WAT E R G L O B A L P R A C T I C E Accounting for  Water Quality Insights for Operational Task Teams Deborah V. Chapman, Poolad Karimi, Svetlana Valieva, Ruyi Li, and Amal Talbi May 2024 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 : @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, the Swedish International Development Cooperation Agency, Switzerland’s State Secretariat for Economic Affairs, the Swiss Agency for Development and Cooperation, U.K. International Development, and the U.S. Agency for International Development. Please visit us at www.worldbank.org/gwsp or follow us on : @TheGwsp. Accounting for Water Quality Insights for Operational Task Teams Deborah V. Chapman, Poolad Karimi, Svetlana Valieva, Ruyi Li, and Amal Talbi May 2024 © 2024 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. The findings, interpretations, and conclusions expressed in this work do not necessarily reflect the views of The World Bank, its Board of Executive Directors, or the governments they represent. The World Bank does not guarantee the accuracy, completeness, or currency of the data included in this work and does not assume responsibility for any errors, omissions, or discrepancies in the information, or liability with respect to the use of or failure to use the information, methods, processes, or conclusions set forth. 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Please cite the work as follows: Chapman, Deborah V., Poolad Karimi, Svetlana Valieva, Ruyi Li, and Amal Talbi. 2024. “Accounting for Water Quality: Insights for Operational Task Teams.” 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. Cover design: Bill Pragluski, Critical Stages, LLC. Cover photo: Poolad Karimi / World Bank Contents Acknowledgments v Executive Summary vii Abbreviations ix 1. Introduction 1 Notes 2 2. Water Quality 3 Impacts on Water Quality 3 Water Quality Guidelines 5 Approaches to Monitoring Water Quality 7 Notes 11 3. Integrated Water Quality and Water Quantity Accounting 12 Notes 14 4. A Framework for Monitoring and Assessing Water Quality for Water Accounting 15 Step 1. Define Scope and Scale of the Water Quality Accounts 16 Step 2. Identify Sources of Impact on Water Quality 16 Step 3. Select Locations for the Collection of Water Quality Data 17 Step 4. Select Water Quality Parameters 19 Step 5. Decide Time Frame and Frequency of Sampling 20 Step 6. Explore Sources of Existing Monitoring Data 21 Step 7. Consider Implementing a Monitoring Program to Fill Data Gaps 22 Step 8. Assemble Water Quality and Quantity Data 23 Step 9. Assess and Present Water Quality Accounting Data 23 Notes 38 5. Conclusions 39 References 41 ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS iii BOXES 4.1. Applying the Framework to a Simple Irrigation Project 27 4.2. Applying the Framework at Basin Scale 30 4.3. Applying the Framework to a Water Storage Reservoir 34 FIGURES 3.1. Water Accounting Should Incorporate Water Quality Monitoring to Support Efficient Integrated Water Resources Management 12 4.1. A Framework for Water Quality Accounting 15 4.2. A Hypothetical Water Basin Showing Potential Sources of Impact on Water Quality and Strategic Monitoring Locations to Facilitate Water Quality Accounting at River Basin Scale 17 4.3. Sample Visualization of Difference in Water Quality Parameter Values at Monitoring Stations throughout a River Basin, Using Guideline Values and an Upstream Station as Comparators 24 4.4. Changes in Water Quality in a River Basin Using a Water Quality Index, by Monitoring Station and Flow Path 26 B4.1.1. A Hypothetical Irrigation Scheme Using Groundwater and Returning Flows via a Drainage Ditch and Infiltration to an Adjacent River 27 B4.2.1. A Hypothetical Example of a River Basin with Different Activities That Use and Return Water to the Basin, Together with Potential Locations for Gathering Water Quality and Quantity Data 30 B4.3.1. A Hypothetical Example of a Water Storage Basin Used for Irrigation, Together with Potential Locations for Gathering Water Quality and Quantity Data 34 TABLES 2.1. Examples of National Water Use and Impact Guidelines and Standards 6 4.1. Examples of Monitoring Parameters and Sampling Frequency for Surface Waters for Various Water Use and Impact Sources That May Be Included in Water Quality Accounts 19 B4.1.1. Potential Water Quality Monitoring Points and the Associated Parameters and Frequency of Monitoring for Figure B4.1.1 29 B4.2.1. Potential Monitoring Stations and the Associated Water Quality Parameters and Frequency of Monitoring for Water Accounting in the Scenario Given in Figure B4.2.1 32 B4.3.1. Potential Water Quality Monitoring Points and the Associated Parameters and Frequency of Monitoring for Water Accounting in the Scenario Given in Figure B4.3.1 36 ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS iv Acknowledgments This note was prepared by a core team comprising of Deborah V. Chapman (Senior Consultant), Poolad Karimi (Senior Irrigation and Drainage Specialist), Svetlana Valieva (Water Analyst), Ruyi Li (Consultant), and Amal Talbi (Lead Water Specialist, Climate Resilient Irrigation Global Solutions Group Lead). The team is very grateful for the support and overall guidance of Saroj Kumar Jha (Global Director), Yogita Mumssen (Practice Manager), and Soma Ghosh Moulik (Practice Manager). The report benefited greatly from discussions and guidance from Pieter Waalewijn (Lead Water Resources Management Specialist). Constructive comments on the report were received from the following peer reviewers: Verena Schaidreiter (Water Supply and Sanitation Specialist), Shafick Hoossein (Senior Environmental Specialist), and Andrea Mariel Juarez Lucas (Water Resources Management Specialist). The team would also like to acknowledge David Gray (Senior Knowledge and Learning Officer) for his suggestions on layout and dissemination. The authors would also like to thank Erin Barret (Knowledge Management Analyst) for production management. The manuscript was edited by EDiPro. Any remaining errors or omissions are the authors’ own. The authors also appreciate the graphic design for the figures by Dudu Coelho (Consultant). The team gratefully acknowledges the financial support provided for the note by the Global Water Security and Sanitation Partnership. ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS v Executive Summary For centuries, management of freshwater resources has focused on monitoring and managing water quantity to ensure supplies for domestic, agricultural, and industrial use and to mitigate the potential effects of floods and droughts. However, the quantity of water is inextricably linked to its quality, yet much less attention has been paid to the latter. Every human use of water, and the aquatic ecosystem itself, has minimum requirements for water quality. At a national scale, managing water quantity and water quality have often been the remit of different government agencies with limited sharing of information. This has had detrimental consequences for water resources and aquatic ecosystems at catchment scale as data gathered for Sustainable Development Goal (SDG) 6 “Ensure availability and sustainable management of water and sanitation for all” highlight (UN 2015; UNEP 2021; UN-Water 2018a). Still, there are opportunities for improved management of freshwater resources if water quality is considered within the context of water accounting. This report summarizes key aspects and presents a framework to assist water accounting teams to evaluate the needs for incorporating water quality monitoring into their operations. Water quality for specific uses is defined by quality standards or guidelines that principally set maximum concentrations of individual physical and chemical parameters in the water. These parameters are measured at the point of abstraction or immediately before use. All uses of water generate wastewater, which usually differs in quality from the water abstracted. Wastewater is either returned to the hydrological cycle, but not necessarily from the same water body as it was abstracted, or it is reused and subsequently returned to the hydrological cycle. The quality of the water returned may be monitored in cases in which regulations or standards exist, or the quality of the receiving water body may be monitored to check for effects on the ecosystem through biological approaches. Monitoring the quality of return flows is essential to determine the physical and chemical changes arising from use. To evaluate the impact on water quality of a single activity, or of multiple activities within a catchment at specific locations, data need to be comparable. For water quality, this requires determining the amount, or load, of each individual pollutant or parameter. Loads are calculated from concentrations and the volume of water over a specific time period at a given location. Ideally, therefore, water quality data should be obtained from locations where water accounting data are gathered. If the monitoring agency does not share such data from existing programs, new monitoring activities may need to be planned and implemented as part of the data collection for water accounting. Some options for doing this are outlined. ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS vii The framework presented in this report introduces a step-by-step approach to defining scope and objectives and to identifying data needs and monitoring approaches for data collection and computation of loads. Data analysis and presentation options are also explored. Implementation of the framework is illustrated with three different scenarios of different scope and scale of water accounting activities: an irrigation scheme, a river basin, and a reservoir. The scenarios illustrate suggested locations for monitoring, relevant water quality parameters for inclusion, the time frame for data collection, and interpretation of the results. ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS viii Abbreviations BOD biochemical oxygen demand EC electrical conductivity EU European Union N nitrogen P phosphorus SDG Sustainable Development Goal SWAT Soil and Water Assessment Tool TDS total dissolved solids TSS total suspended solids UN United Nations UNEP United Nations Environment Programme USEPA United States Environmental Protection Agency USGS United States Geological Survey WWQA World Water Quality Alliance ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS ix 1. Introduction The concept of water accounting has existed for at least one hundred years, with the methods and frameworks to account for water based on the quantity of water used (Karimi 2014; Mul et al. forthcoming; Vardon et al. 2023). The United Nations (UN) established seventeen Sustainable Development Goals (SDG) in 2015 (UN 2015) and included a specific goal for freshwater (SDG 6 “Ensure availability and sustainable management of water and sanitation for all”) in recognition of the importance of both water quantity and water quality for human health, socioeconomic development, and biodiversity. SDG 6 calls for an integrated approach to all aspects of freshwater management, including accounting for water quantity and quality (UN-Water n.d.). Freshwater is fundamental to all life and all human activity and is, therefore, important for other SDGs, such as SDG 1 “No poverty,” SDG 2 “Zero hunger,” SDG 3 “Good health and well-being,” SDG 7 “Affordable and clean energy,” and SDG 11 “Sustainable Cities and Communities” (UN-Water 2016). Therefore, progress toward achieving the targets of SDG 6 has implications for achieving the targets of many others (UN-Water 2021). An important aspect of SDG 6 is integration of monitoring and managing freshwater resources across all relevant sectors at catchment scale (UN- Water n.d.). This includes sectors responsible for water quantity, water quality, drinking water, and wastewater. Every use of water, from human consumption and food production to industry and aquatic life, has minimum requirements for water quality. However, most human activities return used water to the hydrological cycle, and this water is degraded to some extent physically and/or chemically, consequently affecting subsequent users of the water resource and the freshwater ecosystem. The World Bank Environmental and Social Standard 3 (ESS3) on Resource Efficiency and Pollution Prevention (World Bank 2018) recognizes that human activities generate pollution of water resources and promotes appropriate pollution prevention and management as part of the planning and financing of any new activities. This should include assessing effects on surface water and groundwater quantity and quality from current and planned activities within the same water basin. Being aware of potential impacts on water quantity and quality is also an important component of managing environmental and social risks of development projects (ESS1), the associated community health and safety (ESS4), and aquatic ecosystems and biodiversity (ESS6; World Bank 2017). Assessment and management of sources of pollution and physical degradation, and their effects on water quality and aquatic ecosystems, can be achieved only by monitoring the physical, chemical, and biological characteristics of water resources at the relevant management scale—for example, a drainage basin1 or water body.2 Water quality monitoring of surface water and groundwater provides