WORLD BANK TEOHNICAL PAPER NO. 463 Work in progress WTP463 for public discussion March 2000 Groundwater in Rural Development Facing the CiallevQges of Supply and Resource Sus{ainabi/ity Stephen Foster John Chilton Miarcus Moench Franklin Cardy Manuel Schiffler Recent World Bank Technical Papers No. 388 Sanjayan, Shen, and Jansen, Experiences with Integrated-Conservation Development Projects in Asia No. 389 International Commission on Irrigation and Drainage (ICID), Planning the Management, Operation, and Maintenance of Irrigation and Drainage Systems: A Guidefor the Preparation of Strategies and Manuals No. 390 Foster, Lawrence, and Morris, Groundwater in Urban Development: Assessing Management Needs and Formulating Policy Strategies No. 391 Lovei and Weiss, Jr., Environmental Management and Institutions in OECD Countries: Lessonsfrom Experience No. 392 Felker, Chaudhuri, Gyorgy, and Goldman, The Pharmaceutical Industry in India and Hungary: Policies, Institutions, and TechnoZogical Development No. 393 Mohan, ed., Bibliography of Publications: Africa Region, 1990-97 No. 394 Hill and Shields, Incentivesfor Joint Forest Management in India: Analytical Methods and Case Studies No. 395 Saleth and Dinar, Satisfying Urban Thirst: Water Supply Augmentation and Pricing Policy in Hyderabad City, India No. 396 Kikeri, Privatization and Labor: What Happens to Workers When Governments Divest? No. 397 Lovei, Phasing Out Leadfrom Gasoline: Worldwide Experience and Policy Implications No. 398 Ayres, Anderson, and Hanrahan, Setting Priorities for Environmental MAnagement: An Application to the Mining Sector in Bolivia No. 399 Kerf, Gray, Irwin, L6vesque, Taylor, and Klein, Concessionsfor Infrastructure: A Guide to Their Design and Award No. 401 Benson and Clay, The Impact of Drought on Sub-Saharan African Economies: A Preliminary Examination No. 402 Dinar, Mendelsohn, Evenson, Parikh, Sanghi, Kumar, McKinsey, and Lonergan, Measuring the Impact of Climate Change on Indian Agriculture No. 403 Welch and Fremond, The Case-by-Case Approach to Privatization: Techniques and Examples No. 404 Stephenson, Donnay, Frolova, Melnick, and Worzala, Improving Women's Health Services in the Russian Federation: Results of a Pilot Project No. 405 Onorato, Fox, and Strongman, World Bank Group Assistancefor Minerals Sector Development and Reform in Member Countries No. 406 Milazzo, Subsidies in World Fisheries: A Reexamination No. 407 Wiens and Guadagni, Designing Rulesfor Demand-Driven Rural Investment Funds: The Latin American Experience No. 408 Donovan and Frank, Soil Fertility Management in Sub-Saharan Africa No. 409 Heggie and Vickers, Commercial Management and Financing of Roads No. 410 Sayeg, Successful Conversion to Unleaded Gasoline in Thailand No. 411 Calvo, Optionsfor Managing and Financing Rural Transport Infrastructure No. 413 Langford, Forster, and Malcolm, Toward a Financially Sustainable Irrigation System: Lessonsfrom the State of Victoria, Australia, 1984-1994 No. 414 Salman and Boisson de Chazournes, International Watercourses: Enhancing Cooperation and Managing Conflict, Proceedings of a World Bank Seminar No. 415 Feitelson and Haddad, Identification of Joint Management Structuresfor Shared Aquifers: A Cooperative Palestinian-Israeli Effort No. 416 Miller and Reidinger, eds., Comprehensive River Basin Development: The Tennessee Valley Authority No. 417 Rutkowski, Welfare and the Labor Market in Poland: Social Policy during Economic Transition No. 418 Okidegbe and Associates, Agriculture Sector Programs: Sourcebook No. 420 Francis and others, Hard Lessons: Primary Schools, Community, and Social Capital in Nigeria No. 421 Gert Jan Bom, Robert Foster, Ebel Dijkstra, and Marja Tummers, Evaporative Air-Conditioning: Applications for Environmentally Friendly Cooling No. 422 Peter Quaak, Harrie Knoef, and Huber Stassen, Energyfrom Biomass: A Review of Combustion and Gasifica- tion Technologies No. 423 Energy Sector Unit, Europe and Central Asia Region, World Bank, Non-Payment in the Electricity Sector in Eastern Europe and the Former Soviet Union No. 424 Jaffee, ed., Southerni African Agribusiness: Gaining through Regional Collaboration (List continues on the inside back cover) WORLD BANK rECHNICAL PAPER NO. 463 Groundwvater in Rural Development Facing the Chaillenges of Supply and Resource Sustainability Stephen Foster John Chilton Marcus Moench Franklin Carc& Manuel Schiffter The World Bank Washington, D.C. Copyright © 2000 The International Bank for Reconstruction and Development/THE WORLD BANK 1818 H Street, N.W. Washington, D.C. 20433, U.S.A. All rights reserved Manufactured in the United States of America First printing March 2000 Technical Papers are published to communicate the results of the Bank's work to the development community with the least possible delay. The typescript of this paper therefore has not been prepared in accordance with the procedures appropriate to formal printed texts, and the World Bank accepts no responsibility for errors. Some sources cited in this paper may be informal documents that are not readily available. The findings, interpretations, and conclusions expressed in this paper are entirely those of the author(s) and should not be attributed in any manner to the World Bank, to its affiliated organizations, or to members of its Board of Executive Directors or the countries they represent. 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For permission to reprint individual articles or chapters, please fax your request with complete information to the Republication Department, Copyright Clearance Center, fax 978-750-4470. All other queries on rights and licenses should be addressed to the World Bank at the address above or faxed to 202-522-2422. ISBN: 0-8213-4703-9 ISSN: 0253-7494 Stephen Foster is assistant director of the British Geological Survey and visiting professor of hydrogeology at the University of London. John Chilton is principal hydrogeologist at the British Geological Survey. Marcus Moench is president of the Institute of Social and Environmental Transition. Franklin Cardy is senior water resources management specialist in the Africa Technical Family at the World Bank. Manuel Schiffler is an economist in the World Bank's Middle East and North Africa Region Sector Group. 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Protecting Groundwater Quality ............................................... 75 Nature of Diffuse Pollution Threat from Agriculture ............................................... 75 Processes Controlling Nitrate Leaching and Transport ................................................ 76 Risk of Pesticide Contamination ............................................... 77 Controlling the Leaching of Agrochemicals ................................................ 81 Pollution Hazard Assessment and Protection Strategy ............................................... 83 General Approach ............................................... 83 Mapping Aquifer Pollution Vulnerability ............................................... 85 Defining Groundwater Source Protection Areas ............................................... 87 Undertaking Wellhead Sanitary Surveys ............................................... 88 5. The Rural-Urban Interface: An Addendum ................................................ 90 Groundwater Resource Competition and Transfers ............................................... 90 Municipal Wellfield Protection Issues ............................................... 91 Urban Wastewater Reuse for Irrigation ............................................... 91 References ............................................... 94 Boxes Box 1: Groundwater Occurrence and Flow .9 Box 2: Village Water Supplies from the Weathered Crystalline Basement in Sub-Saharan Africa 15 Box 3: Cost Effectiveness of Groundwater Exploration for Livestock-Watering Boreholes in the Botswana Kalahari .20 Box 4: Developing Small-Scale Garden Irrigation Using Collector Wells in Zimbabwe .22 Box 5: Diagnosis of Borehole Deterioration and Rehabilitation Needs in the Indus Alluvial Basin of Pakistan .24 Box 6: Natural Contamination of Groundwater with Arsenic in Bangladesh .29 Box 7: Critical Role and Future Uncertainty of Groundwater in Rural India .45 Box 8: Capacity for Indirect Regulation of Groundwater Abstraction in Bangladesh .64 Box 9: Policy Options for Stabilizing the Groundwater Resource Situation in Mexico .70 Box 10: Jordan Mounts a Primarily Regulatory Offensive to Rationalize Aquifer Exploitation in Extremely Water-Scarce Region .71 Box 11: Leaching of Nitrate from Tropical Agricultural Soils to Groundwater .78 iv Box 12: Risk of Pesticide Leaching from Tropical Agricultural Soils .................................................. 80 Box 13: Groundwater Source Pollution Risk Evaluation and Management around Managua, Nicaragua .82 Box 14: Rural-Urban Competition and Conflict for Scarce Groundwater Resources in the Yemen Arab Republic .86 Box 15: Wastewater Reuse for Agricultural Irrigation in Central Mexico: Benefits, Problems and Solutions ............................................. 93 Figures Figure 1: General Scope, Organization and Application of Technical Paper ........................................ xiv Figure 2: General Trend of Groundwater Recharge Rates from Excess Rainfall and Irrigation with Climatic Type ....................................................4 Figure 3: Correlation between Land Use and Groundwater Nitrate Concentrations ................................5 Figure 4: Variation of Well Yields and Abstraction Requirementus for Different Types of Rural Groundwater Use ............................................................8 Figure 5: Variation of Groundwater Supply Development Options/Costs with Aquifer Type .............. 11 Figure 6: Analysis of Actual and Required Stakeholder Participation in Rural Groundwater Development for Agricultural Irrigation .12 Figure 7: Harmonizing Design of Rural Water Supply Wells with Hydrogeological Conditions in Weathered Basement Aquifers .18 Figure 8: Variation of Borehole Yield Predictability and Drought Security with Principal Hydrogeological Environments ................................................... 25 Figure 9: Major and Trace Elements in Groundwater and their H-ealth Significance ............................. 28 Figure 10: Progressive Deterioration in Operational Performance of a Production Borehole in a Heavily Abstracted Alluvial Aquifer .............................................................. 42 Figure I1: Dewatering of Groundwater Storage in the Tertiary Limestone of Southeastern Cyprus due to Intensive Uncontrolled Development for Agricultural Irrigation ............................................ 43 Figure 12: Historical Development of the Deccan Traps Groundwater System in Maharastra, India ..... 46 Figure 13: Measuring the Costs of Groundwater Abstraction ............................................................... 48 Figure 14: General Conceptual Framework for the Management and Protection of Groundwater Resources .50 Figure 15: Schematic Representation and Classification of Aquifer Recharge and Discharge Processes .54 Figure 16: Categorization of Aquifer Recharge in the more Arid Regions for Practical Groundwater Resource Evaluation and Development .55 Figure 17: Increasing Groundwater Recharge to the Shallcw Alluvial-Deltaic Aquifer of Bangladesh by Controlled Water Table Lowering .58 Figure 18: Organization Scheme for Use of Numerical Aquifer Modeling to Inform Groundwater Management Plans .58 Figure 19: Variation of Groundwater Resource Regulatiorn Requirement with Hydrogeologic Setting and Socioeconomic Circumstances .66 Figure 20: Groundwater Nitrate Concentrations in the Weathered Basement Aquifer of Rural Areas of Central Nigeria ................................................................ 84 Tables Table 1: Statistics on Agricultural Irrigation, Drainage, and Groundwater Use for Selected Nations .... 2 Table 2: Comparative Characteristics of Groundwater and Suriace Water Resources in Relation to Rural Development .................................................................3 Table 3: Characteristics of Principal Hydrogeological Systems ............................................................ 10 Table 4: Suitability of Geophysical Methods in Differen,t Hydrogeological Environments ................. 16 Table 5: General Summary of Drilling Methods and Constrainits for Waterwell Construction ............ 17 Table 6: Average Costs of Rural Water Supply Wells in Weathered Crystalline Basement Regions.. 18 v Table 7: Guidelines for Interpretation of Water Quality for Irrigation ......................................................... 30 Table 8: Key Factors in the Challenge of Groundwater Source Maintenance for Improved Efficiency and Useful Life .................................................. 31 Table 9: Analysis of Factors Reducing Well Efficiency and Useful Life .................................................. 33 Table 10: The "Integrated Approach" to Community Groundwater Supply Planning ................................ 38 Table 11: Consequences of Excessive Groundwater Abstraction .................................................. 41 Table 12: Susceptibility of Hydrogeological Environments to Adverse Side effects during Excessive Abstraction ................................................. 41 Table 13: Summary of Groundwater Resource-Management Functions ................................................. 53 Table 14: Principal Direct Techniques used for Groundwater Recharge Estimation ................................... 56 Table 15: Summary of Economic Methods Applied to Groundwater Valuation.. ........................................ 60 Table 16: Summary of Water-Quality Guidelines Related to Groundwater Contamination through Agricultural Cultivation ........................................................... 75 Table 17: Summary of the Relative Impact of Agronomic Factors on Groundwater Quality .................... 81 Table 18: Principal Hydrogeological Environments and their Associated Pollution Vulnerability .......... 87 Table 19: Definition of Aquifer Vulnerability Classes ........................................................... 88 Table 20: Systems of Scoring for Sanitary Risk and Confirming Fecal Pollution Hazard for Groundwater Sources .89 vi Foreword Groundwater has been the fundamental resource underpinning the rapid provision of more reliable, better quality, low-cost water supplies for the rural population in the developing world over the past 20 years or so. Concomitantly, many nations have witnessed an enormous increase in the exploitation of groundwater for agricultural irrigation. Access to groundwater is thus a major factor enabling rural populations to achieve food security, increase their productivity and move beyond subsistence. Whilst these developments have provided major benefits in termns of rural living standards and poverty alleviation, concerns are arising over certain issues, most notably the operational sustainability of individual water sources, the natural occurrence of groundwater of unacceptable quality in some areas, and, most importantly, widespread evidence of degradation of the resource base itself. The preparation of this paper, which was undertaken by a team, of widely experienced groundwater specialists, has been coordinated by the British Geological Survey and involved in-depth consultation with numerous World Bank staff. The work was financed by the World Eank and the (British) Department for International Development. It provides a systematic in-depth review of issues that have emerged in the 1990s and suggests the way forward towards more efficient and sustainable utilization of groundwater resources in rural development. The target audience includes senior staff of national governnnents responsible for provision of rural water supply and sanitation, for promoting agricultural development and for managing land and water resources, together with the staff of the international support agencies and nongovernmental organizations charged with providing financial and technical assistance in these areas. Numerous World Bank task managers have reported they are encountering serious groundwater overdraft and pollution problems with increasing fiequency, and have emphasized the lack of definitive informatiorn on effective ways to address such problems. The hope is that this paper will: - Raise their awareness of the constraints on and threats to sustainable use of groundwater for rural development * Provide them with a useful guide when considering new project proposals with a groundwater dimension * Persuade them of the urgent need for increased investmenit and more appropriate institutional arrangements for the sustainable management of groundwater resources. Ashok Subramanian S-enior Water Institutions Development Specialist The World Bank vii Abstract Groundwater is of major importance to rural development in many countries of the world. As a result of its widespread distribution, low development-cost and generally excellent quality, it has been the fundamental resource allowing the rapid development of improved domestic water supplies for the rural population and in many areas has also supported a major increase of highly-productive agricultural irrigation. Groundwater resources are thus vital for meeting an array of basic needs, from public health to poverty alleviation and economic development. As a result of the high rates of abstraction required for irrigation, however, in some areas there is significant concern about sustainability of the resource base, because of falling groundwater tables and near- irreversible aquifer deterioration through saline intrusion. There are also additional sustainability concerns as a result of the increasing incidence of groundwater pollution from over-intensive or inadequately managed agricultural cultivation practices. This paper is based on review of the evolving situation during the 1990s in a substantial number of developing nations. It aims to raise awareness of the key linkages between groundwater and rural development, and to identify appropriate technical and institutional approaches for improving the operational reliability of waterwells and the sustainability of groundwater resources as a whole. To achieve this will require recognition that hydrogeologic and socioeconomic diversity necessitates a flexibility of management response. The unifying concept of the paper is the definition of action to reduce the growth in groundwater abstraction and to constrain subsurface contaminant load, withlin a phased process of institutional development built upon sound technical evaluation and increasing stakeholder engagement. ix I~~~~~~~~~~~~~~~~~~~~~~~~~~ Acknowledgments The potential