better out considering effects on downstream users. use of investment funds. » The greater the landholdings, the more each benefi- The output of this exercise consists of six maps with ciary can benefit. information useful for the next steps in the process. » If yields are low due to insufficient water, the greater the These illustrate (a) cascade land and water resources, (b) potential yield gains from tank system improvements. cascade agricultural systems and land use, (c) cascade » If the tanks spill, the greater the cascade water sur- social and management institutions, roads, and other plus of the cascade. infrastructure, (d) proposed improvements to the use of » If the tank systems are in poor physical condition, the land and water resources, (e) proposed improvements to more they will benefit from rehabilitation. agriculture, and (f) proposed changes in land and water » Having groundwater implies that better water sup- management institutions. plies may help the groundwater, or vice versa. » The greater the potential to irrigate new land, the 2. Cascade Outflow Estimation greater the potential to benefit from investment. Once the cascades have been selected, computer sim- No single item in this scoring system is definitive; the scor- ulation models are used to determine the expected ing index must be considered as a whole. The higher the outflow from each cascade.4 The input variables for the score, the better the cascade’s potential for development. simulation typically are (a) mean annual rainfall (govern- These scores can be used to further reduce the number of ment records), (b) cascade area (measured from maps), Case Study | Sri Lanka 113 (c) command areas of cascade tanks (measured from per unit area and the mean annual rainfall. The cascade maps and checked by field visits and records), (d) present outflow per unit area is calculated by dividing the cascade main (Maha) season cropping intensity (from field data outflow by the cascade’s total area. The cascade water collection), (e) crop evapotranspiration values (from pub- surplus is calculated by dividing the cascade outflow lished data and CROPWAT5), (f) drainage return flow coef- per unit area by the mean annual rainfall. For Sri Lanka’s ficients (from Itakura 1994), (g) catchment runoff-rainfall Anuradhapura District, this ratio is greater than 5 percent. relationships (from Ponrajah 1982), and (h) water appli- This 5 percent value was estimated based on the expect- cation, conveyance, and distribution efficiencies, seep- ed runoff in a fully developed cascade under a minimum age, and percolation losses (average values used by the rainfall situation. Irrigation Department). Additional input variables might include ecological flow requirements. 4. Hydrological Evaluation of Individual Tanks Key outputs from the models used are the inflows, water To identify the potential of each tank in a cascade to releases, and expected spilling from each tank. During benefit from repair and improvement, the tank must be field data collection, partially quantified estimates for evaluated using water resource availability, tank stor- these variables, particularly for tank spilling, are gathered age capacity, and agricultural criteria. In this case study, to check the model’s output and ensure that no major mis- three indicators (tank water availability, tank storage ca- takes were made. pacity, and cropping intensity) were used to evaluate the potential of a tank system to benefit from rehabilitation The importance of deriving simple relationships based investment. These indicators are quantified once the over- on easily measurable cascade parameters, especially all cascade water surplus (step 3) has been evaluated. In in contexts where detailed data and information might different settings, alternative water resource availability not be available. In the application of these models to and agricultural criteria might be used, depending on data Sri Lanka’s Anuradhapura District, the simulated outflows availability. from tanks and cascades were related to easily mea- surable parameters such as cascade area, tank catch- » Tank water availability: A cascade may be hydrologi- ment area, tank water surface area, and command area cally well endowed, but the tank within it may not be (Sakthivadivel et al. 1996; Sakthivadivel, Fernando, and so. Water supply adequacy of a tank measures the Brewer 1997). The analysis indicated that the cascade extent to which the effective runoff (R0 ) to the tank outflow is directly related to cascade area, command area, is adequate to meet the irrigation requirement (It) in and tank water surface area of the cascade and indirect- the main (Maha) season. Water supply availability is ly to tank storage capacities and irrigation water demand (Sakthivadivel, Fernando, and Brewer 1997). Hence, a evaluated using the ratio of these two values. If R0 /It direct way to estimate the cascade outflow from simple > 1, the tank has adequate water supply to meet the surface area measurements with a regression equation irrigation requirement; otherwise, additional water was developed. The analysis demonstrated that features is needed to meet this requirement (Sakthivadivel, of individual tank systems affect the cascade outflow Fernando, and Brewer 1997). (Sakthivadivel, Fernando, and Brewer 1997). Furthermore, » Tank storage capacity: The storage capacity (St) of it also validated the use of the simple area ratios for initial a tank measures the extent to which the tank is ca- screening of the cascades. pable of storing the runoff water and releasing it to meet the irrigation requirement (It). This measure is 3. Cascade Water Surplus Evaluation evaluated using the ratio of these two quantities. If, St /It > 0.3, then the tank has the capacity to hold at The cascade outflow estimation in step 2 is followed by least 30 percent of the irrigation requirement. The an evaluation of the cascade water surplus to quantify value of 0.3 is arrived at based on the farmers’ per- how much of the outflow is available to some or all of ception that a tank should have the capacity to hold the tanks in the cascade. The cascade water surplus is at least five weeks of irrigation requirement before evaluated by defining two parameters: cascade outflow starting any irrigation operation. 114 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE » Cropping Intensity: Agricultural performance of a for rehabilitation and (b) the tank system should not have tank is evaluated using the average main season been rehabilitated within the last 10 years. (Maha) cropping intensity for the past few consec- utive seasons (Sakthivadivel, Fernando, and Brewer 1997). In the case of Sri Lanka’s Anuradhapura Dis- SOLUTION AND IMPLEMENTATION trict, it was concluded that a well performing cas- cade or tank would have a Maha season cropping in- The four-step hydrological assessment guide helps en- tensity of 60 percent or more, based on the variability sure that rehabilitation of tank cascades results in great- of rainfall and findings in IIMI 1996. er water availability for increased cropping intensity. It also attempts to ensure that the rehabilitation of any one These indicators, together with the cascade water surplus small-scale system does not cause problems for other indicator are used to guide the final evaluation of tank re- water users in the cascade. The main advantage of the habilitation proposals and prioritize the rehabilitation of methodology described here is that it provides a means specific components of a tank cascade. to rapidly assess water availability and water use without requiring the existence or the creation of a detailed hydro- 5. Evaluating Tank Rehabilitation Proposals logic database for the cascade. Instead, farmers’ knowl- edge of their hydrologic situations is harnessed to provide The four-step hydrological assessment yields a set of the needed data. The knowledge and data gained from hydrological indicators which can be used to inform well-designed rapid assessments are used to estimate recommendations for tank system augmentation or ex- flows among the separate systems within the cascade pansion (table 8A.1). Final investment decisions on tank and outflows from the cascade. cascade rehabilitation also need to be based on other criteria such as costs and benefits, and consideration of Rehabilitation of small tank cascades is an investment other indicators of agricultural performance beyond crop- priority to build resilience against climate change. For ping intensity, potentially including environmental sustain- example, the Climate Smart Irrigated Agriculture Project ability, social acceptability, and economic efficiency. In Sri financed by the World Bank and the “Strengthening Lanka, the number of beneficiaries and the rehabilitation the Resilience of Smallholder Farmers in the Dry Zone history are the two most common parameters used to to Climate Variability and Extreme Events Through an decide on rehabilitation proposals. For the Anuradhapura Integrated Approach to Water Management” project, fi- District example, it was decided that (a) there must be at nanced by the Green Climate Fund with Government least five beneficiaries for a tank system to be considered of Sri Lanka (GOSL) co-financing have updated and TABLE 8A.1 Recommendations on Tank System Augmentation and Expansion TANK SYSTEM CONDITION CASCADE TANK WATER TANK STORAGE CROPPING SURPLUS AVAILABILITY CAPACITY INTENSITY RECOMMENDATIONS No — — — No expansion/augmentation Yes Not adequate — — Tank augmentation Yes Adequate Not adequate — Tank capacity expansion Yes Not adequate Not adequate — Augmentation and capacity expansion (capacity expansion is recommended only if tank augmentation will be carried out) Yes Adequate Adequate High Command area expansion (only if adequate land is available) Source: Sakthivadivel, Fernando, and Brewer 1997. Note: Tank augmentation entails, for example, tapping a stream to augment water supply to the tank. Tank expansion entails construction works to increase tank storage capacity. — = not applicable. Case Study | Sri Lanka 115 implemented this approach to guide investments in tank » Rehabilitation of tanks using a cascade planning ap- cascade rehabilitation in Sri Lanka’s dry zone. proach leads to more sustainable results. Compared to the ad hoc rehabilitation of individual tanks, the These investments implemented a number of innovations cascade approach presented in this case study to the approach presented in this case study, including: helps planners to (a) capture any benefits arising from the joint rehabilitation of tanks in sequence, » Use of nationally determined criteria for the selec- including improved sediment retention and ground- tion of project locations. Target areas were selected water recharge; (b) avoid conflicts between water based on (a) vulnerability of communities to climate users upstream/downstream, as unintended im- change, (b) poverty, and (c) high incidence of chron- pacts such as flooding or shortage are avoided; and ic kidney disease of unknown etiology, believed to (c) improve the overall planning approach to rehabil- be linked to lack of good quality drinking water. itation through structured stakeholder engagement » Hydrological assessments were typically based and project scheduling. on more advanced simulation models, such as the » Participatory planning produces key information, Soil and Water Assessment Tool (SWAT) and Water leads to better decisions, and creates project own- Evaluation and Planning (WEAP) Model, which were ership. Tank cascade rehabilitation projects often used to model hydrological processes and water de- adopt a top-down approach and disregard local mand respectively. knowledge and experience in the design and con- » Utilization of non-hydrological criteria, including insti- struction phase of projects. This case study shows tutional and context aspects (e.g., past and ongoing the advantage of applying stakeholder engagement interventions, rehabilitation and improvement made and participatory planning approaches in tank cas- to the cascade during the last five years, availabili- cade rehabilitation projects. Stakeholder engage- ty of functional user organizations), social aspects ment helps to gather important information on the (e.g., number of people or households benefitted by current state of tanks, on the priorities of users, and the cascade, poverty headcount ratio), and environ- on any potential upstream/downstream issues be- mental aspects (e.g., biodiversity, area under tank tween involved communities. Stakeholder engage- bed cultivation) to prioritize interventions. ment also needs to consider the line agencies in- » All the tanks within the cascade, irrespective of volved in project development. Early orientation on whether such tanks have command areas and ben- tank cascade rehabilitation projects at district and eficiaries, are typically rehabilitated. This is because divisional level helps to create ownership among tanks without command areas capture excess run- responsible government officials and clarifies re- off water, reduce the possibility of breaching the sponsibilities and expectations. In the long term, this tanks below, and act as storage tanks. leads to improved decisions on tank rehabilitation as » The projects designed a comprehensive stakehold- planners are better able to consider the knowledge er engagement program, including beneficiaries, and priorities of beneficiaries. line agency officials, and local authorities. There are » Tank cascade rehabilitation programs can be linked grievance mechanisms in place; monitoring process to broader rural revitalization and connectivity pro- have also been established. grams to maximize impact. Rural development programs that address value addition, market link- ages, and alternative income generation help com- LESSONS LEARNED munities in cascades to generate adequate income and reduce poverty rates. While these activities can There are many lessons learned from this case study maximize the socioeconomic benefits of agricultural and, more broadly, from past and ongoing tank cas- production, they should be planned considering sus- cade rehabilitation projects in Sri Lanka (Aheeyar 2013; tainable water use from the cascade. Tennakoon 2017; Perera et al. 2021). These lessons are » Adoption of the cascade approach shows that tanks relevant to places where tank cascades exist or are being without command areas often need to be rehabili- considered. tated if other tanks in the cascade are to continue 116 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE functioning. Some of the small tanks in tank cas- 3 The main rainfall season, or Maha season, is from October cades do not have command areas or beneficiary to January when around 80 percent of the annual rainfall is received. farmers since they were constructed for specific 4 The computer simulation model is used to calculate two im- purposes, such as water retention and sediment portant parameters: (a) the cascade outflow, or the runoff vol- retention. Through the application of the cascade ume discharging at the foot of the cascade per unit area (Re), approach presented in this case study, planners can and (b) the effective Maha (main) season runoff (R0) to individ- decide whether these tanks need to be rehabilitated ual tanks. R0 is the sum of surface runoff, direct rainfall on the to support other tanks used for irrigation. tank water surface, surplus water from the upstream tank, and irrigation drainage water from the immediate upstream com- » Community training and mobilization are key com- mand area minus the sum of tank evaporation and seepage ponents to ensure the success of tank cascade re- and percolation losses. In the case of Sri Lanka, the Reservoir habilitation programs. Investments in tank cascade Operation Simulation Extended System (ROSES) was specif- rehabilitation should be paired with targeted training ically developed by the International Irrigation Management programs to further strengthen farmers’ knowledge Institute, now the International Water Management Institute (IWMI), to estimate cascade outflow. of the cascade and increase access to information 5 Crop Water and Irrigation Requirements Program (CROPWAT) technology for monitoring and coordinating water is a computer program for the calculation of crop water re- use and releases along the cascade. Furthermore, quirements and irrigation requirements based on soil, climate, continued support for farmer organizations is es- and crop data developed by the Land and Water Division of the sential to ensure the long-term sustainability of re- United Nations Food and Agriculture Organization (FAO). habilitation, as areas without functioning farmer or- ganizations typically experience quicker degradation of tanks. REFERENCES » Ecosystem services need to be considered in cas- cade rehabilitation projects’ economic and financial Aheeyar, M. M. 2013. Alternative Approaches to Small analyses. The bulk of the multiple benefits generat- Tank/Cascade Rehabilitation: Socio-economic and ed by tank cascades belongs to ecosystem goods Institutional Perspective. Colombo, Sri Lanka: Hector and services, which are not readily assessed through Kobbekaduwa Agrarian Research and Training traditional cost-benefit analysis. A narrowly framed Institute. economic analysis considering only on-site bene- Dayananda, D., T. Kulasinghe, C. Wickramasinghe, and fits of restoration related to increased agricultural J. Weerahewa. 2020. "Response of Mahakanamulla production often cannot justify cascade-wide res- Cascade to Challenges of Covid-19." In Ellanga: Tank toration investments. It is only when broader eco- Villages, edited by A. Jayaweera and J. Weerahewa. system services are taken into account that the Peradeniya, Sri Lanka: University of Peradeniya. economic feasibility of cascade-wide rehabilitation FAO (Food and Agriculture Organization). n.d. “Globally becomes evident. Important Agricultural Heritage Systems (GIAHS).” Accessed July 8, 2022. Available at: https://www.fao. org/giahs/en/. IIMI (International Irrigation Management Institute). 1994. ENDNOTES Guidance Package for Water Development of Small Tank Cascade Systems. Report to the International 1 In the context of Sri Lanka, a small tank is a humanmade sur- Fund for Agricultural Development. Colombo, Sri face water reservoir serving an irrigated area of fewer than 80 hectares. Lanka: IIMI. 2 Based on this information, two indicators are calculated: (1) Itakura, J. 1994. Water Balance Model for Reform the ratio of cascade area, Ac, to the total tank water surface Planning of Tank Cascade Irrigation Systems in Sri area in the cascade, Acws, and (2) the ratio of cascade com- Lanka. Colombo, Sri Lanka: International Irrigation mand area, Acca, to the total tank water surface area in the Management Institute. cascade, Acws. In the Sri Lanka case, for a cascade to be chosen for further consideration, the former ratio should ex- Jinapala, K., J. D. Brewer, and R. Sakthivadivel. 1996. ceed 8 and the latter ratio should be less than 2 (IIMI 1994; Multilevel Participatory Planning for Water Resources Sakthivadivel et al. 1996). Development in Sri Lanka. Gate Keeper Series no. 62. Case Study | Sri Lanka 117 London: International Institute for the Environment Ponrajah, A. J. P. 1982. Designs of Irrigation Works for and Development. Small Catchments. Colombo, Sri Lanka: Irrigation Madduma Bandara, C. M. 1985. “Catchment Ecosystems Department. and Village Tank Cascades in the Dry Zone of Sri Lanka: Sakthivadivel, R., N. Fernando, C. R. Panabokke, and C. A Time-Tested System of Land and Water Resource M. Wijayaratna. 1996. Nature of Small Tank Cascade Management.” Strategies for River Basin Management, Systems and a Framework for Rehabilitation of Tanks edited by J. Lundqvist, U. Lohm, and M. Falkenmark, within them. Sri Lanka Country Paper no. 13. Colombo, 99–113. doi:10.1007/978-94-009-5458-8_11. Sri Lanka: International Irrigation Management MI&WR (Ministry of Irrigation and Water Resources and Institute. Disaster Management). 2018. Strategic Action Plan Sakthivadivel, R., N. Fernando, and J. D. Brewer. 1997. for Adaptation of Irrigation and Water Resources Rehabilitation Planning for Small Tanks in Cascades: A Sector to Climate Change 2019-25 and Beyond. Methodology Based on Rapid Assessment. Research Colombo, Sri Lanka: I&WR. Report 13, Colombo, Sri Lanka: International Irrigation MMDE (Ministry of Mahaweli Development and Management Institute. Environment). 2017. Project Document on Tennakoon, M. U. A. 2017. Cascade Based Tank Renovation Strengthening the Resilience of Smallholder Farmers for Climate Resilient Improvement. Colombo, Sri in the Dry Zone to Climate Variability and Extreme Lanka: Ministry of Disaster Management. Events through an Integrated Approach to Water Vidanage, S. P. 2019. Economic Value of an Ancient Management. Colombo, Sri Lanka: MMDE. Small Tank Cascade System in Sri Lanka. Colombo, Panabokke, C. R., R. Sakthivadivel, and A. Weerasinghe. Sri Lanka: Department of Economics, University of 2002. Small Tanks in Sri Lanka: Evolution, Present Colombo. Status and Issues. Colombo, Sri Lanka: International Wijekoon, W. M. S. M., E. R. N. Gunawardena, and M. M. Water Management Institute. M. Aheeyar. 2016. “Institutional Reforms in Small Panabokke, C. R. 2009. Small Tank Systems of Sri Lanka: (Village Tank) Irrigation Sector of Sri Lanka Towards Their Evolution, Setting, Distribution and Essential Sustainable Development.” Kandy, Sri Lanka: Functions. Colombo, Sri Lanka: Hector Kobbekaduwa Proceedings of the 7th International Conference on Agrarian Research and Training Institute. Sustainable Built Environment 2016. Perera, K. T. N., T. M. N. Wijayaratna, H. M. Jayatillake, Witharana, D. D. P. 2020. Details of Irrigation Systems in Sri J. M. A. Manatunge, and T. Priyadarshana. 2021. Lanka. Colombo, Sri Lanka: Department of Agrarian “Framework for the Sustainable Development of Development, Water Management Division. Village Tanks in Cascades as an Adaptation to Climate Change and for Improved Water Security, Sri Lanka.” Water Policy 23, 537–55. doi:10.2166/wp.2021.262. 118 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE ANNEX 8B. CALIFORNIA: FORECAST-INFORMED RESERVOIR OPERATION TO ENHANCE WATER STORAGE EFFICIENCY CASE STUDY BRIEF Summary Forecast-informed reservoir operation (FIRO) “is a reservoir-operations strategy that better informs decisions to retain or release water by integrating additional flexibility in operation policies and rules with enhanced monitoring and improved weather and water forecasts” to maximize various development objectives, potentially including water supply, hydropower production and flood attenuation (American Meteorological Society 2020). The implementation of FIRO has been piloted in Lake Mendocino, California, United States, by a partnership of water managers, engineers, regulators, and scientists from several federal, state, and local agencies, as well as universities. They have teamed up to evaluate whether current technology and scientific understanding can be utilized to improve the reliability of meeting water management objectives of Lake Mendocino, including water supply for agriculture, domestic uses, and environmental streamflow while not impairing—and potentially improving—flood protection. Type of water storage used › Large reservoirs Water service(s) of storage provided › Flood mitigation › Increased water availability › Flow regulation Water requirement(s) of storage met › Prediction and attenuation of excess water for risk reduction › Water provision for ecosystem preservation and restoration › Water provision for domestic needs and industrial processes › Water provision to meet crop/livestock requirements in seasons/locations without precipitation Russian River is a partially managed river system with BACKGROUND reservoir releases controlling river flows, especially Water resources development has been important for the throughout most of the summer and fall, to ensure water Russian River watershed, located in northern California, availability throughout the year. Two major reservoirs to support economic development (map 8B.1). The that provide water supply and flood protection are Lake Case Study | California 119 MAP 8B.1 Schematic of the Russian River Watershed and Water Transmission System IBRD 46774 | SEPTEMBER 2022 Points of Interest 0 5 10 Cities Kilometers GLENN Water Agency Transmission System Russian River Watershed Boundary Potter Valley Project County Boundaries MENDOCINO Highways Lake Mendocino Coyote Valley Dam Russian LAKE Clear Lake COLUSA iverR Warm Springs Lake Dam Sonoma DrD yrC yCre reee kk PACIFIC SONOMA OCEAN YOLO Russian River Diversion Facilities Lake 2 Berryessa 1 3 Santa Rosa NAPA 4 5 6 Petaluma Napa Vacaville Water Agency Transmission System 1 Russian River-Cotati Intertie SOLANO 7 Fairfield 2 Santa Rosa Aqueduct 3 West Transmission Main MARIN 4 Kawana Springs Pipeline Vallejo San Pablo 5 Sonoma Aqueduct Bay 6 Petaluma Aqueduct San Rafael 7 North Marin Aqueduct ALAMEDA Concord C d Source: Adapted from FIRO SC 2015. 