information on the status of the water body, temporal and spatial variations, effects of human activities, and suitability for use ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 1 (Chapman and Sullivan 2022). Monitoring information can also be used to identify relative pressures, sources of impact, and areas requiring remedial action. Monitoring the quality of water abstracted is done to assess whether the water is of suitable quality for specific uses that may be prescribed in guidelines or standards (see section “Water Quality Guidelines”). Similarly, monitoring discharges can provide information on the quality of emissions from human activities and the potential impact on the ecosystems of receiving water bodies. Most water accounting methods focus on blue water,3 its availability for use, and subsequent returns by different water-using sectors (fluxes and stocks4). Water accounting collects data from monitoring networks at points of water abstraction and return. This approach potentially aligns well with water quality monitoring programs that assess quality of water abstracted for specific uses and the water quality in receiving water bodies resulting from water returned after use. The framework presented here introduces the key concepts of monitoring water quality in the context of water accounting. It should be used with the guidance note on water accounting (Molden et al. 2024) to achieve informed and integrated water resource management that takes account of both water quantity and quality. The document highlights important considerations for assessing water quality and for determining and apportioning impacts on water quality. It will therefore be of interest to those involved in financing, planning, developing, implementing, and supporting water accounting projects, especially in the context of the World Bank Environmental and Social Framework (ESF; World Bank 2017). NOTES 1. A drainage basin is the area of land drained by a water body, such as a river and its tributaries. 2. A water body may be a river, lake, or aquifer. 3. Conceptually, the freshwater cycle can be partitioned into two parts—green and blue water—in accordance with the hydrological processes and storage types involved. Blue water represents one-third of the real freshwater resource (or rainfall) stored in rivers, lakes, aquifers, and dams. It flows either on or below the land surface and can be extracted for human use. Green water, on the other hand, refers to the portion of precipitation that infiltrates to become soil moisture, or remains temporarily on top of the soil or vegetation, then eventually returning to the atmosphere via transpiration and evaporation (Falkenmark and Rockström 2006; Rockström et al. 2009). 4. Fluxes refer to water flows, whereas stocks refer to water storage. ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 2 2. Water Quality Impacts on Water Quality Natural water quality is the result of the interaction of the geology of the water basin, climate (principally rainfall), and the biological components (Warner, Chapman, and Dickens 2020) and is free from human influence. It can support diverse communities of aquatic species in the open water and in the associated wetlands. In the context of a water quality monitoring program, natural water quality is taken as the benchmark against which the type and extent of water quality degradation can be assessed. Within a water basin or catchment, it should be found in the headwaters before any influence from human activity, although it is difficult to find water that is totally natural because of the influence of atmospheric transport and deposition of contaminants. Nevertheless, headwaters in rivers or upland lakes are often taken to represent the background water quality of the catchment against which downstream changes can be assessed. Human influence on water quality results from domestic, industrial, and agricultural activities in the water basin (Peters, Meybeck, and Chapman 2005). The effects of these activities can degrade the water quality and make it unsuitable for subsequent human use and for the aquatic communities that rely on good-quality water. Degradation can occur as physical alterations, such as organic and mineral matter causing excessive siltation in reservoirs, on riverbeds, and in wetlands, as well as chemical imbalances caused by the introduction of nutrients, salts, pesticides, and other chemicals. Urbanization—particularly rapid and unplanned urbanization—has significant consequences on water quality arising from treated and untreated domestic wastewater discharges, industrial effluents, and runoff from hard surfaces (for example, rooftops and roads). These can carry a huge variety of contaminants, such as organic matter, pathogens, metals, organic compounds, and pharmaceuticals. In addition, this alters natural runoff and infiltration patterns, contributing to increased flooding during periods of heavy rainfall and reduced infiltration and recharge of groundwaters that consequently reduces base flow to rivers (McGrane 2016). Periods of heavy rain result in highly contaminated stormwater runoff from urban areas carrying particulate matter, debris, and human waste that accumulated in the preceding dry period. Changes in rainfall patterns associated with climate change, particularly intense rainfall events, are likely to exacerbate this problem (Wijesiri, Liu, and Goonetilleke 2020). Agricultural activities mainly lead to runoff that may be contaminated with fertilizers, pesticides, and livestock fecal waste that is high in organic matter and pathogens. Nutrient enrichment of freshwaters arising from the use of fertilizers is a global issue, resulting in ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 3 eutrophication and the associated effects on ecosystems and water quality (Smith 2003). Warmer water temperatures associated with climate change are anticipated to increase the adverse effects on freshwaters associated with eutrophication (Moss et al. 2011). In some regions, mining is an important economic activity that can have severe effects on the quality and quantity of surface water and groundwater (IGF 2022; Wolkersdorfer and Mugova 2022), affecting aquatic ecosystems and suitability for human use. Mining on land can release highly acidic water (acid mine drainage) and metals in dissolved and particulate forms that contaminate surface water and groundwater. Suspended solids concentrations and sedimentation patterns can also be altered, especially by mining for sand in and around rivers (Koehnken et al. 2020). Many of the human activities described earlier need a reliable and continuous source of freshwater, which is often created by damming a river to create a reservoir or by building water storage facilities. These water bodies share many characteristics with lakes or slow-flowing rivers and function in a similar way (Thornton, Steel, and Rast 1996), with the exception that the rate of flow of water though the reservoir can usually be controlled. The water quality of the reservoir or storage facility is affected not only by the quality of the incoming water but also by the biological activity within the reservoir. Incoming water may bring high suspended solids loads that contribute to rapid siltation and gradual loss of volume, as well as nutrients that support levels of algal growth that can impair water use and exacerbate siltation. Upstream activities that discharge wastewater can also lead to an accumulation of potential contaminants in the reservoir. For most human activities within a water basin, some of the water is consumed1 and the remainder is returned to the hydrological cycle (with or without treatment), though not necessarily to the same water body from which it was withdrawn. For example, water abstracted from groundwater for urban use or irrigation may be returned to a river with sewage discharges or drainage water. Water that is returned almost always has a different, and often degraded, quality compared with the water that was initially withdrawn. Water quality changes naturally as it moves down through a catchment, but adverse changes are more pronounced in those with a diversity of human activities. Water users downstream often have to contend with the pollution arising from upstream users. This is of particular concern in transboundary waters, where the incoming water quality measured immediately downstream of the boundary may already be inadequate for many uses without expensive treatment. In arid climates, where accessible freshwater resources are extremely limited or already severely depleted—and to reduce pressure on available water resources worldwide—reuse of wastewater is encouraged to meet the demand for freshwater for human activities, particularly irrigated agriculture. In some countries, the wastewater is used untreated and, because of its high pathogen load, can present serious health risks for agricultural workers and consumers of the irrigated crops (Kesari et al. 2021). Activities within a water basin give rise to both point and diffuse sources of contamination. The former are usually easily identified at a specific location, such as effluent discharges. ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 4 Increased water flows, for example, resulting from heavy rain, can dilute the effluents in the receiving water body and reduce the associated concentrations of contaminants. Diffuse sources arise from activities that occur over wide areas, and the pollutants can reach water bodies through surface runoff with rainfall or infiltration and subsequent discharge to surface water with groundwater base flow. Consequently, the impacts on receiving water bodies may multiply with increased rainfall and during floods. Within a water basin, there may be numerous activities contributing to diffuse pollution. It is difficult to determine the quality of water returned with diffuse sources without high-density spatial monitoring networks and/or the use of modeling approaches. Except for specific projects, the monitoring requirements are generally infeasible because of the financial and technical resources required. Apportioning the resultant water quality within the basin to the sources within its boundaries (river, lake, or groundwater) can be complex, requiring a considerable amount of monitoring data coupled with modeling approaches, such as the Soil and Water Assessment Tool (SWAT)2 and statistical techniques (for example, Bu et al. 2014; Veljkovic, Dopudja-Glisic, and Jovicic 2013). Water Quality Guidelines Water quality is generally managed by the implementation of water quality guidelines and standards that set target values or thresholds for individual water quality parameters (UN-Water 2015). It can be difficult to set guideline values for ambient water quality— more commonly specified as aquatic life—without existing information on natural (or background) water quality and the natural variability at national scale. Consequently, it can be difficult to set guidelines for wastewater impacts on aquatic environments. Advice for preparing guidelines and the associated guideline values is available from countries with many years of experience in devising guidelines, such as Australia and New Zealand.3 Alternatively, some authorities choose to set guidelines based on those available from other sources, such as the Food and Agriculture Organization (FAO), United States Environmental Protection Agency (USEPA), and World Health Organization (WHO). An example of guidelines based on those available from other organizations and agencies is those of the Environment Protection and Development Authority of Ras Al Khaimih (EPDA 2020). Table 2.1 gives some examples of national guideline values from Australia and New Zealand, Bhutan, India, South Africa, Sri Lanka, United Arab Emirates, and the United States for aquatic life, raw (untreated source) drinking water, and irrigation use, as well as examples of standards for wastewater discharges. Although the values for a few guidelines—for example, pH—are similar for all countries, others vary considerably according to local conditions and priorities. As the need to reuse wastewater grows, appropriate policies and guidelines for the quality of the water before reuse are essential (Alcalde-Sanz and Gawlik 2017). Some examples of guidelines exist in countries where reuse is normal practice, but relevant policy in other world regions is relatively new. For example, the European Union introduced wastewater reuse regulations (EU 2020) and published the associated guidelines (European Commission 2022) that would take effect in 2023. ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 5 Table 2.1. Examples of National Water Use and Impact Guidelines and Standards Use Discharge Raw drinking Treated Parameter Aquatic life water Irrigation sewage Industryj Basic Parameters DO (% sat ) min n 80–120 (4) – – – – DO (mg/L) min 4(2), 5(5), 3–8(7) 6(2,6) – – – BOD (mg/L) 4(5) 2(2) 30(1,6) 30(3) COD (mg/L) 4(4), 15(5) – – 125(1) 100–200(3) pH Max 5% change(4,a) 6.5–8.5(2,6) 6.5–8.4(3) 6–9(1) 6–9(3) 6.0–8.5(5) 4.5–9.0(8) 6.5–8.5(2) 6.5–9.0(7) EC (μS/cm) – 800(6) 0–3,000(3) – – 2,250(2) 0–5,500(8,h) TDS (mg/L) Max 15% change(4,a) – 0–2,000(3) – – 0–3,500(8) TSS (mg/L) Max 10% change(4,a) 25(6) – 50(1) 30–80(3) 40(5), 10%(7,b) 100(6) Nutrients Total N (mg/L) Max 15% change (4,a) 0.5(6) – 10(1) – Nitrate-N (mg/L) 10(5) 10(6) – – 50(3) Ammonia as N ≤0.007(4), 1.2(2) 0.05(6) – – 10(3) (mg/L)(e) 0.22–0.94(5) 1.9–17(7,c) Total P (mg/L) – – 3(3) 2(1) – Phosphate-P Max 15% 0.5(6) – – – change(4,a), 0.4(5) 0.025–0.05(7,d) Salts Chloride (mg/L) 230–860(7) 50(6) 0–30(3) – – 30–700(8) Potassium (mg/L) – – 2(3) – – Sodium (mg/L) – – 40 (3) – – Microorganisms Total coliforms – 50(2,6) – 400(1) – (MPN/100 mL) E. coli/fecal – 20(6) 1,000(8) 1,000(6) 200–300(3) coliforms (/100 mL) (Continued) ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 6 Table 2.1. Examples of National Water Use and Impact Guidelines and Standards (Continued) Use Discharge Raw drinking Treated Parameter Aquatic life water Irrigation sewage Industryj Metals and Organics Aluminium (mg/L) ≤0.005 – ≤0.01(4,e), – 5(8) – – f(7) Iron (mg/L) 1(7) 0.2(6) 1(8) – 10(3) Manganese <0.18(4), 1(5) – 0.2(3) – 10(3) 2(8) Mercury (mg/L) 0.00004(4) – 0.002(3) – 0.005(3) 0.001(5) 0.002(8) 0.00077–0.0014(7) Other metals 0.05–1(5) 0.003–0.2(6) 0.1–5.0(3) – 0.03–3(3) Organic – – – – 0.00025–0.5(3,g) micropollutants PCBs 0.000014(7) 0.0002(6) – – 0.00005(3) Pesticides g(7) 0.0005(6,i) – – 0.0002–0.5(3) Sources: 1. IFC 2007; 2. Kerala State Pollution Control Board, India (https://kspcb.kerala.gov.in/standards​ /water-quality/water-quality-criteria); 3. EPDA 2020; 4. DWAF 1996; 5. Democratic Socialist Republic of Sri Lanka 2019; 6. National Environment Commission of Bhutan 2018; 7. USEPA 2022; 8. ANZECC 1992 superseded by ANZECC and ARMCANZ 2000. Note: These numbers are maximum values, except as indicated otherwise. For countries of origin, please see table footnotes. BOD = biochemical oxygen demand; COD = chemical oxygen demand; DO = dissolved oxygen; EC = electrical conductivity; mg/L = milligram dissolved per liter of water; mL = milliliter; MPN = most probable number; N = nitrogen; P = Phosphorus; PCBs = polychlorinated biphenyls; sat = saturation; TDS = total dissolved solids; TSS = total suspended solids, μS/cm = microsiemens per centimeter. a. Change from local unimpacted conditions. b. Should not reduce euphotic depth by more than 10 percent. c. Ranging from thirty-day to one-hour average values. d. Lakes and rivers, respectively, to reduce potential for algal blooms. e. Depends on pH of water. f. Calculated based on other water quality parameters. g. Compound specific. h. Depending on soil type and tolerance of crops. i. Total. j. Generally industry specific. Approaches to Monitoring Water Quality Sustainable management of freshwater to benefit society and the environment should be approached from a catchment perspective, considering both water quantity and water quality. Catchments can be defined at different scales and comprise, for example, single lakes, whole river basins (including transboundary rivers), subcatchments of a large river, and aquifers. For efficient management, all water bodies should be considered, including both surface water and groundwater, because they are linked through the hydrological cycle. However, obtaining adequate water quality information at catchment scale requires considerable financial and human resources, and compromises are often made among the ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 7 spatial density, temporal frequency, and water quality parameters measured. This could present a particular challenge for water quality accounting at basin scale. Lakes and reservoirs4 may be considered separately or as a component of a larger water basin. Their water quality can vary considerably depending on size, depth, complexity of shape, and geographical location (Kalff 2001; Wetzel 2001), thus necessitating multiple monitoring stations. Monitoring is also more difficult because of the need to access open water, usually with a boat, or from a rigid structure, such as a water abstraction tower or a pontoon (UNEP 2023b). The quantity of water within a storage basin is affected seasonally, mainly by rainfall and abstraction for human use. In hot, arid climates, evaporation may also cause water loss. In regions where rivers suffer from high suspended sediment loads, water storage basins may be susceptible to the accumulation of sediment on the reservoir bed over several years. This ultimately reduces their useful life span by reducing the volume (Kondolf et al. 2014). Approximate changes in water volume in a reservoir can be measured using a permanent depth gauge that shows the water level. Most countries lack adequate monitoring of groundwater quality (Ravenscroft and Lytton 2022b), making it difficult to include in the context of water accounting—particularly because of its three-dimensional nature. In addition, specific expertise is required to interpret water quality data obtained from existing abstraction wells and monitoring boreholes and to decide on locations for new wells (Ravenscroft and Lytton 2022a, 2022b; UNEP 2022). Because of the importance of groundwater as a source of water globally, there are several ongoing initiatives at a global scale to increase awareness of the need for monitoring both quantity and quality of groundwater to ensure its sustainable use and to provide useful resources to support monitoring and assessment. The International Groundwater Resources Assessment Center (IGRAC) developed the Global Groundwater Information System (GGIS),5 which is an interactive, online collection of groundwater-related information and knowledge, and the World Water Quality Alliance (WWQA) produced a summary of knowledge and capacity for assessing groundwater quality globally and outlined future needs (WWQA 2021). In Situ Monitoring Water quality can be assessed by examining physical, chemical, and biological characteristics, which vary from one water basin to the next and even within bodies of water. Human influence on water quality is usually assessed by comparing water quality in the area affected by human activity (for example, where wastewater is discharged) with natural water quality. In practice, natural or background water quality must be inferred from monitoring headwaters, upstream locations, or an adjacent water body with no apparent human influence. Traditionally, water quality has been measured using physical and chemical parameters, such as pH, electrical conductivity (EC), nitrate, and heavy metals, in water samples taken at specific locations and times. These grab samples provide a measure of water quality at the instant and location of collection. To capture variability because of seasonal differences or patterns of human activity, measurements are repeated over a specified period and/or from ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 8 several sampling locations to provide an average value for each parameter examined. The range that can be measured to assess water quality characteristics is huge, and monitoring programs must choose the most necessary and useful parameters given financial and technical constraints. All processes involved in obtaining water quality data—including field collection of samples, laboratory or field measurements, and data storage—are vulnerable to human error, contamination, and inappropriate or malfunctioning equipment. To ensure confidence in the water quality data, an appropriate quality assurance plan that includes quality control procedures is essential (UNEP 2023a). Measurements of individual water quality parameters do not illustrate how they might interact or affect the water ecosystem as a whole. Changes within the overall ecosystem are now widely assessed using a combination of physical, chemical, and biological measurements that are compiled into a water quality index and assigned to quality classes, such as bad, poor, satisfactory, good, and very good. The European Union (EU) introduced this approach when it implemented the Water Framework Directive in 2000 (European Commission 2000), requiring member countries to reach both good chemical and good ecological status (European Commission 2005). Member countries share their water quality assessment and data through the WISE Water Framework Directive Database,6 which is visualized through the Water Framework Directive Quality Elements map system.7 The United Nations Sustainable Development Goal (SDG) indicator 6.3.2 “good ambient water quality” requires countries to monitor rivers, lakes, and groundwaters using five basic water quality parameters for rivers and lakes (pH, oxygen, EC, nitrogen [N], and phosphorus [P]), and three for groundwaters (pH, EC, and N). The results are compared with physical and chemical target values or standards for good quality (UN-Water 2018b) to determine whether the water bodies are indeed of good quality. In practice, many countries lack target values for ambient water quality, making it difficult to determine whether activities within water basins are causing a degradation in quality (UNEP 2021; UN-Water 2018a). Remote Sensing Satellite remote sensing data are now freely available and are being used increasingly for various aspects of water resources management, mostly for monitoring and modeling water quantity, sedimentation in reservoirs, algal blooms, and lake productivity (Murray et al. 2022). Progress is also being made in using optical data from remote sensing for monitoring an increasing number of water quality parameters (Larson et al. 2021; Yang, Kong et al. 2022). Compared with in situ data collection methods, remote sensing data have greater spatial coverage and require relatively less technical and human resources to collect and process (Murray et al. 2022). There are several sources of open-access satellite data and products that may be of use for water accounting, such as from the National Aeronautics and Space Administration (NASA),8 the United States Geological Survey (USGS),9 and the European Space Agency (ESA).10 NASA provides information to support agriculture and water management, such as reservoir area, elevation, storage capacity, evaporation rate, and evaporation volume for ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 9 selected reservoirs and lakes with a temporal resolution of eight days.11 The ESA has a suite of water products, including lake surface temperature, lake water quality, water bodies, and water level, which since 2020 have been available on a monthly basis for water bodies with a spatial resolution down to 60 meters.12 However, some aspects of the information provided are still being validated and the information on water quality is restricted to lakes in Africa and Europe. High spatial resolution satellite-based sensors often have low temporal resolution; the range is from half a day to sixteen days, depending on the sensor (Huang et al. 2018). It may be necessary to use data from more than one satellite to achieve optimal spatial and temporal coverage for water quantity and quality monitoring, which increases the complexity of data processing. In addition, the functional life span of a specific satellite is limited, though this is less of an issue for the latest satellites and sensors. The greatest hindrance to continuity in remote sensing data is cloud cover (Huang et al. 2018), which in some world regions is highly variable year-round. For each individual application of remote sensing data, including for water accounting, improvements in spatial and temporal resolution must be weighed against the decreased accuracy and precision when compared with in situ monitoring. Remote sensing of the spatial extent of surface water bodies can be used with water-level data to monitor changes in water storage in reservoirs (for example, Li, Qin et al. 2016; Zhang, Gao, and Naz 2014), even in small (0.5 square kilometers), remote reservoirs (Avisse et al. 2017) and to measure discharge in rivers (Huang et al. 2018). Temporal changes in surface area can also be used to monitor sedimentation in lakes and reservoirs by combining data on water spread (surface) area from remote sensing with known area and water level (for example, Ninija Merina et al. 2016; Wagh and Manekar 2021). Li, Ma et al. (2022) have reviewed various methods available for using satellite data for measuring surface water extent and suggest that it is still difficult for river networks and small rivers. Measuring discharge in rivers is particularly affected by cloud cover because it usually increases during flood events, leading to errors in discharge calculations (Huang et al. 2018). The application of remote sensing data to monitoring water quality is developing rapidly but is restricted to a few water quality parameters, mainly those that are optically active, such as chlorophyll a and turbidity at the surface of larger, slow-moving, or stationary water bodies (lakes, estuaries, and coastal areas; Adjovu et al. 2023; Yang, Kong et al. 2022). Broad spatial coverage at high frequency in lakes and reservoirs is available for key water quality parameters, such as chlorophyll a, turbidity, Secchi depth, and surface water temperature. It has also been achieved in small reservoirs (for example, 1 to 2 square kilometers), provided in situ data are available for validation (for example, Bresciania et al. 2019). The generation of water quality data by combining remote sensing with modeling is in the early stages of development for other water quality parameters, such as nutrients and chemical oxygen demand (COD). However, many other basic water quality characteristics for a wide range of water uses and returns are not yet available (Yang, Kong et al. 2022). ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 10 NOTES  1. Water use at different scales is classified as consumptive and nonconsumptive. Water leaving permanently from a local hydrologic unit (via evapotranspiration or as produced goods) is termed as consumptive use, whereas water returning to a local hydrological cycle is considered part of nonconsumptive use.  2. For more information about SWAT, see https://swat.tamu.edu.  3. For example guidelines, see https://www.waterquality.gov.au/anz-guidelines.  4. The term reservoir is used here to include lakes created by damming a river or stream (also referred to as dams) as well as lakes created by constructing a water basin (also referred to as embanked reservoirs).  5. For more information about the collection, see https://www.un-igrac.org/global​ -groundwater-information-system-ggis.  6. For more information on the database, see https://www.eea.europa.eu/en/datahub​ /datahubitem-view/dc1b1cdf-5fa0-4535-8c89-10cc051e00db.  7. To see the map, visit https://www.eea.europa.eu/data-and-maps/explore-interactive​ -maps/water-framework-directive-quality-elements.  8. For more information about NASA, see https://landsat.gsfc.nasa.gov.  9. For more information about USGS, see https://www.usgs.gov/landsat-missions/landsat​ -data-access. 10. For more information about ESA, see https://dataspace.copernicus.eu/ 11. For more information about these data, see https://www.earthdata.nasa.gov. 12. For more information about these products, see https://land.copernicus.eu/global​ /themes/water. ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 11 3. Integrated Water Quality and Water Quantity Accounting As described in section “Impacts on Water Quality”, water quality and water quantity are inextricably linked because the latter can affect the former by dilution and the addition of certain chemicals and substances with rainfall runoff. The measurement of the two should, therefore, be essential complementary activities, and activities that use and return water to the hydrological cycle should account for both because of potential implications for other users, as well as for the freshwater ecosystems within that catchment. Understanding the sources and magnitude of water quality change can help identify areas in which quantity and quality need integrated management and assist in allocating funds appropriately (figure 3.1). Figure 3.1. Water Accounting Should Incorporate Water Quality Monitoring to Support Efficient Integrated Water Resources Management Water accounting Quantity Water quality volume (for example, m3) Data monitoring manipulation Concentrations Time mass/volume (for example, day; (for example, mg/L) year) Pollutant loads mass/time (for example, g/day; kg/year) In t eg e nt rat e gem d wa a te r r es o u r c e m an Note: g = gram; kg = kilogram; L = liter; m3 = cubic meter; mg = milligram. ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 12 Chemical measurements made on grab samples are reported as concentrations (that is, the amount of substance per unit volume of water—for example, milligrams per liter). Concentrations are useful for indicating potential impact on the ecosystem or human health and are used in standards or guidelines for water quality for specific uses (table 2.1). However, concentrations at any location are influenced by the amount of water in the water body (discharge for rivers and streams; volume for lakes, reservoirs, and groundwaters), which in turn is influenced by rainfall and abstraction. River discharge is the amount of water flowing over a specified period (for example, cubic meters per second) and is influenced by rainfall and runoff, water inputs (for example, from effluent outfalls), and water abstraction and consumption. It is constant in a stretch of any given river regardless of width and depth (which can change substantially), provided there are no additional inputs via effluents or tributaries, or abstractions of water, in that stretch. Increased river discharge because of rainfall and runoff can lead to increased concentrations of substances from land-based sources. Continuous point sources of pollutants to a river, such as effluents from wastewater treatment plants and drainage canals, are diluted with increased river discharge, leading to lower concentrations in the river. Conversely, during periods of low river discharge, the concentrations in the receiving water body may be higher, even though the actual contribution to the river from the effluent remains the same. To express water quality measurements so that they represent the amount of each pollutant in the water body, they are calculated as loads. These are used to facilitate comparisons between one water body location and another and to indicate the amount of a pollutant discharged and fluxes of substances between water bodies or across boundaries. Loads are defined as the amount of substance in a given period of time (for example, kilograms per day). In rivers, they are calculated by the product of the measured concentration of the water quality parameter and the discharge (Meals, Richards, and Dressing 2013). In lakes, the measured concentration is converted to the total lake or reservoir volume for a given period. The measured concentration may not change, but the load may increase or decrease because of changes in the amount of water in the lake or flowing in the river. Water quality parameters expressed as loads enable relative apportionment between sources and areas or stretches of a water body, and because they are associated with the quantity of water, they are compatible with the concept of water accounting. The World Bank Environmental and Social Standard 3 (ESS3) recommends monitoring emission flows and emission loads as part of pollution prevention and management measures for the implementation of new projects that may affect water resources (World Bank 2018). Calculation of loads requires simultaneous measurement of flow (to calculate discharge) and concentrations at the same locations. Although this is often done for wastewater to check compliance with discharge standards, it is rarely done for rivers,1 lakes, and reservoirs. For these, alternative options may need to be considered, such as using flow data from the nearest gauging station within the same river network or by taking water level or flow measurements when collecting water quality samples. ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 13 Detailed information on measuring discharge and calculating loads is available in WMO (2010) and Meals, Richards, and Dressing (2013). Lake volume can either be approximated by estimating lake surface areas and multiplying it by average depth or by using a detailed bathymetric map of the lake basin created from depth readings at known positions to create depth contours. Bathymetry data are also available online for a very large number of lakes and reservoirs worldwide2 (Khazaei et al. 2022). NOTES 1. Many countries have well-established hydrological networks measuring river flow for managing water allocation and flood protection. These networks are often the responsibility of different departments or agencies from those responsible for monitoring water quality. Hence the colocation of monitoring stations for water quantity and water quality is not common. Water-level gauges in reservoirs are often placed close to the edge of the water body, which is rarely an appropriate location for taking water quality samples. 2. For more information about these data, see https://gee-community-catalog.org/projects​ /globathy/. ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 14 4. A Framework for Monitoring and Assessing Water Quality for Water Accounting This proposed framework (figure 4.1) is based on the principles for designing and imple- menting a water quality monitoring program for any specific purpose (Chapman, Meybeck, and Peters 2005). Following the framework will enable an assessment of water quality in relation to the quantity of water used by a defined project. It will assist in determining the relative contribution to water quality throughout the water system of different activities within the defined catchment and hence indicate locations that require management. The process of assessment is more effective if water quality guidelines exist in relation to water use and ambient (ecosystem) water quality, but in cases in which guidelines do not already exist, the framework can provide information that can assist in the development of relevant guidelines. Figure 4.1. A Framework for Water Quality Accounting STEPS 6–7 Explore STEPS 3–5 availability of existing STEP 2 Identify monitoring potential data for water STEP 8 STEP 9 Identify locations for quality and potential monitoring. flows at, or Gather quality Compare STEP 1 sources of close to, monitoring and quantity impact on water Select the required data and data with Decide scope quality on the monitoring relevant necessary water convert water (basin, defined water locations. guidelines or quality quality data to subbasin, resource. baseline monitoring individual activity, and station data. Find relevant parameters. parameter project). national or Consider loads, or Select international Decide on the implementing calculate water presentation guidelines for time frame for additional quality index. approach. water quality. calculating monitoring to water quality fulfill minimum accounts. data needs (parameters, locations, and time frame). Guidance for each step of the framework is given in this chapter, followed by examples of applying the framework to water quality accounting at the project and water basin levels using three hypothetical situations (boxes 4.1, 4.2, and 4.3). ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 15 Step 1. Define Scope and Scale of the Water Quality Accounts The scope of the intended water quality accounts outlines the expectations for the outputs and may include specific objectives. The scale defines the spatial and temporal extent of the requirements for water quality data and the associated monitoring activities. The scale should align as closely as possible with the water accounting scale and could range from an individual local project to a whole water basin, including rivers and lakes. In the former case, there may be one major activity, such as agriculture, that returns water to the water basin with different water quality characteristics than at the time of withdrawal. In the latter, there may be many multiple activities contributing to the quality of the water body in various locations. The greater the spatial scale and variety of activities within the scope of the project, the more complex the water quality monitoring requirements become. Step 2. Identify Sources of Impact on Water Quality Potential sources of impact on water quality will include all activities within a defined catchment area, including point and diffuse sources. The former could include domestic wastewater effluents and industrial discharges, surface drains from urban areas, livestock compounds, crop irrigation schemes, and any tributaries joining the water body. The latter could include surface runoff from agricultural and urban areas or small settlements without wastewater collection and treatment, as well as infiltration from agricultural activities to groundwater and subsequent groundwater discharge to rivers and lakes. Visual inspections, maps, satellite imagery, and abstraction and discharge license registers can help determine likely sources of impact on the catchment area. In the example of a typical river basin shown in figure 4.2, the main river has several tributaries that drain areas with various activities that might affect water quality. The river arises in a mineral-rich area where mining occurs and where the water quality may be naturally high in mineral content. Mining activities abstract and return water to the basin and can be a major source of water pollution. Downstream of the river in figure 4.2, but before the confluence with the tributary, there are forestry, agriculture, and small settlements that may make diffuse contributions to water quality through runoff, groundwater infiltration, and multiple small drains. The headwaters of the major tributary are dominated by forestry and agricultural activities, but downstream there is an industrial plant with wastewater discharges to the river. Below the confluence there is a major urban development that would contribute wastewater discharges. The water quality at the river mouth is the result of the natural water quality of the river, modified by the impacts of the combination of all activities upstream. ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 16 Figure 4.2. A Hypothetical Water Basin Showing Potential Sources of Impact on Water Quality and Strategic Monitoring Locations to Facilitate Water Quality Accounting at River Basin Scale A Legend Monitoring station Potential sources of C water quality impacts: Effluent flow Industrial operation Mining operation Arable farming F Pastoral farming Forest plantation B Urban dwelling E G H J D Note: The letters in the figure denote the sampling and data collecting locations. It is useful during this step to find relevant water quality guidelines or target values that will provide a basis for determining which water quality parameters to select in step 4 and against which an assessment of water quality can be made at each monitoring location in the catchment (step 8). In the absence of guidelines for ambient (natural or ecosystem) water quality, a background station in the headwaters of the catchment, such as station D in figure 4.2, can be used. If national water quality guidelines do not exist, guidelines from other countries or organizations can be used until suitable guidelines can be developed. Step 3. Select Locations for the Collection of Water Quality Data The assessment of observed water quality changes in a river from upstream to downstream should consider those that occur naturally as it picks up materials from erosion and runoff from different geological formations in the catchment. For the purposes of this framework, it is assumed that natural changes are usually minimal compared with the changes in water quality because of human activities. ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 17 Ideally, monitoring locations should facilitate water quality data collection above and below major abstractions and returns to the water body, including from groundwater. This allows an assessment of change in water quality because of a particular activity. Practically, this is often not possible at basin scale because the number and range of activities that may be using and returning water to the hydrological cycle would require substantial monitoring resources. Instead of collecting data from all abstraction and return points into the main river—and allowing for diffuse inputs—monitoring locations can be selected strategically within the main river and its tributaries to provide indications of water quality arising from the aggregated inputs upstream of each location. They should provide data on both water quality and quantity. If flow or discharge information is not available at each, it should be available from other locations within the basin that record the changes in flow between confluences with major tributaries, thus facilitating the conversion of water quality data as concentrations into loads. Obtaining monitoring data from water users may reduce or eliminate the need for a monitoring station within the water body itself. Activities that abstract and monitor water quality before use are effectively monitoring the water quality resulting from the combined activities upstream of the abstraction point. Determining the water quality of known effluent discharges is relatively straightforward (and sometimes legally required) by sampling the actual effluent at the point of discharge. However, few utilities or agencies responsible for the effluent discharges measure the quality of the receiving water body downstream of their specific discharges. Provided water quality and quantity data are available for the receiving water body, the impact of the effluent discharge on water quality may be modeled (for example, Yang, Wei et al. 2022; Young and Muneer 2019). For water quality accounting at the project level, the number of locations required to collect water quality and quantity data may be few and easily identified. Principally, these would be in the water body just upstream of the abstraction point, or the water in the abstraction pipe or channel just after it is abstracted and just downstream of the return point or likely area of runoff. If it is not possible to monitor water quality in the receiving water body, the drainage can be monitored and the water quality of the receiving water body can be modeled. In figure 4.2, monitoring locations A (main tributary), C, and D (main river) are used to measure background or natural water quality across the basin. Location B, situated below the confluence of the two branches of the river in the subbasin, is included to indicate the aggregated water quality arising from all activities in the two arms of the river upstream and any changes from the water quality at location A. Locations C and D also help establish whether there are significant differences in natural water quality in different areas of the catchment, perhaps arising from the geology. Location E enables an assessment of the impact of the mining on the river by comparing water quality at locations D and E. Location F assesses the water quality of the two subcatchments upstream, including the combined effects from mining and the forestry plantation. The influence of these two activities may differ and their individual impacts may be assessed with specific water quality parameters (see step 4). ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 18 Location G integrates the water quality for all activities upstream, but when compared with F, it could provide a measure of the impact of the urban settlement and its effluent. Location H assesses water quality in the main river downstream of the confluence with the main tributary. This location integrates the effects on water quality from all aforementioned activities and indicates water quality before the major urban development at the river mouth. The impact of the urban development is assessed by comparing monitoring station J at the river mouth before it enters the sea or lake (or crosses a boundary in the case of a transboundary river) with location H. The final monitoring station, J, also represents the water quality arising from all aggregated activities within the basin. Step 4. Select Water Quality Parameters Whether accounting for water quality at the project or basin scale, it is necessary to ensure that the data gathered reflect potential impacts from all relevant activities within the catchment. Many potential water quality parameters can be included in any water quality monitoring program. The greater the number, the more resources that are needed for in situ measurements, sampling, laboratory analysis, and data handling. The selection of parameters needs to be considered carefully to ensure the desired information is collected without unnecessary financial outlay. Whether gathering data from existing networks or establishing a new network, basic parameters that characterize the water body (for example, oxygen concentration and electrical conductivity [EC]) or that may have an influence on other parameters (such as pH and temperature) should be included. Additional parameters that are measured to check for compliance with water use requirements (table 2.1) or impact assessment after water is returned should also be included. Information on activities and emissions in the water basin already gathered during step 2 will assist with selecting relevant parameters to include in the water quality data gathering. Examples of parameters for different activities within the water basin are given in table 4.1. Table 4.1. Examples of Monitoring Parameters and Sampling Frequency for Surface Waters for Various Water Use and Impact Sources That May Be Included in Water Quality Accounts Arable and livestock Ambient quality agriculture Domestic/urban Industrialb Usec Impact Use Impact Use Impact Use Impact Frequency of sampling a C B A/B A/B A A/B A A Basic parameters Temperature ✓✓ ✓✓ d d d d ✓ ✓ pH ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ Dissolved oxygen ✓✓ ✓ ✓✓ ✓ ✓✓ ✓ ✓✓ (Continued) ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 19 Table 4.1. Examples of Monitoring Parameters and Sampling Frequency for Surface Waters for Various Water Use and Impact Sources That May Be Included in Water Quality Accounts (Continued) Arable and livestock Ambient quality agriculture Domestic/urban Industrialb Usec Impact Use Impact Use Impact Use Impact Frequency of sampling a C B A/B A/B A A/B A A BOD ✓✓ ✓✓ ✓✓ ✓ ✓✓ ✓ e ✓✓f EC/TDS ✓ ✓✓ ✓✓ ✓ ✓ ✓✓ ✓✓ Suspended solids ✓ ✓✓ ✓✓ ✓✓ ✓ ✓✓ ✓✓ Chlorophyll ag ✓ ✓ ✓ ✓ Nutrients Nitrogen (nitrate and/or ✓ ✓ ✓✓ ✓✓ ✓✓ ✓ organic nitrogen) Ammonia-N ✓✓ ✓ ✓✓ ✓✓ ✓ Total phosphorus ✓ ✓✓ ✓✓ Phosphate ✓ ✓ Additional parameters Sodium ✓✓ ✓ ✓ Chloride ✓ ✓ ✓✓ ✓✓ ✓ ✓ ✓✓ Fecal coliforms ✓✓ ✓ ✓✓ ✓✓ ✓✓ 4 ✓4 Pesticides ✓ ✓ ✓ Metals h ✓ ✓ ✓ ✓✓ ✓ Organic micropollutants i ✓ ✓ ✓ ✓ Note: For information on groundwater monitoring, please see text. Based on Chapman and Kimstach (1996). ✓ = relevant; ✓✓ = highly relevant; BOD = biochemical oxygen demand; EC = electrical conductivity; N = nitrogen; TDS = total dissolved solids. a. The frequency of measurement is dependent on the associated risk to the user or receiving water body, together with the known or anticipated variability in concentrations. A = high frequency (daily or weekly) or continuous measurements; B = seasonal or monthly measurements; C = annual measurements. b. Many parameters are industry specific—for example, fecal coliforms for food industry, metals for mining and heavy industry, organic micropollutants for the pharmaceutical sector. c. Use for ambient quality refers to aquatic life and fisheries. d. Temperature is often measured by default with other measurements. e. Organic matter may be measured as total organic carbon. f. Only relevant for certain industries, such as food processing and dairy products. g. Mainly for lakes and reservoirs. h. Specific metals may be monitored where they are of concern—for example, mercury, arsenic, and lead for protection of human health; copper, zinc, lead, and so on for mining impact. i. Mostly important for drinking water sources and irrigation, including groundwater use where there is risk of contamination, and for discharges from certain industrial activities, such as the pharmaceutical sector. Step 5. Decide Time Frame and Frequency of Sampling Water accounting may be done over different time frames, such as months or years, depending on the reason for its use (Vardon et al. 2023); hence it will be necessary to obtain representative water quality data for similar time frames. The temporal frequency with which monitoring data are collected may be prescribed by guidelines, but if not, it should be based on the anticipated or known variability in the water quality and the reason ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 20 for monitoring. Variability can range from hours—for example, at the surface of nutrient-rich lakes or in domestic wastewaters—to decades in deep aquifers. The frequency of monitoring should enable the calculation of an average value with low variability for each parameter. This often means monthly or, at a minimum, seasonal sampling. Table 4.1 indicates the likely frequency for data collection in relation to some common uses and discharges. Most water quality monitoring is done by taking grab samples or making in situ measurements at intervals throughout the year. To minimize variability, grab samples should be taken at the same time of day on each occasion and, for annual sampling, at the same time of year. The data obtained from repeated measurements can be averaged to match the water accounting time frame, but the deviation around the average values should be noted because it could have a significant effect on interpretation of the results. If the frequency of monitoring for water quality is less than optimal, it could lead to wide margins of error in the water quality accounts that could be improved only by increasing the frequency of water quality monitoring. In the worst-case scenario, monitoring may be done only once a year. In this case, to compare results from one year to the next, it is important the monitoring event take place at the same time of year each year. In some situations, water quality is monitored continuously or with a very high frequency of measurements to account for all events that may affect quality over a given period, such as extreme rainfall events or droughts. On rare occasions, this might coincide with automatic gauging stations continuously recording data for river discharge computations. High frequency or continuous monitoring is usually done only for special purposes (such as calibrating remote sensing data), highly sensitive water uses (such as drinking water sources or industrial abstractions), or short-term projects because of relatively high technical and financial resource requirements. Step 6. Explore Sources of Existing Monitoring Data Before embarking on the design and implementation of a monitoring program to collect data specifically for water quality accounts, potential sources of water quality and quantity data that may be already available should be investigated, including the precise sampling locations, the frequency of monitoring, the parameters being monitored, and whether the data are readily accessible. Depending on the level of accuracy that is acceptable, existing water quality data may be available from national monitoring networks, water utilities, public and private users, and global databases. Water flow or river discharge data may need to be obtained from different sources, and the quality and quantity monitoring stations may not coincide adequately. There is immense variability in access, suitability, and usability of data in water quality databases (Larson et al. 2021). In addition, the most recent data may not be available, other than in summarized form. If the summarized data are provided in the form of mean concentrations over a time frame that matches the accounting framework (for example, annual means), they may be adequate. Obtaining water quality data from private sector effluent discharges