value of producing a World Bank Technical Paper on this subject was identified by John Briscoe (World Bank-Senior Water Adviser), following an internal review of the past 10-15 years of World Bank experience with projects on rural water supply and agriculural development with a significant groundwater-related component. This review was undertaken by Stephen Foster (British Geological Survey) and Franklin Cardy (World Bank-Africa Technical Department) during April-July 1998, having been instigated by the World Bank"s Water Resources Management: Themnatic Group, led at that time by Ashok Subramanian. He and Andrew Macoun (of the World Bank-MENA Region), who subsequently took over as coordinator of this work, are both thanked for their personal interest and valuable inputs to the production of the paper. The work has been encouraged by the interest of John 1Hodges and Ian Curtis of the (British) Department for International Development-Engineering Division. The Management Committee of the Thematic Group (Geoff Spencer, Theodore Herman, and Ashok Subramanian) is to be thanked for their continued interest and support. The authors wish to acknowledge the practical assistance of numerous World Bank staff in issue identification, data collection, policy discussion and editorial view, including Keith Pitman, Stephen Mink, John Shepherd, Lee Travers, Douglas Olson, David Grey, Salman Salman, Karin Kemper, Christopher Ward, Adel Bichara, and Ariel Dinar. The authors also wish to thank the following British Geological Survey colleagues for providing valuable data on groundwater in the context of the development of rural water supplies and agricultural irrigation: Adrian Lawrence, David Kinniburgh, Pauline Smedley, and Jeff Davies. The first author also acknowledges valuable discussions and written contributions on the general theme of this report with Dr Hans Wolter (UN-FAO-Director of Land and Water Development Division), Professor Ramon Llamas-Madurga (Universidad Complutense of Madrid, Spain), Ing Ruben Chavez-Guillen (Comision Nacional del Agua-Gerente de Aguas Subterraneas, Mexico), and Prof K. Palanisami of Tamil Nadu Agricultural University, India. Ing Ignacio Lopez-Cortijo (UN-FAO) provided assistance in abstracting data from the AQUASTAT system. Lastly a very special thank you to Theresa Blackwell and Gill Tyson for their major efforts in handling the presentational aspects of the document, through its various drafting stages. xi Executive Summary Sink in despair on the red parched earth, An aquifer that is almost always full, and then ye mnay reckon what water is worth. is almost as badly managed, Traverse the desert and then ye can tell, as one that is almost always empty. What treasures exist in the cool deep well. Elisa Cook David Burdon (poet: Southern Africa 19th Century) (hydrogeologist: Ireland 20' Century) The utilization of groundwater resources has facilitated the rapid, low-cost provision of more reliable, good quality, water supplies for the rural population across extensive areas of Asia, Africa and Latin America. While many key issues in this respect have been addressed, some persistent problems (such as improving the operational reliability of groundwater sources) and other ermerging concerns (such as the hazardous or unacceptable natural quality of certain groundwaters) require systematic attention. In many nations there has been a major increase in the use of groundwater for agricultural irrigation. This has not been restricted to semi-arid regions, but has also occunred in more humid areas, to provide a greater intensity, or more security, of cropping on existing cultivated land, rather than bringing new land into production. Moreover, there is increasing evidence that the use of groundwater can be an important factor in promoting increased irrigation efficiency and water productivitv. However, there are concerns about the operational reliability of irrigation wells. As a result of the much higher rates of abstraction required for irrigation, in some areas there is an even greater concern about the sustainability of the resource base itself, including falling groundwater tables, interference with downstream users and irreversible aquifer deterioration through saline intrasion and ground compaction. An additional issue is groundwater pollution from inadequately managed or over-intensive agricultural practices. The principal objectives of this paper are thus: * To highlight the major benefits of groundwater use in terms oi rural well-being and income, and raise awareness of the various important (but complex') linkages between groundwater and rural development * To provide balanced analyses of the factors influencing the reliability of individual groundwater supplies and the degradation of the overall groundwater resource * To identify appropriate technical and institutional approaches to the challenge of improving the operational reliability of waterwells and the resource sustainability of aquifers in the context of rural development. The organization of the paper is summarized in Figure 1, which serves as a general guide to its scope and application. It is important to appreciate that in areas where groundwater utilization is restricted to the level of domestic water supply and livestock watering, interest will be confined mainly to Chapters 1 and 2, and sometimes to Chapter 4. Chapter 1 (General Introduction) details the importance of groundwater for domestic and agricultural water supply, and introduces the key linkages between rural development and groundwater resources. A hierarchy of issues and concerns is defined, which ranges from the constructional adequacy and operational reliability of groundwater sources for both domestic and irrigation water supply to resource degradation issues arising out of the development of intensive irrigated agriculture. The degree of difficulty in managing xiii groundwater resources for rural development shows wide variation with environment and this chapter provides an introduction to hydrogeological diversity, whose appreciation is essential if the development process is to work with (rather than against) nature. It also identifies the diverse group of stakeholders in groundwater use for rural development and analyses the way in which they should be involved in the promotion, construction and operation of groundwater supply projects. Figure 1: General scope, organization and application of technical paper : _~~~I - Chapter Hierarchy of Issues, S ° Concerns and Issues 'ae EIII | GENERAL INTRODUCTION j GROUNDWATER SUPPLY: 1 DESIGN AND INTRODUCTION | | 1!~~~~~~~~~~~~~~~~~~~~~~~~~0 PLANNING * economic access to adequate 0 " DESIGN AND supply (quantity) (quality) 2 1 CONSTRUCTION * mitigating drought impacts OPERATION AND * technical problems MAINTENANCE * organization and cost recovery 0 GROUNDWATER RESOURCE | SUSTAINABILITY 0) REGULATION AND * technical diagnosis 131 ~~MANAGEMENT OF o management functionso 3 institutional arrangements ABSTRACTION * economic instruments PROTECTING * pollution hazard assessment GROUNDWATER * aquifer vulnerability mapping QUALITY * source protection strategy RURAL-URBAN INTERFACE (an addendum) L Chapter 2 (Groundwater Supply: Design and Operation) discusses the issues relating to the provision and operation of groundwater supplies for rural development, both at a small scale for domestic use and livestock watering, and where higher rates of water supply are of interest for piped water supply in rural towns and villages, and for intensive irrigated agriculture. Much progress was made in this context during the 1980s but there is still widespread need to ensure that: xiv * Well siting and design procedures benefit from being more closely correlated with aquifer * Hydraulic structure and from systematic hydrogeological evaluation of the security of supply during extended drought * Operational reliability of water supply sources is improved by community participation, initially through defining the required service level and subsequently through taking responsibility for both the physical and financial aspects of well maintenance * Natural hydrogeochemical controls on groundwater quality, and the hazard of encountering unacceptable quality for potable supply are appreciated; since these act as a given, constraining the siting, design and cost of new sources, they are dealt with in this chapter (rather than later under protecting groundwater from pollution). The key role of local water-user associations in improving inigatior-water allocation and distribution, and their potential in promoting cost-effective well maintenance, is also stressed. Groundwater management is among the most important, least recognized and highly complex of natural resource challenges facing society. Chapter 3 (Groundwater Resources Sustainability) is thus the core of the paper and argues that a new approach is widely required, putting emphasis on the value of groundwater resources and the need for proactive participatory management in areas where resources are subjected to heavy demand for irrigated agriculture. Among the key issues analyzed in detail are: * The historical context of much groundwater resource development which helps define major obstacles that have to be overcome * The key management functions, including the need for realistic hydrogeological evaluation of aquifer recharge, discharge and response to abstraction, strategic planning on the role, priorities and valuation of groundwater, definition and review of water rights allocation * The promotion of effective tiered institutional arrangernents and flexible management schemes, with user participation at the appropriate scale through aquiifer mranagement committees * The potential role and limitations of economic instruments (such as abstraction charges and water markets) in groundwater management, and the neecd to eliiminate progressively certain subsidies (especially on electrical energy for pumping) which can act as an incentive for excessive abstraction. A critical question in the definition of many aquifer managrement strategies will be the optimum role for groundwater storage. In many ways the vast natural storage of groundwater systems is their most valuable strategic asset. On the one hand important components of the economic and environmental value of groundwater (such as pumping costs, individual accessibility for the poor, sustaining some freshwater wetlands and dry weather stream flow) depend on the depth to water table and not on the volume in storage. On the other hand, in many situations groundwater storage is the only major source of freshwater in extended drought, and ways need to be found to exploit this asset whilst mitigating the impacts on groundwater level related services, in particular by adequate compensation of those dependent on shallow wells for water supply. A further issue discussed in some detail is the scope and constraints on undertaking the artificial recharge of aquifer storage. Chapter 4 (Protecting Groundwater Quality) summarizes the evidence of increasing degradation of groundwater quality and the threat to its potability due to leaching of nutrients and pesticides from agricultural soils, as well as the salinization of groundwater as a result of agricultural practices. The threat appears more severe and imminent in low-efficiency irrigated agriculture, and can arise regardless of the source of water supply involved. This subject, which is noit always well appreciated by the agricultural development sector, is reviewed in some detail. The management response proposed is to focus much needed pollution control measures in more vulnerable aquifer recharge areas of potable groundwater sources used for piped water supply. xv Overall, wide hydrogeologic and socioeconomic diversity represents a major challenge for groundwater resources management, and it is not possible to be highly prescriptive in this context. Nevertheless, diagnostic tools can be (and have been) identified to enable resource managers and project planners to characterize the key elements of common situations and define a more sustainable way forward. Although groundwater management and protection appear complex, the actual process of beginning to develop capabilities need not be. Furthermore, while strategies must ultimately reflect local conditions, the overall approach to strategy development can utilize common starting points. Where justified this might include immediate action to reduce the growth in groundwater abstraction and/or to constrain subsurface contaminant load within a phased process of institutional development built upon sound technical evaluation, raising public awareness and increasing stakeholder involvement. In many cases, entry points will exist in the form of specific regional concerns or local interest groups. They can be used to mobilize stakeholder participation, highlight policy issues and develop pilot activities. Proactive participatory management will represent a significant cost increment for groundwater development, but this may be a small price to pay for a secure source of reliable water supply in drought, compared to the cost of surface water supplies for irrigation. It is recognized that the distinction between rural and urban development is somewhat arbitrary; nevertheless it is considered valid given the project focus of this paper. Urban groundwater resource management issues have been systematically treated in World Bank Technical Paper 390 (Groundwater in Urban Development). As a corollary Chapter 5 deals with some special concerns about groundwater resources at the rural-urban interface and especially to three specific aspects: * Competition for groundwater resources between agricultural irrigation users and urban water supply companies * The fact that siting of urban groundwater sources in adjacent rural areas may lead to demands for constraint on local agriculture in the interest of protecting groundwater quality in wellfield capture areas * The benefits that can accrue from substituting urban wastewater for local groundwater as a source of irrigation water supply, and the potential impact on water quality in aquifers that can occur if this is not adequately evaluated and planned. xvi 1 GENERAL INTRO)DUCTION Importance of Groundwater Supply in Rural Developmnent Domestic and Livestock Water Supply Groundwater has been the fundamental resource allowing the economical and rapid development of more reliable, improved quality, water supplies for a large proportion of the rural population across extensive areas of Asia, Africa and Latin America (Clarke and others, 1996). This crucial and formidable task gained momentum during the IJN Drinking Water and Sanitation Decade of the 1980s and continues to this day. The successful development of groundwater has led to significant irnprovements in human health and the quality of life in innumerable village communities of Africa and Asia, in particular. Many areas with favorable hydrogeology now have cover,age of domestic waterwells for rural village populations. The major residual development challenges are: * To tackle areas with less favorable hydrogeological conditions • To address the need for improved maintenance and operational sustainability of systems already developed. In the African and Latin American context, waterwells have also been of primary importance in the development of extensive livestock rearing in the semiarid regions. 'This aspect of agricultural development, however, has not been without its problems. In some areas there has been a tendency in wetter years to overstock in relation to land capacity during drought, resulting in subsequent heavy over-grazing and soil erosion in the vicinity of livestock-watering boreholes. Agricultural Irrigation During the last 10 to 20 years, there has been an enormous increase in the utilization of groundwater resources for agricultural irrigation, because of their widespread distribution and low development cost (Clarke and others, 1996). Groundwater has been at the heart cf the "green revolution" in agriculture across many Asian nations, and has permitted cultivation of high-value crops in various arid regions. Groundwater has also provided security against drought in areas where irrigation with surface water resources has been deficient during dry years. Moreover, the use of groundwater can be a major factor in promoting increased irrigation water-use efficiency and agricultural water productivity. This is because the energy costs associated with pumping are often higher than for surface water, providing an incentive to increase water conservation or to irrigate high-value crops, because groundwater sources are generally far more reliable during drought and because groundwater is sediment-free, readily allowing the introduction of water-efficient irrigation technology. Furthermore, the scale of groundwater development has facilitat:ed tubewell operation at the level of individual farmers or small collective groups, and this has offered greater flexibility of irrigation scheduling and much simpler distribution systems, resulting in generallly higher crop yields and irrigation water I General Introduction Groundwater in Rural Development productivity. Moreover, it has allowed responsibility for maintenance to be devolved. Such developments, can, however, result in: * Poor standards of irrigation well construction, which may comprornise water-source reliability in unfavorable hydrogeological conditions * The proliferation of waterwells which may lead to groundwater resource competition and storage overdraft, in situations where resources are significantly constrained by limited recharge. Groundwater Use Statistics Comprehensive statistics on the use of groundwater for agricultural irrigation are not available, but Table 1 gives an idea of its relative importance in a range of countries. One very important example is the current situation in India (World Bank, 1998). Here groundwater supplies directly about 80 percent of domestic water use in rural areas, together with more than 50 percent of that used for irrigated agriculture. The resource is thus of major importance as a source of drinking water and food security and is vital for meeting an array of basic needs from public health, poverty alleviation to economic development (Kahnert and Levin, 1993). The sustainability of the resource base is thus a critical issue in these contexts. Table 1: Statistics on agricultural irrigation, drainage and groundwater use for selected nations Irrigation Origin of water Irrigated area water use Drained area Country Year (kha) (mml3a) Sw(%/1) gw (No) (%o) Bangladesh 1993/95 3,750 12,600 31 69 40 China 1990/93 48,000 407,800 78 18 42 India 1990/93 50,100 460,000 41 53 12 Indonesia 1990196 4,430 69,200 99 1 ? Malaysia 1994/95 360 9,700 92 8 ? Nepal 1994/95 1,130 