120 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE Mendocino and Lake Sonoma. This water infrastructure reservoir operations for flood control. Storms not related has been supporting the economic development in the to atmospheric rivers, however, will contribute less to total watershed, contributing to sustaining several economic precipitation. This means California could vacillate even activities, such as water supply for domestic uses, agri- more wildly between extremes of drought and flooding, culture, hydropower, and recreation. requiring more space to manage the extremes. In the fu- ture, increasing demands for water will put more stress on The multipurpose Coyote Valley Dam, which formed the ability of Lake Mendocino to meet water management Lake Mendocino in the Upper Russian River watershed, objectives reliably for the region, especially with more vari- also significantly contributes to environmental flows. able hydrologic conditions predicted. The Coyote Valley Dam has been operated cooperatively by a local agency, Sonoma Water, and the United States The water storage in the Coyote Valley Dam fluctu- Army Corps of Engineers (USACE) since 1958. Water ates as per seasonality, and the operation of the dam stored in Lake Mendocino is the product of inflows from is heavily governed by flood control. As a federal dam, the Russian River and water transferred from the Eel operation of Coyote Valley Dam is governed by USACE River to support hydroelectric generation, via trans-basin rules—the project water control manual (WCM). Initially transfer, which is released downstream to mainstream created in 1959 and then updated to mitigate effects on flows in the Upper Russian River. These storage releases the endangered fish, those rules allocate available stor- can account for all water in the river during dry periods, age to a flood control pool at the top of the reservoir and protecting endangered coho salmon, Chinook salmon, a conservation pool (water supply pool) below that. The threatened steelhead, and multiple other species, as well storage allocation strikes a balance between the need to as supporting municipal and agricultural uses (CalEPA keep an empty reservoir for managing excess flood water 2021). It is also critical to the region’s thriving viniculture and a full reservoir for meeting water management objec- sector. tives and environmental flows. Current rules require the flood pool to be empty except briefly in periods of greatest The Russian River Basin experiences one of the most inflow. Then flood runoff is stored and released at a rate variable climates in the United States, with atmospheric that avoids or minimizes the exceedance of downstream rivers and their extreme precipitation driving this vari- flow targets to reduce flood risks. The conservation stor- ability (FIRO SC 2017). Average annual precipitation is as age, used for water management objectives and meeting high as 80 inches in the mountainous coastal region of the minimum instream flow requirements (for fisheries and/ watershed and 20 to 30 inches in the valleys. Precipitation or environmental purposes, herein referred to as envi- can also vary significantly from season to season, which ronmental flows), is filled as water is available to do so can result in a large amount of variability in flows in the (FIRO SC 2017). However, operation following the WCM Russian River, with 93 percent of annual precipitation rules strictly does not permit storage in the flood pool for from October to May. The climate is highly influenced by conservation purposes. Figure 8B.1 shows the 2015 rule atmospheric rivers—California’s version of a hurricane. curve (also called the guide curve) for Lake Mendocino, Atmospheric rivers originate in the Pacific Ocean and can with its seasonally varying storage allocation, before FIRO make landfall along the coastline, with extreme rainfall, was introduced. high winds, and coastal storm surges. When these storms occur, runoff flows rapidly into valleys and coastal areas, potentially creating widespread flooding. In the Russian PROBLEM DEFINITION River, atmospheric river events often account for a large percentage of the rainfall during three or four major winter Over time, it became apparent that Lake Mendocino was storms, and can also produce 30–50 percent of the region’s not meeting water resources and flood control needs annual precipitation in a few days (Ralph et al. 2013). In a downstream as efficiently as it could be. Releases of warming climate, atmospheric rivers are anticipated to in- large amounts of water during wet seasons to make room crease in intensity (Gershunov et al. 2019), becoming even for potential future flood attenuation were followed by dry bigger contributors to California’s annual precipitation periods; water was being released when it was not needed total, posing greater flood risk hazards, and complicating downstream to prepare for floods that were not coming, Case Study | California 121 FIGURE 8B.1 Simplified Lake Mendocino Guide Curve 120,000 Flood Control Pool 110,000 Water Supply Pool 100,000 90,000 80,000 Flood Control Pool 70,000 Acre-feet 60,000 Water Supply Pool 50,000 40,000 30,000 20,000 10,000 0 Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Month Source: FIRO SC 2015. Note: Water must be released from the lake between November 1 and March 1 when water levels are above 68,400 acre-feet. and more water was needed downstream during dry peri- defined the flood storage volume and the release require- ods. For example, in December 2012, a large storm asso- ments to keep flood storage empty in anticipation of future ciated with an atmospheric river filled space available in flood events. Since the rules do not allow the use of stor- the conservation pool. USACE dam operators followed the age in the flood pool for other purposes, stored floodwater WCM rules and released this water from the flood pool, that could potentially be used for water management ob- ensuring space was available to manage potential future jectives has to be released to manage floods anticipated floods, even though no storms or flooding were forecast. with 1950s estimates, which are based on the technology Storage in Lake Mendocino began to decline significantly available at the time. Moreover, the guide curve of Lake through the late winter and early spring of 2013 because Mendocino does not account for upstream flow reduction no additional storm events occurred, which turned out due to a reduction in the trans-basin diversion from the Eel to be the beginning of a severe and extended drought. If River as a result of changes in upstream hydroelectric op- stored water had been retained in Lake Mendocino from erations. This inflexibility of the existing operational rules the December 2012 storm and atmospheric river event, has contributed to the underperformance of the dam from drought impacts to the Upper Russian River could have a water supply perspective during extreme events. been postponed and moderated. Consideration of various elements need to be included in The current maximum allowable reservoir storage to the operation of Lake Mendocino to perform at a higher meet flood control objectives (guide curves) for Lake level. A more robust operation of Lake Mendocino would Mendocino are based on hydrologic analyses at the time require the incorporation of the following aspects: natu- of dam construction and do not consider inflow varia- ral weather variability due to the number and intensity of tions or forecasts. Conventionally, the guide curves, a atmospheric river events; consideration of actual climate major element of the WCM, were determined to reflect av- variability and extreme events due to climate change; and erage seasonal patterns and by using historical data. For significant decreases and variability in trans-basin diver- Lake Mendocino, data included streamflow and weather sions from the Eel River into the East Fork of the Russian patterns available at the time of dam construction, which River. Starting in 2006, Lake Mendocino has experienced was used to estimate seasonal flood potential and so significantly reduced water supply reliability since flows 122 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE were decreased from the Eel River. This provides the and are updated if conditions or the physical attributes opportunity to assess the applicability of FIRO that in- of the project change—but many WCMs have not been corporates streamflow predictions to adaptively man- meaningfully updated for several decades due to a lack age reservoir storage to provide downstream flood risk of USACE appropriations. When dam construction in the management and limit unwanted emergency releases, United States peaked in the 1960s, skill in weather and while improving storage availability for water supply and water forecasting was less advanced than present day. ecosystems. To reflect average seasonal runoff patterns and basin conditions, guide curves were developed using available observational hydrologic information. This information INSTITUTIONS AND INSTITUTIONAL was usually derived decades ago at the time of reser- FRAMEWORK voir construction and updated as conditions required (Howard 1999; Delaney et al. 2020). These procedures As a partner in the operation of the Coyote Valley Dam, are codified in the WCM, and water managers are large- Sonoma County Water Agency needs to follow state and ly compelled to use them. USACE has a process where federal regulations and also is entitled to water rights requests for temporary deviations from the existing from the state authority. Since Coyote Valley Dam start- WCM rules can be submitted, evaluated, and approved. ed operations, Sonoma Water has been authorized by Deviations can be either minor (5 percent or less devia- the State Water Resources Control Board—the regulatory tion from existing guide curve levels) or major (greater body for water permits and water uses in California—for than 5 percent deviation). the rights to appropriate Russian River water. As the local project sponsor for the construction of the Coyote Valley At the same time, there are many stakeholders for Dam, Sonoma Water retains rights to some of the water water resources management around Lake Mendocino. stored in the reservoir and controls the releases from the The Integrated Water Resources Science and Services reservoir water supply pool. Sonoma Water is required to (IWRSS) is a consortium of federal agencies with com- maintain minimum streamflows in accordance with its plementary missions in water science, observation, man- water rights permits (Sonoma Water n.d.). At the same agement, and prediction, such as the Federal Emergency time, Sonoma is required to comply with federal regula- Management Agency, NOAA, USACE, and the United tions. Since Lake Mendocino has been receiving lower an- States Geological Survey (USGS). The overarching ob- nual inflows due to changes in upstream uses since 2006, jective of IWRSS is to enable and demonstrate a broad, the National Oceanic and Atmospheric Administration integrative national water resources information system (NOAA)’s National Marine Fisheries Service has issued a to serve as a reliable and authoritative means for adap- biological opinion with restrictions on inflow and outflows tive water-related planning, preparedness, and response to support the endangered and threatened salmonids in activities. It promotes inter-agency collaboration, such the Russian River. Sonoma Water is also required to con- as between the National Weather Service and Sonoma duct a stress test and self-certify the level of available County Water Agency. Under IWRSS, the Russian River water supplies it has, assuming three additional dry years, Basin was selected as a demonstration area to implement as well as the level of conservation necessary to assure pilot projects, including forecasting to improve reliability adequate supply over that time (Water Boards 2016). and resiliency in Lake Mendocino, enhancing monitor- ing capability, taking stock of hydrologic modeling and As the Coyote Valley Dam is also federally owned, its identification of gaps, and centralizing data to facilitate operations are governed by USACE operational policy. common data access. At the local level, the Mendocino When federal funds are used to construct—partially or County Russian River Flood Control & Water Conservation fully—a dam that includes flood mitigation as an autho- Improvement District is responsible for managing the rized purpose, the USACE becomes responsible for man- water resources of the Upper Russian River for the bene- aging that purpose, pursuant to Section 7 of the United fit of the people and environment of Mendocino County. It States Flood Control Act, and a WCM is developed to is the local sponsor for the development of Coyote Valley guide water release decisions for the dam. WCMs are Dam and Lake Mendocino, and monitors water levels of generally completed within a year of project completion the lake and river flows to ensure regulatory compliance. Case Study | California 123 Alongside water resources agencies, national and across the region, regulatory perspective on enforcement local forecast and weather agencies are also import- related to biological opinion in the Russian River, and tech- ant stakeholders for water resources around Lake nical perspective on weather forecasting capability), USGS Mendocino. NOAA’s California Nevada River Forecast (research perspective from federal agency on scientific Center (CNRFC) provides reservoir inflow information and information for water resources management), United river flow forecasts, including the Russian River water- States Bureau of Reclamation (federal agency perspective shed. The California Department of Water Resources, and on management, development, and protection of water USGS California Water Science Center also provide river resources in the West), and the California Department of flow information. The California Water Data Exchange Water Resources (state perspective on water resourc- Center disseminates various water-related information es from climatological perspective) (Talbot, Ralph, and and data (IWRSS and NOAA 2014). Related to atmospher- Jasperse 2019). As such, committee membership was ic rivers, NOAA’s Hydro-Meteorological Testbed (HMT) purposefully chosen to bring together representatives conducts research on precipitation and weather condi- from the relevant organizations that had responsibility for tions and accelerates the infusion of new science and operations and regulation not only at Lake Mendocino but technology into daily forecasting. The HMT maintains a also for conducting research into the relevant physical pro- coastal atmospheric river observatory in the southern part cesses that impact water management operations, name- of the Russian River Basin (IWRSS and NOAA 2014). At ly meteorological forecasts and hydrologic and hydraulic the same time, the Center for Western Weather and Water modeling (Talbot, Ralph, and Jasperse 2019). Extremes (CW3E) at the University of California—San Diego’s Scripps Institution of Oceanography conducts re- The Steering Committee collaboratively developed a work search on atmospheric rivers, including atmospheric and plan to assess the viability of FIRO for Lake Mendocino. soil moisture observations in the Russian River Basin and The first full meeting of the Lake Mendocino FIRO Steering data collection over the Pacific Ocean. Committee was held in December 2014, where terms of reference1 for the committee were agreed upon. The com- mittee agreed to meet at least quarterly, but smaller sub- THE EVOLUTIONARY PROCESS: A SYSTEMS committees would meet and interact more frequently as APPROACH needed to ensure delivery of products of the effort. It was also determined that a work plan was needed to guide the The first step toward the implementation of FIRO at Lake research effort in exploring the viability of using forecast in- Mendocino involved the creation of an interagency steer- formation in an operational setting. It was also recognized ing committee of water managers and scientists from that the input and interaction between engineers, scientists, several federal, state, and local agencies, and universi- operators, and regulators would be crucial to the success ties. Participation in IWRSS activities for the Russian River of the development of the work plan as well as the execu- demonstration area led to discussions among federal, tion of that work plan over the course of the effort. Between state, local, and academic partners regarding how a new December 2014 and September 2015, a five-year work plan approach—building on improvements in atmospheric rivers was developed, published in October 2015 (Jasperse et al. science, and in response to a long-lasting drought—could 2015). This work plan presents an approach for conducting explore the potential viability of using forecasts to inform a proof-of-concept FIRO viability assessment using Lake operations at reservoirs, with Lake Mendocino as a pilot. In Mendocino as a model (f igure 8B.2), including whether 2014, the Lake Mendocino FIRO Steering Committee was FIRO can support adjustments to the WCM. The work plan formed to guide the project, with an overarching role in ex- describes current technical and scientific capabilities and ploring methods for better balancing flood management outlines technical/scientific analyses and future efforts and the reliability of meeting water management objec- needed to demonstrate the potential of FIRO to improve tives through utilizing FIRO in the Russian River watershed. reservoir management (FIRO SC 2015). The Steering Committee is co-chaired by the CW3E and the Sonoma County Water Agency, and includes USACE The Lake Mendocino FIRO work plan laid out a multi- and other federal and state agencies, including NOAA (fed- step strategy to assess the viability of FIRO. The first eral agency responsible for operational river flow forecasts step in the plan was to carry out a preliminary viability 124 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE FIGURE 8B.2 Flow Diagram Depicting the FIRO Viability Assessment Process Preliminary Viability Assessment What improvements in Is FIRO currently a scientific knowledge and viable strategy to NO-FIRO decision tools need to occur improve water supply is NOT currently so that FIRO is viable and 1 and environmental a viable strategy can meet the needs conditions without to improve reservoir of water managers? impairing flood operations (Work plan section 9.0) protection? (Work plan sections 4-8) How can FIRO Science and Technical Programs become incorporated (Work plan section 10) YES-FIRO into reservoir IS a viable strategy • Data collection & monitoring operations? (watershed, hydrometric) (Note: some FIRO • Process • Weather forecasting strategies may be • Decision support - QPI currently viable tools/model - QPE while others are not) - ARs (Work plan section 9.0) • Decision support models • Data interoperability Source: Jasperse et al. 2020. Note: QPI = quantitative precipitation information. QPE = quantitative precipitation estimator. AR = atmospheric river. assessment (PVA), conducted over two years, to be fol- developed. If the necessary components do not ex- lowed by a full viability assessment (FVA), which would ist, [research and development] programs would be require substantial additional effort over roughly another identified in the FVA as appropriate, and work initiated three years (FIRO SC 2017): to develop the components. Finally, necessary chang- es to the operation rules, as defined in the project’s » The PVA was an “assessment intended to inform the WCM, and the process for modifying the rules would [Steering Committee’s] decision (1) to take steps to be identified in the FVA consistent with USACE pro- deploy FIRO components with existing technology; cedures and protocols to support consideration of (2) to delay FIRO implementation until enhancements policy modifications by the USACE as it contemplates to the technology are available; (3) to take an incre- approaches to enhance reservoir operations.” mental approach, implementing FIRO with available » “If the PVA found FIRO implementation not viable, the technology, then refining Lake Mendocino operation project team would identify scientific and operational as enhanced technology becomes available; or (4) enhancements necessary to make FIRO viable. The to seek a different solution.” Given the analysis was team then would initiate a research and development preliminary, “the PVA relied on representations of effort to provide those enhancements.” FIRO system components, reasonable simulation of performance of those components, and anticipated IMPLEMENTATION flexibility in operation of Lake Mendocino under FIRO.” » “In the subsequent FVA, candidate components of the Several activities were undertaken toward the assess- Lake Mendocino FIRO system would be identified; the ment and piloting of FIRO for Lake Mendocino (figure forecast parameters and associated forecast skill re- 8B.3). As outlined in the work plan, deliverables included quirements would be quantified; research to improve the PVA and the FVA. Annual workshops were held for con- forecast skills to meet those requirements would be necting and sharing ideas, challenges, and results with the conducted; alternative components formulated, as- broader research and application communities. All the de- sessed, and compared; and a plan for implementation liverables were managed by the Steering Committee and Case Study | California 125 FIGURE 8B.3 Lake Mendocino FIRO Development Pathway, 2014–20 2014 2015 2016 2017 2018 2019 1st FIRO 2nd FIRO 3rd FIRO 4th FIRO 5th FIRO 6th FIRO workshop workshop workshop workshop workshop workshop August 2014 July 2015 June 2016 August 2017 August 2018 August 2019 Final viability assessment completed Steering Work plan Draft PVA Final PVA Major 2nd Major 2020 Committee completed December July deviation deviation formed September 2016 2017 Fall 2018 Fall 2019 June 2014 2015 Source: Adapted from CW3E n.d. the workshops were organized by the Steering Committee several research investigations, refinement of developed leadership. Subsequent findings from the activities of the procedures, the development and testing of a decision work plan are elaborated below. support system (DSS), and operational testing through the USACE’s operational deviation process (CW3E n.d.). The PVA was structured around three interconnected The USACE agreed with the finding and subsequently ap- research questions. Each question was supported by a proved the Steering Committee’s request for a major devi- leading expert agency, with the objective of analyzing the ation from the Lake Mendocino water control plan (WCP). feasibility of FIRO to improve operational performance of This temporary deviation permitted greater flexibility in Lake Mendocino. The PVA considered the following ques- managing Lake Mendocino flood control storage, pending tions (FIRO SC 2017): additional investigation that would support incorporating FIRO procedures in a formal revision of the WCM. Valuable A. “If FIRO is implemented, will operations improve data regarding how decisions are made by the water man- reliability in meeting water management objec- agers at Lake Mendocino while operating under major de- tives and the ability to meet environmental flow viations would serve to make modifications to additional requirements, and if so, to what extent?” major deviation requests in coming seasons until a final B. “If FIRO is implemented, will operations adversely WCM update request is made at the conclusion of the affect flood risk management in the system? If so, FIRO effort at Lake Mendocino. where and to what extent can that be mitigated?” C. “What meteorological and hydrological forecast A DSS was developed