and relevant monitoring locations in the water body downstream of ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 21 activities and emissions is often more difficult because such data may be commercially sensitive. To report on Sustainable Development Goal (SDG) indicator 6.3.2 for water quality, countries need to have a monitoring network for basic physical and chemical parameters in all major water bodies (UN-Water 2018b). This could be a source of useful data for water quality accounting in the future as national networks are established and expanded. However, there is huge variability in the density of active monitoring stations worldwide and the frequency with which data are gathered (UNEP 2021; UN-Water 2018a), and the raw data are not always publicly available because countries are required to submit their calculated indicator results only to the United Nations (UN). Several organizations are attempting to bring together water quality data from regions or countries worldwide and to make it freely available online, such as the United Nations Environment Programme (UNEP) global database GEMstat,1 the European Environment Agency Waterbase,2 and the Water Quality Portal of the National Water Quality Monitoring Council of the United States.3 GeoAquaWatch has also compiled a water quality database inventory.4 Other sources of water quality data that may be useful include citizen monitoring networks (Hegarty et al. 2021; Thornhill et al. 2019; Yevenes, Pereira, and Bermudez 2022) and remote sensing activities (Yang, Kong et al. 2022). Citizen monitoring data for water quality is usually based on a few parameters with limited accuracy but often with a high density of data collection for any given water basin. Such data are also often shared on public data platforms, such as FreshWater Watch.5 Step 7. Consider Implementing a Monitoring Program to Fill Data Gaps The overview given in chapter 2 can be used to gauge the complexity and possible resource requirements for any additional or new monitoring activities. Implementing a completely new monitoring program specifically for water quality accounting is probably technically and financially feasible only for small-scale projects. A strategic approach would be to supplement the existing monitoring activities of national agencies, research projects, and so on, but this would still involve considerable resources for field collection of samples and laboratory analysis. If the accounts are based on basic water quality parameters only, a citizen monitoring program conducted four times a year would be a suitable option for a water basin if citizens receive adequate training and support. However, discharge data would also be needed to calculate loads. Simple techniques for estimating discharge are available for citizen use (for example, UNEP 2023b), but for safety reasons, these would be possible only in shallow water bodies. Guidance on how to plan and implement water quality monitoring programs for surface water and groundwater are available in Bartram and Ballance (1996); Chapman (1996); ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 22 Chapman, Meybeck, and Peters (2005); Ravenscroft and Lytton (2022a); and UNEP (2022, 2023a). A review of different approaches taken is available in Behmel et al. (2016). Step 8. Assemble Water Quality and Quantity Data Some of the data identified as necessary for water quality accounts for water bodies may be available from existing sources. These will have been originally gathered to meet the objectives of the primary users, with their own expectations for comparability and compatibility. The reliability and suitability for use in water quality accounts must be checked because poor-quality data can lead to incorrect conclusions and potentially inappropriate management actions. When all the data are gathered, the loads for each selected parameter need to be calculated for each location included in the accounts and presented in an informative way that is appropriate for users of the information. In its simplest form, this would involve multiplying an annual average concentration for a given water quality parameter in milligrams per liter by the total volume of the water storage basin in cubic meters, or by the annual average discharge in cubic meters per second for the monitoring location in a river or pipeline, together with a conversion factor that depends on the time frame of the calculated load. For example, for annual loads: Lake load (kg/yr) = annual average concentration (mg/L) × 10–3 × lake volume (m3) River load (kg/yr) = annual average concentration (mg/L) × annual average discharge (m3/s) × 31.536 In cases in which the water quality accounts focus on only a few parameters, the results for each can be presented individually. If many parameters are involved, it may be necessary to focus on those that show the most significant changes through the water basin or to consider using a suitable water quality index that aggregates the information into a water quality score. Index values facilitate comparison from one location to another and could be useful for water quality accounting. They are often used to simplify reporting of water quality data to a wide audience, including nonscientists. The index assimilates measurements for specific parameters, with a weighting factor for each parameter that reflects its relative importance (Uddin, Nash, and Olbert 2021). There are many different water quality indexes, most of which have been tailored for specific uses. Before deciding to use a particular index for water accounting, it would need to be tested for suitability for different water quality accounting scenarios (DESA 2012). Step 9. Assess and Present Water Quality Accounting Data The mode of assessment and presentation of the data are related to the scale and complexity of the accounting project. The simplest approach is to compare the loads for each parameter at each monitoring location or to compare the water quality index values of the quality of the water abstracted and the quality of the water body immediately downstream of the return flow. If a suitable downstream monitoring location is not available ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 23 for lakes and groundwaters, the effect of the activity would need to be assessed based on the difference between abstraction quality and return water quality—one that does not indicate the impact on the water resource but may provide data for which the quality of the receiving water body can be modeled. In cases in which guidelines exist, the values for monitored parameters can be compared with the guideline or target values, bearing in mind that they are usually given as concentrations rather than loads (for example, figure 4.3, panel a). In the absence of guidelines, loads at each location are compared with an upstream or background monitoring location (figure 4.3, panel b). Ideally, the presentation of the data should be simple and easily interpreted by a nontechnical audience. For example, graphs can provide percent change from the background or guideline values rather than actual loads, as in figure 4.3. When combined with a map, the relative impact of different and multiple activities in the catchment can also be visualized (figure 4.3). Figure 4.3. Sample Visualization of Difference in Water Quality Parameter Values at Monitoring Stations throughout a River Basin, Using Guideline Values and an Upstream Station as Comparators a. Compared with guideline values 900 A Legend Monitoring station 800 Potential sources of C water quality impacts: Effluent flow 700 Industrial operation Mining operation Percent difference from guideline value Arable farming 600 F Pastoral farming Forest plantation B Urban dwelling 500 E G 400 H J D 300 200 100 0 A B C D E F G H J Monitoring station Conductivity Nitrate–N Fecal coliforms BOD Iron (Continued) ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 24 Figure 4.3. Sample Visualization of Difference in Water Quality Parameter Values at Monitoring Stations throughout a River Basin, Using Guideline Values and an Upstream Station as Comparators (Continued) b. Compared with the background water quality at initial station, station A (percent difference) A 25 60 20 50 40 15 C 30 10 20 5 10 900 0 0 800 Fe itr ity ol N s D n Fe itr ity ol N s D n 700 rm rm Iro Iro BO BO – – N iv N iv ca ate ca ate ifo ifo ct ct 600 du du lc lc n n 500 Co Co 400 F 300 200 100 0 B ity N s D n rm Iro BO e– tiv E ifo at uc itr ol nd lc N Co ca Fe G H J D 250 200 150 100 50 0 ity N s D n rm Iro BO e– tiv ifo at uc itr ol nd lc N Co ca Fe Note: BOD = biochemical oxygen demand; N = nitrogen. If a water quality index is used to assess the impact of combined activities on water quality at defined locations, the resulting categories of water quality—for example, ranging from bad to very good—can be color coded and added to a map as in figure 4.4, panel a. This can be further simplified to a schematic representation of the index categories for the flow paths that have been included in the assessment (figure 4.4, panel b). ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 25 Figure 4.4. Changes in Water Quality in a River Basin Using a Water Quality Index, by Monitoring Station and Flow Path b. Along flow paths in the a. Individual monitoring locations catchment assessment A Legend Legend Water quality Water quality accounting index: accounting index: C Very good Very good Good Good Satisfactory Satisfactory Poor Poor Bad Bad F E B G H J D ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 26 Box 4.1. Applying the Framework to a Simple Irrigation Project In the schematic representation of the project in figure B4.1.1, water is abstracted from groundwater and applied to an irrigated land area that is drained by a network of channels that collect the water and return it to the river downstream at a single discharge point. Scope and Scale In this example, the scope and scale encompass a single irrigation project and its impact on a section of the river and its underlying aquifer. Figure B4.1.1. A Hypothetical Irrigation Scheme Using Groundwater and Returning Flows via a Drainage Ditch and Infiltration to an Adjacent River A B C D Note: Potential locations for gathering water quality data for water quality accounting are indicated in a circle. Sources of Impact on the Water Resource In addition to the single discharge of the drainage network, water infiltrates through the soil to groundwater, which provides base flow to the river. The project therefore has potential impacts on the adjacent river from both point and diffuse sources and on the groundwater from infiltration. (Continued) ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 27 Box 4.1. Applying the Framework to a Simple Irrigation Project (Continued) Sampling and Data Collection Locations The amount of water that is abstracted for irrigation is monitored at point A, together with the water quality before its distribution to the irrigation network, to ensure it is fit for use according to the applicable guidelines. These measurements also represent the concentrations of relevant water quality parameters in the groundwater and can be used to monitor the changes to groundwater quality that may arise from infiltration from the irrigation scheme over time. They can also be used to calculate the loads of the same parameters going into the irrigation network. The water quality and associated loads of the river upstream of the irrigation scheme require a monitoring station for both quality and quantity at point C. The impact on the river from the point and diffuse flows to the river from the irrigation scheme are measured at point D using the same water quality parameters as for C. Discharge also needs to be measured at D because it may be affected by the return flows from the irrigation drains, which could affect the calculation of loads for the relevant parameters. The quantity and quality of the drainage from the scheme is measured at the discharge point B before entering the river and converted to loads to indicate a potential change in water quality when compared with abstraction point A and with the receiving water at C. Measuring water quality in groundwater flow would not normally be carried out for such a small- scale project unless there are existing wells upstream and downstream of the irrigation scheme. An experienced hydrogeologist would be needed to interpret the data. Point D would represent all, if any, additional diffuse and point source inputs to the river along both banks bordering this irrigation scheme. The likelihood of significant inputs (discharges) can be checked with a visual inspection of the riverbanks, but this would require considerable monitoring effort. Selection of Water Quality Parameters In the project-scale scenario, the only obvious potential impact on water quality for that stretch of river is the irrigation scheme. In this situation, basic parameters (see table 4.1) are measured at the abstraction point of the irrigation scheme to assess the natural water quality before abstraction together with additional parameters specified in applicable irrigation use guidelines—for example, sodium and chloride (table 2.1). Although the basic parameters will give an indication of changes in the river water quality arising from irrigation drainage and infiltration (table