28,700 74 12 ? Pakistan 1990/91 14,330 150,600 66 34 36 Mexico 1995/97 5,370 61,200 63 27 ? Peru 1992/95 1,200 16,300 89 11 ? Argentina 1994/95 1,550 18,600 75 25 ? Kenya 1990/92 70 1,570 99 1 ? South Africa 1991/94 1,270 9,580 82 18 ? Zambia 1992/94 50 5,320 95 5 ? Egypt 1992/93 3,250 45,400 96 4 90 Tunisia 1990/91 310 2,730 39 61 52 Morocco 1989/91 1,090 10,180 69 31 ? Mali 1987/89 80 1,320 97 3 7 Jordan 1991/93 60 740 40 55 6 Iran 1993/93 7,260 64,160 50 50 1 Saudi Arabia 1992/93 1,610 15,310 3 96 3 Syria 1992/93 640 13,600 40 60 43 Note: Although the best available, these figures do not distinguish supplementary from near-continuous irrigation, or the type and value of crops grown from different water sources, and they also do not adequately represent conjunctive, use which is known to be practiced in numerous areas. Source: From UN-FAO-LWDD AquaStat database. Groundwater Resource Characteristics The characteristics of groundwater utilization for rural development are compared with those of conventional surface water schemes in Table 2. These factors explain not only the major development of groundwater 2 General Introduction Groundwater in Rural Development resources for rural development in many nations, but also the illogical approach to groundwater resource development in some others. The interaction of groundwater and surface water resources greatly favors their conjunctive use in irrigated agriculture, since this is capable of: * Providing greatly increased water supply security during dry seasons and drought episodes * enabling tail-end users in irrigation-canal command areas to inmprove water-service levels * Reducing evaporation losses from surface water impoundments by allowing their storage to be exploited earlier in the dry season * Improving drainage and reducing the possibility of rejected groundwater recharge in the wet season. Table 2: Comparative characteristics of groundwater and surface water resources in relation to rural development Characteristics Groundwater resources and aquifers Surface watercourses and reservoirs Hydrogeological * Storage volumes very large small-to-moderate * Resource areas relatively unrestricted restricted to watercourses and canals * Flow velocities very low moderate-to-high for watercourses * Residence times generally decades/centuries mainly weeks/months * drought propensity generally low generally high * evaporative losses low and localized high for reservoirs * resource evaluation high cost, significant uncertainty lower cost, but still uncertainties * abstraction impacts delayed and dispersed immediate * natural quality generally (but not always) high very variable * pollution vulnerability variable natural protection largely unprotected * pollutant persistence often extreme mainly transitory Socioeconomic * public perception mythical, unpredictable aesthetic, predictable (but implies loss of valuable land) * development cost modest very high (unless also for power generation) * development risk less than often perceived more than often assumed style of development mixed public and private finance, larger publicly financed and operated individual or community operated schemes * project promotion time short-to-moderate long * irrigation efficiency frequently high generally low Note: Various constrasting, and inadequately appreciated, features are revealecd. Source: Llamas, 1998) Effects of Agricultural Development on Groundwater Recharge and Drainage Modifications The importation of surface water and introduction of irrigated agriculture causes major modifications to the soil moisture regime, and generally results in substantially increased infiltration (Foster and Chilton, 1998). Not all soil infiltration results in groundwater recharge to deep aquifers, but excess irrigation is a major 3 General Introduction Groundwater in Rural Development source of groundwater recharge and under arid climatic conditions may reinitiate deep infiltration in areas where little if any has occurred in decades, centuries, or even millennia. The above also applies when local groundwater is the major source of irrigation except that in this case no net increase of groundwater resources will occur (only recirculation). Irrigation efficiency is defined as: (water taken up by irrigated plants)/(water supplied for irrigation). Of the fraction of applied water not taken up by the irrigated crop: * Some will be lost directly through (non-beneficial) evaporation or evapotranspiration * Some will become surface runoff either directly or indirectly via the soil drainage system or perched water tables (together termed "irrigation return flow") * Some will infiltrate into the unsaturated zone and recharge the main groundwater system below. In more arid situations (and in the absence of regional aquifer flow systems) excess irrigation is likely to be the dominant component of local aquifer recharge (Foster and Chilton, 1998) (Figure 2). The corollary is that if irrigation efficiency is increased groundwater recharge decreases, but this obvious fact is often overlooked in catchment-level water management planning. Figure 2: General trend of groundwater recharge rates from excess rainfall and irrigation with climatic type 2000 POTIINIAL CONIBIDOWVN FROM IRRIGATION LOSSES 0 c 500 . . . > s (varying with proportion of .~50 irrigated land, irrigation efficiency and subsoil profile) 200 100 0 E 50 20 HOT HUMID ITEMPERATURE EMI-ARID I AI ~2000 500 200 Note: This refers to well-drained soils overlying an unconfined aquifer and illustrates the major significance of irrigation losses for groundwater recharge in the more arid climates; the quality of this recharge, however, can in some circumstances be relatively saline. 4 General Introduction Groundwater in Rural Development Groundwater recharge from irrigated agriculture occurs by three distinct mechanisms: * Directly from unlined (and in some cases lined but leaky) primary and secondary canals, and even from some agricultural drains * Directly from irrigation water distribution systems below this 'level * Through irrigation in excess of plant requirements at field level. The potential for groundwater recharge will vary across and along irrigation areas, with higher rates from unlined canals on alluvial terraces, for example, and with groundwater discharge (rather than recharge) to the agricultural drainage systems in some low-lying areas. Where groundwater is the major (or only) source of irrigation water, the areas will normally be well drained. In very low-lying areas, or where the soil profile is generally cf low permeability (or has some low permeability horizons), rising water level or shallow perched water bodies are likely to develop. This ultimately leads to soil water-logging and salinization through direct evaporation, unless drainage is introduced to remove excess groundwater. Although this issue is oultside the scope of the present paper, it should be noted that groundwater salinization caused by this process is more extensive worldwide than that resulting from saline intrusion of aquifers due to inadequate resource mnanagement. Quality Impacts The fact that an important proportion of groundwater recharge in nmany areas originates as infiltration on agricultural land (especially where irrigation is practiced) also has a negative side - namely the risk of excessive leaching of nutrients and pesticides (Foster and Chilton, 1998). A close correlation between agricultural development and groundwater quality in underlying, shallow phreatic aquifers is widely observed (Figure 3). Figure 3: Correlation between land use and groundwater nitrate concentrations WHO drinking water guideline concentrations MIXED FARMING O _ AREAS INTENSIVE CASH- * z CROP CULTIVATION o20 150- o100 - - - - X- 0 0-- ° 50- - -- _ __ __ 0 _ a z COCONUT GROVES/ | CZ °- IUN O >0[CULTIVATED LAND c <0 20 40 60 80 100 120 140 160 chloride concentration (mg Cl/I) Note: The data shown refer to a thin shallow coastal limestone aquifer in northwestern Sri Lanka that reacts quickly to land-use change; the conversion of land to intensive irrigated "cash crop" cultivation has clearly had a major impact on groundwater quality 5 General Introduction Groundwater in Rural Development In practice, the rates of leaching will vary widely with cropping regime, soil type and hydrogeological conditions (aquifer vulnerability), with irrigation water efficiency and the continuity of crop coverage being especially critical factors. In certain monocultures on permeable soil profiles, especially those involving soil ploughing and fallow periods, the leaching losses may be severe. The principal impact is on the potability of groundwater for rural water supply, at farm, village and small town level. It is rare that the level of contamination is such that it can prejudice the use of groundwater for agricultural irrigation itself, except in a few cases of exceptionally severe nutrient and/or pesticide leaching adjacent to an area of cultivation of highly sensitive crops. Transpiration of water by plants concentrates dissolved salts in the root zone, and periodically there may be considerable leaching of salts from irrigated agricultural soils. In extreme cases where major groundwater recirculation occurs, salt fractionation can cause a troublesome quality impact. The situation is further aggravated where excess irrigation gives rise to leaching of salts held in arid zone soil profiles. Such processes may be just as widespread as the problems of saline intrusion due to overabstraction of groundwater, but less commonly recognized. Thus in areas of major development of irrigated agriculture from groundwater in arid climates, it is important to evaluate both the water and the salt balance. Key Groundwater Development and Management Issues The process of identifying key issues can be usefully initiated from a "development project focus" by adopting the following subdivision: i Internal factors within projects (those that can be controlled by the project and which determine its cost effectiveness and operational reliability) * External impacts of projects (side effects caused by projects on third parties and the environment). Beyond the scope of individual projects is a range of emerging resource management issues at aquifer level which require a much broader approach. Thus overall, three major groups of issues have been identified. These are analyzed in detail sequentially in the chapters that follow, but the underlying concepts involved are introduced briefly below. Economical Access and Operational Reliability of Supply Hydrogeological factors are dominant in determining whether a groundwater source can be constructed at tolerable cost to provide a supply of initially adequate yield, acceptable natural quality and drought reliability. Operational reliability relates to the longer-term sustainability of yield for the individual groundwater source (as opposed to total yield of the aquifer system) and is influenced by its design, operation and maintenance, together with adequate financial resources and administrative arrangements for this purpose. Aquifer Depletion-Related Effects This concept recognizes that all aquifer systems are to varying degree susceptible to such effects as interference between production wells, diminution of groundwater discharge affecting downstream riverflows, freshwater wetlands or brackish water lagoons, the encroachment of saline water through lateral intrusion or up-coning, and in certain cases land subsidence. These may threaten the sustainability of the resource base itself (Reisner and Bates, 1990) and the agricultural food production dependent upon it, although current estimates of the potential impact are not based on sound concepts or data (Postel, 1999). Sooner or later, and to varying degrees, groundwater abstraction needs to be controlled to avoid or mitigate the more serious of these effects. 6 General Introduction Groundwater in Rural Development Diffuse Groundwater Pollution The development of agriculture, whether rainfed or irrigated (and regardless of water source), can result in excessive leaching of agrochemicals to aquifers and lead to long-term deterioration of groundwater quality (in relation to use for potable water supply), especially where intensive monocultures are sustained through large applications of fertilizers and pesticides. The issues of aquifer pollution control and groundwater source protection thus need to be addressed. Variation of Issues with Scale of Groundwater Exploitation The question of scale of groundwater exploitation is important, since the extent to which projects have external impacts will vary widely between the extremes: * Small-scale domestic and livestock water supply * Large-scale agricultural irrigation schemes. Within this range, there was traditionally a distinction between small-scale garden cultivation and large-scale (institutionally promoted) irrigation schemes. In reality today there is a near-continuum between the two, with much successful groundwater irrigation occurring at the intermediate scale of multi small-well development since this allows: * Private (individual or group) operation of each well, avoiding some of the past problems of centralized operation * Small water distribution networks, avoiding the high leakage losses of many larger schemes. The most logical subdivision of groundwater development scale is thus now that summarized in figure 4, which is based essentially on the distinction between manual and motorized pumping. Resource overexploitation problems relate mainly to grounclwater supply for agricultural irrigation, since in the case of domestic/livestock water supplies resource sustainability issues are only significant for shallow (low-storage) aquifers in arid regions during extreme drought. Variation of Issues with Hydrogeological Regime The (natural) hydrogeological environment exerts the dominant control over the availability of groundwater resources for any type of rural development and the corresponding water supply development costs and difficulties. Geodiversity, in general, and hydrogeological variability in particular, are still poorly appreciated by many working in water/land resource management and in promotinig rural development projects. There is need that they recognize intrinsic constraints on groundwater development, and try to work with nature rather than against it, when identifying and promoting groundwater developmient schemes for the benefit of the rural community. Moreover, hydrogeological setting influences the scale of potential side effects of large-scale land development for agricultural cultivation since it determines: * the susceptibility of groundwater resource exploitation to negative consequences * the vulnerability of groundwater resources to pollution from agricultural land-use practices. 7 General Introduction Groundwater in Rural Development Figure 4: Variation of well yields and abstraction requirements for different types of rural groundwater use WELL YIELD (1/s) (assumes appropriate construction) 0.1 0.2 0;5 1 2 5 1,0 20 50 100 DOMESTIC & LIVESTOCK WATER SUPPLYmany(uno _exclusively) GARDEN IRRIGATION and-pump PRIVATE MULTI-WELL IRRIGATION SCHEMES AND PIPED VILLAGE awy ooie WATER SUPPLIES p ng plant (diesel engines or LARGE-SCALE COMMUNAL eeti-rdpwr IRRIGATION SCHEMES 2 10 20 100 200 1000 2000 TYPICAL ABSTRACTION RATES (m3/d) (allowing for intermittent pumping) overall and typical ranges indicated Note: Those which do not require motorized pumping plant do not threaten groundwater resource sustainability and thus need only mninimal regulation, appropriate hydrogeological investigation and engineering design protocols A general indication of the occurrence and flow of groundwater in major regional aquifers, and its variation with climatic regime, is given in box 1 (Foster, 1993). A highly simplified classification and description of the more common hydrogeological environments in the developing world is given as table 3. In reality, certain other factors must also be considered, such as the degree of aquifer confinement, the prevailing climatic regime, the constraints on groundwater recharge, and the natural aquifer discharge. The hydrogeological environment imposes constraints on the access to groundwater for rural development. Such constraints can be absolute in terms of large-scale groundwater development for irrigation in certain environments. There is a clear correlation between groundwater supply development costs and hydrogeological complexity (that is decreasing hydrogeological predictability), which varies widely with hydrogeological environment; figure 5 gives an indication of the relative position. Analysis of Issues from Stakeholder Perspectives From an early stage in rural development projects, it is important that the full range of stakeholders is specifically identified, and their interests in groundwater sketched out in a general way. The actual and potential role of these various stakeholders in groundwater project development, system operation and/or maintenance, and even in resource/environmental management, is a recurrent and developing theme of this paper. 8 General Introduction Groundwater in Rural Development BOX 1: Groundwater Occurrence and Flow * All freshwater found underground must have had a contamination incident will normally take a long time source of recharge. This is normally rainfall, but can to affect deep water-supply boreholes, a fact which also sometimes be seepage from rivers, lakes or canals. has major policy implications for pollution control. nfiltrating water accumulates above an imperneable bed (aquidclude) forming an underground reservoir * Aquifers in recharge areas are generally uncornined (aquifer). The strata above the aquifer water table, but elsewhere, and normally at greater depths, through which vertical infiltration occurs are termed groundwvater is often found to be confined by virtually the vadose (or unsaturated) zone. Aquifers tend to impermeable layers. In this instance, when wells are fill up until water reaches the land surface, where it first drilled, water is encountered under pressure and flows from the ground as springs or seepages at some rises on its own, sometinmes even to the ground surface. locations, the discharge providing the dry-weather The piezometric head/surface is the level to which the flow (or baseflow) of lowland rivers. The aquifer water fiom a given aquifer will rise. In some cases, becomes saturated to a level where outflow matches the overlying strata are less permeable but do not recharge. From the management viewpoint, note that compleLely prevent the vertical passage of water, and most continuous groundwater abstraction, for the aquilfer is then said to be semi-confined, below an consumptive use in (or export from) the catchment, aquitarcl. Such semi-confined aquifers can still receive will have some impact on dry-weather riverflows, the vertical recharge, but at much lower rates, which will discharge of captured springs and/or groundwater be significant in terms of the long-term sustainability levels in wetlands. of groundwater abstraction. * The aquifer flow regime, storage capacity and yield (b) semni-arid regions productivity depend upon the hydraulic characteristics of the porous and/or fractured media involved, and aquifer recharge area var widely with the geology. / , ~~~~~~~minor perennial * Groundwater systems are dynarmic with groundwater ' h continuously in slow motion from zones of recharge to areas of discharge. Tens, hundreds or even thousands of years may elapse, since flow rates do not normally exceed a few metres per day and can be as low as a metre per year. It will thus be apparent that a surface Inset: Typical groundwaterflow systems MILLENNIA (Foster & lirata,1988) ......