to provide water managers with a skill is required to enable FIRO to be implement- set of tools to bring together the various pieces of data ed? Is current forecast skill for ... extreme precipi- for decision-making. Data embedded in the DSS included tation events adequate to support FIRO, and what ensemble forecasts of atmospheric river conditions from improvements would be needed to enable full im- atmospheric models, CNRFC inflow forecasts, and water- plementation of FIRO for Lake Mendocino?” shed, reservoir, and downstream conditions. With all of these various pieces of data together in one place, water A set of analytical pieces were produced by the Sonoma managers have ready access to more information upon County Water Agency, USACE, and CW3E to address the which to make operational decisions. A schematic of how three questions, respectively. A final report was generated the FIRO DSS works in practice is shown in figure 8B.4. to summarize findings on FIRO alternatives, recommen- Lake Mendocino operators were trained in the use of the dations, and further work needed. FIRO DSS in 2019. The PVA found that Lake Mendocino could be managed The FVA shed light on the strategy to implement FIRO more efficiently by integrating reservoir inflow forecasts in Lake Mendocino. The objective of the FVA was to explicitly in release schedule decision-making. The PVA identify, through appropriate detailed technical analyses confirmed that if FIRO procedures were used, water sup- and other considerations, the best FIRO strategy for Lake ply benefits could be increased without adversely affecting Mendocino, along with the manner in which the strategy the flood risk reduction capability. The PVA recommended could be implemented in real-time operation by Sonoma 126 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE FIGURE 8B.4 FIRO Decision Support System 2020—the third driest year on record in the Russian River Basin—FIRO increased water storage by nearly 20 percent, roughly equivalent to the water used by 22,000 house- igure 8B.5. holds, as illustrated in f Observed CNRFC Conditions CDEC Forecasts In addition to the baseline, four FIRO alternatives were evaluated through the FVA. In line with USACE guidance, the Steering Committee prepared a hydrologic engineer- Russian River Forecast Coordinated Operations (FCO) ing management plan (HEMP) that is “a technical outline of the hydrologic engineering studies necessary to formu- Lake Mendocino Proposed Russian River EFO Model Release HEC ResSim late a solution to a water resources problem” (FIRO SC 2019). The objective of the HEMP was to identify and eval- Process Iterative Refinement Repeated uate Lake Mendocino FIRO alternatives in a systematic, Each Day defendable, repeatable manner, providing information to Reservoir Release the Steering Committee so it may identify the best FIRO Operators Decision strategy. Three of the alternatives were types of ensemble Source: Adapted from Talbot, Ralph, and Jasperse 2019. forecast operations (EFO)2 plans, and the fourth was de- Note: FIRO DSS elements and how reservoir operators can use it to inform release decisions. CDEC = California Water Data Exchange Center; CNRFC veloped by USACE Hydrologic Engineering Center (HEC) = California Nevada River Forecast Center; EFO = ensemble forecast oper- and USACE San Francisco District to leverage the five-day ations; HEC = USACE Hydrologic Engineering Center; ResSim = Reservoir System Simulation. deterministic forecasts issued by the CNRFC and employ a simpler operation approach. To ensure direct compari- Water and USACE and enable the WCP changes neces- son, each WCP had to meet hard (inviolable) operational sary to implement that change permanently (FIRO SC constraints, as well as a set of operational considerations 2019). The FVA also evaluated potential adaptive strat- that could be measured. All four alternatives have various egies that allow operators to utilize new technology and forms of flexibility in operations to allow more water stor- improve forecast skills as they become available in the age to be carried safely into the dry season to avoid water future. The FVA was informed by collecting observation- supply shortages, and to allow reservoir levels to be low- al data, conducting research, modeling FIRO alternatives, ered below the guide curve to enable additional flood pro- and testing FIRO operations via USACE-approved major tection when major storms are predicted. The FVA found deviations from the Lake Mendocino WCM. that all the FIRO WCPs considered fully met the objective of a significant improvement when compared to existing Operational testing was instrumental to demonstrate WCM operations. and test the preliminary findings identified in the PVA and better inform the FVA. The development of the en- Analysis shows that all four FIRO alternatives would semble forecast operations decision support tool provid- improve water supply reliability while retaining, or even ed an objective way to consider ensemble forecasts and enhancing, flood risk management and environmental manage risk associated with the inevitable uncertainty in objectives relative to baseline operations (table 8B.1). forecasting. This led to the decision to request a planned After considering all evaluation criteria, the Modified major deviation from normal operating procedures for Hybrid EFO is the preferred option for near-term imple- the reservoir based on the FIRO tools that had been de- mentation. This option ranks favorably in terms of oper- veloped. USACE experimented with FIRO with planned ational performance, can be implemented feasibly with major deviations from the WCM during water years 2019 USACE standard decision tools, explicitly uses the un- and 2020—including one winter with significant flooding in certainty in streamflow forecasts, and offers a pathway water year 2019, and one that was a drought in water year for growth with improving forecast skill and model refine- 2020. In both years, FIRO increased water supply benefits ments. The Steering Committee also identified EFO as an and managed flood risks, and did so in the context of two option to consider pursuing in the future, thus increasing years representing opposite extremes in the weather. In storage capacity of Lake Mendocino. Case Study | California 127 FIGURE 8B.5 Release Curve and Modeled Release Curve, 2019–20 100,000 Storage curve 95,000 with FIRO 90,000 Volume of water in Lake Mendocino (acre-feet) Storage curve 85,000 without FIRO 80,000 75,000 Water storage FIRO SPACE with FIRO 70,000 (actual) 65,000 19% additional storage 60,000 Water storage WATER SUPPLY POOL without FIRO 55,000 (modeled) 50,000 0 Oct Nov Dec Jan Feb Mar Apr Source: Sonoma Water n.d. October 2019 Through April 2020 Note: Comparison between the actual release curve with FIRO and the modeled release curve without FIRO, showing an increase of 19 percent in the water storage. TABLE 8B.1 Water Control Plan Alternatives and Increases ALTERNATIVE DESCRIPTION INCREASE IN MEDIAN STORAGE (%) Existing operation (baseline) Includes the seasonal guide curve and release selection rules from the 0 1986 USACE WCM and 2003 update to the flood control diagram. EFO Operates without a traditional guide curve and uses the 15-day 27 ensemble streamflow forecasts to identify required flood releases. Hybrid EFO A combination of the baseline approach and the EFO. This option was 15 used for major deviation operations in water years 2019 and 2020. Modified Hybrid EFO Identical to Hybrid EFO but with a “corner-cutting” strategy that allows 20 for greater storage to begin February 15 to aid with spring refill. Preferred option for near-term implementation. Five-day deterministic Defines alternative guide curves with 11,000 acre-feet encroachment 18 forecast space and 10,000 acre-feet draft space above and below the baseline guide curve. Uses five-day deterministic streamflow forecasts to choose the guide curve and make release decisions. Source: Jasperse et al. 2020. Note: May 10 Lake Mendocino reservoir storage over baseline water control manual (WCM) operations. Modified Hybrid ensemble forecast operations (EFO) is the Steering Committee’s preferred option. 128 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE The FVA proposes a path to update and modify the WCM The successful FVA process now opens the door to a in an adaptive manner as conditions change. While the potential WCM update. Implementation included a set of WCM update is a USACE process, it is recommended that scientific and technical tasks across several disciplines, the Lake Mendocino FIRO Steering Committee remain in- which formed the foundation for the water control plan tact and contribute to the effort and process. The pathway development, and demonstrations through the PVA and for an updated future WCM is illustrated in figure 8B.6. through real-world testing in operations through planned major deviations. Lessons from the scientific and techni- FIRO alternatives demonstrated significant benefits cal studies, plus the demonstrations (i.e., PVA and major with limited downside. The Steering Committee conduct- deviations) fed into the FVA, which formally recommends ed complementary analyses to examine the impact of the adoption of FIRO at Lake Mendocino. These steps rep- FIRO on other dimensions: economic, environmental, and resent the culmination of the full five-year study. However, flood risk mitigation. An economic assessment quantified it is important to note that they feed into the vital steps the benefits of FIRO for dam operations, water supply, required to codify and implement the FIRO recommenda- fisheries, recreation, and hydropower, showing that FIRO tions through a WCM update. This, and the five-year FIRO will lead to positive benefits in all these areas except hy- major deviation to be used in the meantime, are activities dropower (Jasperse et al. 2020). The Modified Hybrid EFO beyond the formal FVA laid out in the original goals and results in total estimated annual benefits of $9.4 million. FIRO work plan in 2015. The EFO alternative has estimated total annual benefits of $9.9 million. The Steering Committee also conducted a fisheries temperature study, which concluded that EFO LESSONS LEARNED and Modified Hybrid EFO would offer the greatest benefits to summer rearing juvenile steelhead, while an analysis of The success of the FIRO effort is due in large part to high-flow frequency concluded that FIRO is unlikely to neg- the Steering Committee, a common vision among stake- atively affect Chinook salmon spawning and migration. A holders, and by building institutional trust among part- flood risk study found no significant difference between ners. The formation of the Steering Committee and the the baseline and the FIRO alternatives when measuring development of its internal culture of trust, cooperation, damages to structures and contents. However, when con- engagement, and processes successfully brought togeth- sidering populations at risk, in addition to damages, all er groups with separate institutional mandates, with a FIRO alternatives would significantly reduce risk upstream common vision that a better balance between operational from Hacienda Bridge (near Guerneville). objectives is possible through cooperation and advances FIGURE 8B.6 FIRO Process to Develop an Adaptive Water Control Manual Changes in Baseline Conditions (e.g.,climate change or regulations) Weather and WCM Water Forecasts Flood Risk Management Adaptive Water Control Plan Objectives Formulation and Ongoing Evaluation of Met/Exceeded Research and Revised Development Management Alternative Improved Water Supply Reliability Environmental Conditions Observations Societal Benefits Source: Adapted from CW3E n.d. Case Study | California 129 in science and engineering. Additionally, with the connec- the Lake Mendocino FIRO effort was developed as a pilot tion and interaction of FIRO Steering Committee mem- case, the FIRO study methodology and analysis are all well bers and staff from the respective organizations that are documented and publicly available, forming a valuable re- engaged in the research and operations aspects of water source base for those considering FIRO application. The management, the FIRO effort eliminated the gap that can multi-stakeholder process, and structured analytical pro- exist between research that investigates and makes sci- cess including the PVA and FVA, also yield lessons on how entific advances, and operations who need tools that are processes can be structured to update operating rules, ready for application to real world problems with requisite and can be simplified for less complex cases, including reliability and assurance. Research, operations, and reg- those where flood-causing atmospheric conditions or ulatory perspectives have blended into the FIRO effort forecasting capabilities are less advanced. to produce science to inform policy and bring about im- proved efficiency in water management for the simultane- ous benefit of flood risk management, water supply, and NEXT STEPS ecologic concerns. Expanding the FIRO community by sharing lessons learned and openly sharing and transfer- Transferability of FIRO to other locations. USACE and ring tools is essential to the FIRO approach (CW3E n.d.). CW3E are actively assessing FIRO opportunities in other settings, starting with systems dominated by atmospher- FIRO represents a major policy change for USACE, con- ic rivers. Efforts are underway to apply FIRO to Prado Dam tributing to the incorporation of forecast information on the Santa Ana River, New Bullards Bar Reservoir, and into dam operational decision-making. In May 2016, the Lake Oroville in California, as well as the Howard Hanson USACE regulation governing Water Control Management Dam in Washington. These projects will yield valuable in- (ER 1110-2-240) was updated to include “Forecasted condi- sights on the characteristics of FIRO viability for very dif- tions may be used for planning future operations, but releas- ferent sites. This knowledge is being incorporated into a es should follow the water control operations plan based screening process that will help prioritize further FIRO via- on observed conditions within the watershed to the extent bility assessments at other sites across the United States. practicable.” Thanks to the support from multiple levels of The Prado Dam was selected after careful consultation USACE, the FIRO effort contributed to defining how this with water management technical leaders, engineers, could be implemented on the ground, setting an important and operators within the USACE Los Angeles District, and policy application precedent for USACE and other partner the South Pacific Division. Additionally, the selection of a agencies, and a groundbreaking experience to improve dam in this area was supported by the FIRO atmospheric water availability without affecting water allocation. science team members, based on the differences in how atmospheric rivers behave in southern California versus There is an opportunity for continued improvement in northern California, and on the differences in watershed FIRO at Lake Mendocino. Given the many promising leads characteristics that would yield new insights into FIRO in ongoing atmospheric rivers research and significant potential. The Santa Ana River watershed is highly urban- improvements in forecast skills that have been possible ized, with fast hydrological response and a large elevation in just the past decade, there is ample reason to believe difference from the upper to lower watershed, including that even greater benefits may be possible with enhanced some snow-impacted areas. An additional important dif- FIRO in the future. This future phase—FIRO 2.0—will be ference is that direct groundwater recharge, as opposed important to further improving water supply reliability and to surface storage, is a key water management practice adapting to a changing climate (Jasperse et al. 2020). in this basin. FIRO 2.0 will require support for enhanced observations and forecasting, modeling, and decision support tools and A procedure for conducting screening-level FIRO as- investing in research to improve precipitation and stream- sessments will be developed and applied to addition- flow forecasts. al dams in the states where atmospheric rivers affect water management operations. The criteria for selecting The Lake Mendocino FIRO process produced lessons these dams will be similar to that used for selecting addi- that can be adapted to local circumstances. Because tional reservoirs for full FIRO assessments. The screening 130 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE process will not be as detailed or complete as the full vi- J. Brown, D. Reynolds, S. Evett. 2020. “Forecast ability assessments for Lake Mendocino, Prado Dam, or Informed Reservoir Operations Using Ensemble the other full assessments. However, the screening pro- Streamflow Predictions for a Multipurpose Reservoir cess will provide important guidelines for how FIRO via- in Northern California.” Water Resources Research 56 bility can be assessed at potential candidate reservoirs in (9). doi:10.1029/2019WR026604. the West and across the rest of the United States. This Dinar, A., D. Parker, H. Huynh, and A. Tieu. 2020. “Chapter 5. approach will systematically grow the scientific and engi- The Evolving Nature of California’s Water Economy.” neering knowledge base needed to perform well-founded In The Evolving Nature of California’s Water Economy. future assessments of FIRO applicability across a much Accessed July 8, 2022. Available at: https://s.gianni- broader range of conditions than has been explored in the ni.ucop.edu/uploads/pub/2021/01/22/chapter_5_ first pilot reservoir, Lake Mendocino. These guidelines will water_2020.pdf. assist water management agencies in deciding where and Ehlers, R. 2017. Managing Floods in California. Sacramento, how FIRO principles and tools can be incorporated into fu- CA: Legislative Analyst’s Office. Accessed July 8, ture WCM updates (Talbot, Ralph, and Jasperse 2019). 2022. Available at: https://lao.ca.gov/publications/ report/3571. ENDNOTES Escriva-Bou, A., J. Mount, and J. Jezdimirovic. 2019. Dams in California. San Francisco, CA: Public Policy Institute 1 The terms of reference is a non-binding agreement between of California (PPIC). Accessed July 8, 2022. Available the members of the Steering Committee that describes how at: https://www.ppic.org/wp-content/uploads/JTF_ the committee will function, make decisions, share informa- DamsJTF.pdf. tion, and work together. This is a key element of developing an FIRO SC (Forecast-Informed Reservoir Operations environment of transparency and trust. 2 EFO is a risk-based approach to reservoir flood operations that Steering Committee). 2015. A Comprehensive Plan to incorporates ensemble streamflow predictions (ESPs) made Evaluate the Viability of Forecast-Informed Reservoir by the CNRFC (Delaney et al. 2020). Operations (FIRO) for Lake Mendocino. Accessed July 8, 2022. Available at: https://evogov.s3.amazonaws. com/185/media/164714.pdf FIRO SC. 2017. Preliminary Viability Assessment of Lake Mendocino. Accessed July 8, 2022. Available at: REFERENCES https://cw3e.ucsd.edu/FIRO_docs/FIRO_PVA.pdf. FIRO SC. 2019. Hydrologic Engineering Management American Meteorological Society. 2020. Glossary of Plan (HEMP) for Lake Mendocino Forecast-Informed Meteorology: Forecast-Informed Reservoir Operations. Reservoir Operation (FIRO) Evaluation of Water Control Accessed July 8, 2022. Available at: https://glossary. Plan Alternatives within the Final Viability Assessment ametsoc.org/wiki/Forecast-informed_reservoir_ (FVA). Appendix B. Accessed July 8, 2022. operations. Available at: https://cw3e.ucsd.edu/FIRO_docs/ CalEPA (California Environmental Protection Agency). Lake_Mendocino_FVA_Appendix/Appendix_B_-_ 2021. Water Unavailability in the Russian River Water_Resources_Engineering_Studies/ Watershed. Fact Sheet, Sacramento, CA: State LakeMenocino_FVA_HEMP_V3.pdf. Water Resources Control Board. Accessed July 8, Gershunov, A., T. Shulgina, R. E. S. Clemesha, K. Guirguis, 2022. Available at: https://www.waterboards.ca.gov/ D. W. Pierce, M. D. Dettinger, D. A. Lavers, D. R. Cayan, drought/north_coast/docs/faq_russian_river_water_ S. D. Polade, J. Kalansky, and F. M. Ralph. 2019. unavailability.pdf. "Precipitation Regime Change in Western North CW3E (Center for Western Weather and Water Extremes). America: The Role of Atmospheric Rivers." Scientific n.d. “Forecast Informed Reservoir Operations Reports 9 (9944). doi: 10.1038/s41598-019-46169-w. Process.” Accessed July 8, 2022. Available at: https:// Hanak, E., J. Lund, B. B. Thompson, W. B. Cutter, B. Gray, cw3e.ucsd.edu/firo_process/. D. Houston, R. Howitt, K. Jessoe, G. Libecap, J. Delaney, C. J., R. K. Hartman, J. Mendoza, M. Dettinger, Medellín-Azuara, S. Olmstead, D. Sumner, D. Sunding, L. D. Monache, J. Jasperse, F. M. Ralph, C. Talbot, B. Thomas, and R. Wilkinson. 2012. Water and the Case Study | California 131 California Economy. San Francisco, California: Public Accessed July 8, 2022. Available at: https://www. Policy Institute of California (PPIC). Accessed July 8, ppic.org/wp-content/uploads/californias-water-pre- 2022. Available at: https://www.ppic.org/wp-content/ paring-for-floods-november-2018.pdf. uploads/rs_archive/pubs/report/R_512EHR.pdf. PPIC. 2018b. Storing Water. San Francisco, California: Howard, C. D. 1999. “Death to Rule Curves.” 29th Annual PPIC. Accessed July 8, 2022. Available at: https:// Water Resources Planning and Management Con- www.ppic.org/wp-content/uploads/californias-wa- ference. Tempe, Arizona: American ter-storing-water-november-2018.pdf. Society of Civil Engineers. doi:10.1061/40430(1999) PPIC. 2018c. Climate Change and Water. San Francisco, 232. California: PPIC. Accessed July 8, 2022. Available at: IWRSS (Integrated Water Resource Science and Services), https://www.ppic.org/wp-content/uploads/californi- and NOAA (National Oceanic and Atmospheric as-water-climate-change-and-water-november-2018. Administration). 2014. Russian River Basin Partner pdf. Meeting Report. Santa Rosa, California. Accessed Talbot, C. A., M. Ralph, and J. Jasperse. 2019. “Forecast- July 8, 2022. Available at: https://www.weather.gov/ Informed Reservoir Operations: Lessons Learned media/water/IWRSS_RR_PartnerForumReport.pdf. from a Multi-Agency Joint Research and Operations IWRSS and NOAA. 2016. Stakeholder Engagement to Effort.” Federal Interagency Sedimentation and Demonstrate Integrated Water Resources Science and Hydrologic Modeling Conference. Reno, NV. Services. Russian` River Basin Partner Report, Santa Sandoval-Solis, S. 2020. “Water Resources Management in Rosa, California. Accessed July 8, 2022. Available at: California.” In Integrated Water Resource Management, https://www.weather.gov/media/water/IWRSS_RR_ edited by E. Vieira, S. Sandoval-Solis, V. Pedrosa and PartnerForumReport_Jan1116.pdf. J. Ortiz-Partida chapter 4, 35–44. New York: Springer Jasperse, J., F. M. Ralph, M. Anderson, L. Brekke, N. Cham. doi:10.1007/978-3-030-16565-9_4. Malasavage, M. D. Dettinger, J. Forbis, J. Fuller, Sonoma Water. n.d. “Water Supply.” Accessed July 8, C. Talbot, R. Webb, and A. Haynes. 2020. Lake 2022. Available at: https://www.sonomawater.org/ Mendocino Forecast Informed Reservoir Operations. water-supply. Final Viability Assessment, UC-San Diego: Lake Sonoma Water. n.d. “Forecast Informed Reservoir Mendocino FIRO Steering Committee. Accessed July Operations: A Flexible and Adaptive Water 8, 2022. Available at: https://escholarship.org/uc/ Management Approach.” Accessed July 8, 2022. item/3b63q04n. Available at: https://www.sonomawater.org/firo. Mendocino County. 2021. Mendocino County Russian Water Boards. 2016. “Certification of Self-Certified River Flood Control & Water Conservation Conservation Standard.” Sacramento, CA: State Improvement District Staff Report: Agenda Item Water Resources Control Board. 6: Water Resiliency Planning. Accessed October Water Education. n.d. “California Water 101.” Sacramento, 7, 2022. Available at: https://secureservercdn. California: Water Education. Accessed July 8, 2022. net/192.169.221.188/ahg.e5a.myftpupload.com/ Available at: https://www.watereducation.org/ wp-content/uploads/2021/12/Agenda-Item-6-Water- photo-gallery/california-water-101. Resiliency-Planning.pdf. Woodside, G. D., A. S. Hutchinson, F. M. Ralph, C. Talbot, Mount, J., and E. Hanak. 2019. Water Use in California. R. Hartman, and C. Delaney. 