B4.1.1), they could be affected by runoff from the opposite side of the river. However, the sodium and chloride measurements are unlikely to be affected by diffuse inputs from the opposite side (unless there are irrigation schemes there) and will reflect the impacts of the irrigation project under consideration. Time Frame and Frequency of Sampling As groundwater quality remains stable for long periods of time, water quality at the abstraction point needs to be measured only once a year. The water quality of the drainage water will vary according to seasonal differences in runoff, cultivation practices, fertilizer, and pesticide use (Continued) ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 28 Box 4.1. Applying the Framework to a Simple Irrigation Project (Continued) and thus requires at least weekly monitoring. The water quality of the river must be monitored at least once a month to capture natural seasonal variations and the impacts of the irrigation scheme (table B4.1.1). Table B4.1.1. Potential Water Quality Monitoring Points and the Associated Parameters and Frequency of Monitoring for Figure B4.1.1 Monitoring station Purpose Parametersa Frequency A. Groundwater Requirement for Basic parameters for Annual abstraction point irrigation; groundwater agricultural use quality B. Drainage channel Quality of irrigation Agricultural impact Weekly just before discharge return flows to river C. River upstream of Background surface Ambient quality use Monthly irrigation scheme water quality D. River downstream of Impact of drainage Agricultural impact Monthly irrigation scheme and and runoff from drainage discharge irrigation scheme a. See table 4.1 for suggested parameters. Sources of Existing Data and the Need for New Monitoring Activities For an individual project, it is unlikely that there will be existing sources of water quality data unless there are local or national monitoring stations upstream and/or downstream of the irrigation area that may provide quantity and quality data for locations C and D. Therefore, it may be necessary to begin new monitoring at these locations. Impacts on the river’s ecosystem could be assessed using a biological index validated for local or national use, rather than physical and chemical measurements. If the local hydrogeology is known, it may be possible to obtain groundwater quality data from a local abstraction well or borehole that is monitored for other reasons. Data Assessment and Presentation Temporal changes in groundwater quality over time, including possible impacts of infiltration from irrigation, can be assessed from concentrations at point A (table B4.1.1). Spatial and temporal changes in water quality in the river catchment associated with the irrigation scheme are obtained by comparing loads at points C and D. Compliance with guidelines for irrigation use and potential impact on receiving water bodies is obtained from values for the relevant parameters at points A and D. Simple-column graphs (for example, figure 4.3 for points C and D that include a time dimension on the X-axis can be used to illustrate the change in water quality in the river over time for individual parameter loads and for point A for groundwater. ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 29 Box 4.2. Applying the Framework at Basin Scale This example depicts many activities within a river basin, all of which use water from the river and/or the associated aquifer and return water as direct discharges or diffuse sources, including infiltration to groundwater (figure B4.2.1). Scope and Scale The scenario presented in figure B4.2.1 covers a river basin (or a subbasin of a large river basin) where there is a need to ascertain the relative impact of different activities on the water body to support catchment-scale management. Figure B4.2.1. A Hypothetical Example of a River Basin with Different Activities That Use and Return Water to the Basin, Together with Potential Locations for Gathering Water Quality and Quantity Data Potential monitoring points: Use-related Discharge Ambient quality A1 D1 U1 U2 D2 U4 U3 A2 D3 U5 A5 A4 A3 Note: The letters with numbers in the figure denote the sampling and data collecting points. Sources of Impact on the Water Resource The principal activities in the catchment are agriculture (including forestry), industry, and rural and urban development. Industry, an irrigation scheme, and rural and urban settlements all abstract, use, and return water to the river along its length, potentially affecting river water (Continued) ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 30 Box 4.2. Applying the Framework at Basin Scale (Continued) quantity and quality. A second irrigation scheme abstracts groundwater, but return flows are by infiltration to groundwater. Other agricultural activities also contribute to impacts associated with infiltration and diffuse runoff at several locations. Sampling and Data Collection Locations The quality of water in the river will change in relation to the activities as it travels downstream. At a minimum, monitoring stations are needed for background quality (A1) and to assess the integrated impacts of all activities above the urban development (A4) and the additional impacts on ambient quality from urban runoff and wastewater (A5). The quality of the groundwater and any potential impacts from infiltration from activities within the catchment should be measured upstream in the groundwater flow path (A2) and downstream in the region where the groundwater discharges to the river (A3). Water quality in relation to designated water uses should be monitored at abstraction points U1 for industry, U2 and U5 for domestic use, and U3 and U4 for irrigation. To monitor whether wastewater discharges are compliant with standards or guidelines and to assess their potential impacts on the river, monitoring stations are needed at D1 for industry, D2 for irrigation return flows, and D3 for urban wastewater. Selection of Water Quality Parameters The complexity of activities within the basin require data for parameters indicating ambient water quality and relevant to their impact. This is because activities downstream could affect the natural concentrations measured in the river at A1. Most monitoring locations measure the integrated impact of various activities, but to quantify the impact of each, activity-specific parameters must be considered—for example, biochemical oxygen demand (BOD), fecal coliforms, and selected heavy metals and organic compounds. Agriculture may lead to an increase in nitrogen and phosphorus levels from fertilizer use, and human settlements and agriculture may lead to an increase in BOD and fecal coliforms or other fecal markers (Hagedorn, Blanch, and Harwood 2011) from runoff and wastewater discharges. Industry can cause emissions of specific heavy metals and organic micropollutants, which would be less common in return flows from agricultural activities. In cases in which guidelines or standards exist for specific activities, monitoring parameters and frequency of measurement are specified. Time Frame and Frequency of Sampling The variability in river flow because of seasonal rainfall, combined with the seasonal nature of some activities in the catchment (such as fertilizer and pesticide application) mean that water quality and quantity measurements would need to be made over a full year, and preferably repeated for several years. Table B4.2.1 suggests how relevant parameters can be selected together with the optimal frequency for data collection. Associated flow and discharge data will also be necessary for each monitoring location. (Continued) ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 31 Box 4.2. Applying the Framework at Basin Scale (Continued) Table B4.2.1. Potential Monitoring Stations and the Associated Water Quality Parameters and Frequency of Monitoring for Water Accounting in the Scenario Given in Figure B4.2.1 Monitoring Station Purpose Parametersa Frequency A1 Unimpacted natural/background Basic parameters and Annual average river water quality nutrients of four quarterly samples A2 Background groundwater quality pH, EC, nitrate, chloride, Annually fecal coliforms A3 Impacts on groundwater quality pH, EC, nitrate, Annually from infiltration chloride, fecal coliforms (pesticides and organic micropollutants) A4 Impacts on river water quality Basic plus industrial Monthly from point and diffuse sources impact plus agricultural upstream, including infiltration impact via groundwater A5 Integrated impacts of upstream Ambient quality impact Minimum point and diffuse sources quarterly (industry, forestry, livestock, rural settlements, irrigation, urban area) U1 Requirements for use; Basic parameters; Continuous or background river water quality industrial use-related hourly U2 Requirements for use; integrated Domestic/urban Minimum impacts of upstream point and and agricultural use weekly for use diffuse sources (industry, forestry, requirements; industrial parameters livestock) and agricultural impact parameters U3 Requirements for agricultural use Basic parameters for Annually agricultural use plus sodium, chloride, fecal coliforms U4 Requirements for agricultural use; Basic plus agricultural Monthly integrated impacts of upstream use plus nutrients point and diffuse sources (industry, forestry, livestock, rural settlements, irrigation) U5 Requirements for domestic/ Basic plus domestic use Minimum daily urban use; integrated impacts plus nutrients of upstream point and diffuse sources (industry, forestry, livestock, rural settlements, irrigation) (Continued) (Continued) ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 32 Box 4.2. Applying the Framework at Basin Scale (Continued) Table B4.2.1. Potential Monitoring Stations and the Associated Water Quality Parameters and Frequency of Monitoring for Water Accounting in the Scenario Given in Figure B4.2.1 (Continued) Monitoring Station Purpose Parametersa Frequency D1 Discharge quality compliance Industrial impact Daily D2 Drainage water quality Agricultural impact Weekly D3 Urban wastewater discharge Domestic/urban impact Continuous— compliance daily Note: a. See table 4.1 for suggested parameters. EC = electrical conductivity. Sources of Existing Data and the Need for New Monitoring Activities There are various possibilities for collecting existing quality and quantity data at use-related (U1–U5) and discharge (D1, D2, D3, A5) monitoring points for parameters that are included in the relevant guidelines (table B4.2.1). Data may be available from the individual utilities or from the local authority responsible for enforcing guidelines. The catchment and aquifer may be included in national water quality and quantity monitoring programs, and the nearest national monitoring locations may substitute for monitoring points A1, A4, and A5. Contaminants, such as heavy metals and organic micropollutants, are often measured infrequently in ambient waters because of the high complexity and cost of analysis. However, relevant data may be available from commercial activities that, as part of their operational license, measure contaminants in the receiving water body. Therefore, unless additional monitoring can be implemented to support this water quality assessment scenario, it may be necessary to base the assessment on basic parameters and nutrients only, with pH, electrical conductivity (EC), nitrogen, and phosphorus being the most useful at basin scale. Data Assessment and Presentation The difference in water quality at groundwater stations A2, U3, and A3 reflect the impact of livestock (difference between A2 and U3) and livestock and irrigation combined (difference between A2 and A3) on groundwater. The loads for individual parameters at abstraction point U2 may be used to reflect water quality resulting from industry, forestry, and livestock farming upstream, whereas the loads at abstraction point A4 will reflect the combined impacts of industry, rural settlements, and diffuse agricultural inputs from runoff. Station U5 reflects all activities upstream, including the impact of the irrigation drainage. The difference in water quality between U2 and U5 will specifically highlight changes in water quality arising from both irrigation schemes. Water quality in the river and the aquifer could be presented for each station as changes in loads or as percentage variation for each parameter from background values at A1 (for example, figure 4.3). If a suitable water quality index is available, it would enable a simple visualization of changes in quality within the catchment (for example, figure 4.4). ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 33 Box 4.3. Applying the Framework to a Water Storage Reservoir In the scenario presented in figure B4.3.1, a small river has been dammed to provide water for irrigation. Water is abstracted and distributed to agricultural land where drainage is collected and returned to the river below the dam. Scope and Scale This project encompasses the storage basin, its direct drainage area, and the wetlands and river below the dam. Figure B4.3.1. A Hypothetical Example of a Water Storage Basin Used for Irrigation, Together with Potential Locations for Gathering Water Quality and Quantity Data A1 R1 U1 R2 R3 R4 A2 D1 R5 U2 R6 A3 Note: The letters and numbers in the figure denote sampling and data collecting locations. Sources of Impact on the Water Resource The storage basin is fed by the river from upstream and by intermittent rainfall. Water is abstracted at two locations for one large and one small irrigation scheme. If the rate of abstraction exceeds natural inflows, the water level in the storage basin falls and the volume of available water for use and for release downstream will decrease. This could potentially affect downstream wetlands and the ecosystem of the river below the dam through dehydration and reduced nutrient inputs. (Continued) ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 34 Box 4.3. Applying the Framework to a Water Storage Reservoir (Continued) Drainage and runoff from irrigation and from the surrounding catchment enter the reservoir directly as surface flows or through infiltration and percolation to groundwater. The runoff may carry excess sediment, together with fertilizer and pesticide residues. If the water in the storage basin is not replenished adequately by inflows and outflows, it may be susceptible to accumulation of sediments that will decrease the water storage potential, nutrients that will lead to eutrophication, and other contaminants that make it less suitable for use. Sampling and Data Collection Locations As water is abstracted directly from the reservoir, the water quality within the reservoir needs to be measured to assess whether it meets guideline values for irrigation use. If the reservoir is shallow and the water well mixed by wind action and flow from inlet to outlet, a single monitoring location (U1) just below the surface near the center may be adequate for this. However, in deeper reservoirs, there may be differences in water quality between the surface layer and at depth caused by the growth of microscopic photosynthetic algae (phytoplankton) at the surface and settling of particulate material, including suspended solids, at depth. An additional monitoring station at U2 will allow assessment of vertical differences in water quality and provide information to determine the appropriate depth to abstract water to meet the necessary water quality guidelines for use. Monitoring locations R1 through R6 could be used instead of U1 and U2 if the reservoir receives a high load of suspended solids from the catchment or is large and suffers from water movements and/or thermal stratification, which affect water quality horizontally and vertically. The agricultural activities around the storage basin may affect both the reservoir water quality and the river downstream through runoff and return flows directly to the river. Therefore, in addition to the monitoring stations within, it is necessary to have water quality monitoring stations in the river above (A1) and below (A2 and A3) the reservoir to assess whether both water bodies are meeting the basic water quality guidelines for ambient water and aquatic life. The irrigation network drainage should be monitored at D1 before joining the river to check for compliance with guidelines for agricultural impacts and to determine the likely impacts on the downstream wetlands. Selection of Water Quality Parameters To determine the impact of water storage on the river, the water quantity and quality entering and leaving at points A1 and A2, respectively, need to be measured. The key parameters for the storage basin are those necessary for irrigation water use and for use and impact on ambient water quality and aquatic life (table 4.1). Phosphorus is a key driver of nutrient enrichment in lakes and reservoirs, the consequences of which lead to high densities of aquatic plants and planktonic algae that affect the potential use of the water. The growth of algae in the water column is monitored with the green photosynthetic pigment, chlorophyll a, or a simple Secchi disc.1 If sedimentation of the reservoir is a major concern and it is infeasible to carry out frequent depth profiles, it is helpful to include suspended solids in the routine water quality monitoring in the inlet, in the outlet, and within the basin. This will (Continued) ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 35 Box 4.3. Applying the Framework to a Water Storage Reservoir (Continued) facilitate assessment of the amount of suspended material being deposited on the bottom of the reservoir. The parameters measured in the reservoir, together with any additional requirements for impact from agricultural use, should also be measured at discharge point D1 (see table B4.3.1). Table B4.3.1. Potential Water Quality Monitoring Points and the Associated Parameters and Frequency of Monitoring for Water Accounting in the Scenario Given in Figure B4.3.1 Monitoring Station Purpose Parametersa Frequency A1. River upstream of Background surface Basic parameters and Monthly reservoir water quality and nutrients for ambient suspended solids and quality use plus total nutrients load into the phosphorus (excluding reservoir chlorophyll a) A2. Main river outflow Impacts of water Basic parameters and Monthly from reservoir storage and runoff from nutrients for ambient irrigation quality impact plus total phosphorus (excluding chlorophyll a) A3. River downstream Impact of drainage Basic parameters and Monthly or of reservoir and discharge from irrigation nutrients for ambient weekly if irrigation scheme scheme and agricultural quality suggested drainage discharge impacts plus additional by results parameters for from D1 agricultural impacts D1. Drainage channel Quality of irrigation Agricultural impact Weekly just before discharge return flows to river U1–U2. Just below Average water quality of Basic parameters Monthly the surface and just the whole storage basin; and nutrients for above the sediment suitability for irrigation ambient quality use in the center of the use; appropriate depth and impact, including basin for extraction of best chlorophyll a, plus water quality; potential additional parameters impact from diffuse for agricultural use and agricultural sources impact R1–R6. Just below the Horizontal and vertical Basic parameters and Weekly surface, just above variation in water quality nutrients for ambient the sediment and in the storage basin; quality use and impact, midwater depth in deposition of suspended including chlorophyll a the open water, close sediment and particularly to the main water suspended solids inflow, and in front of the dam Note: a. See table 4.1 for suggested parameters. (Continued) ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 36 Box 4.3. Applying the Framework to a Water Storage Reservoir (Continued) Time Frame and Frequency of Sampling If the frequency of monitoring is not prescribed by the relevant regulations, it may be necessary to take measurements weekly if there is high variability in the quality of the discharge. The relevant parameters for aquatic life in rivers should be measured at A1, A2, and A3 at monthly or quarterly intervals (table B4.3.1). Repeating measurements of depth annually over many years will allow assessment of changes in volume of the storage basin because of sedimentation. Sources of Existing Data and the Need for New Monitoring Activities Depending on the scale and range of uses of the water storage unit, quantity and quality monitoring data may be available from the managing utility or the local or national monitoring programs. The nearest national monitoring location may substitute for monitoring points A1 and A3, provided there are no major human activities in the catchment other than those associated with the reservoir. It is likely that a dedicated monitoring program would need to be established to facilitate appropriate management of the reservoir. If the water storage basin is large enough (more than 1 to 3 square kilometers), spatial and temporal information on water quality (chlorophyll a, turbidity, and surface temperature) and rate of sedimentation may be determined from remote sensing (see section “Remote Sensing”). Data Assessment and Presentation Calculating loads for a chosen parameter in the reservoir is done using the water volume at the time of measuring water quality. The impact of water storage on the river and the associated wetlands is assessed by comparing loads for key parameters at locations A1 and A2, and the additional impact of the irrigation scheme drainage is assessed by comparing locations A1 and A3. This can be done graphically. Comparing the monitoring results of the irrigation discharge at D1 with the water quality within the reservoir (U1) provides a direct indication of the change in water quality arising from irrigation use. Note 1. An approximate indication of the density of planktonic algae and other suspended particles that affect light penetration in the water column can be obtained using a simple Secchi disc, which is a flat, weighted disc painted in black and white quarters and attached to a graduated cord (UNEP 2023a). ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 37 NOTES 1. For more information on the GEMstat database, see https://gemstat.org/. 2. For more information on the Waterbase, see https://www.eea.europa.eu/en/datahub​ /datahubitem-view/fbf3717c-cd7b-4785-933a-d0cf510542e1. 3. For more information on the portal, see https://www.waterqualitydata.us/ 4. For more information on GeoAquaWatch, see https://www.geoaquawatch.org/water​ -quality-database-inventory/. 5. For more information on FreshWater Watch, see https://www.freshwaterwatch.org/pages​ /explore-our-data. ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 38 5. Conclusions Managing water resources cannot be achieved solely by accounting for the quantity of water used and returned to the hydrological cycle within a defined water basin. As water travels through a water basin, it is subject to fluctuations in quantity and quality caused by different activities within the basin. Each use of water relies on satisfactory water quality that ensures there is no risk to the user and the associated activities. The required quality can usually be defined by physical, chemical, and biological characteristics that are given in guidelines or standards for use. To ensure the water meets the necessary guidelines before use, it is monitored to determine concentrations or quality indicators and to compare the results with the guidelines. Every water body, and even different locations within a water body, have a natural water quality resulting from geological and climatological conditions in the water basin. In most situations, water that is abstracted and used is eventually returned, but with water quality that differs from that originally abstracted. This results in changes in the natural quality of the water bodies receiving the returned wastewater, which may have implications for the suitability of the water quality for subsequent downstream users. Accounting for water quality within a water basin should, therefore, involve monitoring water quality at an unimpacted location (usually an upstream site) and again just downstream of each potential source of impact on water quality to quantify the relative contribution of each activity to changes in water quality. As most water quality monitoring for many key parameters is based on measuring concentrations in grab samples taken at a specific location and time, sampling needs to be repeated, at least seasonally, to enable a time and/or spatial series to be averaged. Changes in the quantity of water at any point in a water basin can influence the concentrations of physical and chemical parameters. Therefore, to facilitate comparisons of water quality between different sections of a water body, or apportionment of different sources for particular parameters, water quantity (discharge or volume) should be combined with water quality data (concentrations) to give the amount or load of each parameter. The quantity and quality data should be collected from the same location wherever possible. There are many different physical and chemical parameters that can be measured and are included in different water quality guidelines. The cost and complexity of monitoring a wide range of parameters on a regular basis result in most monitoring programs selecting parameters that characterize the natural water quality (basic parameters), together with a limited number of others that are relevant to the specific use or return of water. Although there are many public and private entities monitoring water quality, many do not openly share the data. Thus, any attempt to account for water quality at basin scale is likely to require some additional monitoring. A framework is provided here to guide decisions on ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 39 the necessity for additional monitoring and the scope and scale of additional monitoring that may be necessary. In addition to traditional sampling and laboratory analysis of water samples, the rapid growth in citizen monitoring and remote sensing of water quality offer opportunities to supplement traditional sources of data for a limited, but expanding, range of parameters. ACCOUNTING FOR WATER QUALITY: INSIGHTS FOR OPERATIONAL TASK TEAMS 40 References Adjovu, G. E., H. Stephen, D. James, and S. Ahmad. 2023. “Overview of the Application of Remote Sensing in Effective Monitoring of Water Quality Parameters.” Remote Sensing 15 (7): 1938. doi.org/10.3390/rs15071938. Alcalde-Sanz, L., and B. M. 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