_ intermittent (a) humid regions aquifer discharge area major perennial recharge area discharge area l unsaturated zonI artesian fdischarge area discharge area t i ' KEY -t discharge ¶%. groundwater piezometric l / pF i, * st\\< YFA ; g t I --- level (with maximum and l' t \ ~ ,| minimum levels in the non- confined aquifer) CEN-WRIES I LLENNI (low-permeability strata) aquiclude (virtually impermeable strata) 9 General Introduction Groundwater in Rural Development Table 3: Characteristics of principal hydrogeological systems Hydro- geological Type of environment deposits Mode offormation Distribution and thickness MajorAlluvial Gravels, sands, unconsolidated detritus deposited in both areally extensive and of Formations silts and clays riverbeds and deltas, primary significant thickness (a) inland porosity/permeability usually high (b) coastal (MAF) Inter-Montane Basins pebbles, formed by in-filling of faulted troughs less extensive than most (a) colluvial gravels, sands in mountain regions and can include alluvial and coastal plain (b) volcanic and clays; lake deposits; recent lavas and sediments but can be very (IMB) sometimes pyroclasts also usually highly porous thick with lavas and (but older volcanic deposits more pyroclastics consolidated) Consolidated (a) sandstones compacted marine or continental difficult to generalize, but can Sedimentary Aquifers (sometimes deposits; degree of consolidation form extensive aquifers of (CSA) also stratiform increases with depth/age and reduces substantial thickness basalts) primary porosity/permeability but with significant fracturing (b) limestones derived from shell fragments/reef difficult to generalize, but can detritus; compacted and often with form extensive aquifers of karstic fissures enlarged by solution substantial thickness Recent Coastal limestones and coral limestones and skeletal detritus limited extension, fringing Limestones (RCL) calcareous often only loosely cemented; porosity/ coastlines or islands sands permeability very high Weathered Crystalline grading from deep weathering of very extensive, but aquifers of Basement (WCB) weathered rock igneous/metamorphic rocks usually small capacity and normally to residual producing mantle of moderate restricted to upper 20 m or clays porosity/low permeability less Note: The five broad groups of aquifers commonly occurring in tropical latitudes of the developing world are shown; the Major Alluvial Formations and Weathered Crystalline Basement are by far the most extensive in geographical distribution. The main groups of stakeholders directly involved with groundwater in rural areas, and the normnal (traditional) timing of their involvement in relation to project evolution is given in Figure 6. The timescale can be from 1 to 5 decades, as a result of the considerable inertia of the development process, coupled with the large storage/slow response of aquifer systems to changes in groundwater abstraction and in contaminant load. A complexity of interests is revealed and there is obvious need for water users and energy suppliers to be involved from the project promotion stage, and for development agencies to continue their involvement throughout (not just up to project commissioning), if sustainability issues are to be fully addressed. It is necessary also to look beyond those stakeholders benefiting directly from groundwater development to other groups who become incidentally involved or impacted by the activity (Figure 6). The role of government is particularly difficult to generalize and present, but the trend (which needs to be encouraged) is for governments to play more of a facilitating role than a developmental one. However, in reality some parts of national and provincial government inevitably will be involved with the promotion and construction side 10 General Introduction Groundwater in Rural Development of development, while other arms of the same government are involved in resource regulation and environmental protection. These activities can come into conflict. The scale and timing of benefits and disbenefits to the various stakeholder groups are also indicated in a general way. It is important that the perspective of these stakeholder groups on groundwater, in terms of resource accessibility, ownership, limitations, linkages and externalities is fully appreciated. There is also a need for public awareness to bring the various groups of stakeholders on to a "common playing field" so that they can participate more equally in groundwater project development, and to develop a consensus among them for action on groundwater resource management. Figure 5: Variation of groundwater supply development options/costs with aquifer type co) 0 0~~~~~~~~~~~~~~~~~~1 DOMESTIC/LIVESTOCK T SMALL-SCALE r LARGE-SCALE |SUPPLY IRRIGATION IRRIGATION yield of individual wells (I/s) MAF Major Alluvial Formations IMB Inter-Montane Basins CSA Consolidated Sedimentary Aquifers RCL Recent Coastal Limestones WCB Weathered Crystalline Basement Note: This much generalized figure indicates both the overall yield limitations for rural development of some aquifer types and the general way that costs escalate if exploration for larger supplies is embarked u:pon 11 General Introduction Groundwater in Rural Development Figure 6: Analysis of actual and required stakeholder participation in rural groundwater development for agricultural irrigation PARTICIPATION OF STAKEHOLDER IN DEVELOPMENT PHASES STAKEHOLDER GROUPIII PROJECT ODESIGN & OPERATION & RESOURCE PROMOTION CONSTRUCTION MAINTENANCE MANAGEMENTt DIRECTLY- INVOLVED WATER USERS * village community * crop irrigators GGGG OG e * livestock rearers DEVELOPMENT AGENCIES * national/provincial governmentt * multilateral/bilateral funders GO0 DG e * non-governmental organisations * private developers ENGINEERING SERVICES & SUPPLIERS * drilling contractors _ * pump, pipe, irrigation equipment GG manufacturers/retailers * maintenance contractors ENERGY SUPPLIERS * electricity grid operators ---4 * fuel supply/distribution 7 ee 7 e INCIDENTALLY-INVOLVED AGRICULTURAL SUPPLIERS _ * seed, fertilisers, pesticides 9 e AGRICULTURAL MARKETS _ . wholesale/retail IMPACTED PARTIES * shallow well users * downstream irrigators * environmental conservation groups eee * urban water-supply * urban infrastructure - normally major involvement in this phase normally some involvement in this phase (should be more) rarely adequate involvement in this phase (some should be arranged) @003 scale and timing of potential benefits and disbenefits eee for corresponding stakeholder groups other branches of government will normally be concemed with groundwater resource management Note: The horizontal time-scale may be from I to 5 decades; both the typical current situation and the preferred approach is indicated; the corresponding picture for domestic water supply development is less complex but stakeholder participation is equally necessary. 12 2 Groundwater Supply: Installation, and Operation Context of Main Issues During the International Drinking Water Supply and Sanitation Decade (1980s) rural water supply coverage increased from 30 to 63 percent and the population with basic services decreased from 1613 to 989 million, despite the large growth in rural population during the period (Subrarnanian and others, 1997). The program depended heavily upon groundwater to meet the demand for dornestic water supply in rural areas, rapidly and economically. Although much has been achieved, the need to meet the demand from steadily expanding populations remains a major challenge. Moreover, the sustainability of establishecl supplies, through adequate operation and maintenance, was recognized as a key issue. Full consultation and participation of the "beneficiary community" is also now regarded as essential, and the importance of cost recovery, adequate maintenance and source protection are seen as critical to operational sustainabtility. The international NGOs led the way in helping communities develop the improvements in water supply they wanted. While these organizations were regarded with suspicion by some governments, much progress was made in demonstrating the effectiveness of community participation in the development, operation and maintenance of rural domestic water supply wells. Large-scale groundwater resource development for irrigated agricu:lture has a relatively short history. The possibilities for groundwater exploitation changed radically with advances in the turbine pump, deep drilling technology and geological knowledge, notably from the mid 1960s in Pakistan and more widely in the 1970s. Groundwater development itself was often carried out on an indiviclual, or small-scale cooperative, basis without the parallel development of an effective institutional framework for water provision. Hence there is now a considerable challenge to maintain groundwater supplies operationally and to promote sustainable use of groundwater resources as a whole. In order to meet the expanding demand for rural water supply, certain hydrogeologicalfactors are critical to well siting and design. The nature of groundwater occurrence and broad range of hydrogeological environments has been summarized in Box 1 and Table 3 respectively. The ability of aquifers to store and transmit (or yield) water exhibits substantial variation frorn place to place and not all the defined hydrogeological environments can meet the needs of all users (Figure 5). If the global range of climatic regimes is superimposed on hydrogeological setting, then the complexity of intrinsic constraints on groundwater development is accentuated. Some environments will provide only modest yields, and then only if the most favorable locations can be selected. Others will provide moderate-to-high yields from almost anywhere in the aquifer, provided the well is correctly constructed. More specifically, where there is adequate surface water, crystalline basement rocks are often not considered to be aquifers, but if rainfall is lower and surface water scarce or intermittent, then the crystalline basement can form the only economically exploitable source of rural water supply. 13 Groundwater Supply: Installation and Operation Groundwater in Rural Development Access to Adequate Water Supply Domestic and Livestock Well Construction During the International Drinking Water supply and Sanitation Decade much effort was concentrated on improving rural water supply in Sub-Saharan Africa and South Asia. Although, with a few notable exceptions (Arlosoroff and others, 1987; Wright and Burgess, 1992; Van Dongen and Woodhouse, 1994), the technical experience gained has not been systematically reported and disseminated, knowledge of the corresponding hydrogeological environments has still increased substantially. Thus, for example, the position of the crystalline basement rocks in Figure 5, invariably having low-to-moderate yield potential and small volumes of storage, has been confirmed by extensive bodies of field data (Box 2), collected in rural water supply projects (Chilton and Foster, 1995). Siting and Design Criteria. Exploration for groundwater has been a key task for geologists for many decades. Early practitioners generally used electrical resistivity geophysics in simple standard ways, having been assigned to (rather than trained in) groundwater exploration. More recently, with the greater availability of trained hydrogeologists and the extension of projects into more difficult terrain, a wider range of siting techniques and better interpretation have been employed. Groundwater exploration should be phased, employing increasing levels of sophistication. Five successive levels of investigation can be defined: * Inventories of existing geological, hydrogeological and borehole data * Remote sensing using satellite imagery and aerial photographs * Reconnaissance hydrogeological fieldwork (including geomorphological characterization and examination of existing water supply sources) * Surface geophysical surveying by various techniques (according to their cost and to local conditions) * Detailed hydrostratigraphic survey, including exploratory drilling and pump testing. Each successive level adds more detailed information concerning hydrogeological conditions. In reviewing well siting approaches in Africa, Van Dongen and Woodhouse (1994) found that geophysical surveys were often employed where the first three phases listed above were only cursorily performed. If this happens, very useful and inexpensive information is neglected, increasing the overall cost of siting. Further, each geophysical site survey is often treated as an entirely individual task. While the survey operator may have some degree of accumulated local knowledge of the relafionship between geophysical soundings and hydrogeological conditions, usually no systematic use is made of the body of existing data. Moreover, lack of communication between those responsible for siting and construction (for various reasons) may mean that there is also no proper feedback from the actual drilling results to improve the operation and interpretation of future geophysical siting surveys. Although significant geophysical effort may be put into the borehole site selection process, success even in terms of modest hand-pump yields is not guaranteed. Comparative studies of the "success" of different approaches to borehole site selection are complicated by the differing definitions of success. It may not be easy to evaluate rigorously the benefits of a specific methodology because "with" and "without" technique performance data rarely exist in comparable environments, such that other factors can be eliminated. There is thus little "control" in the scientific sense and the best than can be hoped for is a comparison between figures before and after a certain method was employed. This can make the selection of the most suitable approach difficult, and the choice of geophysical technique in particular is too often made without proper regard for the hydrogeological environment (Table 4). 14 Groundwater Supply: Installation and Operation Groundwater in Rural Development BOX 2: Village Water Supplies from the Weathered Crystalline Basement in Sub-Saharan Africa * Crystalline basement rocks underlie much of Sub- PARAMETER LIVULEZ ULO GWE DOWA WEST Saharan Africa, and their mantle of weathering products _ no. mean no. mean no. mean forms a shallow but low-productivity aquifer. This borehole depth (m) 145 23.1 212 17.9 103 25.6 provides a vital source of water-supply for the rural regolih thickness (mn) 7S 21.5 101 12.0 25 25.1 water struck (m) 75 10.2. 191 8.6 95 14.4 population and their livestock who inhabit these areas. saturated regolith (mi) 80 t .9 192 9.9 97 11.5 water level (m) 139 7.3 185 5.7 97 10.1 * The ancient land surface of the region has been boneh oleld (Is)_ 139 0.75 187 0.73 94 0.43 exposed to prolonged weathering which has formed Inset 1 Characteristics of weathered crystalline basement a mantle of alteration products, known as the regolith. aquifer in Malawi rural water-supply projects This can be up to 30 or 40 m thick, and comprises the residual soil and underlying weathered (disaggregated * The most favourable locations are often associated and sometimes clay-rich) crystalline rock. The with geological features (such as fault zones and physical and chemical processes of weathering have fractures) which encourage deeper weathering, and produced dissolution and leaching of the less stable may also be local focii of recharge. This variability minerals, leading to increases in porosity and is illustrated by Inset H. For this reason, considerable permeability. The transition to fresh, unweathered effort is required in site selection to determine locations rock is usually gradual, and the basal part of the with thick saturated regolith. Even so, the potential weathering sequence is likely to be the most permeable for achieving higher yields for small reticulated and productive. supplies is nct great, although the use of collector wells can help to maximise the productivity of the Remarkably consistent hydrogeological conditions shallow regol-ith aquifer. have been revealed from detailed investigations for rural water-supply provision in western, eastern and 1 oo numbers in a southern Africa, and experience gained there is also F parentheses Moalawest(80) - applicable to similar environments elsewhere. ° sampe/ize Q 30 - * The ability of the regolith to provide adequate yields , for rural water-supply or small-scale irrigation depends on the available saturated thickness. This is in turn o a function of climate; shallow water tables are more m ( Iir.: a likely in the less arid parts of the region where recharge al is greater. Where the regolith is thick and the water- C/ table shallow, yields may sustain a handpump, but a) / ,4 where the weathering sequence is much thinner and <, 20 Nigeria (16 *; , Matawji the water-table deeper, the regolith is unlikely to be E1 ' Uvulezi (82) usable. ' 7/ - 0.001 0.01 0.1 1 Experience from projects in Malawi (Inset 1) suggest specific capacity (1is/m) that 10-12 m of weathered material below the water- table is sufficient, providing appropriate borehole 0.2 0.5 1 2 511s designs are selected (Chilton & Foster, 1995). While (borehole yield for 10m drawdown) the mean values suggest a rather consistent and uniform aquifer, in practice groundwater conditions Inset It: Cumulative distributions of specific capacityfor greatly ver shot distanes depeding onboreholes in weathered crystalline basement vary greatly over short distances depending on aquifers in Zimbabwe, Nigeria and Malawi. (most local hydrogeological and geomorphological factors. can achieve the minimum of 0.2 I/sfor handpumps, butfew 1.0 /s for motorised pumps). KEY ISSUES: * the water-table depth and the thickness of weathered basem[ent should dictate the approach to siting, design and construction of