2021. “Increasing San Francisco, California: Public Policy Institute of Stormwater Capture and Recharge Using Forecast California (PPIC). Accessed July 8, 2022. Available at: Informed Reservoir Operations, Prado Dam.” https://www.ppic.org/wp-content/uploads/jtf-water- Groundwater. doi:10.1111/gwat.13162. use.pdf. PPIC (Public Policy Institute of California). 2018a. Preparing for Floods. San Francisco, California: PPIC. 132 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE ANNEX 8C. CAPE TOWN: RESILIENCE THROUGH DIVERSIFICATION OF WATER SOURCES AND INCREASED STORAGE CASE STUDY BRIEF Summary Cape Town has depended on a regional surface water storage scheme for 95 percent of its water, shared with agriculture and other small towns. The region experienced a 1-in-590-year drought in the period 2015 to 2018, which demonstrated the city’s reliance on limited water storage and on rainfall, and with little access to water from other sources. In the short term, the city was able to manage by substantially reducing water demand and taking measures to optimize water use from the regional storage system, including the transfer of water from agricultural to urban uses. Severe restrictions on agricultural water use were applied, affecting fruit production, exports, related jobs, and the gross domestic product (GDP) of the region. In response to the event, the city developed a Water Strategy with the objectives of diversifying its water sources to include reuse and desalination along with more substantial groundwater supplies, with implications for how water storage is augmented and managed. Activities to increase the resilience of the regional water storage system are underway, including an analysis of the hydro- economy, planning for optimal integration of ground and surface storage systems, removing invasive vegetation, and reviewing and updating water allocations in light of climate change and environmental commitments. Type(s) of water storage used › Large reservoirs › Aquifers Water service(s) of storage provided › Increased water availability › Flow regulation Water requirement(s) of storage met › Water provision for domestic needs and industrial processes › Water provision to meet crop/livestock requirements in seasons/locations without precipitation › Water controlled for electricity generation Case Study | Cape town 133 CONTEXT Water Use and the Regional Water Storage System Geography, Demographics, and Economy Cape Town is entirely dependent on the region’s built water storage and distribution system to meet its water Cape Town is a city of approximately 4.2 million people needs (photo 8C.1). The storage system is fed by sur- surrounded by an agricultural hinterland with extensive face water (96 percent) and groundwater (4 percent). The wine and fruit farming served by small towns. The econ- Western Cape Water Supply System (WCWSS), the pri- omy of the Western Cape is dominated by the city, which mary provider of water in the region, comprises six large accounts for 70 percent of the province’s GDP. Key indus- dams, managed as an integrated system (map 8C.1), with tries include the financial and business services industry, a combined storage of close to 900 million kl and an as- manufacturing, wholesale, and trade. The region produces sured yield of 517 million m3 per year. between 55 percent and 60 percent of South Africa’s agri- cultural exports and contributes approximately 20 percent The primary purpose of the storage dams is to increase toward South Africa’s total agricultural production (OECD the yield and reliability of the system as a whole, and to 2021). make this water available to urban and agricultural water users. However, in recent years, there has been a reduc- Not situated near any major rivers, the region receives tion in the yield of the system, a significant contributor to most of its water from rainfall, which is quite variable which has been the spread of invasive vegetation, leading throughout the year and predominantly comes in win- to potential over-allocation of the system. ter from cold front systems. Average precipitation for the area varies between 300 and more than 900 millimeters Urban use: The WCWSS is primarily an urban system, with per year, with the higher rainfall areas in or close to the two-thirds of the yield allocated for this purpose. Cape mountains, compared to an average of 495 millimeters Town relies on this system for 95 percent of its water, and per year for South Africa as a whole. its allocation from the system makes up 90 percent of the PHOTO 8C.1 Cape Town’s Reservoirs Source: Hansueli Krapf (User Simisa [talk · contribs]), CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=13294313. 134 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE MAP 8C.1 Western Cape Water Supply System Surface Water Source Lee u Groundwater Source Lower Berg Irrigation Board ● Rivers and Dams Misverstand ● Water Treatment Plant Dam Pipeline and Tunnels 24-Rivers Water Abstraction Irrigation Board West Coast Municipal Boundary District Municipalities B Protected Areas er g Kl ei n Ber g West Coast District Voelvlei Municipalities ● Dam Voelvlei WTP ● Upper Berg Irrigation Board ● ● Silwerstroom ● WTP ● Witzlands WTP Paarl ● Wemmershoek Dam SOUTH Be ATLANTIC ● rg ● Wemmershoek OCEAN ● WTP ● Blackheath Berg WTP River Dam ● Table Mtn ● Stellenbosch Theewaterskloof ● Dams Faure Dam WTP Kleinplaas ● Dam Zonderend Water False Bay Users Association Simons Town Steenbrad ● WTP Groenland Water Dams Users Association Vyeboom Steenbras : Irrigation Board (Lower) iet Dam P a lm 0 15 30 Kilometers Source: Stafford et al. 2018. Case Study | Cape town 135 total urban allocation and 60 percent of the combined al- Environmental services. The intention (in policy and leg- location for urban and agricultural use from the system.1 islation) is for the system’s storage reservoirs to be op- erated in such a way that minimum environmental flows Irrigation: The other one-third of the yield is allocated to in the downstream rivers are protected. These flows form agricultural irrigation. However, not all water for irrigation part of what is known as The Reserve, which enjoys prior- in the region is provided through the WCWSS. Water for ity in the allocation process set out in the legislation. The irrigation could come from a combination of sources: on Reserve needs to be accounted for in the calculation of farm storage, small irrigation schemes, and allocations the system yield and taken into account in the allocation from the WCWSS (either as direct abstraction from the of water rights for other uses.2 storage reservoirs or as run-of-river abstraction). Hydropower: Two pumped-storage systems are linked to Institutional and Governance Arrangements the system, providing peak capacity of 580 MW, making up roughly 34 percent, 15 percent, and 2 percent of Cape Ownership: Three of the six storage reservoirs are owned Town, southwestern Cape, and national peak demand, re- by the City of Cape Town and three by national govern- spectively. These are operated in such a way so as to not ment. The six storage reservoirs are managed as an inte- reduce the yield of the system (box 8C.1). grated system (table 8C.1). BOX 8C.1  Hydropower Linked to the Western Cape Water Supply System There are two hydropower pump-storage schemes linked with the WCWSS that contribute to peak demand, Steenbras (180 MW), which is owned by the City of Cape Town and directly linked to its electricity supply system, and Palmiet (400 MW), which is owned by the national electricity company, Eskom, and integrated into the national electricity grid. Peak electricity demand is about 1,700 MW for the City of Cape Town, 4,000 MW for the southwestern cape region, and 34,000 MW for South Africa as a whole. Steenbras Pumped-Storage Hydropower Scheme. When constructed over 40 years ago, the City of Cape Town-owned 180 MW Steenbras pumped storage scheme was the first hydroelectric scheme of its kind in Africa. It has been a key source of stable electricity supply to residents of Cape Town and, in recent years, has helped avoid or minimize the impact of load-shedding on Capetonians. Each of the station’s four 45 MW generator units acts as a pump-motor in one mode and a turbine-generator in the other. The peak performance of the scheme allows the city to work towards having spare generation capacity, which can help prevent load-shedding or reduce the load-shedding level for Cape Town residents (City of Cape Town 2020). Palmiet Pump-Storage Hydropower. The Eskom-owned 400 MW pumped storage scheme is integral to the Palmiet River Government Water Scheme situated near Grabow in the Western Cape Province. The scheme has also a dual purpose similar to the Drakensberg pumped storage scheme, providing for the generation of hydro-energy between the upper 17 million m3 Rockview Dam and lower 15 million m³ Kogelberg Dam storages and supplementing water to nearby Steenbras Dam reservoir. From the Rockview Dam, the overspill water supplements the water supply system of Cape Town Metropolis. This is also an inter-basin water transfer scheme, developed jointly by Eskom and the Department of Water and Sanitation, and commissioned in 1988 after some five years of construction, predominantly within the Kogelberg Nature Reserve. The Palmiet pumped storage scheme was awarded the 2003 Blue Planet Prize from the International Hydropower Association for its contribution to sustainable devel- opment and good practice in utilizing hydropower resources (Barta 2017). 136 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE TABLE 8C.1 Summary, Yields, and Allocations of Dams Supplying the WCWSS, 2019 DAM NAME OWNERSHIP CAPACITY YIELD PA ALLOCATIONS BALANCE (yeara) million m3 million m3 (urban) (irrigation) million m3 Theewaterskloof DWS (1978) 480 184 99 179 -56 Run-of-river (Berg) 38 Voëlvlei DWS (1971) 164 99 94 14 -9 Berg River DWS (2009) 130 82 80 10 -2 Wemmershoek CCT (1957) 59 52 54 0 -2 Steenbras Lower CCT (1921) 33 43 Steenbras Upper CCT (1977) 32 63 0 0 Transfer (Palmiet) 20 Total 898 517 390 203 -76 System integration 30 - 46 (returns to system) Source: DWS 2019. Note: CCT = City of Cape Town; DWS = Department of Water and Sanitation; PA = per annum. a Year commissioned. Allocation of use rights: In terms of South Africa’s constitu- and recommendations were provided on options to main- tion, water resources management is primarily the respon- tain a balance between demand and supply over the medi- sibility of national government,3 and water use rights are um and long term in the context of growing urban demand granted by the national Department of Water and Sanitation.4 (DWA 2007). Water allocations from the system are based on a calcula- tion of a yield at a defined level of assurance of supply, taking Participatory governance: A steering committee chaired into account The Reserve (see “Environmental services” in by the national Department of Water and Sanitation, that the preceding section). The yields are based on stochastic comprises all major WCWSS stakeholders, was estab- modeling of a synthetic probabilistic distribution of forecast lished in 2007. The purpose of this committee was to over- inflows, derived from historical hydrological records. The see the implementation of the recommendations from the yield for urban water use is based on a 98 percent assurance Reconciliation Strategy (to maintain a balance in demand of supply, and the agriculture water use allocation is based and supply over the medium and long term) and to make on a 95 percent assurance of supply. The implications of this recommendations on interventions to maintain balance system are that irrigated agriculture is expected to manage in the system in the short term (next hydrological year), more frequent, but milder, restrictions and, for urban areas, based on the annual update of the hydrological model. less frequent, but more severe, restrictions. Decisions to restrict abstractions: During periods of low System modeling and monitoring: The national rainfall, the Steering Committee would be informed of, Department of Water and Sanitation is responsible for and respond to, recommendations on the level of restric- maintaining an up-to-date hydrological model of the sys- tions to be applied based on defined operating rules for tem, to run this model annually to inform decision-making, the system. The actual restriction decision is made by the and to monitor (and report on) rainfall, dam inflows, dam national minister responsible for water, and the decision is levels, and abstractions from the system. published in the official government gazette. System augmentation: A thorough study was undertaken Decisions to augment supply through additional storage in 2007 of the demand and supply balance in the system, or other interventions: The intention was for an annual Case Study | Cape town 137 System Status Update to be produced by the National A MAJOR DROUGHT WITH SERIOUS Department of Water and Sanitation.5 This report would ECONOMIC CONSEQUENCES inform the Steering Committee on progress with the im- plementation of interventions to maintain a balance be- Cape Town and its environs experienced four succes- tween demand and supply over the medium and long sive years of low rainfall from 2015 to 2018 (figure term. The Steering Committee was not a decision-making 8C.1). Based on historic hydrological records available at body. Augmentation decisions needed to be made by the the time, this was considered to be a 1-in-590-year hydro- national Department of Water and Sanitation (as custodi- logical event (City of Cape Town 2019). an of the national unitary water resource) in conjunction Aggregate reservoir storage levels in the WCWSS dropped with the City of Cape Town (as a major user in the sys- precipitously from overflowing in the winter of 2014 to just tem), and other users. 20 percent at the end of summer in 2017 (figure 8C.2). Transparency: Transparency in the above system was fa- Severe restrictions were imposed on both agriculture cilitated by making all reports and meeting minutes avail- and urban water users. In the case of urban users, the able on a website dedicated to the WCWSS Reconciliation restrictions were to avert what would become known in- Strategy.6 ternationally as “Day Zero” and to prevent dams from be- coming empty. Catchment management: The Breede-Gouritz Catchment Agency undertakes catchment management functions for The economic costs of the crisis have been estimated to part of the area of the WCWSS.7 The rest of the area is man- be in the region of $1 billion to $1.5 billion as a result of aged by the national Department of Water and Sanitation. reduced agricultural output, tourism, and investment, and The national policy intention is for the establishment of associated job losses of approximately 37,000, among wall-to-wall catchment management agencies.8 others (Pegasys 2021). FIGURE 8C.1 Annual Inflows into the Large Water Supply Dams, Cape Town, 1928–2020 1,400 10-year moving average 1,200 Annual inflows (million m3/year) Long-term average 2000s 1,000 drought 1920/30s 1970s 2014–18 drought drought drought 800 600 400 200 0 19 8 30 19 8 19 0 19 8 19 0 19 8 19 0 19 8 19 0 19 8 19 6 80 19 8 19 6 90 20 8 19 6 20 0 20 8 19 6 19 6 19 6 19 6 20 6 20 0 20 8 20 20 6 19 2 19 2 19 2 19 2 19 2 19 2 19 2 20 2 20 2 19 4 19 4 19 4 64 74 19 4 19 4 20 4 20 4 2 3 3 4 4 5 6 6 7 7 8 9 0 0 1 4 5 5 6 7 8 9 0 1 1 3 4 5 6 7 8 9 0 1 3 4 5 8 9 0 1 19 19 19 19 19 19 Hydrological year Source: City of Cape Town 2022. Note: Hydrological years start on November 1 of the prior year. 138 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE FIGURE 8C.2 Aggregate Dam Levels in WCWSS, Cape Town, 2008–22 120 100 80 Percentage full 60 40 20 0 Feb-08 Feb-09 Feb-10 Feb-11 Feb-12 Feb-13 Feb-14 Feb-15 Feb-16 Feb-17 Feb-18 Feb-19 Feb-20 Feb-21 Feb-22 Feb-23 Source: City of Cape Town 2022. BUILDING WATER RESILIENCE FOR THE After weathering the 2014–18 drought, the next step MEDIUM AND LONG TERM was to evaluate actions to carry out in the medium and long term that would help mitigate the impact of future 120 Getting through the drought itself primarily focused on droughts in the region. The use of built water storage for reducing 100 water use while supply augmentation and addi- nearly all Cape Town’s needs has been the case for the last 120 tional storage are part of the longer-term strategy for re- 125 years, with the first dam for water supply constructed silience. 100 In response to the drought, water use went from 80 in 1896, and this has served the city well, up until recently. Percentage Full (%) summer peak season water use of 1,200 million liters Liters per day (millions) 60 80 before the drought (December 2014) to a low of per day But the circumstances around which Cape Town must 500 million 40 liters per day during the height of the crisis navigate in terms of its water security have changed. 60 (February 2018), saving 700 million liters per day (figure Economic and population growth in the Cape Town metro- 20 8C.3). And while demand management is a critical part of 40 politan area is rising significantly, and even with increased water management, 0 especially in areas prone to drought, demand management measures in place, there is a cor- 20 looking at alternate water supply sources and additional responding Feb-08 Feb-09 Feb-10 Feb-11 Feb-12 Feb-13 Feb-14 Feb-15 rise in Feb-16 Feb-17 demand—though waterFeb-19 Feb-18 Feb-20 Feb-21this increase Feb-22 is Feb-23 water0 storage, rather than depending solely on rainfall and still lower than it was prior to the last drought. Rainfall is Feb-09 Feb-10 Feb-08 storage, built water became Feb-11 Feb-12 for a necessity Feb-13 CapeFeb-14 Town.Feb-15 becoming Feb-16 Feb-17lessFeb-18 Feb-19inFeb-20 predictable Feb-21 the face Feb-22 change, of climate Feb-23 FIGURE 8C.3 Cape Town Gross Water Use, 2011–21 1400 1200 Liters per day (millions) 1000 800 600 400 200 0 Feb-11 Feb-12 Feb-13 Feb-14 Feb-15 Feb-16 Feb-17 Feb-18 Feb-19 Feb-20 Feb-21 Feb-22 Source: City of Cape Town 2022. Case Study | Cape town 139 meaning less water is available for storage, but the po- secure in practice.9 A group of scientists concluded, based tential capacity of surface water storage has reached on historical data on rainfall and reservoir inflows, that cli- its upper limit, as suitable sites for additional dams are mate change led to a threefold increase in the likelihood scarce, unavailable, or insufficient to meet the rising de- of the 2015 to 2017 drought (Otto et al. 2018; Ziervogel mand. Ultimately, the system is too dependent on one 2019). water source (rainfall) to fill all the dams and meet the water demand needs of the city. It needs to diversify its Three lessons arise from these facts: water risk and sources, while expanding overall storage capacity. Updating models. The importance of regularly updating hydrological and forecasting models as well as operating Prior to the 2014–18 drought, Cape Town’s system for rules of the system is heightened in the context of climate planning, implementing, and managing the regional change. Integrated storage systems can result in a sense water storage system was reasonably advanced and of complacency, with stakeholders acting as if the system robust by international standards (Muller 2018). More were able to reliably deliver water in most instances, mak- than a decade ago, sophisticated long-term planning was ing users unaware and unprepared for extreme shortages. based on climate and hydrological monitoring and fore- casting (Muller 2018); multiple interventions were evalu- Scenario-based planning. Stochastic models based on ated and ranked (DWA 2007); a system of water rights historic hydrological records are insufficient. While the was put in place; and a multi-stakeholder governance models used before the onset of the drought did factor in arrangement with transparent processes had been es- climate change, these models assumed a gradual change tablished to oversee interventions to maintain a balanced over time and did not adequately account for the possibil- system in both the short and long term. Why, then, were ity of step changes in climate (and hence dam inflows). the impacts of the drought so much more severe than In its new Water Strategy (City of Cape Town 2019), Cape had been planned for, exposing weaknesses in the sys- Town has explicitly adopted a scenario planning ap- tem that needed to be addressed? Efforts to address both proach, taking the possibility of a step-change in rainfall are discussed below. into account. Planning and Security of Water Rights in the Context Updating and revising water rights. Water allocations of Climate Change (and associated water rights) from the integrated system need to be regularly updated to ensure that these rights The onset of the drought occurred after three years of fall within the available yield for a given assurance of sup- spilling reservoirs. In fact, the storage reservoirs had ply. In the absence of this, the system will be less secure spilled toward the end of winter in five of the seven years and the impacts of droughts more severe. in the period 2008 to 2014. While a number of activities were underway to augment supplies, there was not a Diversification of Sources and Storage Types sense of urgency and even, perhaps, a level of compla- cency. As a result of effective demand management from The overdependence on the WCWSS integrated storage the previous drought in 2000, Cape Town was well within system means that Cape Town is particularly vulnera- its allocated assured supply at the onset of the drought ble to multiyear droughts and hence climate change.10 in 2015. In retrospect, Cape Town did not have adequate However, few opportunities exist to build further tradition- water storage. al water storage reservoirs, dependent on runoff from rain, in the region.11 Therefore, the growth in urban water de- Additional allocations from the integrated storage sys- mand (as the population and the economy grow) will need tem had also been made to agriculture but the calculat- to be met largely from a combination of increasing water ed system yields were not updated at the time. Revised use efficiency (including addressing nonrevenue water) yields, based on up-to-date hydrological records, showed and the exploitation of diverse sources of water, including that the system was actually over-allocated (table 8C.1) water reuse, desalination, removal of invasive vegetation, and therefore the water use rights "on paper" were not and further developing groundwater sources and stores. 