water-wells. * the development of larger supplies requires greater investment to locate the most favourable zones of higher transmissivity and maximum available drawdown 15 Groundwater Supply: Installation and Operation Groundwater in Rural Development In the national rural water supply program in India, from the late 1960s to the late 1990s some 2.8-3.0 million hand-pump boreholes were constructed, of which perhaps 80 percent are in the more difficult hydrogeological environments (weathered crystalline basement of the "peninsula states" and basaltic volcanic rocks of the Deccan plateau). In spite of investment in geophysical equipment and training, and the gradual adoption in some states of additional aids such as aerial photographs and remote sensing, the overall "success rate", measured against the target hand-pump yield of 0.2 I/s appears to have increased only from 75-80 percent to 85-90 percent. Although site selection procedures have improved, this has been partly offset by progressive movement into more difficult areas as rural water supply in India approaches full coverage. Table 4: Suitability of geophysical methods in different hydrogeological environments Hydrogeological Electrical resistivity Seismic Electro-magnetics environment refraction Sounding Profiling Major Alluvial Formations ++ + X o Consolidated Sedimentary Aquifers + + + o Volcanic Formations + + o + Weathered Crystalline Basement (regolith) ++ + ++ + Weathered Crystalline Basement + ++ ++ ++ (fractured bedrock) Fresh/Salt Water Interfaces ++ + o + ++ very suitable + suitable o not suitable Note: This gives a general overview of the more commonly used techniques. Source: Van Dongen and Woodhouse, 1994. Site selection must take account of the views of the commnunity who will use the supply. Experience has shown that a strong sense of community ownership is required from the technology choice and site selection stage, if the users of the supply are to operate and maintain it effectively. However, this will tend to slow down the construction process, and hence add to overall cost. In the World Bank Swajal Project in Uttar Pradesh, the use of local NGOs as support organizations to promote community involvement (including the choice of supply technology) has increased the per capita well cost far above the national average, but results suggest that construction standards are also higher. In early programs, in which social mobilization components were weak, sites were often chosen far from communities or such that certain people had preferential access and others were excluded. Exclusion has been such a serious and prolonged issue that the latest guidelines from the Rajiv Gandhi National Drinking-Water Mission for the provision of rural water supply specifically allocate disproportionate funding to redressing previous anomalies. Finally, the precise choice of site, after hydrogeological and community criteria have been satisfied, must take account of risks associated with local sources of pollution, flooding and erosion, physical accessibility for construction and future development in the neighborhood. One outcome of the extensive programs in Africa of the 1980s and 1990s was the increased attention given by hydrogeologists to the weathered crystalline basement. While reference has already been made to the impact this had on siting techniques, attention was also tumed to applying sounder design principles. Traditionally, boreholes were drilled through the weathered zone (regolith) deep into the unweathered rock below in the hope of finding water-yielding fractures. The weathered regolith was cased out, and the fresh rock left as open hole, resulting in inefficient boreholes with high hydraulic losses allowing entry of fine materials. As the potential of the regolith zone became apparent it was evident that the relative position of the water table and base of the regolith should dictate well siting and design (Figure 7). Another outcome was the 16 Groundwater Supply: Installation and Operation Groundwater in Rural Development realization that the choice of drilling equipment was a key issue in relation to cost and success, and that in many cases simpler technology was more appropriate (Table 5). Table 5: General summary of drilling methods and constraints for waterwell construction Hand- Drilling Hand operated Cable-tool Small air Multipurpose equipment digging rig l;ig flush rig rotary Rig Capital cost approx (US$K) 1 1-5 20-100 100-250 200-500 Running cost very low low low medium very high Training needs very low low low-rnedium medium very high Repair skills very low low low-rmedium medium very high Back-up support very low low low-raedium medium very high Range of penetration rates 0.1-2.0 m 1-15 m 1-L5 m 20-100 m 20-100m (mr8-hr day) 200 mm holes to 15 m slow fast fast impossible very fast unconsolidated formation 200 mrn holes to 50 m generally slow and fairlly fast impossible very fast unconsolidated formation impossible difficult 100 mm holes to 15-50 m extremely impossible veryr slow very fast very fast consolidated formation slow Note: The very fast rates of drilling which are possible with more sophisticated drilling machines can only be sustained if careful attention is paid to planning their logistic support. Source: Arlosoroff and others, 1987. Financial and Economic Considerations. The relationship between hydrogeological factors and overall waterwell costs is given in Figure 7. For the crystalline basement rocks, costs can rise relatively rapidly but with little chance of achieving large yields. Consolidated sedimentary aquifers will generally have relatively high costs, due to deep drilling and high pumping lifts. Other formations are more unpredictable due to greater lithological variability and depth range; within these the lowest overall costs are associated with shallow water table situations, which have low drilling costs ancd small pumping lifts. Actual costs would provide a clearer picture, but it is difficult to find country or region comparative figures because of differing labor costs and differences over what is included in the costing, and (of course) because such figures are rarely published. The cost data from a questionnaire survey of rural water supply projects in the late 1980s are shown in Table 6. The exploration costs (at up to 10 percent) include significant effort in remote sensing, aerial photo-interpretation and geophysical survey. 17 Groundwater Supply: Installation and Operation Groundwater in Rural Development Figure 7: Harmonizing design of rural water supply wells with hydrogeological conditions in weathered basement aquifers DUG WELL COLLECTOR WELL BOREHOLE VARIANTS (a) (b) (c) (d) (e) 3-11Om 6-1 2m 1-0 3-1 I v4hhihcf*gt I I a -- 1 >~~~~~~~~ - -- - i-i -;---- - - VERY LOW Low MEDEI II HIGH PREDICTABILITY OF 'YIELD 4 WCB 4 IMB __ _ _ _ RCL CSiF MAF VARIATION WITH MAIN AQUIFER TYPES (see Table 3 for key) Note: The weathered crystalline basement (WCB) and some types of minor consolidated sedimentary aquifers (CSA) show the highest propensity to drought impacts. 25 Groundwater Supply: Installation and Operation Groundwater in Rural Development A useful strategy for addressing the issue of groundwater droughts is the preparation of "drought vulnerability maps" (Calow and others, 1997) (perhaps better termed "drought propensity maps" to avoid confusion with other uses of the word "vulnerability"). Because drought propensity can be predicted, maps combining the factors of physical vulnerability to drought (aquifer recharge, permeability and storage) can be combined with the factors of human vulnerability (supply coverage and population demand) to produce an overall map. Thus, in areas of difficult hydrogeology (with dependence on traditional sources), and where supply coverage is low but population density high, drought impact could be most severe. Such maps could be used for: * Warning of impending drought impacts on groundwater resources * Allocating scarce resources in the most sensitive areas in pre-drought periods * Making appropriate technology choices (for example, between dug wells and boreholes) * Ensuring adequate approaches to siting and construction (particularly depth) are made. A problem is that all too often monitoring of groundwater levels is interrupted in droughts, just when it is most required to observe minimum water table levels and the aquifer response to pumping. Building an element of "drought resistance" into water- supply programs has included the provision of extra well-lining rings for future deepening, drilling a limited number of extra boreholes in favorable strategic locations to be uncapped and used in emergencies, and ensuring adequate borehole depth. In India, experience of drought impacts on groundwater sources led UNICEF to recommend a minimum drilling depth ("norm") of 60 m for hand-pump boreholes in the hard-rock areas to allow for large drawdowns in dry conditions. Intrinsic Groundwater Quality Problems Hydrogeochemistry and Health Nine major chemical constituents (Na, Ca, Mg, K, HCO3, Cl, S04, NO3 and Si) make up 99 percent of the solute content of natural waters. These constituents provide the hydrochemical characterization of waters and their proportions reflect the geological origin (type of rock), groundwater flow paths and history of groundwater. Elevated concentrations of solutes can occur in certain hydrogeological environments, such as increases in salinity due to evaporative concentration, high sulfate concentrations associated with weathering of basement rocks, dissolution of evaporites in sedimentary sequences, hardness associated with carbonate rocks, and from association with some types of geothermal activity. The key objective of groundwater quality monitoring programs is to zone areas where groundwater is unsuitable for potable supply. It should be noted that concentration of some of the above constituents can be increased as a result of polluting activities at the land surface, and it will also be important for management to differentiate human impacts from natural quality problems. Reactions between rainwater and bedrock during percolation provide groundwater with its essential mineral composition (Freeze and Cherry, 1979). Rainfall infiltrating through the soil takes-up carbon dioxide and the resulting weak carbonic acid dissolves soluble minerals from the underlying rocks. In humid climates with significant recharge, groundwater moves continuously, contact time is short and only the most readily soluble minerals will be dissolved. Groundwater in outcrop recharge areas in such regions is likely to be low in overall mineralization compared to that in arid or semi-arid regions in which the combination of evaporative concentration and slow movement can produce much higher concentrations. Groundwater in igneous rocks, for example, is often of exceptionally low mineralization because groundwater movement is via joints and fractures and many such rocks are highly insoluble. 26 Groundwater Supply: Installation and Operation Groundwater in Rural Development Minor and trace constituents make up the remaining 1 percent of the total, and can sometimes give rise to health problems or unacceptability for human and/or animal use/consumption (Freeze and Cherry, 1979). Many trace elements are essential for human health in small quantities (Figure 9), and are taken in from both drinking water and food. The desirable concentration range is, however, small and some are harmful at slightly higher concentrations. Others are not essential for health but are also harmful at low concentrations. Low concentrations of essential elements in drinking water can cause community health problems, particularly if supplements are not provided by a healthy diet. Perhaps the most important problem associated with drinking water are linked to iodine deficiency. It has been estimated that up to 1000 million people are at risk globally from iodine-deficiency disorders, of whom some 200-30() million are goitre sufferers and some 6 million are affected by cretinism. The rocks of the earth"s crust are relatively depleted in iodine, whereas the highest concentrations are found in the oceans. Maritime rain has adequate amounts of iodine compared to continental rain and the problem is' largely one of the continental interiors. Fluoride is also an element that is sometimes deficient, but in the provision of rural water supplies from groundwater, excess is more likely to be a problem. The range of desirable concentrations of fluoride in drinking water is relatively small. At concentrations below about 0.5 mg/Q, dental caries may result, and fluoride is added to many toothpastes and some water supplies to promote dental health. Concentrations above 2.0 mg/c in drinking water can begin to cause dental flucrosis and above 5.0 mg/Q can cause crippling skeletal fluorosis. High fluoride concentrations in groundwater are quite extensive. In India, 20-60 million people are affected, as are those living in some hydrogeological environments of China, East Africa and the Middle East. High fluoride in groundwater is thus a fairly widespread, and usually underrated, constraint on the provision of rural water supplies. The trace element of greatest concem, however, is arsenic, which is both toxic and carcinogenic. Toxicity depends on the form of arsenic ingested, notably the oxidation state and whether organic or inorganic. Arsenic intake may be larger from food, but drinking water represents the greater hazard since the arsenic is present in the inorganic form. The WHO guideline has recently been reduced from 50 to 10 gg/Q. Most drinking waters have arsenic concentrations well below this, but concentrations in excess of 1.0 mg/n are recorded in some areas. Documented cases of chronic arsenic poisoninhg are known for a number of different hydrogeological environments in Taiwan, Chile, Argentina, Mexico, C'hina, India and Bangladesh. The latter, which appears to be the most widespread, is detailed in Box 6. There are also major quality issues linked to soluble iron and nitrates in groundwater. In many places, especially but not only in crystalline basement areas, high iron concentrations cause water supply acceptability problems. Under reducing conditions, concentrations of dissolved iron may reach several mg/a, and the solubility is greater at the low pH values which prevail in such regions. As the water is drawn to the surface and encounters oxygen, the dissolved iron is oxidized. There is also evidence (Lewis and Chilton, 1984; Langenegger, 1994) that the use of galvanized iron pump components or mild steel borehole casing can make the situation worse, by adding iron and zinc to the abstracted water. Often beneficiaries do not fully utilize affectad supplies and go back to traditional sources which have low iron concentrations but very poor bacteriological quality. The occurrence of elevated nitrate (and sometimes ammonium or nitrite) concentrations in groundwater supplies is normally related to pollution from agricultural practices and/or sanitation arrangements and as such is dealt with in Chapter 4. However, elevated concentrations may occasionally occur in arid regions as a result of natural soil-plant processes. Effects on Irrigated Crops The quality of irrigation water quality is judged against criteria based on the adverse effects of the constituents of the water on the growth and development of irrigated crops, on the soils which are being irrigated, on agricultural workers and on consumers of the harvested products. These criteria have been developed over time from data which have often been empirical rather than scientific. Field experience has shown that knowledge of the quality of groundwater to be used for irrigation is essential. The main water quality problems related to irrigated agriculture are salinity, constituents that reduce soil infiltration rate, the toxicity of specific solutes and miscellaneous effects such as excessive nutrients (Table 7). 27 Groundwater Supply: Installation and Operation Groundwater in Rural Development Figure 9: Major and trace elements in groundwater and their health significance TRACE ELEMENTS MAJOR ELEMENTS measurement requires expensive equipment mainly simple and cheap to measure 0*0001 - o0001 - 0.01 - 01 0*1 -1 0 1.0 - lo lo -100 i >100 0.001 mg/I 0 01 mg/I mg/I . mg/I mg/l mg/l mg/l ,Rb . Li Sr Mga*] La I Ba B K-i1 I E W CU Br S SO4[ Se* Mn' * ELI . 1 T ,As*; U Zn FN0 Cd* .L.I. Cod ESSENTIAL ELEMENTS W _co considered essential for l |*. Cu human/animal health .Sr probably essential for health Pb* . . . B non-essential elements Al . also considered to be toxic or , * undesirable in excessive y , , ', amounts N.B. 0.001 mg/l (or ppm) 1.0 pg/l (or ppb) Note: The concentration ranges indicated are the normal levels of occurrence, but much higher concentrations may be encountered under certain conditions. Source: Edmunds and Smedley, 1995. Salinity begins to become a problem if salt accumulates in the crop root zone to a concentration which prevents the crop from extracting sufficient water because of the osmotic pressure, and the plant growth rate is reduced. Because of evaporation from fields and remobilisation of soil salts, soil water is usually 2-3 times (and often 5-10 times) more concentrated than applied irrigation water. The recommended restrictions on the salinity of irrigation water (Table 7) refer to typical grain and fodder crops, and vary with the water application method and the soil type. For certain tree crops (such as citrus, groves and date palms) and various other crops the salinity limits are lower. 28 Groundwater Supply: Installation and Operation Groundwater in Rural Development BOX 6: Natural Contamination of Groundwater wit'hArsenic in Bangladesh * Use of groundwater in Bangladesh for rural domestic in water supplies gives rise to a number of severe water-supply has increased greatly over the last 20 health problems, including skin disorders (keratosis), years, and the shift from more traditional surface water as well as internal cancers, cardio-vascular and sources has reduced the human health hazard related respiratory problems. The number of people in to pathogenic contamination. Nonetheless, the natural Bangladesh potentially exposed to drinking water quality of groundwater cannot always be guaranteed exceeding 0.05 mg/l exceeds 20 million. and purity can be impaired through natural build-up of toxic trace elements (notably arsenic) derived from * The relatively high content of recent organic matter long-term reaction with minerals in host aquifers. maintains the reclucing condition of the aquifers, as a result of the limiled supply of dissolved oxygen. This * In Bangladesh groundwater is abstracted from the process also results in the reduction of most nitrate hydrostratigraphically-complex alluvial and deltaic and sulphate, and high alkalinity following the aquifer over various distinct depth ranges. The bulk generation of carbon dioxide. Bangladesh groundwaters of rural domestic water-supply is derived from the also have relatively high concentrations of phosphorus shallow aquifer (above lOOm depth) of Quaternary and some exceecd the WHO drinking water guideline age. Fine-grained alluvium covers much of the surface, for boron. acting in part as a semi-confining bed for the shallower aquifer restricting the ingress of atmospheric oxygen. * The detailed maechanisms that give rise to the high arsenic groundwaters are not yet fully understood. PabnaS } / <\ f - Under anaerobic conditions, the reductive dissolution a17% i of iron oxides with release of bound arsenic is likely 60%/ .28% 1 38% r to be the dominant process. Lack of opportunity for { /4/40 < 24% \ U 237% $ 240/ e g flushing and oxicdation of the shallow sediments in the '_ °/ / UJ , current floodplain (as a result of their young age and 7:) 26% 19% < 66% g<3%t \ 65% " the low hydraulic gradients) are also significant v esso_e 0%n 96%/oa \ X contributing factors. There are indications that both 0 * & 43% ) __ ° g \ ( _< 1 l \ deep and shallow groundwaters in areas of geologically- 2 51% 94% w 4 ° older alluvial terraces have lower concentrations of - Khuln 63% 66% M 'k.. soluble arsenic. Such areas are likely to have been > 75%/ V 24%/ If999 < subject to significant flushing by meteoric water during 66% periods of low-stand of Quaternary sea level. X / I 1 ) * Although the potential exposure to arsenic has (I / 6 S / / vincreased in southern Bangladesh through increased ,' h y tz y f o use of groundwater, relatively few aquifers globally are impacted by such arsenic problems. It would therefore be unwise to abandon groundwater resources Inset : Distribution of hazardous arsenic in shallow in developing countries in favour of alternatives such southern Bangladesh groundwaters (expressed as as surface water without proper hydrogeological and percentage of samples by district exceeding 0.05 geochemical assessments. mg/i in 1998 survey) DETERMINAND StHALLOW AQUIFER DEEP AQUIFER Groundwaters are almost entirely reducing and this (mg/I, except frst (lowntE) (DEEA5I) two listedI mda maximum' medilan maximum' is a key factor in the mobilisation of toxic t 7.0 6.5 6.9 concentrations of arsenic, in solution as both As(III) Eh (mv) -3' 77 32 98 and As(V). Arecent survey of more than 2,000 samples _ _ - l l southern Bangladesh (Inset I) Ca6.5 74 5.0 18.3 in southem Bangladesh (Inset I) has revealed that 35% s04 <0.03 0.76 0.03 0.45 exceeded 0.05 mg/l, while 50% exceeded 0.01 mg/l HCO3 271 489 167 285 N03 .1.3 4.4 .x1.3 <1.3 (the WHO recommended limit in drinking water) NH4 <0.08 1.3 <0.08 0.21 NH <00 1.37 <0.0 0.21 (BGS-MMD, 1998). However, groundwater from P 009 0.67 0.3 0.09 B 0.004 0.032 0.3 01 deeper Lower Pleistocene aquifers generally has lower Mn 0.04 0.30 0.010 0.04 arsenic concentrations (Inset II) and is being As _ C00054 0030 0.0006 0.003 investigated as one alternative option for domestic maximum L; reprsente,d by 5 percentile value (where values below analytical water-supply. detecton lirnit, halt this limit has been used in statistical analysis) Inset I: Groundwater chemistry of southern Bangladesh * Chronic exposure to high concentrations of arsenic aquifers 29 Groundwater Supply: Installation and Operation Groundwater in Rural Development Leaching of salts below the soil zone is the key to controlling problems related to the applied water, but this requires the periodic application of excess low-salt water, which may not be feasible in groundwater irnigation. In practice, even if some leaching is possible, this may merely displace salt from the soil to underlying groundwater, and the concentrating effect of continuous recycling of salts is often observed in groundwater irrigation. In parts of northwestem Sri Lanka, intensive groundwater abstraction from a shallow sand aquifer has established a series of flow cells in which the abstracted water is applied to the ground and infiltrates back to the water table. Within this recycling system, groundwater chloride concentrations have risen by 100-200 mg/l over the 20-30 year period of irrigation (Figure 4). The two factors which affect the rate of infiltration are the salinity of the applied water and its sodium content relative to calcium and magnesium (SAR). High salinity water will tend to increase infiltration, but low salinity water tends to remove salts from the soil, reducing its stability. High sodium-to-calcium ratio promotes dispersion of soil aggregates close to the surface and smaller particles clog pores reducing water movement. The potential for these problems to occur is measured by the electrical conductivity (EC) and sodium adsorption ratio (SAR) of the applied water (Table 7). Table 7: Guidelines for interpretation of water quality for irrigation Potential irrigation problem Degree of water use restriction required Harmful constituents Low Moderate High SALINITY (affects crop water availability) Electrical Conductivity (EC-pLS/cm) <700 700-3000 >3000 Total Dissolved Solids (TDS-mg/I) <450 450-2000 >2000 INFILTRATION (soil infiltration rate) SAR = 0 - 3 and EC of > 700 700-200 < 200 SAR = 3 - 6 and EC of >1200 1200-300 < 300 SAR = 6 - 12 and EC of >1900 1900-500 < 500 SAR = 12 - 20 and EC of >2900 2900-1300 <1300 SAR = 20 - 40 and EC of >5000 5000-2900 <2900 SPECIFIC ION TOXICITY (affects sensitive crops) Sodium (Na-meqAl) - surface irrigation < 3 3-9 >9 - sprinkler irrigation < 3 > 3 Chloride (Cl-meqAl) - surface irrigation < 4 4-10 >10 - sprinkler irrigation < 3 > 3 Boron (B-mg/I) < 0.7 0.7-3.0 > 3.0 MISCELLANEOUS EFFECTS (on susceptible crops) Nitrate (N03-N-mgA)* < 5 5-30 >30 Bicarbonate (HCO3 -meq/1) < 1.5 1.5-8.5 > 8.5 (overhead sprinkling only) pH <6.5 6.5-8.4 > 8.4 * ammonia and organic nitrogen should be included where wastewater used Note: This shows the restrictions recommended by the UN-FAO on water use to avoid damage to crops and/or soil for a wide range of chemnical constituents Source: Ayers and Westcot, 1985. 30 Groundwater Supply: Installation and Operation Groundwater in Rural Development Toxicity problems occur if individual constituents from the soil or water are taken up by plants and accumulate to concentrations which cause crop damage or reduce yields. The degree of damage depends on root uptake and crop sensitivity. Perennial crops such as trees are mere sensitive to toxicity problems. Ayers and Westcot (1985) provide considerable detail conceming crop sensitivity to toxic elements: the most important are Cl, Na and B (Table 8) but problems may also arise as a result of Se, As, Ba, Cd, Cr, Pb and Ni (mainly in situations where drainage waters are reused for irrigation or where wastewater reuse is involved, rather than irrigation from groundwater sources directly). The last group of problems (Table 7) includes the effects of excessive nitrate content in the applied water, which may cause vegetative overgrowth, crop lodging and delayed maturity. High bicarbonate concentrations, which are not unusual in limestone aquifers, can cause unsightly deposits on fruit or leaves from overhead sprinkler irrigation, and low pH can encourage corrosion of distribution systems. Well Encrustation and Corrosion Clogging is an important cause of deterioration in borehole performanice (Howsam, 1995). It is caused by the physical processes of redistribution of fine material in the aquifer, the gravel pack and infilling the borehole itself, and by chemical encrustation on screens and pumps. T'he deposits formed by both sets of processes reduce the permeability of the well screen, gravel pack and adjacent aquifer, and increase surface roughness, causing flow turbulence. Table 8: Key factors in the challenge of groundwater source mairntenance for improved efficiency and useful life Relative importance* Domestic Irrigation Factors Consequences/comments wells wells TECHNICAL Quality of Design and . increases reliability of supply * Construction . reduces need for major maintenance and rehabilitation Complexity of Wells and . increases need for personnel training * Pumps . reduces opportunity for local maintenance and spares manufacture Accessibility of Area and . complicates logistics of energy supply, spares, ** ** Wellheads etc. * constraints on vehicles HUMAN Ownership and Responsibility . accountability needs to be clearly established * ** * community or user owners hip pref'erred Operational Supervision and . ensure systematic monitorirag and diagnosis **T Organization a procedures for supply of basic spares critical a incentives for operational performnnce Personnel Training . essential, especially for water users ** encourages user participation * resolves cultural barriers Note: In practice many of these interact and overlap. 31 Groundwater Supply: Installation and Operation Groundwater in Rural Development Clogging by chemical precipitation can affect the borehole, pump and pipework and the aquifer immediately around the borehole, reducing borehole capacity and pump efficiency. The most commonly- reported encrustations are those of iron oxyhydroxides, (sometimes in association with manganese deposits) and calcium carbonate. The former occurs (as described above) when anaerobic groundwater becomes oxygenated, causing conversion from ferrous to ferric iron and precipitation of insoluble ferric hydroxides. Precipitation of calcium carbonate is often quoted but less commonly observed. The contribution of microbial processes to clogging, either by enhancing iron reactions or by deposition of sludges or slimes of biological material (biofouling), is becoming recognized as important. Rehabilitation processes for dealing with deterioration due to encrustation normally include the use of acids to dissolve calcium carbonate and iron hydroxides, including cases where microbial activity has contributed to the problem. The most effective agent for removing such deposits is hydrochloric acid, which is made up to 15 percent by volume and left in the borehole for up to 24 hours. For biofouling, biocides such as strong oxidizing agents and chlorine-based compounds are commonly used, but physical processes such as surging and jetting may be needed to dislodge biofilms from well screens so that the biocides can reach active bacteria (Howsam, 1995). Corrosion of iron, steel and other metals (such as zinc) in aqueous solutions is essentially an electrolytic process involving anodic and cathodic areas in corrosion microcells. Large numbers of such microcells are present on metal surfaces due to differences in surface stresses, surface deposits, metal inclusions and other non-uniformities. Larger corrosion cells can result from differences in water temperature, flow conditions, concentrations of solutes, and also where dissimilar metals join to form galvanic couples. Electrochemical corrosion affects well casing and screens, pumps and pipework. The quality of groundwater includes consideration of its pH (acidity) and Eh (oxidation-reduction) status. Many areas in which groundwater is drawn for rural supplies from the crystalline basement are subject to low pH and low concentrations of dissolved minerals. Groundwater is generally soft with high concentrations of free carbon dioxide. Such waters are indicative of the widespread corrosion problems described by Langenegger (1994) from several West African countries. In a comprehensive study of handpump components, 70 percent of groundwaters in the region were found to be corrosive. The effect is to impair mechanical performance by weakening pump rods and damaging rising mains. The cost-effectiveness of rural water supply schemes can be significantly affected by hand-pump corrosion. Not only will recurrent costs be increased by the necessity for frequent repairs, but the investment in boreholes and pumps may be wasted if the quality of the water produced renders them unused. Langenegger (1994) suggested that handpumps drawing water with over 5 mgIQ soluble iron are generally not used for drinking water, and 60 percent of boreholes in the West African study area had iron concentrations which at times exceeded 10 mgIQ. Corrosion and encrustation processes are complex and interactive and, for this reason, no single test or index is an infallible indicator for predicting borehole life. However, because corrosion of screens and pumps is such an important cause of deterioration, some effort has gone into the development and use of indices and tests to assist in selecting construction materials and predicting borehole performance. The main direct measurements used are pH, free C02 saturation and stability indices, chloride and sulfate ratios, together with corrosion-resistance meters. The key to overcoming corrosion problems lies in the choice of construction materials (plastic, fiberglass or stainless steel) for screens, casing and pump components. In the rural water supply sector, much effort has gone into the development of corrosion-resistant rising mains and rods, since where groundwater is moderately-to-highly aggressive (pH < 6.5) galvanizing of mild steel does not protect from corrosion. 32 Table 9: Analysis of factors reducing well efficiency and useful life MANIFESTATION OF TIMING OF POTENTIAL UNDERLYING CAUSES CORRECTIVE RELATIVE PROBLEM CAUSES AND/OR ACTION(S) IMPORTANCE OCCURRENCE . , , Description of process Physical 1 Chemical Domestic Irrigation l___________________ l ] wells wells commissioning casing-off productive aquifer horizons DC Excessive Pumping Costs __ --_-________________incomplete well development DC/OM progressive well screen/pump encrustation 0 OM/DR aquifer overexploitation 0 AM non-vertical borehole DC commissioning inappropriate pump specification 0 DC sand pumping due to inadequate well- 0 DC screen/gravel pack Premature Pump Failure pump pitting due to air entrapment (see above for causes) _ =========== during excessive drawdown excessive wear of pump bearings * | OM .. progressive _ __i_i pump corrosion * j DC sand pumping due to well screen | 0 DC corrosion l l l l l Well Siltation & Collapse commissioning inadequate well screen/gravel pack DC |Well Siltation & Collapse lDClll progressive well screen corrosion 1 0 j - DC Note: Primary (.) and secondary (0) causes are distinguished where appropriate. DC improve future well design and/or construction. DR employ well diagnosis and rehabilitation techniques. OM improve routine well operation and maintenance practices. AM improve aquifer management/groundwater abstraction controls. Groundwater Supply: Installation and Operation Groundwater in Rural Development Operational Sustainability of Rural Water supplies Maintenance-Functional Sustainability All waterwells need to be properly operated and carefully maintained if they are to sustain their yields and efficiency. Arlosoroff and others (1987) emphasized this, saying that "success or failure depends primarily on one factor, whether the new water supply can be maintained." Yet the proper operation and adequate maintenance of groundwater supplies is frequently overlooked until something goes wrong. When this happens, it may be too late to retrieve the situation effectively. It is always likely to be more expensive to resolve than to prevent a problem, and is also likely to take considerable time during which the water supply source may be inoperable. A major effort was made in the late 1980s to increase the attention given to operational sustainability issues, and efforts to bring about widespread improvements are still on-going with varying degrees of success. Operational sustainability involves institutional, legal, financial, social and cultural issues, as well as a broad group of technical factors, and the interaction between them. The first major challenge is to meet the cash-flow requirements of operation and maintenance. There are legal and administrative issues to be resolved, including: * Who owns the source? * Who is ultimately responsible for ensuring the source is operational? * How can they be held accountable? Who collects the fees and how is financial accounting done? * What is done with the fees collected? * Who is authorized to order spare parts and/or to install them? * How can their availability be ensured? * What external support is required or desirable? The key issues are summarized in Table 8. Technical issues also need to be addressed, in particular construction standards, maintenance equipment and personnel training. If boreholes are poorly constructed, they are more difficult and costly to maintain, will deteriorate in efficiency and may become contaminated. The importance of ensuring sound selection of well sites and tailoring design and construction to local hydrogeological conditions (including the use of screens and gravel packs if required) cannot be over-emphasized in the search for operational sustainability in rural areas. Many domestic water supply schemes are relatively small in scale and often obtain groundwater from shallow aquifers, typically from depths of less than 100 m and often less than 30 m. While the total investment in large numbers of small rural water supply sources is high, the impact of temporary (or even permanent) loss of some individual sources, while causing increased local hardship, may represent relatively little overall loss of investment. Irrigation schemes, on the other hand, utilize high-yielding wells from both shallow and deep aquifers, reaching several hundred meters. These require much more sophisticated design, construction, operation and maintenance, and have much higher capital and operating costs. They are more susceptible to externalities (such as power fluctuations or interruptions), government subsidy policies (affecting choice of fuel), and impacts of drought and changes in surface water availability for conjunctive use. Maintenance of boreholes and pumps for irrigation is not substantially different from that for domestic water supply. Some factors, however, have greater relative importance (Table 8) and there are additional factors which may have an impact. In some irrigated regions, boreholes may be widely scattered among flooded fields with limited access. The availability of energy for pumps (electric or fuel), the accessibility for regular inspection and maintenance may be limited and the degree of supervision may be less than for 34 Groundwater Supply: Installation and Operation Groundwater in Rural Development domestic supplies, where the consequences of supply problems may be instantly discernible and quite rapidly reported. In irrigation systems, individual farmers may suffer severely from a failing borehole but may not receive the rapid response to their needs that domestic consumers can often obtain. Unavailability of water at crucial times in the growing season