140 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE Cape Town has developed and is implementing a plan Balancing resilience and costs. More resilient systems to add 300 million liters per day of new capacity from will be more costly to build and maintain because of diverse sources over the period to 2030 (figure 8C.4).12 the need to make greater use of more expensive sourc- Of this additional capacity, less than 15 percent is from es of water. However, in countries such as South Africa, new surface water storage. As this system evolves, new resources are scarce, which, in some provinces, makes approaches to managing the entire system will be need- options such as wastewater reuse less expensive than ed to optimize cost and system operation and ensure buying bulk water. The challenge is therefore to find an resilience.13 This is particularly important given the fact appropriate balance between resilience and costs, that that the costs of reuse and desalination are substantially is, "enough resilience" at an "affordable" cost. While this is higher than water from traditional surface water storage partly a technical design issue, the tradeoff is likely to be systems. more art than science. This means that the technical staff involved in system design must also appreciate the role of Two lessons arise in this context: communication and trust-building in getting political buy- in for the required investments, allowing elected represen- Resilience through diversification. Greater resilience can tatives to make informed choices related to the spending be achieved through the diversification of sources, rather of public money (and any commercial financing) and in than an overdependence on one water source. This helps the approval of the necessary associated tariffs. to build flexibility and redundancy into the supply system, increasing security of supply in context of climate change Opportunities from Aquifer Storage Potential risks. This will require sophisticated systems design, in- cluding storage, and greater technical capacity to both The Cape Flats aquifer provides several opportunities implement and manage these systems. Cape Town’s new to strengthen the water security of Cape Town as a new Water Strategy (2019) indicates a move in this direction source of water supply and storage facility, enabling (figure 8C.5). water reuse and storage of desalinated water. The Cape FIGURE 8C.4 Water Availability, Anticipated Demand, and the Augmentation Program, Cape Town, 2004–40 600 Anticipated demand 500 Cubic meters per year (millions) 400 Berg River Dam Water augmentation 300 200 Water availability 100 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022 2024 2026 2028 2030 2032 2034 2036 2038 2040 Existing water resources Unconstrained water demand Committed augmentation program Base case water demand Acceptable augmentation program Base case water demand with water conservation/water demand management Actual (historic) water demand Low water demand Source: City of Cape Town 2020b. Case Study | Cape town 141 FIGURE 8C.5 Cape Town’s Plans to Diversify Water Sources Desalination Groundwater 11% Groundwater 4% 7% 7% Reuse CURRENT 2040 WATER RESOURCES WATER RESOURCES SPLIT SPLIT 96% 75% Surface water Surface water Source: City of Cape Town 2019. Flats Aquifer is large: over 400 km2 in extent with a depth risks, saltwater intrusion, and geographic distribution of of between 15 and 40 meters. Annual rainfall over the good abstraction and recharge sites, among others. aquifer equates to 200 million kl per year, representing close to 40 percent of the yield of the integrated surface Environmental Services water storage system.14 Total aquifer storage could be of the order of 800 million kl,15 almost as significant as the Negative storage. Studies have shown that the spread total surface water storage in the regional system of close of certain invasive non-indigenous species in the catch- to 900 million kl. The City of Cape Town is developing an ments reduces runoff into storage reservoirs and hence aquifer recharge and recovery scheme for the Cape Flat the yield of the system. This could be considered "nega- and aims to abstract 50 million liters per day (18 million kl tive storage." Interventions to address this through ongo- per year), which is within the sustainable yield of the aqui- ing programs to clear alien invasive species are a low-cost fer and meets the terms of a water use license granted by method of increasing system yield (or preventing yield the national Department of Water and Sanitation (Mauck from declining) and have been prioritized in the Cape and Winter 2021). Cape Town already operates a 20 mil- Town Water Strategy. lion liters per day managed aquifer recharge and recovery scheme that supplies the satellite town of Atlantis, in the Protecting estuaries. The National Water Act of 1998 pri- northern part of the metropolitan area. This scheme is pri- oritizes an allocation of water, called The Reserve, to pro- marily used for water recycling. It was developed in 1979 vide for a basic supply of water for human needs and to and rehabilitated and expanded in 2017, during the height protect rivers and estuaries. In the latter case, the purpose of the drought (Walton 2017). is to preserve minimum flows during the dry summer months. The system of water rights authorizations needs Cape Town’s Water Strategy commits the city to transi- to take The Reserve into account as a priority. tioning to a water sensitive city. Integrated use of Cape Flats Aquifer, together with stormwater and wastewater, Strengthening Institutional and Governance forms part of this transition. While there appears to be Mechanisms considerably more potential to make use of the aquifer as a storage amenity, a number of complex factors need The significant stress placed on the system exposed to be considered including water quality, the height of the weaknesses in the institutional and governance mecha- water table (which is very shallow in many areas), flood nisms described in "Context" earlier. Cape Town’s Water 142 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE Strategy commits the city to work with other stakeholders silted, and some pumps were in disrepair. A robust system to strengthen the resilience of the regional water system. requires a clear set of policies, rules, and procedures that are effectively implemented. Improving the information base and building trust. The ef- fective functioning of the system depends on trust across Improving institutional capacity and governance. The ca- institutions and between major stakeholders. Both irriga- pacity to undertake the actual operations of the WCWSS tors and urban citizens were unhappy with the sacrifices sits within the national Department of Water and the City asked of them. A robust governance system is needed of Cape Town, and governance of the system is through to manage these tensions and to support difficult deci- a multi-stakeholder committee. The existing catchment sion-making and implementation. A hydro-economic study management agency, which covers only part of the areas was completed in 2022 to improve stakeholder knowledge of the WCWSS, plays a limited role. Options for improving of the system, how it works, and the trade-offs needing to institutional capacity and governance of the system were be managed going forward as demand increases and more explored as part of the hydro-economic study. One pro- expensive supplies are introduced into the system. A highly posal put forward and under consideration is to establish consultative process is being followed with a key objective a single catchment management agency that coincides of building understanding and trust across the system. with the WCWSS, and for the system to be governed under the umbrella of the catchment management agen- Strengthening the licensing process. South African water cy. Another option would be to delegate the operations policy must juggle the triple goals of equity (including re- and management of the system to the City of Cape Town, dress), economic efficiency (make best use of a scarce which would need to be able to do longer-term financial resource to support economic growth) and environmen- planning than it currently does due to the constraints of tal sustainability. Proposed policy changes in 2013 pri- planning and financial cycles of municipal government. oritized equity, and new allocations were made in this light.16 However this, together with the explicit inclusion Maintaining political support for investments in water of The Reserve requirement, resulted in the system being security. It is harder to maintain support for the necessary over-allocated, exacerbating the impact of the drought. investments in infrastructure to secure water security into Farmworkers, among the least advantaged in society, the future when the dams are full. The technical experts were negatively affected through loss of jobs and income. involved in the planning and management of the system Licensing processes need to be robust and disciplined, need to be able to communicate effectively with the polit- only (re)allocating water that is available. ical leadership to get and sustain their support for the in- vestments and associated tariffs that are both necessary A role for water transfers. The transfer of stored water to finance these investments. between irrigated agriculture and urban users played a small but important role during the crisis, underscoring the importance of water rights and institutional arrange- LESSONS LEARNED ments around storage. There has been some uncertainty regarding the trade of water in South Africa. At the time, Planning and Water Rights government policy was against the transfer of rights; how- ever, the courts have subsequently affirmed the right to » Update hydrological and planning models regularly transfer water in defined circumstances.17 and explicitly incorporate climate change into models; » Adopt planning methods that properly incorporate A more robust system. Full dams in the years prior to the climatic and non-climatic risks; and drought had possibly led to a sense of complacency in the » Regularly review and update water rights. overall management of the system. Restrictions had been applied late, there was uncertainty as to the accuracy of A Changing Role for Storage the operational modeling results, licenses had been allo- cated that exceeded the system yield, the hydrology had » Don’t over-rely on water storage. Diversify sources not been updated, canals had been allowed to become and build flexibility and redundancy into the supply Case Study | Cape town 143 system, increasing security of supply in context of storage system that relies solely on rainfall. The Strategy climate change risks (system design/technical), as includes the objectives of decreasing its dependence well as drought preparation plans. Storage can im- on the built water storage system that is dependent on bue a false sense of security, resulting in over-reli- rainfall, through developing water reuse and desalina- ance on the storage system; tion as well as substantially increasing groundwater use » Understand resilience-cost trade-offs and make in- and storage, with implications for how water storage is formed decisions; augmented and managed. Activities to increase the resil- » Use aquifers as an integrated part of water storage ience of the regional water storage system are underway, system (system design/technical); including an analysis of the hydro-economy, planning for » Develop approaches that optimize the integration optimal integration of expensive sources with ground of expensive water into the system (system design/ and surface storage, and reviewing and updating water technical); allocations in light of climate change and environmental » Understand the role of "negative storage" and miti- commitments. gate effects; and » Protect minimum river flows in the allocation pro- It is not possible to build yourself out of a drought. cess and how the system is managed. Although relatively good governance and institutional sys- tems were already in place, the severe drought exposed Strengthening Institutional and Governance several weaknesses that are now being addressed. A key Mechanisms challenge is to win the necessary political support for institution-building and investments that will provide se- » Improve information base and build trust across curity into the future and to obtain approvals for the tariffs stakeholders; that are necessary to finance these investments, especial- » Strengthen the licensing process; ly as the reductions in water demand have had the unin- » Make use of water transfers; tended consequence of generating less revenue for the » Build more robust systems through clear policies, city. Sound governance systems, with accountability and rules, and operating procedures; transparency, are a critical foundation for building water » Locate functions where there is institutional capacity security. (or build institutional capacity) and strengthen gov- ernance through clearer and stronger accountability mechanisms; and ENDNOTES » Maintain political support for investments in water security even when the dams are full through good 1 Cape Town gets the remainder of its water from some communications and stakeholder engagement (po- small local dams on the top of Table Mountain, springs, and groundwater. litical/leadership). 2 The difference between policy (theory) and practice is dis- cussed later in the case study. 3 South Africa is a constitutional republic with three spheres of CONCLUDING SUMMARY government: national, provincial, and local, each with elect- ed representatives, powers, and functions derived from the Cape Town and its surrounding areas depend almost constitution and funded by a combination of a legislative- ly-guaranteed share of national income together with allowed 100 percent on built water storage for their water sup- revenue-raising powers. ply, 96 percent of which comes from a regional sur- 4 Water use rights could be in the form of a general authoriza- face water storage scheme fed by rainfall. The region tion, an existing lawful use or a water use license. See www. experienced a 1-in-590-year low drought in the period dws.gov.za/ewulaas/WUA.aspx. 2015–18. The city responded by developing a new Water 5 See, for example, DWS (2019). 6 See www.dws.gov.za/iwrp/RS_WC_WSS/default.aspx. Strategy, acknowledging that due to population and eco- 7 www.breedegouritz.co.za. nomic growth, increased rainfall variability, and the lim- 8 Hydrological years start on November 1 of the prior year. ited potential for additional surface water storage, Cape 9 Water rights allocations exceed the available yield by 9 percent Town needed to diversify its water supply beyond a built (table 8C.1). 144 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE 10 The ratio of storage to system yield is 1.64. This means that, DWA (Department of Water Affairs and Forestry). 2007. without any rainfall and any reduction in allocations, the dams Western Cape Water Supply System Reconciliation would empty in less than 20 months. This ratio is much lower Strategy Study. than in many urban systems. For example, the ratio for the storage system supplying Sydney, Australia, is 4.8, so that the DWS (Department of Water and Sanitation). 2013. National dams can provide 57 months of supply. Sydney’s sustainable Water Policy Review: Updated Policy Positions to supply is 540 million kl per year and dam storage 2,582 million Overcome the Water Challenges of Our Development kl (NSW 2021). State to Provide for Improved Access to Water, Equity 11 These opportunities are identified in the 2007 reconciliation and Sustainability. Government Gazette, Notice 888 strategy (DWA 2007). 12 This is set out in the City’s Water Strategy (City of Cape Town of 2013. Cape Town: DWS. 2020). DWS. 2019. Western Cape Water Supply System 13 A study, supported by National Treasury and implemented Reconciliation Strategy, Status Report 2019. Cape through the World Bank, is currently underway to understand Town: DWS. the economic trade-offs between urban and agricultural water Gintamo, T. T., H. Mengistu, and T. Kanyerere 2021. “GIS- use and implications of different options for managing the augmented supplies vis-a-is the existing system. Based Modelling of Climate Variability Impacts 14 Average annual rainfall over the aquifer is a little more than on Groundwater Quality: Cape Flats Aquifer, Cape 500 millimeters (Gintamo, Mengistu, and Kanyerere 2021). Town, South Africa.” Groundwater for Sustainable Not all of the rainfall will result in aquifer recharge, but the Development 15. doi:10.1016/j.gsd.2021.100663. aquifer is also recharged from stormwater outside of the area Hay, R., D. McGibbon, F. Botha, and K. Riemann. n.d. "Cape as well as treated wastewater. 15 Assuming an average water column depth of 2 meters. Flats Aquifer and False Bay, Opportunities to Change." 16 “Decision-making in reallocation of water will have equity as Institute of Municipal Engineering of Southern Africa, the primary consideration” (DWS 2013). Westville. 17 Updated policy positions (DWS 2013); Lötter NO and Others Mauck, B., and K. Winter. 2021. “Assessing the Potential v Minister of Water and Sanitation and Others (725/2020) [2021]; ZASCA 159 (November 8, 2021). for Managed Aquifer Recharge of the Cape Flats Aquifer.” Water SA 47(4): 505–14. doi:10.17159/ wsa/2021.v47.i4.3801. Muller, M. 2018. Cape Town’s Drought: Don’t Blame REFERENCES Climate Change. Nature 559 (7713):174–76. doi: 10.1038/d41586-018-05649-1. Barta, B. 2017. The Contribution of Pumped Storage NSW (New South Wales). 2021. "Draft Greater Sydney Schemes to Energy Generation in South Africa. Energy Water Strategy." 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Available at: https://www.nature.org/ Lessons Learned. Cities Support Programme, South content/dam/tnc/nature/en/documents/GCTWF- Africa: African Centre for Cities. Business-Case-April-2019.pdf. Walton, B. 2017. “To Avoid Drought Calamity, Cape Town Restricts Water Use.” Circle of Blue. Accessed July 146 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE ANNEX 8D. MEXICO: GREEN WATER STORAGE TO ADAPT TO EXTREME HYDRO-CLIMATIC EVENTS IN MONTERREY CASE STUDY BRIEF Summary This case study demonstrates the application of a multi-stakeholder planning approach supported by quantitative decision analysis to identify green water storage solutions for a rapidly urbanizing area in Mexico, the Monterrey Metropolitan Area (MMA). Ensuring that the hydrological services provided by these areas are well maintained and preserved is crucial to maintaining the city’s water security. Following a sequence of floods and droughts between 2010 and 2013, multiple efforts were initiated by national authorities, the private sector, and civil society to respond to the metropolitan area’s water security challenges. As part of these efforts, the MMA Water Fund (FAMM, for its acronym in Spanish, Fondo de Agua Metropolitano de Monterrey) was set up by a multi-stakeholder consortium to maximize the environmental services provided by the San Juan River Basin, in particular its capacity to regulate water flows, provide water supply, and reduce erosion. Since its inception in 2013, the activities of the FAMM provide a valuable case study on a systems approach to identify green storage solutions to secure water supplies and reduce flood risks in urban areas. In particular, the case study focuses on two aspects of the FAMM’s experience: First, the multi-stakeholder planning processes and champions, which provided an institutional and science-based platform to guide the FAMM’s activities; and second, the application of multistep watershed conservation planning process to quantify opportunities for ecosystems to store water and regulate its flows. As Monterrey continues to grapple with the prospect of Day Zero and as policy makers consider options to enhance the city’s water security, the systematic approach to planning and identifying green storage solutions described in this case study becomes even more relevant. Type(s) of water storage used › Landscapes and watersheds › Soil moisture › Aquifers Water service(s) of storage provided › Flood mitigation › Increased water availability Water requirement(s) of storage met › Water provision for domestic needs and industrial processes › Prediction and attenuation of excess water for risk reduction › Water provision for ecosystem preservation and restoration Case Study | Mexico 147 BACKGROUND Boca Dam, began operations in 1993 primarily to supply water to Monterrey and involved the reallocation of water Monterrey, Mexico, is one of Latin America’s econom- from irrigators to domestic users (Aguilar-Barajas and ic centers and industrial capitals. The MMA, anchored Garrick 2019). A new reservoir (Presa Libertad) is currently by the City of Monterrey, is the second largest and most under construction. The 2021–22 drought highlights that productive area in Mexico, with an estimated population Monterrey remains highly vulnerable to hydro-climatic ex- of 5.3 million people, and a gross domestic product of tremes and climate change, further motivating the need to $140 billion. Monterrey is northern Mexico’s commercial identify and implement a range of storage solutions. center and is home to many national and international corporations. PROBLEM DEFINITION Monterrey is prone to intense floods and droughts— threats that are likely to increase because of climate The catastrophic floods and droughts of the early 2010s change. Rainfall is scant and highly variable, with mean provided a strong rationale and motivation for the city to annual precipitation of approximately 600 millimeters. pursue the systems planning approach described here. Most rainfall is seen in September, with dry periods from In this case, climate extremes provided openings to foster January to March and November to December. This high collective action and pursue evidence-based investments intra-annual freshwater variability is exacerbated by high in solutions for water storage and ecosystem conserva- inter-annual variability, which results in intense droughts tion. Building upon the recognition that crisis fostered and floods. The 2011–13 drought caused major drops action, the case study explains how green water storage in the city’s reservoirs and led to intense pressure on the solutions were adopted to achieve two key development MMA’s water supplies. Rural water users bore the brunt of objectives: reducing the impacts of flood-related disasters the impact: The drought damaged over 50,000 hectares of and strengthening resilience and maintaining access to crops and killed more than 10,000 livestock. The 2011–13 safe and affordable drinking water. drought was preceded by extraordinary rainfall events linked to Hurricane Alex, which caused widespread flood- Reduce the Impacts of Flood-Related Disasters and ing and destruction in 2010, costing some $1.35 billion. Strengthen Resilience High freshwater variability alone cannot be blamed for While the MMA receives less than 600 mm of rain per these impacts. Monterrey was founded in the 16th cen- year on average, intense rainfall events occur every tury in a flood-prone area along the Santa Catarina River, three to four years. When these extreme events occur, part of the San Juan River Basin. The city’s vulnerability often associated with tropical cyclones, the city, and the to hydroclimatic hazards (floods and droughts) has in- San Juan River Basin where it is located, receive as much creased over time due to poor land management, expan- as 100 mm of rainfall within a 24-hour period. These sion of urban areas, and a limited water supply portfolio. downpours result in flash floods, which often overwhelm the city’s storm drainage system and can cause the Santa To confront freshwater variability, Monterrey has long Catarina River to overflow its banks (Aguilar-Barajas and invested in gray water storage solutions. There are three Garrik 2019). Some of the worst flood-related disasters main reservoirs that make up 60 to 70 percent of the MMA’s are linked to hurricanes, which generate large amounts current supply. First, La Boca Dam, constructed in 1936 of precipitation over critical areas of the San Juan River just upstream from where the Río San Juan meets the Río Basin, causing the Santa Catarina River to swell and flood Bravo, with 829,900,000 m3 active capacity, and second, the city, as observed in 1988 during Hurricane Gilbert the Cerro Prieto Dam, which was built in the early 1980s and in 2010 during Hurricane Alex. In the sparsely pop- in the adjacent Río San Fernando watershed to supply the ulated upper reaches of the San Juan River Basin, flood MMA with domestic and industrial water (Cháidez 2011). events are also associated with significant erosion and It was the first case of inter-basin transfer of freshwater to some landslides (in part due to deforestation), which re- cope with water shortages in Mexico’s northeast. Finally, sult in a great accumulation of sediments downstream El Cuchillo Dam, located 75 kilometers upstream to La in the city and in water quality degradation. Therefore, a 148 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE comprehensive approach to reduce flood risks needs to » The Nature Conservancy (TNC): a global environ- take a basin-wide perspective, integrating the sub-basins mental nonprofit that advances environmental con- of the San Juan River Basin upstream of the city where servation through conservation projects, extensive most of the flash floods are generated. collaboration and partnerships, and developing and analyzing best-available conservation science to Access to Safe and Affordable Drinking Water guide action and measure results. » A range of private sector actors, including FEMSA, a Approximately 60 percent of Monterrey’s drinking water Monterrey-based multinational operating in the bev- supply comes from upstream areas in the San Juan erage and retail sectors. River Basin that have been degraded from land-use » International financial institutions: Inter-American change, forest fires, industrial pollution, and invasive Development Bank (IDB) and the Global Environment species. Degradation has led to erosion, changes in run- Facility (GEF) as partners. off, and decreasing water quality. Industrial expansion, urban growth, and agricultural development have also led Following the catastrophic flood of 2010 and drought to over-extraction from groundwater and surface water of 2011–13, TNC convened these stakeholders to dis- reservoirs. Areas that have not been degraded equally ne- cuss options to advance the city’s water security. Out of these stakeholder engagement processes, the FAMM cessitate protection and conservation actions to ensure was established in 2013. The FAMM was established by they continue to provide hydrological services. Like gray a multi-stakeholder consortium to maximize the environ- infrastructure, green infrastructure also needs mainte- mental services provided by the San Juan River Basin, in nance to continue providing safe and affordable drinking particular its capacity to regulate water flows. This initia- water. Furthermore, the city’s expansion has meant that tive was initially spearheaded by TNC, IDB, the FEMSA water use has increased at a much faster rate than water Foundation, and the GEF, and rapidly included more than supply. From 2000 to 2013, water use in the MMA grew 40 partners, including the federal government through by around 45 percent, while water supply only increased CONAGUA, local government, non-governmental organi- by 12 percent (Magaña et al. 2021). All these factors zations, civil society groups, and universities. combined mean that the reliability and quality of water services for drinking and other purposes are under threat, The FAMM was established building upon the lessons requiring a basin-wide approach connecting the city to its and experiences of water funds in other parts of Latin water sources. America. Water funds are an Investment in Watershed Services (IWS) mechanism program, whereby individu- als and organizations are compensated using different INSTITUTIONS AND INSTITUTIONAL methods for protecting watersheds. The payers in an IWS FRAMEWORK program are the water users that rely on the services of the watershed, for example, water utilities and industries. The main institutions involved in the case study are: Large water users who depend on the continuation of ser- vice for their business can make contributions that will » Servicios de Agua y Drenaje de Monterrey (SADM): preserve the basin (Calderon 2013). FAMM’s establish- Under the government of the state of Nuevo León, ment and subsequent conservation activities were also SADM is an autonomous public water and sewer supported through grants from charitable foundations or utility that both supplies water in the MMA and is the international financial institutions. water authority throughout the MMA. » The National Water Commission (CONAGUA): An The objectives of the FAMM are to reduce flooding, administrative, technical advisory commission with- improve infiltration, and create environmental aware- in Mexico’s Ministry of the Environment and Natural ness among the public. At the time of its creation, the Resources, CONAGUA administers national waters, FAMM contemplated a range of solutions to achieve its manages, and controls the country’s hydrological objectives. These included a combination of green and system, and promotes social development. gray infrastructure, such as reforestation, firebreaks, Case Study | Mexico 149 erosion barriers, fencing, retaining walls, runoff traps, was included through the four steps. The engagement check-dams, earth dikes, and large-scale urban rain- targeted the small number of people living in the area water harvesting areas, along with public awareness of maximum impact (see step 1 below) and the City of campaigns. Following its initial success and the devel- Monterrey, where the conservation plan was discussed opment of the watershed conservation plan, in 2016 with the institutions identified in the section above. the FAMM changed its name to Monterrey Metropolitan Stakeholder engagement was centered on (a) explaining Environment Fund (retaining the same acronym FAMM) the plan’s focus on ecosystem services and the function- to expand its remit to broader environmental conserva- ing of the water fund; (b) identifying the major water-re- tion issues beyond water. lated threats (step 2) and (c) discussing the type and feasibility of the interventions (steps 3 and 4). THE EVOLUTIONARY PROCESS: A SYSTEMS The four-step approach to the plan included: APPROACH Step 1: Identification of the area of maximum impact To help guide FAMM’S activities, TNC developed a wa- tershed conservation plan to identify where and what to Limited resources were available to address Monterrey’s prioritize to achieve its objectives (reduce flooding and water problems; therefore, the evolutionary process- erosion, improve infiltration, and create environmental es began with the identification of a priority area to be awareness among the public). This section of the case targeted by the plan. This priority area is called area of study is based on the detailed technical report underlying maximum impact (AMI). It was identified based on two the conservation plan (Hesselbach et al. 2019). criteria: (a) contribution to the metropolitan’s area water supplies and (b) level of biological and ecosystem diver- The development of the watershed conservation plan sity and connectivity. Existing studies of the city’s water was led by TNC in collaboration with local and inter- supplies and hydrological time series data were used to national experts. The plan focused on identifying solu- rank the upper sub-basins based on their contribution to tions to reduce flood risk and erosion in selected areas surface water flows and aquifer recharge, upon which of the San Juan River Basin. The basin is responsible for the city’s water supplies depend. The sub-basins were producing Monterrey’s water supply, and it is also the then overlaid onto a map of key biodiversity areas (most major source of riverine flood risk for the city. The water- important places for species and habitats) to identify shed conservation plan was guided by four overarching areas with potential to generate benefits in terms of questions: hydrological services and biodiversity conservation. Based on this assessment, a large part of the San Juan A. What is the watershed’s runoff control capacity, River Basin was identified as the AMI. This area is re- and how does this capacity change under alter- sponsible for generating about 70 percent of the city’s native conservation scenarios? water supplies and also contains six protected areas, B. What are the threats and pressures? including two major areas (Cerro de la Silla, Cumbres C. By how much does vegetation cover reduce rain- de Monterrey). fall-induced erosion, and how is this phenome- non related to runoff? Step 2: Identification of threats D. How can green and gray infrastructure be com- bined to achieve the plan’s objective? A stakeholder workshop was used to identify threats to the AMI´s hydrological and ecological services. Stakeholders To address these questions, the plan followed a four- were also asked to rank threats according to their sever- step approach that resulted in two key outputs: (a) a ity, coverage, reversibility, and frequency, following the GIS-based tool for suitability mapping and guiding the scoring matrix shown in table 8D.1. Based on this scoring selection of target areas and (b) a watershed conser- matrix, erosion, invasive species and pests, deforestation, vation plan, which includes maps of priority areas for and quarrying emerged as key threats to the basin’s sus- green water storage solutions. Stakeholder engagement tainability that required specific attention. 150 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE TABLE 8D.1 Criteria Used to Score Threats is applied only to areas that are currently covered by vegetation, and it is therefore particularly important THREAT CRITERIA SCORE as it helps to track the potential contribution of veg- etation conservation activities for reducing erosion Severity Light damage 1 risk. Moderate damage 2 » Potential erosion. This criterion quantifies the ero- Very substantial 3 sion risk in areas not covered by vegetation, for ex- damage ample, degraded lands or lands that have been al- Footprint Localized 1 tered by agricultural and livestock grazing activities. These areas cover approximately 10 percent of the Widespread 2 AMI’s surface area. Reversibility Reversible 1 » Surface runoff reduction potential. This criterion Not reversible 2 measures the quantity of surface runoff generated Frequency Sporadic 1 by each sub-basin following a precipitation event. It is calculated as the difference in surface runoff per Recurring 2 area (cubic meters per hectare) generated for a giv- Source: Hesselbach et al. 2019. en precipitation event under different conservation and degradation scenarios (see step 4). Step 3: Multi-criteria analysis framework » Flood control potential. This criterion examines the flood control potential of different parts of the basin The AMI is a large region of over 151,000 hectares, mak- and for floods with different return periods. Flood ing it difficult and expensive to carry out conservation control potential is estimated as the difference in actions in the entire area. Therefore, multi-criteria analy- peak flood discharge between the baseline and con- sis was used to identify specific priority sub-basins with servation/degradation scenarios in cubic meters per greater potential for provisioning of water storage ser- second. vices, in terms of flood risk reduction and erosion control. » Active river area (ARA). The ARA includes both the The analysis was supported by quantitative models and channels and the riparian lands necessary to ac- a GIS platform through which thematic maps and maps commodate the physical and ecological processes of relationships between themes were generated, and re- associated with the river system (Smith et al. 2000). sults from other quantitative models were visualized and Given the importance of this indicator as a proxy for queried. The multi-criteria framework rests on three main overall ecosystem health, it was selected to shed components: inputs, criteria, and tools. light on sub-basins that are particularly important for ecosystems and biodiversity. Inputs Input data cover the physical geography characteristics of Tools the area, the vegetation and soil type, and hydro-climatic The criteria above were used to guide to the multi-crite- information. This information was collected from histor- ria analysis and were quantified through the application ical datasets (maps of soils, water availability), remote of four tools. Results from the four tools were combined sensing, and field work. to generate a map of priority sub-basins for the conserva- tion of the green infrastructure of the sub-basins, and a Criteria GIS-based tool to inform the selection of investments. The The analysis comprises five criteria. These criteria were four tools included: included to cover different aspects of the suitability of the sub-basin for flow regulation, flood risk reduction, and ero- » Revised Universal Soil Loss Equation (RUSLE). sion control. The multi-criteria analysis focused on: The RUSLE model is a commonly used method to estimate average annual soil losses, map erosion, » Soil vulnerability to vegetation loss. This criterion and inform environmental restoration and soil con- quantifies the erosion risk due to vegetation loss. It servation plans. For the AMI, the RUSLE equation Case Study | Mexico 151 quantifies the potential of the area to be eroded conditions of the vegetation cover and are expected to re- by diffuse erosion, that is, laminar erosion and in duce erosion and regulate runoff. streams. The output is the average annual soil loss per unit area under the alternative scenarios. RUSLE The conservation scenario includes the following mea- was used to quantify criteria #1 and #2. sures: (a) protection and restoration of vegetation cover; » Surface runoff reduction calculator. The “Guide (b) erosion control; (c) forest management; (d) good ag- for Replenishment,” prepared by TNC and Quality ricultural and livestock practices; and (e) gray infrastruc- Consulting Services S.A. (2014), is a tool for deter- ture, specifically, a new flood peak attenuation dam. For mining the surface runoff reduction potential (cri- the first three, some practices are common and dual or terion #3) that a given type of vegetation cover can multipurpose, such as the typical case of revegetation, achieve. This calculator was used to estimate the and sometimes they are a combination of vegetation surface runoff reduction potential. management with small structural measures, such as » ARA model. This model estimates the river active soil and water conservation works. The analysis also in- area, that is, the flood area that allows for lateral riv- cluded a tool for species selection to be used in revegeta- er connectivity. The delimitation of the ARA is based tion, designed in such a way that users could select them on the methodology presented in Smith et al. (2008). according to the objectives of the interventions, such as The ARA is fundamental to determine the flood flood and erosion control, soil protection, or improvement zones that allow lateral connectivity of rivers. It is of riparian zones. calculated starting from the digital elevation models. » HEC-HMS hydrological model. HEC-HMS is a To correctly model plant growth dynamics, the conserva- semi-distributed hydrological model. This means tion and degradation scenarios also take into account the that users need to define specific hydrological units different stages of plant growth. The process simulates (i.e., a sub-basin) with specific parameters describ- a gradual increase or loss of vegetation density, but with- ing their hydrological behavior (e.g., infiltration ca- out assuming a change in the type of potential vegetation pacity, runoff coefficients). The rainfall-runoff model cover. For the conservation scenario, the analysis differ- was used to test the performance of interventions— entiates the impacts that vegetation cover conservation and combinations of interventions—on the ability of activities would have on different types of cover, such as the priority areas to reduce peak flood discharge in revegetation in pine forests and revegetation of scrub- the sub-basins located in the AMI. For the sub-ba- lands, in such a way that changes in vegetation cover that sins outside the AMI, the hydrological model only are not feasible on the ground or contrary to the ecological simulated rainfall-runoff processes without model- dynamics of the study area are not proposed. ing the impact of conservation or degradation pro- cesses (i.e., outside of the AMI, the model assumes The tools were run to generate maps for each criterion that no degradation/conservation processes take under each alternative scenario. In this way, the sub-ba- place). sins with greater or lesser need for action according to each one of the five criteria were identified. For each crite- Step 4: Scenario analysis and identification of rion, a sensitivity score from 1 to 5 was assigned to each responses sub-basin, defining quantitatively the lower or higher risk of degradation in the area or the greater or lesser influence To estimate the current and potential supply of hydrologi- of the area on the result of the analysis (in the case of the cal environmental services, three scenarios were modeled: flood peak control criterion). baseline, conservation, and degradation. The conserva- tion and degradation scenarios consist of a simulation of Results for each criterion were combined by summing changes in the hydrological condition of the vegetation each sensitivity score, resulting in a map of total sensi- cover and soils and the runoff coefficient with respect to tivity score where the highest score identifies sub-basins the baseline, either by recovery and regeneration process- in which actions are most necessary (those in which the es, or by deterioration of the current conditions. Recovery sensitivity values are highest). This results in a map of the and regeneration processes contribute to improve the AMI in which it is possible to clearly identify the priority of 152 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE actions in the different sub-basin, depending on the total and located in parts of the watershed that produce ap- sensitivity score and also the underlying five criteria. proximately 60 percent of Monterrey’s water supply (Abell et al. 2017). This highlights the importance of carefully tar- geting rehabilitation of green water storage through quan- SOLUTION AND IMPLEMENTATION titative analysis to maximize the impact of interventions. The multi-criteria analysis demonstrated the ability of Based on the watershed conservation plan, FAMM is green infrastructure solutions to provide water storage implementing the following actions over an initial area services in terms of reduced runoff and erosion and im- of about 5,500 hectares. The interventions include: 1,300 proved water infiltration. More importantly, the analysis hectares of active reforestation; 3,000 hectares placed demonstrated that under a no action scenario, the basin’s under conservation through payment for ecosystem ser- degradation processes would lead to higher runoff and vices (PES); 1,200 hectares acquired for conservation; 77 erosion as compared to baseline levels. In other words, hectares benefitting from passive reforestation; and 58 loss of green water storage leads to significant negative hectares from soil conservation. At the time of writing, downstream impacts in terms of heightened flood risk about $10 million (IDB 2018) has been contributed into and water quality deterioration. The latter impact can also the fund and invested in reforestation, targeted land pro- increase the cost of water supply provision by increasing tection, soil conservation, and PES.1 The PES spans 124 the costs of treatment. participants, including both private landowners and farm- ers on communal land property. While the modeling demonstrated that conservation ac- tivities can reduce runoff and help control erosion, it also Building upon the experience of the creation of the water showed that green infrastructure may not be enough to fund and the identification of green storage options in prevent flooding during extreme events. Given that the the upper catchment, the FAMM began a multi-stake- MMA has been built on both flood-prone areas of the holder and long-term water planning process in 2016 Santa Catarina River, green infrastructure alone might not for Monterrey and the State of Nuevo León. This resulted be sufficient to regulate flood peaks during events such as in the development of the Nuevo León 2050 Water Plan, Hurricane Alex, which impacted the area in 2010. Hence, a long-range water strategy informed by decision-making the watershed conservation plan also recommends the under deep uncertainty methods and stakeholder consul- construction of a flood peak attenuation dam to reduce tations (Molina-Perez et al. 2019). The 2021–22 drought flood risks for events with return periods greater than 100 demonstrates that Monterrey remains highly vulnerable to years. hydro-climatic extremes. As the city grapples with more severe drought and the prospect of Day Zero events, the The basin area where conservation interventions could be relevance and urgency of implementing a broad portfolio implemented is 124,608 hectares (82 percent of the AMI), of storage solutions grounded in evidence and systematic which excludes rocky outcrops, river channels, urban analysis increases even further. areas, water bodies, and roads. For green water storage measures, areas with the following characteristics were excluded: slopes greater than 50 percent; a predominantly LESSONS LEARNED south-facing azimuth, since the high exposure to solar ra- diation increases potential evapotranspiration, reducing the » Don’t wait for a crisis but don’t waste one. The im- speed of plant growth and survival rate; and stone slab out- petus for creating the water fund and then promot- crops, where vegetation growth is naturally limited. ing a watershed conservation plan came from the impact in 2010 of a huge flood (Hurricane Alex), fol- The conservation plan gives a strong direction to the lowed by an extensive drought (2011–13). Climate water fund’s work, concentrating it on a strategically tar- extremes provide openings to raise the profile of geted area covering over 124,000 hectares. While this water management issues on the political agenda covers only around 5 percent of the San Juan River Basin, and oftentimes to build the necessary momentum the conservation plan shows that they are highly sensitive around beneficial investments in water storage. Case Study | Mexico 153 » Intermediaries and special purpose instruments, Economic and Community Benefits of Source Water such as water funds, are strong enablers for in- Protection. Arlington, VA: The Nature Conservancy. vestments in nature-based solutions for water Aguilar-Barajas, I., and D. E. Garrick. 2019. “Water storage. This is because they facilitate partnership Reallocation, Benefit Sharing, and Compensation in for innovation, ensure coordination among stake- Northeastern Mexico: A Retrospective Assessment holders, and are pooling resources and mitigating of El Cuchillo Dam.” Water Security 8. doi:10.1016/j. financial risks. This means that without the FAMM, wasec.2019.100036. investments in nature-based solutions were not go- Calderon, C. 2013. “Monterrey, Mexico Uses Fund ing to take place. Mechanism for Clean Water and Storm Protection.” » Appraisal of green storage options and quantifica- Ecosystem Marketplace. Accessed July 8, 2022. tion of their benefits require utilization of multiple Available at: https://www.ecosystemmarketplace. performance criteria and tools. The case study’s com/articles/monterrey-mexico-uses-fund-mecha- multi-criteria approach demonstrates the impor- nism-for-clean-water-and-storm-protection/. tance of (a) considering multiple criteria when evalu- Cháidez, J. 2011. “Water Scarcity and Degradation in the ating the benefits of green storage solutions and (b) Rio San Juan Watershed of Northeastern Mexico.” employing different tools to quantify these benefits. Frontera Norte 23 (46):125–50. A plurality of tools is also required to ensure that the Hesselbach M. H., J. A. Sánchez de Llanos, F. Reyna- interactions of green storage solutions with other Sáenz, F. J. García Moral, S. J. León, F. Torres-Origel, components of the sub-basin (e.g., topography, soil and A. Gondor. 2019. Plan de Conservación del Fondo cover type) are taken into account when quantifying de Agua Metropolitano de Monterrey, Primera Parte. benefits such as flood peak attenuation and erosion México. Arlington, VA: The Nature Conservancy. risk reduction. IDB (Inter-American Development Bank). 2018. Monterrey » Conservation and protection of ecosystems is a Metropolitan Water Fund (FAMM): Monterrey, Nuevo key measure to rehabilitate water storage. The Leon. Accessed July 8, 2022. Available at: https:// case study shows that ecosystems provide key www.fondosdeagua.org/content/dam/tnc/nature/ water storage services, notably to reduce surface en/documents/latin-america/Monterreye.pdf. runoff and erosion risk. Investments to rehabilitate Magaña, V. O., E. Herrera, C. J. Abrego, and J.A. Avalos. ecosystems, protecting them from degradation and 2021. “Socioeconomic Drought in a Mexican actively improving their conditions, need to be an Semiarid City: Monterrey Metropolitan Area, A Case integral part of a diversified water storage portfolio. Study.” Frontiers in Water 3:579564. doi:10.3389/ frwa.2021.579564. Molina-Perez, E., D. G. Groves, S. W. Popper, A. I. Ramirez, ENDNOTES and R. Crespo-Elizondo. 2019. Diversification and Adaptation for Coping with Climate, Economic, and 1 Hilda Hesselbach, interview by World Bank, 2022. Technological Uncertainties. Santa Monica, CA: Rand Corporation. Smith, M., R. Schiff, A. Olivero, and J. MacBroom. 