may mean total or partial crop loss. More sophisticated organization is required to operate and maintain large irrigation wells properly and more competent water-user associations are required if government wishes to hand over responsibility. In some countries there are a complex mix of public and private irrigation boreholes and this may further complicate the situation. The scattered rural nature of the installations and often poor road access increase the difficulties of monitoring inspection. A properly operated and maintained waterwell should have a long working life or be essentially permanent. In Iran many ancient "qanats" have been operating for centuries, because they were well constructed and carefully maintained. In general, a new groundwater source should be sustainable if the "recommended yield" is not exceeded and if equipment is properly maintained and replaced as necessary. This care and attention is not always provided and wells fail through over-pumping, pump encrustation, corrosion or contamination. The development of deep irrigation boreholes has widely facilitated cheaper food production and thereby contributed to poverty alleviation. However, in certain hydrogeological environments (notably thick multi- aquifer alluvial systems), they have led to permanent or seascinal lowering of the water table in the phreatic aquifer and caused failure of shallow domestic wells, reintroducing inequity of access to drinking water (World Bank, 1998). In such situations, effective resource regulation would require compensation (in terms of money or water) to those so affected. Maintenance costs have important hydrogeology-related components, and correct diagnosis of these is critical (Table 9). Poor construction leads to hydraulically- inefficient boreholes and this produces excessive drawdowns, high pumping lifts and heavy wear on pump conmponents. Sand pumping due to poor design or installation of screen and/or gravel pack also leads to heavy wear on pump components and infilling of boreholes. The former increases pump maintenance costs and the latter may produce total borehole failure, as in the case of the Lower Indus Valley of Pakistan (Box 5). Borehole construction standards are of particular importance, and there is generally inadequate investment of public funds in this regard. It is essential that waterwells are properly constructed, that screens and pumps are correctly installed and that the wellhead is properly sealed to protect against direct ingress of polluted water. Without these essential elements, groundwater supplies are unlikely to be long-lasting. In the national rural water supply program in India, for example, simtple and economical borehole designs which are generally suited technically to the local hydrogeological conditions have evolved over time. However, the understandable drive to achieve full national coverage of the rural population places such pressure on state implementing agencies that short cuts are often taken. The enormous task of field supervision of some 800 government drilling rigs means that inspection to help prevent poor standards of construction is inadequate. This situation is compounded by the increasing use of private drilling contractors without adequate supervision to help meet coverage targets; they now construct about 80 percent of all new rural water supply boreholes. Thus a significant proportion of the 3 million or so domestic boreholes and 6-10 million irrigation boreholes will have been poorly constructed, perhaps in several respects. The outcome will be shortened life and/or increased operating and maintenance costs. However, without adequate monitoring programs neither the degree to which design lives (20 years) have been shortened nor the proportion of boreholes affected is known. Thus, the cumulative national cost of poor construction standards can neither be assessed or addressed. Preventive maintenance of waterwells is not yet a part of the local culture of many countries. Staff who undertake maintenance and repair of pumps may not adequately maintain the vehicles they drive and coming to terms with the maintenance requirements of modem machines is a process which is going to take a few more years, especially in remote areas. Future projects need tD target support at this area, and make training and education a more integral part of project implementation. 35 Groundwater Supply: Installation and Operation Groundwater in Rural Development Cost Recovery-Financial Sustainability Village Water Supply. Various ways of financing new groundwater sources may be available, including loans from commercial banks, central or local government support, and international grants/loans. Water user charges, however, are a critical factor, not only for cost recovery and helping to ensure sustainable operation, but also to obtain committed involvement and participation of the users. Water has so often been available at heavily subsidized prices, or essentially as a free good, that the move to raise prices towards economic levels is widely resisted and politically very difficult in some countries. There are still many systems and supplies worldwide that do not even recover a significant proportion of the costs of operation, maintenance and distribution. Approaches have been tried to establish "fair prices," "politically acceptable prices," or "economically satisfactory prices" (Dinar and Subramanian, 1997). Surveys of "willingness to pay" are frequently used to help justify economic charges, but the fact remains that in many developing countries the poor pay the most in real terms for water and they often receive the poorest service. Their payment may be in the form of labor as well as money. Water is an essential of life, and people will pay whatever they are able to get it. Since the poor in general have to pay proportionally the most, the importance of increasing access of the poor to potable groundwater supplies cannot be over-emphasized as a major contribution to the alleviation of poverty. It is now broadly accepted that the most effective means of achieving sustainability is to involve communities and to have them assess and collect water charges in sufficient amounts to at least cover the costs of operation and maintenance. Capital costs have hitherto often been fully provided by governments or aid agencies, but it is now becoming normal for projects to at least investigate the potential for communities to contribute to the capital cost and, if so, to collect an "up-front contribution" so that community commitment is ensured. The full or partial costs of maintenance are now often covered by the recipient communities, and the costs of spares procurement and distribution need to be built in. A further level of comrnmitment is required to incorporate sufficient accumulated balances to cover predictable replacement of pumping equipment every decade or so. Various methods of collecting charges have been tried (Dinar and Subramanian, 1997) but it is important that the community develop or adopt the one that they are most comfortable with and can implement most successfully. In the mid 1980s, Arlosoroff and others (1987) wrote: "capital costs of various levels of service depend very much on local conditions but the relative costs of the different groundwater-based technologies are apparent even though the range of costs may be quite wide." With some 1800 million rural people in need of improved water supply by the end of the century, the extra costs of a high-level service can be justified only when beneficiaries are willing and able to pay the extra costs in full. Nevertheless, higher service levels have been provided even when communities or beneficiaries only contribute a fraction of the cost and such arrangements are not likely to be sustainable. Experience with recovering operation and maintenance costs has been mixed. In the developing countries, irrigation operation and maintenance cost recovery ranges from a low of 20-30 percent by the India and Pakistan govemments to a high of about 75 percent in Madagascar, where water-user groups responsible for collecting water charges and maintaining physical facilities have been established. Collection, accounting and auditing costs also have to be covered. Collection in a small community is no small task if left to an individual, but where it has been established as a community responsibility, water charges can be collected more promptly than in urban centers. Considerable experience in community water supply development has been acquired in the last 20 years and techniques for setting-up and maintaining effective community-run systems are now well established (Subramanian and others, 1997). There is still much to be done, however, to ensure that these are widely implemented and effectively monitored. Most of these community supplies use groundwater and the recovery of costs for groundwater differs from surface water in so far as the actual abstraction costs may be higher and the wells may require more regular maintenance than surface water intakes. However, treatment, storage and distribution costs are likely to be lower. 36 Groundwater Supply: Installation and Operation Groundwater in Rural Development Iriigation Water Supply. There is still much variance in t:he prices set for different uses (Dinar and Subramanian,1997). Irrigation water is typically much cheaper than wvater for domestic supply, and there is often little relationship between the prices set and the actual availability of water. Subsidies, direct, indirect and geographical are common. Countries have different reasons for charging for water; sorme wish to recover costs, some want to transfer income between sectors through cross-subsidy and others want to use charges to improve water allocation as a component of an overall water conservation and resource management strategy. Several countries are exploring unique pricing-related issues. Israel and Jordan are considering scaling prices for irrigation water of different quality (saline, reclaimed wastewater, fresh water), adjusting prices to reflect water supply reliability and implementing a resource-depletion charge. Several countries are considering adjusting charges to reflect regional differences in water supply costs. There is an argument that prices for irrigation water be set to reflect opportunity costs. However, a more realistic immediate objective is to recover sufficient revenue to ensure the viability of water entities. Evidence from the field suggests that farmers are willing to pay for reliable supplies of water, but the practical problems of pricing for irrigation services are complex. Fees are often set on the basis of irrigated area, which is by no means a direct or reliable measurement of the water received. The water drawn from boreholes can be directly measured, and one way to circumvent some of the problerms of area-based charging is to measure the water delivered to a water-user association which has been delegated responsibility for allocating amongst farmers. The record of non-payment of fees for water reflects two prob:lems: lack of political and managerial comrnitment and weak incentives to collect and limited willingness to pay because services are poor. Failure to recover costs and to reinvest in systems leads to a vicious circle in which service declines and consumers, in turn, become less willing to pay for the poor-quality service provided. Conversely, higher collection rates often reflect decentralized management and enforced financial autonomy, which in turn deliver a high-quality service for which users are willing to pay. Concerted efforts are being made to move towards full capital-cost recovery so as to establish and sustain viable water entities, but there is considerable variation in the progress that has been made (Dinar and Subramanian, 1997). One experience quoted in this paper comes from Korea, were farmland improvement associations (water-users associations) are responsible for recovering costs from farmers for projects completed and transferred to them. They set irrigation charges at levels to cover all operating and maintenance costs and a share of the capital costs amortized over 35 years, with government providing a grant for whatever capital costs are not paid for by the farmers. This has been very successful in collecting charges from farmers and repaying the government loan. Experience elsewhere has shown that water-user associations may be slow to get established, but that once the benefits are apparent and the water is available, effective participation and substantially-improved cost recovery becomne possible. Community Action-Social Sustainability Community-Driven Objectives. There is now broad consensus among the developmental sector that rural water supplies can only be sustainable with the full involvement of local people. This raises the question of how best communities can determine their own objectives and achieve these within the range of available physical, financial and technical options. Groundwater development presents particular problems because of the often invisible and somewhat mysterious nature of the resource. Some communities have good understanding of groundwater potential but for others groundwater may not even be recognized as an option, or there may be little understanding of the special techniques required to operate groundwater supplies on a sustainable basis. The traditional donor approach of sending professionals ito developing countries to initiate, design and implement projects resulted in successes, but many projects have not been sustainable because the beneficiaries were not fully involved so as to ensure continuation after disbursement ceased. From the 1980s, as expertise gradually became available in-country, national professional staff gradually supplemented and then replaced those from overseas. Even if these new professionals were potentially more sensitive to local 37 Groundwater Supply: Installation and Operation Groundwater in Rural Development capabilities, both the national institutional framework and the donors approach meant that local people were still rarely involved and little attention was paid to local experience at community level. It is now clear that it is the role of the community itself to determine what its priorities are. Outsiders can provide technical or other support and outline alternatives for them, but the decision has to be with the community. Having decided what they want to do, the next task for the community is to realize it. There has been substantial funding available in the past from donors and from NGOs to support the construction and other capital costs of establishing water supplies. It is now recognized that the beneficiaries should invest when (and so far as) possible in the capital costs of source construction and equipping. In this changed situation, outside support is best provided in the form of training in the process of making appropriate decisions, and for technical and administrative training within the community, as well as for drillers, plumbers, equipment suppliers and installers. Tariff barriers on the importation of waterwell construction materials may also need to be removed. Table 10: The 'integrated approach" to community groundwater supply planning Process Condition or component • Effective Community Involvement * in design, implementation, maintenance, financing * communities wishes reconciled with capacity and willingness to pay * Provision for Full Recurrent and Capital Cost . support of capital costs for poorer communities only Recovery * Maximum Use of National Services and Supplies a in respect of drilling contractors, pumps, spares * appropriate quality control to improve reliability * Appropriate Technological Level . Compatible with human and financial resources available * Institutional and Manpower Development * Closely mapped to needs of planned water supply system * Parallel health/sanitation education Note: This remains a blueprint for improving operational sustainability of rural groundwater supplies. Source: Arlosoroff and others, 1987. In many instances, the NGOs led the way in working at the "grass roots level" helping communities to develop the type of groundwater supplies which they most wanted, and as far as possible at the locations which they most preferred. Even though NGOs were sometimes regarded with suspicion by govemments, they were able to demonstrate the effectiveness of genuine community development based on the wishes and efforts of the rural people themselves. However, the process takes time and money, so that the rate of coverage is necessarily slowed down and the per capita cost is higher. Role of Water-User Associations. The establishment of water-user associations (WUAs) has been encouraged (or even required by more recent projects) with promising results, particularly in respect of maintenance of rural water supplies and water allocation within irrigation projects. It has been shown, however, that obliging people to form water-user groups is often less effective than providing support for a process of helping the community determine what their objectives really are, within a range of available options. When the water becomes available for use, then people more readily see the need for a mechanism for sharing it fairly. Some irrigation projects have had little success in encouraging effective user groups until the benefits are clearly within reach. On the other hand, there is much less difficulty if the project objectives have been designed to meet the expressed needs of an established community or user group. Water-user groups can be set up in a variety of ways, and it is important that their characteristics should be selected by the participants to suit local capacities and culture. Partnerships, co-operatives, stock companies and bulk-supply companies have all been established in different locations and contexts. The more 38 Croundwater Supply: Installation and Operation Groundwater in Rural Development sophisticated are normally reserved for larger community supplieos and for irrigation systems. It is absolutely essential that they are kept to a level of simplicity and transparency that is appropriate for the users themselves. Water-user associations can contribute to better performance of irrigation systems because of their advantages over a public agency on the one hand, and over uncoordinated activity by individual water users on the other (Subramanian and others, 1997). Nevertheless it is safe to say that one cannot expect WUAs to achieve sustainable levels of system performance by themselves. Along with the institutional structure of WUAs a combination of appropriate technology, supportive state agencies/policies and economic forces (including clear property rights and profitability of irrigation enterprises) is