2008. REFERENCES The Active River Area: A Conservation Framework for Protecting Rivers and Streams. Boston, MA: The Abell, R., N. Asquith, G. Boccaletti, L. Bremer, E. Chapin, A. Nature Conservancy. Erickson-Quiroz, J. Higgins, J. Johnson, S. Kang, N. TNC (The Nature Conservancy) and QCS (Quality Karres, B. Lehner, R. McDonald, J. Raepple, D. Shemie, Consulting Services) SA. 2014. Guía para E. Simmons, A. Sridhar, K. Vigerstøl, A. Vogl, and S. Reabastecimiento. Arlington, VA: TNC. Wood. 2017. Beyond the Source: The Environmental, 154 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE ANNEX 8E. INDONESIA: GETTING MORE FROM EXISTING BUILT STORAGE: PRIORITIZING REHABILITATION INVESTMENTS CASE STUDY BRIEF Summary Indonesia shifted its approach to dams from a project-by-project approach to a “portfolio approach” that recognizes the strategic function of existing dams in addressing water stress and water insecurity in the country. Because of Indonesia's unique geography as the world’s largest archipelago, with extreme rainfall variability yet limited natural storage, its built water storage infrastructure plays a significant role in improving the local availability and reliability of water to its population and industries as well as in the country’s resilience against droughts and floods. However, despite decades of investment in new dams, the performance of many dams is declining due to aging, sedimentation, and lack of funding for operation and maintenance. Indonesia evolved its institutional framework from establishing basic dam safety and management provisions to the introduction of integrated water resources management (IWRM) as a guiding framework. The shift to a portfolio approach also includes the adoption of portfolio risk assessment and risk management for dams to prioritize investments as well as measures to improve the sustainability of financing for operation and maintenance. Type(s) of water storage used › Large reservoirs › Small reservoirs/retention structures Water service(s) of storage provided › Increased water availability › Flood mitigation › Flow regulation Water requirement(s) of storage met › Water provision for domestic needs and industrial processes › Water provision to meet crop/livestock requirements in seasons/locations without precipitation › Water provision to meet crop/livestock requirements throughout the growing season › Water controlled for electricity generation › Prediction and attenuation of excess water for risk reduction Case Study | Indonesia 155 BACKGROUND capacity is limited, Indonesia has sought to increase its available water storage through the construction of Water storage is key to Indonesia’s growth and devel- small and large dams (World Bank 2017a). Most large opment. Indonesia is the largest archipelago in the world cities, such as Greater Jakarta, Surabaya, Makassar, and and the fourth most populous nation with over 276 million Semarang, depend on reservoirs and barrages for a major inhabitants. Gross national income per capita has risen portion of their water supply. One large reservoir accounts steadily from $4,430 in 2000 to $11,750 in 2020, halving for about 80 percent of Greater Jakarta’s tap water (World the poverty rate from 19.1 percent in 2000 to 9.8 in 2020 Bank 2009a and 2017b). Today, the country has an exten- (World Bank 2022). Notwithstanding these massive eco- sive network of more than 2,200 dams, 213 of which are nomic gains over the past 20 years, Indonesia still has classified as large. These dams provide the full range of a large share of its population living below the national enabling storage services, including improving the avail- poverty line and significant wealth disparities across dif- ability of water for irrigation, and regulating flows for hy- ferent parts of the country, especially in rural areas. Water dropower generation, and some provide storage of peak security and water storage are key to resolving some of flood waters. In 2014, there were 228 large dams regis- the constraints to Indonesia’s development and achieving tered with a volume of 13.8 bm3, of which 186 were owned shared prosperity. by the Ministry of Public Works and Housing (MPWH). Another 42 dams with storage volume of 6.65 m3 were Even though Indonesia has abundant water resources privately owned. Since then, the government has em- in aggregate terms, these resources are unevenly dis- barked on a program to construct 61 new dams, of which tributed across an archipelago of more than 17,000 is- 29 are completed. The dams serve a number of purposes, lands that extends across 5,000 kilometers in length. In including irrigation, flood control, bulk water supply, and Kalimantan and Papua, there are larger river basins, but hydropower generation, and many of the dams are multi- the more densely populated areas, where water demands purpose interventions (MPWH 2022). are higher, are served by smaller river basins with limited retention capacity (World Bank 2021). For three quarters of the basins, demand for water is already close to or PROBLEM DEFINITION outstripping supply, leading to conditions of water stress (World Bank 2017a). Closing the Water Storage Gap In addition to the country’s unique geography and the Despite decades of investment, Indonesia ranks low in pressures of population growth and urbanization, there per capita storage capacity, and this is severely con- is significant seasonal variability with pronounced wet straining its economic development and achievement of and dry periods. This high degree of seasonality leads its food security goals. With an estimated reservoir stor- to seasonal water shortages, which is especially acute in Java, home to Indonesia’s capital city, Jakarta. Java has age capacity of 71 m³/capita, Indonesia lags far behind less than 5 percent of the nation’s water resources for its neighbors such as Malaysia (710 m³/capita), Thailand nearly 60 percent of its population. The densely populated (1,006 m³/capita), Vietnam (310 m³/capita), Japan (228 and rapidly urbanizing islands of Java and Bali are also m³/capita), and India (190 m³/capita) (World Bank 2021). prone to drought and flood hazards, which are linked to the El Niño-Southern Oscillation and increasingly being Indonesia’s natural storage capacity is also being threat- worsened by climate change. Water storage is essential ened by progressive degradation of the country’s catch- for increasing water availability in higher density areas, ments as well as sedimentation induced by soil erosion managing seasonal variability, and building resilience to linked to volcanic activity. Land-use change is also a floods and droughts (World Bank 2017a). challenge with approximately 20,000 hectares/year of prime irrigated paddy fields being converted to other uses As most of the rivers surrounding its larger popula- to accommodate the needs of its urbanizing population tion centers have steep gradients and their retention (World Bank 2017a). 156 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE The government seeks to grow the country’s per capita that need to be addressed. Of the 213 large reservoirs in water storage capacity to 100 m³/capita to increase water, the country, 31 were built before 1980, and of those 31, 16 food, and energy security. Toward this goal, it is in the pro- were built before 1950. The ability of those reservoirs to cess of developing 61 new dams by 2025 while safeguard- deliver storage services is being hindered by old or dam- ing its existing reservoir storage capacity through improved aged electromechanical systems that no longer function, operation, maintenance, and safety (MPWH 2022; World and premature sedimentation that has reduced storage Bank 2017a) (map 8E.1). volume in approximately 30 reservoirs and increased safe- ty risks for those dams (World Bank 2009a). Better Operation and Maintenance Is Needed In addition to the physical condition of the dams and res- Indonesia’s fleet of existing dams is aging, and many ervoirs, their performance is also affected by operation- dams have declining performance and safety deficiencies al and management practices. At the time that Indonesia MAP 8E.1 Distribution of Existing and Planned Dams in Indonesia BENEFIT COST BENEFIT COST NO VOL NO VOL Irr WS HP TRILLION Irr WS HP TRILLION DAMS (103 m3) DAMS (103 m3) Ha m3/sec MW IDR Ha m3/sec MW IDR 20 2,850,000 118,467 988 7.97 – 9 506,055 36,684 515 2.5 – 11 985,000 88,002 9.59 108.34 11 9 1,380,620 75,217 9.20 35,68 10 BENEFIT COST NO VOL Irr WS HP TRILLION DAMS (103 m3) BENEFIT COST Ha m3/sec MW IDR NO VOL Irr WS HP TRILLION 9 1,225,713 5,303 0.40 1.78 – DAMS (103 m3) Ha m3/sec MW IDR 5 916,570 33,472 13.30 22.35 8.5 2 275 - - - - 1 15,000 2,900 1.04 3.20 1.6 Sumatera Kalimantan Sulawesi Maluku Papua Jawa Bali NTB NTT BENEFIT COST NO VOL Irr WS HP TRILLION BENEFIT COST DAMS (103 m3) NO VOL Ha m3/sec MW IDR Irr WS HP TRILLION DAMS (103 m3) 0 – – – – – Ha m3/sec MW IDR 91 8,600,000 726,048 4,609 51.94 - 1 200,000 – – 50.00 4.7 24 2,674,370 222,841 24.93 154.96 26 BENEFIT COST NO VOL BENEFIT COST Irr WS HP TRILLION NO VOL DAMS (103 m3) Irr WS HP TRILLION Ha m3/sec MW IDR DAMS (103 m3) Ha m3/sec MW IDR 15 33,525 4,926 – – – 5 27,158 5,230 1.5 0.53 - 7 216,590 14,696 1.44 3.90 5.6 3 29,600 7,586 3.74 3.86 2 BENEFIT COST NO VOL Irr WS HP TRILLION DAMS (103 m3) Ha m3/sec MW IDR 62 270,148 51,229 0.48 0.47 - 4 99,920 12,134 0.75 10.30 2 Source: World Bank 2018. Note: HP = hydropower; Irr = irrigation; NTB = Nusa Tenggara Barat (West Nusa Tenggara); NTT = Nusa Tenggara Timur (East Nusa Tenggara); WS = water supply. Case Study | Indonesia 157 was launching its program to restore dam performance which the institutions responsible for dam safety are and safety, several dams lacked basic operations manuals, established. Under the MPWH are: sufficient instrumentation for hydrological and dam safety ¡ The Dam Safety Commission (DSC), which monitoring, and dam safety plans (World Bank 2009a). is chaired by the Minister of Public Works and Housing. The DSC is responsible for the certifi- Funding for operation and maintenance of dams is cation of dams during construction and special also a challenge. Dam operation and maintenance is events during operation. All development stages funded from national budgets through government are subject to licenses issued by the minister transfers to provincial-level and ultimately district-lev- upon recommendation by the DSC. el institutions, but funding is constrained by resource ¡ The national Dam Safety Unit (DSU), established availability and complexity of the fiscal arrangements. in the Directorate General of Water Resources Irrigation spending is largely focused on capital invest- (DGWR) within the MPWH, serves as the im- ments for new construction and rehabilitation, with in- plementation unit for the DSC and carries out sufficient allocations for operation and maintenance. In inspections, evaluation of requests for licenses, 2012, the MPWH estimated that the funds needed for op- and provision of guidelines related to dam opera- eration and maintenance were approximately Rp 250,000/ tion, maintenance, and safety. hectare on average for the national irrigation system, ¡ The Central Dam Monitoring Unit (CDMU), which but the actual budget for that year was only Rp 180,000/ was established in the Directorate of Operations hectare, increasing to Rp 200,000/hectare in 2013 (World and Maintenance, executes oversight of the port- Bank 2017a). It is currently in the range of Rp 500,000 to folio of existing dams under the responsibility of 800,000/ha depending on the locations and needs. the MPWH. ¡ Dam Monitoring Units (DMUs) within river ba- The government has sought not only to remedy the im- sin organizations carry out day-to-day manage- mediate challenge of declining reservoir performance ment of individual dams and carry out system- but more broadly to ensure the safety and performance atic monitoring and reporting on the situation of of all existing and newly constructed dams in Indonesia. each dam to the CDMU (World Bank 2017a). Beyond the rehabilitation works for the dams currently at risk, the challenge includes providing an enabling institu- tional framework for managing dams, securing a dedicat- THE EVOLUTIONARY PROCESS: TOWARD A ed revenue stream to support long-term operation and SYSTEMS APPROACH maintenance, and strengthening Indonesia’s technical capacity with more skilled professionals to improve dam 1990s: The First Dam Safety Project management and safety. This requires a shift away from the facility-by-facility approach to managing dams and In 1994, the Government of Indonesia began its first reservoirs to more of a systems approach, implementa- Dam Safety Project (DSP), aimed at reducing the risk tion of a long-term program with phased investments, and of dam failure in Indonesia. It was the World Bank’s first continued progress on the institutional reforms needed to project dedicated to dam safety in Indonesia and its sec- support such a shift. ond ever after the India DSP, approved three years prior. The Indonesia DSP supported the government in intro- ducing a basic institutional framework for dam manage- INSTITUTIONS AND INSTITUTIONAL ment and safety, including the constitution of the DSC, FRAMEWORK DSU, and CDMU under the DGWR (World Bank 2009b). A 2004 Ministerial Decree for Dam Safety was passed, fol- The main institutions involved in this case study are (fig- lowed by 1997 Ministerial Regulation No. 72/PRT/1997 ure 8E.1): “Regarding Dam Safety,” which laid out the first national guidelines for dam safety (World Bank 2009a). Under » The MPWH, which owns the vast majority of the large the project, the provincial DMUs were also established in dams in Indonesia and is the umbrella ministry under eight provinces. 158 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE FIGURE 8E.1 Organogram of the Dam Safety Institutions within the MPWH, Indonesia National Steering Committee Minister Panel of Experts for Water Resources Dam Safety Inspector Secretary Commission General General Agencies (Badan) Directorate General Research & Human Water Water Housing Housing Construction Infrastructure Toll Road Roads CK Development Resources Supply Resources Provision Finance Guide Directorate General Supply Units Directorates Centers Water Dam Dam Safety B/B/WS B/B/WS B/B/WS Operation & Irrigation River & Resources BWRM/P Bulk Water Construction Unit Cluster 1 Cluster 2 Cluster # Maintenance & Swamp Coastal Planning Dam Dam Dam Central Dam Management Management Management Management Unit Unit Unit Unit Source: Adapted from World Bank 2017a. Note: Dam safety institutions within the Ministry of Public Works and Housing (MPWH) are shown in dark blue. Late 1990s to 2000s: Institutional Reform and the » Ministerial Regulation No. 11a/PRT/M/2006 by the Introduction of IWRM MPWH, which defines 133 river territories. » Government Regulation on Dams (37/2010), which In 1999, the Government of Indonesia began a process lays out an improved framework for dam safety of reforming the legal, regulatory, and administrative and management for the large dams managed by framework for its water resources sector, including MPWH (figure 8E.1). on dam safety. The 2004 Law on Water Resources (UU » Government Regulation on Dams (37/2013), which 7/2004) paved the way for the introduction of decentral- provides improved regulations, guidelines, and ad- ized, basin-based IWRM. Under this law, all river basins ministrative capacity (World Bank 2017a). were to have long-term strategic plans and master plans focused on water resources conservation, high-quality However, Law 7/2004 on Water Resources was overturned service delivery, and increasing institutional capacity of by Indonesia’s Constitutional Court,1 thus reinstating water management institutions. The law also aimed to im- the previous 1974 Water Law as the controlling legisla- prove governance of hydraulic infrastructure and enable a more programmatic approach to dam and reservoir man- tion (Library of Congress 2015). From 2015 to 2019, the agement (World Bank 2017a). construction and management of dams was temporarily governed through Ministerial Regulation No. 27/2015 and A series of regulations were subsequently introduced by Ministerial Decree No. 03/KPTS/M/2016 on DSC (World MPWH, including: Bank 2017a, 2018). Case Study | Indonesia 159 2010s: Shifting to a Portfolio Approach for Managing 2. Factors related to the dam, including poten- Dams and Reservoirs tial downstream consequences of dam failure, evacuation requirements, and business risks. With the first DSP, the Government of Indonesia began to invest in better management and development of The risk values are determined and arranged into risk dams, but still these dams were being treated as indi- classes: extreme, high, moderate, and low (Soentoro, vidual pieces of infrastructure without a broader stra- Purnomo, and Susantin 2013). tegic perspective on how they fit together. For decades, the government prioritized rapid development of new in- Under the Dam Operational Improvement and Safety frastructures without due consideration to the resources Project (DOISP) Program, the MPWH initially identified needed for operation and maintenance. While this focus a short list of 63 dams for safety and functionality im- on new construction spurred economic growth and in- provement works. Among those, 30 were being affect- creased productivity in agriculture, it contributed to de- ed by accelerated sedimentation. These 63 dams had a ferred maintenance and sub-optimal use of existing dams total downstream population at risk of 9.5 million peo- and reservoirs (World Bank 2009a). ple and could cause flood damage and loss of irrigated area of 310,000 hectares (World Bank 2009a). Using the A new program spearheaded by the MPWH intro- modified ICOLD risk assessment method, a prioritized duced a portfolio approach for management of dams list of 34 dams was developed in order to give priority in Indonesia, whereby dams and reservoirs are treated treatment to more urgent rehabilitation works given the as infrastructure of strategic importance for securing funding available (DGWR 2008). These dams were suc- bulk water and providing other critical water storage cessfully rehabilitated under the program between 2009 services. A series of projects financed by internation- and 2017, and an additional 120 dams were then includ- al development partners such as the World Bank and ed under subsequent phases of the program with the aim the Asian Infrastructure Investment Bank supported the of reducing the safety risks in the portfolio by more than introduction of portfolio risk assessment and portfolio 20 percent (World Bank 2017a). Under the World Bank­ - management to inform the prioritization of investments financed DOISP phase 2 project, a new guideline on risk to improve the safety and functionality of large MPWH- assessment for dams using the modified ICOLD method owned reservoirs (World Bank 2017a). has been prepared but has not yet been institutionalized. Sustainable Financing for Operation and Maintenance SOLUTION ADOPTED AND IMPLEMENTATION of Existing Dams Applying Portfolio Risk Management Approaches to To improve cost recovery and to ensure the financial Existing Dams and Reservoirs sustainability of river basin management systems, the Government of Indonesia established two self-financ- The MPWH developed a dam risk assessment to pri- ing state enterprises, or river basin corporations (PJT I oritize the rehabilitation of the most at-risk dams. The Banta’s and PJT II Jatiluhur), under the Ministry of State method used has been modified from the one introduced Enterprises. These state-owned companies are respon- in ICOLD Bulletin 72 “Selecting Seismic Parameters for sible for the operation and maintenance of hydraulic in- Large Dams” (ICOLD 1989) (figure 8E.2). The risk assess- frastructure with funding derived from raw water sales, ment criteria used can be divided into two groups: hydroelectricity, and various fees (World Bank 2017a). Under the DOISP program, the MPWH has adopted needs- 1. Characteristics of the dam itself, including res- based budgeting and piloting of performance-based ervoir capacity, dam height, and construction, as contracts (World Bank 2017a). To date, allocations for op- well as maintenance data, monitoring data from eration and maintenance of dams have increased, com- instruments, and previous remedial works done ing closer to the needs-based budget for operation and to address safety deficiencies; and maintenance. 160 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE FIGURE 8E.2 Modified ICOLD Risk Analysis Method Collect Data, i.e., technical data, Calculating total Start End inspection data, risk score and demographic data, prioritizing based and geographic on total risk score data 8. Prior Level of Effort in Safety Evaluation Source: Adapted from Soentoro, Purnomo, and Susantin 2013. Preventative and Mitigating Measures for Reservoir 7/2004 and the eventual passage of the new 2019 Water Sedimentation Resources Law. Comprehensive sediment management, employing a Risk analysis methodologies and phased approaches community incentive-based approach for watershed are useful for prioritizing investments for large infra- management, is also a key part of the program to pro- structure portfolios. In the case of Indonesia, with more long the life of Indonesia’s reservoirs, increase their per- than 2,200 dams, including more than 200 large dams, it is formance with regard to water availability, and reduce not always possible to address rehabilitation needs in the the incidence of flooding and landslides. Corrective mea- scope of a single project. The use of a programmatic ap- sures include dredging, reservoir flushing, sediment traps, proach to financing the needed rehabilitation work coupled check dams, and stabilization works while preventative with the use of the modified-ICOLD risk analysis method measures such as catchment management is addressing was important for prioritizing investments to where they sedimentation at the source (World Bank 2017a). are most critical given limited financial resources. Recognizing the need to safeguard and prolong the life LESSONS LEARNED of existing water storage assets is an essential part of addressing a water storage gap. The Government of A focus on institutional development needs to be sus- Indonesia has a target for new storage investments but tained over the long term. Starting with the DSP, which also has prioritized the rehabilitation and restoration of launched in 1999, the Government of Indonesia initiated existing reservoir capacity lost to sedimentation, aging the development of a basic institutional and regulato- structures, and deferred maintenance. Dam safety invest- ry framework for the management and safety of dams, ments were also essential in safeguarding against dam- which was followed by subsequent reforms over two de- age and loss of life downstream that could have occurred cades. This included changes at the legislative level and due to dam failure, which would also have exacerbated the promulgation of more detailed regulations. Legal and the storage challenge by removing reservoir capacity from institutional reform is a continuous process, which may the system and likely making it more politically and admin- not be linear as demonstrated by the repeal of Water Law istratively difficult to invest in new dams. Case Study | Indonesia 161 Soentoro, E. A., A. B. Purnomo, and S. H Susantin. 2013. ENDNOTES “Study on Dam Risk Assessment as a Decision- 1 Law 7/2004 was repealed because it had permitted private Making Tool to Assist Prioritizing Maintenance sector companies to sell packaged tap water, which was of Embankment Dam.” Paper presented at the ruled unconstitutional because, under the Constitution, the 2nd International Conference on Sustainable right to water is a basic right and its control is a mandate of Infrastructure and Built Environment. 205–19. government. World Bank. 2009a. Dam Operational Improvement and Safety Project. Project Appraisal Document. Washington, DC: World Bank. REFERENCES World Bank. 2009b. Indonesia: Dam Safety Project. Washington, DC: World Bank. DGWR (Directorate General of Water Resources). 2008. World Bank. 2017a. Indonesia—Second Phase of Dam Project Implementation Plan for Dam Operational Operational Improvement and Safety Project: Improvement and Safety Project Directorate General Restructuring and Additional Financing. Project of Water Resources. Jakarta, Indonesia: Ministry of Appraisal Document. Washington, DC: World Bank. Public Works. World Bank. 2017b. Dam Operational Improvement and ICOLD (International Commission on Large Dams). Safety Project. Implementation Completion and 1989. Selecting Seismic Parameters for Large Dams. Results Report. Washington, DC: World Bank. Guidelines, Bulletin. Paris: ICOLD. World Bank. 2018. Maturity Matrices for Institutional Library of Congress. 2015. “Indonesia: Water Law Benchmarking of Dam Safety in Indonesia. Overturned by Court.” Accessed July 8, 2022. Washington, DC: World Bank. Retrieved from http://www.loc.gov/item/global- World Bank. 2021. Indonesia Vision 2045: Toward legal-monitor/2015-03-03/indonesia-water-law- Water Security. Washington, DC: World Bank. overturned-by-court/. Available at: https://openknowledge.worldbank.org/ MPWH (Ministry of Public Works and Housing) handle/10986/36727. Indonesia. 2022. "Information Material: Dams and World Bank. 2022. World Bank Databank. Retrieved from Lakes." Unpublished presentation. MPWH, Jakarta, www.data.worldbank.org. Indonesia. 162 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE ANNEX 8F. NAMIBIA: CONJUNCTIVE SURFACE AND GROUNDWATER MANAGEMENT FOR DROUGHT RESILIENCE IN WINDHOEK CASE STUDY BRIEF Summary Motivated by chronic water shortages and frequent droughts, the City of Windhoek, together with national water institutions, has responded with a wide range of measures to improve the city’s water security. This included raising new built storage infrastructure, investing in direct potable reuse, implementing water demand management and conservation measures, and exploiting the strategic potential of the Windhoek Aquifer as a “water bank” that is protected from the high rates of evaporation experienced by its surface storage and conveyance infrastructure. Though most of the elements of the current water storage and bulk water supply system pre-date the adoption of an integrated water resources management (IWRM)–guided planning framework, the city’s many innovations have resulted in a physically interconnected system of surface and groundwater storage that utilizes diversified water sources to improve drought resilience, reduce evaporative losses, and provide flexibility. Type(s) of water storage used › Aquifers › Large reservoirs Water service(s) of storage provided › Increased water availability Water requirement(s) of storage met › Water provision for domestic needs and industrial processes Case Study | Namibia 163 UGANDA KENYA REP. OF GABON CONGO RWANDA BACKGROUND MAP 8F.1 Perennial Rivers of NamibiaBURUNDI In Sub-Saharan Africa, Namibia is one of the driest coun- DEM. REP. OF TANZANIA CONGO SEYCHEL tries. Situated between the Namib and Kalahari deserts, ANGOLA Namibia has an arid climate with limited, sporadic rainfall 6 COMOROS and low soil moisture. Its mean annual precipitation be- 4 MALAWI tween 1901 and 2016 was just 277.6 millimeters (World ZAMBIA 1 Bank 2021b), which ranks in the bottom sixth of countries worldwide (World Bank 2017). Rainfall is extremely vari- MOZAMBIQUE 3 5 able throughout the year with virtually no rainfall between 2 ZIMBABWE June and August (figure 8F.1). High solar radiation and NAMIBIA temperatures combined with low humidity produce very BOTSWANA high evaporation rates that vary between 3,800 millime- ters per year in the southern parts of the country to 2,600 ESWATINI millimeters per year in the northern parts (World Bank 7 Catchment Areas 1 Kunene 2021a). Like other countries in Southern Africa, drought is SOUTH 2 Cuvelai a frequent occurrence in Namibia and poses a significant AFRICA LESOTHO 3 Okavango risk for the agriculture sector, which is the mainstay of the 4 Cuito 5 Kwando-Linyanti country’s rural population (World Bank 2021c). 6 Zambezi 7 Orange Both surface and groundwater resources in Namibia Source: Adapted from Mendelsohn et al. 2002. are very limited. About 97 percent of Namibia’s rainfall is lost to evaporation and evapotranspiration, with precipita- tion often evaporating before it reaches the ground. This Namibia and its capital Windhoek, the country’s largest leaves only 3 percent of precipitation available to form sur- city, rely heavily on surface and groundwater storage to face runoff or recharge aquifers. All of Namibia’s perennial meet its bulk water supply needs. Perennial border rivers rivers are transboundary rivers shared with other coun- account for 33 percent of Namibia’s water supply while 22 tries (map 8F.1), including the Orange River in the south percent comes from impoundments on ephemeral rivers and the Okavango, Kunene, Kavango and Zambezi Rivers that carry water in the interior of the country. Groundwater in the north (World Bank 2021a). accounts for 45 percent, including alluvial groundwater stored beneath ephemeral rivers (World Bank 2021b). The FIGURE 8F.1 Distribution of Precipitation in Namibia City of Windhoek relies on its “three-dam system,” man- aged by the Namibia Water Corporation Ltd. (NamWater), 300 as well as the Windhoek Aquifer to the south of the city and other aquifers in the northern areas of the city for Precipitation (millimeters) 250 most of its bulk water supply. The city also recycles its wastewater, which is put back into the city’s water supply 200 as well as stored underground during periods of excess (City of Windhoek 2019; Taylor 2019). 150 Windhoek is considered a world leader in manag- 100 ing scarce water resources. Windhoek is a small but fast-growing city located in the Central Area of Namibia. 50 At the time of the most recent census in 2011, Windhoek had a population of 325,858, with a high annual growth Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec rate of 3.3 percent (NSA 2011). Windhoek is home to 36 Source: World Bank 2021b. percent of the total urban population in the country, and its 164 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE population is expected to more than double by 2050 (Scott 1.5°C and 2.97°C in mean temperature by 2040–59 and a et al. 2018; Murray et al. 2018). The city is well-known for decrease in annual precipitation by 40.9 millimeters (RCP its innovation in water management and is recognized as 8.5, Ensemble), which will increase the impacts of drought the first city that implemented wastewater recycling for (World Bank 2021b). The share of gross domestic product direct potable reuse (Taylor 2019; World Bank 2021c). potentially affected by drought is currently about 41 per- cent on average—this is equivalent to $4 billion each year (UNDRR and CIMA 2018). Under future climate and socio- PROBLEM DEFINITION economic conditions, however, the share of GDP produced in areas hit by drought could reach 90 percent, equivalent to Population and economic growth are putting increasing almost $10 billion (World Bank 2021b). pressure on Windhoek’s already limited water resourc- es. Around the time of its original settlement in the late 1800s, Windhoek was considered to have sufficient water INSTITUTIONS AND INSTITUTIONAL because of its natural springs, but as the city grew and FRAMEWORK developed, existing groundwater sources became inad- equate (Mapani 2005). New boreholes were drilled to in- Main Institutions and Responsibilities crease pumping from the Windhoek Aquifer, and by 1942 the aquifer was depleted. Still, large-scale abstraction con- The main institutions governing water storage and bulk tinued, and Windhoek was considered to have exceeded water supply in Windhoek are NamWater, the City of its natural geographic water resources availability (Taylor Windhoek, and Namibia’s Ministry of Agriculture, Water 2019; Mapani 2005; MAWLR 2020). By 2010, even with the and Land Reform (MAWLR), formerly the Ministry of development of alternative sources, it was becoming ap- Agriculture, Water and Forestry. parent that the city’s supply was approaching the capacity of the system to meet demand. In 2019–20, water demand NamWater is the national agency that owns and operates in Windhoek was estimated at a managed 24 million m3 bulk water infrastructure across the country and is tasked (projected at 28 million m3 without demand management with providing bulk water to different types of customers, and conservation). By 2034, demand is expected to reach including municipalities and local authorities, government 36.47 million m3, including demand management and con- institutions, industrial customers, and mines. It also sup- servation measures (MAWLR 2020; Zheng et al. 2021). plies water to a select number of retail customers that live in proximity to its pipelines. For the Central Area, where In addition to its natural water scarcity, Namibia gener- Windhoek is located, NamWater operates seven surface ally and the City of Windhoek specifically have been ex- periencing more frequent and more severe droughts due water dams and 297 boreholes. NamWater was estab- to climate change. In 2015–16, much of Southern Africa lished in 1997 and is fully owned by the Government of experienced a rapid but devastating “flash drought," when Namibia (NamWater 2020). the onset of drought is unusually rapid, a type of event that has occurred much more frequently since the 1960s. MAWLR has overall responsibility for water resourc- This was followed by a severe drought in 2015–17, which es management in Namibia. It has eight directorates, caused inflows into the Von Bach Dam—one of the three including: main dams in the Central Area around Windhoek—to fall to zero for the first time since its construction. The 2018–19 » The Directorate of Water Resources Management, drought that followed was considered the worst drought to tasked with promoting sustainable and equitable hit the country in 90 years, with the lowest rainfall record- water resources management and use, allocating ed in Windhoek since 1891 (van Rensburg and Tortajada water and regulating abstraction, and strategic plan- 2021). This drought resulted in widespread food shortages, ning; and some 60,000 livestock deaths across Namibia, and a de- » The Directorate of Water Supply and Sanitation Co- cline in cereals production by up to 80 percent. With climate ordination, tasked with providing access to potable change, Namibia is expected to see an increase of between water supply and sanitation in rural areas, coordi- Case Study | Namibia 165 nating urban water supply and sanitation services THE EVOLUTIONARY PROCESS: A SYSTEMS (MAWF 2017). APPROACH The Department of Infrastructure, Water and Technical Groundwater Overexploitation and Surface Water Services (City of Windhoek) supplies, distributes, and Impoundments ensures the quality of water in the Windhoek urban area. It supplies water to city customers from the Windhoek Before 1933, all of Windhoek’s water came from the Aquifer through several production boreholes that it owns Windhoek Aquifer. But as the city’s population growth (with permits from MAWLR), reclaimed water, as well drove water demand to exceed the sustainable yield of as with bulk water purchased from NamWater (Scott the aquifer, efforts were made to diversify its water supply, et al. 2018). The city is the owner and operator of the specifically the construction of Avis Dam on the Avis River, Windhoek Managed Aquifer Recharge Scheme (WMARS) which runs through Windhoek, with a reservoir capacity of and has developed plans for water demand management 2.4 million m3. However, the catchment area of Avis Dam that helps the city manage water supply and use under is very small, and the dam was often unable to supply varying supply conditions, including drought. Its actions any water at all; today, it is part of a nature reserve and are informed by supply situation indicators provided by used exclusively for recreation (du Pisani 2006). A second NamWater (City of Windhoek 2019). The city also has dam was completed in 1958 to the west of the city—the an operations and maintenance contract with Windhoek Goreangab Dam with a reservoir capacity of 3.6 million m3 Goreangab Operating Company (WINGOC), a private con- (du Pisani 2006; Mapani 2005). sortium of Veolia and VA Tech Wabag, which is responsi- ble for operating the New Goreangab Water Reclamation Despite the investments in surface water impoundment, Plant that provides reclaimed water treated to potable however, exponential growth in water demand led ground- standards. water abstraction at Windhoek to an unsustainable 4.28 million m3/year by 1969. For comparison, the natural Enabling Framework recharge rate of the aquifer is estimated at around 1.73 million m3 per year on average. This water crisis inspired Over the last decade, Namibia has been enacting efforts to augment the city’s supply with water from other homegrown water legislation and regulations. Until 1990, Namibia was a protectorate under the stewardship parts of the country (Mapani 2005; Murray et al. 2018). of South Africa, and because of this, much of the legisla- tion in force during the development of major elements 1968: Introducing Direct Potable Reuse of its bulk water supply and storage infrastructure has origins in South African law. This includes the Water Act Spurred by the growing crisis, the City of Windhoek in- of 1956. troduced its first direct potable reuse facility in 1968, informed by a research project conducted jointly by In 2000, the Namibian government issued the National the City of Windhoek and the National Institute of Water Policy White Paper, which provided a guiding Water Research in South Africa (Haarhoff and Van der framework for the adoption of IWRM, including alignment Merwe 1996). The conventional water treatment plant at of Namibia’s policy framework with the Agenda 21 action Goreangab Dam was converted into a reclamation plant plan from the 1992 Earth Summit and the Dublin Principles to treat both the water impounded in the Goreangab from the 1992 International Conference on Water and the Reservoir and the effluent coming from the Gammams Environment (MAWLR 2020). National legislation and reg- wastewater treatment plant, the main wastewater treat- ulations pertaining to water resources management were ment facility for the city (du Pisani 2006). Much of the also enacted over the last decade, including the Water water behind Goreangab Dam, however, was unfit for rec- Resources Management Act (Act 11/2013), which is in- lamation as the whole city, including industries and infor- tended to replace the Water Act (Act 54/1956), but at the mal settlements, was located in the catchment area for time of this case study, the new law had not yet entered the dam. Thus, the city undertook to separate domestic into force (MAWLR 2020). and potentially harmful industrial wastewater, diverting 166 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE industrial wastewater to a different facility. It also un- The three dams are operated as a system by NamWater; dertook zoning reform to locate certain industries in the raw water is transferred from the Swakoppoort and northern part of the city so that its wastewater could be Omatako reservoirs via pipeline to the Von Bach separated (du Pisani 2006; Haarhoff and Van der Merwe Reservoir. The purpose of the transfer scheme is twofold: 1996). This industrial zoning would also become part of to bring the water closer to the treatment plant at Von Bach, the city’s strategy to protect the Windhoek Aquifer re- which is the closest of the three dams to the city, and more charge areas later on. importantly, to limit the amount of water lost to evaporation (Sirunda and Mazvimavi 2014; van Rensburg and Tortajada 1970s–1980s: The Three-Dam System 2021). The reservoir at Von Bach is deeper and narrower, giving it a smaller surface area than that of Swakoppoort Meanwhile, efforts were also being made to increase and Omatako. To gauge the significance of evaporative the amount of surface water available to the city. In losses, consider that the comparative water remaining 1970, the Von Bach Dam was commissioned on the in Omatako, Swakoppoort, and Von Bach dams after one Swakop River—the first of the three interconnected dams year’s evaporation, assuming they are 100 percent full at that are often referred to as Windhoek’s “three-dam sys- the start of the year and have no inflow during the year, tem.” The other two dams are the Swakoppoort Dam, would be about 39 percent, 75 percent, and 78 percent, re- also on the Swakop River, commissioned in 1977, and the spectively. This operational regime improves the 95 percent Omatako Dam on the Omatako River, commissioned in safe yield to 20 million m3 per year compared to if the dams 1982. All three dams are built on ephemeral rivers to cap- were operated on an individual basis (MAWLR 2020). ture and store water for dry periods and are designed to store up to three times the mean annual runoff (Sirunda 1990s: Demand Management and Recognizing and Mazvimavi 2014). Aquifers as Storage In addition to annual inflows, water in the three-dam sys- The 1990s marked a shift toward optimization of the sys- tem is augmented by transfers from the karst aquifer near tem. Following Namibia’s independence from South Africa Grootfontein, north of the Central Area. Despite high evap- in 1990, Windhoek’s urban population grew at a rapid rate, orative losses, this three-dam system and water transfer but whereas previous decades were focused on increas- scheme significantly increases the amount of water avail- ing bulk water supply by constructing new water storage able to Windhoek, and under normal meteorological condi- infrastructure, the 1990s saw the emergence of system tions, supplies between 70 and 75 percent of the city’s water optimization as priority as well as demand management (Taylor 2019; van Rensburg and Tortajada 2021) (table 8F.1). (MAWLR 2020). In 1994, the city began introducing demand TABLE 8F.1 Three-Dam System: Features FEATURE VON BACH DAM SWAKOPPOORT DAM OMATAKO DAM THREE-DAM SYSTEM River Swakop River Swakop River Omatako River Year completed 1970 1977 1982 Distance from Windhoek (km) 70 90 160 Capacity (Mm )3 48.56 63.48 43.50 155.54 Catchment area (km ) 2 2,920 5,480 5,320 Surface area at full supply level (km ) 2 4.89 7.81 15.54 95% assured yield (Mm3) 6.5 4.5 2 20 Primary purpose Water supply Water supply Water supply Sources: MAWLR 2020; Sirunda and Mazvimavi 2014; van Rensburg and Tortajada 2021; ICOLD 2020. Case Study | Namibia 167 management strategies, including leak detection, public en- SOLUTION IMPLEMENTATION gagement, and the use of semi-purified effluent for irrigat- ing gardens and public spaces, which successfully reduced Interconnected Storage Facilities potable water demand by 20 percent; but these measures did not sustain a reduction in demand beyond the 1996–97 Windhoek manages its surface and groundwater con- drought (Taylor 2019; van Rensburg and Tortajada 2021). junctively with measures across both natural and built storage types to reduce water losses due to evapora- During the 1996–97 drought, the government invested tion and to increase the availability of freshwater during in feasibility studies for artificially recharging the city’s drought (figure 8F.2). Specifically: groundwater resources, including first injection testing to establish proof of concept (Taylor 2019). By 2004, it was » Water is impounded in three dams around the city to ultimately determined that a large-scale managed aquifer capture and store flows from the ephemeral rivers recharge (MAR) scheme using the Windhoek Aquifer was running through the interior of the country. feasible and cost-effective. Given groundwater was less sus- » Water is also transferred from the karst aquifer near ceptible to evaporation, MAR offered a more resilient storage Grootfontein north of the city to Windhoek via canals alternative than the surface reservoirs around the city. New to Omatako Dam (Mapani 2005). laws and regulations were passed in 2005 to protect the re- » Water in the Omatako and Swakoppoort reservoirs is charge areas, and the first period of artificial recharge began transferred to the Von Bach Reservoir with a smaller in 2006. Between 2006 and 2012, a total of 2.83 million m3 surface area before it is treated and sent to the city. was recharged using direct injection in six boreholes, which » This water is comingled with water from boreholes brought the aquifer to its highest levels since the start of in the Windhoek Aquifer and surrounding aquifers large-scale abstraction in the 1950s, but demand was still as well as recycled water from the New Goreangab well above the sustainable yield (Murray et al. 2018). Water Reclamation Plant—a larger, more advanced facility commissioned in 2002 (van Rensburg and 2010s: Operationalizing WMARS Tortajada 2021). From 2015 to 2017, the area was hit by another severe » The Windhoek Aquifer is recognized as a conve- nient and resilient natural water storage facility drought and water crisis. In 2015, the Central Area re- with excess water “banked” underground as a buf- ceived 197 millimeters of rain compared to the long-term fer against drought. The scheme is recharged with average of 360 millimeters, and NamWater was expecting surface water dams to be empty by late 2016. During this treated water that is a 3:1 blend of dam water and time, the groundwater reserves in the Windhoek Aquifer, reclaimed water (Murray et al. 2018). It is estimat- as well as direct potable reuse, emerged as the most fea- ed that the WMARS could eventually store up to 71 sible supply alternatives (van Rensburg and Tortajada million m3 of water if deep aquifers are included (van 2021). After repeated requests, the Ministry of Agriculture, Rensburg and Tortajada 2021; Zheng et al. 2021). Water and Forestry mobilized funding through NamWater The fully developed WMARS system is expected to for emergency implementation of abstractions from have a recharge capacity of 12 million m3 per year the Windhoek Aquifer to draw on the reserves from the and an abstraction capacity of 19 million m3 per year WMARS (Scott et al. 2018). Twelve additional boreholes (Zheng et al. 2021). were drilled, and the project came online in December » Water demand management is a key response 2016, which was about the time the three-dams system mechanism for Windhoek in times of low water sup- was expected to “run dry” (van Rensburg and Tortajada ply. An index based on percentages below average 2021). At the same time, direct potable reuse produc- supply levels in the three dams is implemented with tion capacity was increased, and the City of Windhoek categorizations with varying degrees of severity, put in place the first version (2015) of its Water Demand starting with calls on the public to reduce consump- Management Strategy and Drought Response Plan.1 By tion in times of normal and slightly low supply levels, 2017, its public campaign to “Save Water” had achieved to enforced restrictions as the situation becomes 33 percent reduction in water demand (Scott et al. 2018). more severe (City of Windhoek 2019). 168 WHAT THE FUTURE HAS IN STORE: A NEW PARADIGM FOR WATER STORAGE FIGURE 8F.2 Elements of Windhoek’s Water Storage System NamWater Operations Karst Aquifer and Kombat Scheme Omatako Grootfontein- Omatako Dam Von Bach ch Canal Ba Dam and -Von tako r Swakoppoort WTP Oma Transfe n Bach Dam Swakoppoort-Vo Transfer Windhoek Terminal Goreangab City of Windhoek Dam Distribution Network Windhoek Aquifer Production Boreholes WINGOC and Redamation Windhoek Managed Aquifer Recharge City of Windhoek Scheme (WMARS) Sanitation Network City of Windhoek Operations Source: Original figure for this publication based on MAWLR 2020. Note: WINGOC = Windhoek Goreangab. Operating Company; WTP = water treatment plant. » For the dam water used to recharge the system, the supply options have been fully developed with the excep- City of Windhoek pays NamWater a cost recovery tar- tion of the WMARS, for which there are plans to increase iff; an additional charge (profit for NamWater) is then its capacity. The system also has a lot of complexity, and realized when the artificially recharged water is sup- operating costs are high for its energy-intensive water plied by the city to customers (Murray et al. 2018). transfer systems. Additionally, infrastructure aging and lack of preventative maintenance are a growing concern, Challenges considering much of the major bulk water storage and conveyance infrastructure is several decades old. Windhoek is recognized globally for its innovation and leadership in urban water management under scarci- On the institutional side, while there have been efforts ty, but the city still faces a number of challenges to its to adopt and operationalize IWRM principles, major gaps water security. There are very real concerns about the remain in the legal and regulatory framework with the ability of the water supply system to deliver service with national Water Resources Act not yet in force since its high levels of assurance into the future given the trajectory passage in 2013. According to most recent indicators on of future demand growth. Virtually all of Windhoek’s water SDG 6, Namibia’s degree of IWRM implementati