required to sustain the WUAs themselves, as well as for sustainable irrigation systems. With regard to water supply and sanitation associations (WASAs) "there are no ready solutions or instant rnethods of promoting sustainable water and sanitation service delivery." There are situations and contexts where WASAs are appropriate, but there are also cases where the institutional costs of operating through WASAs could be extremely high. A water and sanitation project manager planning to decentralize service provision and production through WASAs is therefore best advised to aidopt a flexible "doing and learning" approach, rather than following a fixed blueprint or rigid guidelines (Subramanian and others, 1997). For the purposes of this discussion, it is worth repeating a table by Arlosoroff and others (1987) on the integrated approach to community groundwater supply planning (Table 10). The principal elements that must be taken into consideration are highlighted, and they closely mirror the contents of this section. More than 12 years have passed, but the spread of the WUAs in the 1990s illustrates that serious efforts are now being made to improve the operation of groundwater supplies, whether forl domestic or agricultural purposes. IMuch, however, remains to be done in all of these areas so as to achieve operational sustainability on a long- term basis. lResume on Groundwater Supply Development Since the first modem guidance manual on rural water supply (Arlosoroff and others, 1987) there have appeared various other major reference works on this subject (IUTDP-PROWESS, 1990; WHO-IWSC, 1993; D]FID)-WELL, 1998). These deal in depth with most of the technical, financial and social aspects of the development and maintenance of rural water supplies (summarized above) in relation to any type of water source. However, none of these guidance manuals enter into any detail on the investigation and evaluation of the hydrogeological factors that control the availability of groundwater supplies to wells and springs and that influence the natural intrinsic quality and the vulnerability to pollution of these supplies. Given the general complexity and dependence on local detail associated with successful vwell siting, design and protection, it is essential to engage a competent hydrogeologist in the early stages of planning groundwater-based rural water supply development programs. This, together with the effective databasing of waterwell records and hydrogeological data, are key roles for government action. G3overnments also still have a role to play in supporting the development of community objectives for water supplies. Several are now actively encouraging the establishment of water-user groups for both domestic and :rrigation water supply. Approaches vary somewhat from the "top-down targeted style" to a "more subtle and supportive line." The latter is likely to be more effective as it involves the people to a much larger extent in a process which they can help design and maintain. Experience has shown this to be the key to operational sustainability. 39 3 GROUNDWATER RESOURCE SUSTAINABILITY Context and Challenge for Management Hydrogeological Constraints on Resource Availability All groundwater abstraction by wells results in some decline in aquifer water level (or piezometric surface) over a certain area. Some reduction can be considered not only as necessary but also desirable since it often improves land drainage and maximizes groundwater recharge rates, by providing subsurface storage space for the infiltration associated with high rates of excess wet-season rainfall. However, if the overall abstraction rate in a given area, or aquifer system as a whole, exceeds the long- term average rate of replenishment, there will be a continuous decline in water level, overdraft or mining of aquifer storage and consumption of aquifer reserves. The same applies to abstraction from deeper semi- confined aquifers in which the long-term rate of leakage induced to flow through the confining beds from overlying shallow aquifers is less than the abstraction. An important factor which should constrain abstraction is the need to maintain groundwater levels in, and discharges to, the surface water environment (for example, groundwater-fed wetlands and brackish coastal lagoons), because of ecological, commercial and/or recreational interests. For groundwater abstraction to be regarded as sustainable the constraints imposed by aquifer recharge rates must be respected, albeit that there may be significant difficulty in estimating these with adequate precision (Foster, 1992). There are a number of significant complications: * General uncertainties about aquifer recharge mechanisms and rates as a result of inadequate field data * The area for which the groundwater balance should be evaluated, especially in situations where pumping is very unevenly distributed * The period for which this balance should be evaluated, especially in the more arid climates where major recharge episodes may occur as infrequently as once a decade or even once a century. The way in which the latter two factors are interpreted in practice will vary considerably with the storage volume of the aquifer system, and its propensity to irreversible side effects as a result of short-term overdraft. Both will be a function of aquifer type and hydrogeological setting. Small (very localized) aquifer systems with low storativity and recharge rates will give rise to the most immediate concern. Consequences of Uncontrolled and Excessive Abstraction Groundwater resource (or aquifer) overexploitation is an emotive, but useful, expression (Foster, 1992). Although not capable of precise scientific definition (for the reasons given above), groundwater scientists and water resource managers must realize that it has clear register at the political level. However, in practice, we are more concemed about the consequences of abstraction than with its actual level. These include reversible interference with other wells and with springs, but can also include quasi- 40 Groundwater Resource Sustainability Groundwater in Rural Development irreversible aquifer degradation due to ingress of saline or polluted water (Custodio, 1992; Foster, 1992; Llamas, 1992; Collin and Margat, 1993). hi reality, there is a wide range of exploitation-related effects (Table 11) and it is not always appreciated that differing hydrogeological environments show varying susceptibility to the side effects of excessive abstraction (Table 12). Such side effects will, in many instances, be difficult to predict with precision until some systematic monitoring of aquifer response to abstraction has been undertaken. Table 11: Consequences of excessive groundwater abstraction Consequences of excessive abstraction Factors affecting susceptibility Reversible * pumping lifts/costs increase - aquifer response characteristic Interference * borehole yield reduction - drawdown to productive horizon * springflow/baseflow reduction - aquifer storage characteristic * phreatophytic vegetation stress - depth to groundwater table (both natural and agricultural) * aquifer compaction/ * transmissivity reduction - aquifer compressibility Irreversible * saline water intrusion - proximity of saline/polluted water Deterioration * ingress of polluted water (from perched aquifer or river) * land subsidence and related impacts - vertical compressibility of overlying/interbedded aquitards Note: The two effects in the mniddle band may be either reversible or irreversible depending on local conditions and the period during which the excessive groundwater abstraction persists; the immediate groundwater level response to abstraction and the longer-term trend will be controlled respectively by the aquifer response characteristic (ratio of tratsmissivity to storativity) and the aquifer storage characteristic (ratio of storativity to average annual recharge) Source: Foster, 1992. Table 12: Susceptibility of hydrogeological environments to adverse side effects during excessive abstraction Type of side effect Saline Intrusion Hydrogeological environment or Upconing Land Subsidence Induced Pollution Major Alluvial Formations * coastal ** ** ** * inland * (few areas) * ** Inter-Montane Basins * with lake deposits ** (some areas) * * * without lake deposits * (few areas) * (few areas) * Consolidated Sedimentary Aquifers ** (some areas) - * (few areas) Recent Coastal Limestones * (related solution features) * Weathered Basement Complex - * Note: The number of asterisks gives a relative indication of the severity of potential side effects, which may only be of restricted geographical distribution in some instances. 41 Groundwater Resource Sustainability Groundwater in Rural Development Significant reversible side effects (well pumping cost increase and yield reduction) occur if an excessive number of boreholes are drilled in relation to the available resource and its optimum exploitation pattern, and this can be particularly marked where the hydraulic structure of an aquifer is such that its most productive horizons occur at shallow depths and are thus prone to early dewatering (Figure 10). While such effects are essentially reversible in a physical sense, their consequences upon groundwater users mnay be terminal, bearing in mind the time scales involved. More serious are near irreversible side effects, especially those involving the encroachment of saline water (UN-FAO; 1997). This may intrude laterally from the sea (Figure 11), if coastal hydraulic gradients are reversed, but rather commonly also occurs from above in layered coastal aquifers. Such aquifers often have a strong upward component of natural hydraulic gradient which may reverse with pumping from deeper freshwater horizons inducing the ingress of overlying saline water. Figure 10: Progressive deterioration in operational performance of a production borehole in a heavily abstracted alluvial aquifer static water-level 1ailing continuously during 1964-84 r due to excessive aquifer abstraction and overdraft r yield (1/s) 0 20 40 60 O - I l_ I 0 20 -0 rdcinbrhl 20 00 0 00 _T oO _D 0 moeprebehrzni In Eg~ 404 60 II production borehole Hwell screen/slotted lining tubes CPmore permeable horizon in ac alluvial sand-gravel aquifer O pumping test data points 80 b and interpolation Note: As a result of dewatering of the most productive horizon due to excessive abstraction, maximum, ield decreased from 60 to 10 UIs during 1964-84 white pumping lift increased from 15 to 55 m. 42 Groundwater Resource Sustainability Groundwater in Rural Development Figure 11: Dewatering of groundwater storage in the Tertiary limesltone of southeastern Cyprus due to intensive uncontrolled development for agricultural irrigation Lamaca Bay/~ ~ +40 i20- / 196 °+20 X - o 970 ~ ~ ~ > i X i \, s15 ><\U PPER MIOCENE MARLS -20- (base of aquifer) -20 @ q | s t ;/ ~~ ~~~~~~0 3 km CD -40. 1t t l i Jthorizontal scate -40 -*--|| groundwater table during -60 year indicated liootg groundwater chloride concentration in 1980 Nlote: Over a 20-year period major reduction in the saturated aquifer thickness has occurred as a result of both water table decline and saline intrusion. The effects are quasi-irreversible since saline water, which first invades macropores and fissures, diffuses rapidly into the porous aquifer matrix under the prevailing high salinity gradients (Foster, 1992). It will then take decades to be flushed out, even after the flow of fresh water has been re-established. The ingress of saline water is terminal for virtually all uses, and can also result in clamage to overlying soils if farmers continue to irrigate with increasingly brackish water in an attempt to obtain some return on their investment in wells. By way of contrast, inland thick alluvial and sedimentary-basin aquifers in the more humid climates exhibit much less risk of significant exploitation-related side effects. However, even here there is the potential problem of increasing social inequity if deeper, larger-capacity irrigation boreholes lower the regional water table and reduce access to water supply for users of shallow domestic wells. There are some who have argued that economic constraints, imposed by free market competition, are the only effective control over groundwater abstraction (Young, 1992). The larger capital cost of completing wells of increasing depth and decreasing yield, and escalating recurrent cost associated with pumping from ever greater depths will, it is suggested, rapidly result in achieving an optimum level of resource development and more efficient use of the groundwater produced. If the only externalities of groundwater exploitation are hydraulic interference with other groundwater users, then this approach may be tolerable. Although even here there is failure to recognize the cost of drilling a disproportionately large number of wells to greater than optimum depth for the overall yield obtained, and the range of social and environmental costs associated with groundwater level declines (Foster, 1992). M4oreover, social inequity may be further aggravated when the access to groundwater supply of those dependent upon shallow wells is compromised by water table lowering through heavy abstraction from deep, high-capacity, irrigation boreholes. The position is likely to be far wCose if unrestricted abstraction causes quasi-irreversible aquifer degradation, most notably if increases in salinity are involved. 43 Groundwater Resource Sustainability Groundwater in Rural Development Socioeconomic Problems and Obstacles Historical and Political Perspectives. Groundwater abstraction is not new, but development on the large scale is. Wells have been excavated ever since pre-historical times, but the potential changed radically as advances in rotary drilling technology, in the turbine pump and in geological knowledge spread, most notably during the 1960s and 1970s. This is so despite the fact that churn drills originated in early Chinese history and percussion techniques were developed by the Flemish in the 12th century. Early techniques of groundwater abstraction had very limited capacity and by comparison resources appeared infinite. This divergence led to a common misconception which lies at the heart of overexploitation concerns. In reality the situation changed drastically with the spread of deep drilling and motorized pumping, but perception lagged considerably behind reality (Figure 12). In many areas, government policies encouraged unrestricted development of groundwater resources. In India, although rudimentary procedures for estimating the balance between groundwater abstraction and recharge have been available to guide investment policies since the late 1970s, well drilling and pump energy sources remained highly subsidized (Box 7). The irony is that a policy aimed at making groundwater more economical for all is a primary cause of shallow domestic water supply wells drying up, thus exacerbating the economical access to water for the poorest members of the rural community. Furthermore, virtually all Indian government organizations concerned with groundwater were developed to promote resource exploitation rather than resource management (World Bank, 1998). Such patterns were repeated in many countries worldwide. Large-scale groundwater resource development for irrigated agriculture has a relatively short history when compared to its counterparts dependent upon surface water impoundments and diversions. Irrigation with surface water resources was one of the key historical elements in the promotion of civil society, because it generally needed cooperation amongst water users, and between water users and state governments, to make it possible. This was only locally the case for groundwater development, since it was often carried out on an individual (or small cooperative) basis and did not require the development of an effective institutional framework for water provision. Hence it now represents a considerable challenge to promote sustainable use of groundwater resources as a whole. The challenges inherent in this history are compounded by the increasingly critical role groundwater resources play in the livelihoods of individual users in many developing nations. Access to groundwater for irrigation is making a very positive impact on subsistence and income for poor farmers, and in many cases also reduces the need for the rural poor to migrate during droughts by increasing income security (Chambers and Shah, 1989). These direct individual benefits make any subsequent constraints on groundwater use politically sensitive. In some cases, governments have initially encouraged groundwater development for sound social and economic reasons to meet the needs of rural populations, albeit without consideration of the resource base (Reisner and Bates, 1990). This pattern is particularly well documented in the case of India, where electrical power for agricultural uses (which are dominated by groundwater pumping) is often supplied at nominal rates. In the longer-term this has imparted political legitimacy and popularity, and led to a situation in which policy reform initiatives have then been strongly opposed (World Bank, 1998). 44 Groundwater Resource Sustainability Groundwater in Rural Development BOX 7: Cnitical Role & Future Uncertainty of Groundwater in Rural India * Groundwater is central to rural development and Nadu End Punjab) is provided free of charge. Because food security in India. Over 50% of the irrigated area of these high subsidies, power consumption in is dependent on groundwater. Agricultural yields are agriculture has grown dramatically. Official estimates generally 30-50% higher in groundwater irrigated indicatLe that it exceeds 40% of total energy use in areas. In addition some 85 % of drinking water needs many states. in rural areas are met from groundwater. *Addressing groundwater overpumping in India is These statistics, however, understate the critical role complex. Centralised regulatory arrangements have groundwater plays in the lives of rural inhabitants, existeci since the 1970s, when a model regulatory bill since access to groundwater reduces agricultural risk was first circulated to state governments by the Central and enables poor farmers to invest and to increase Groundiwater Floard. Although a few states have passed production (Chambers & Shah, 1989; World Bank regulations, it is questionable whether they could be 1998). implemented given the millions of individual well owners on small land holdings (Dhawan, 1995), the 1968-69 1984-85 inadequate administrative set-up and that reduction in STATE Private Private! Private Private subsiclies generates strong political opposition. Dug Public' Dug Public* Wells Tube Wells Wells Tube Wells Andhra Pradesh 0.660 0.016 0.982 0.085 * Nevertheless, some states are developing Bihar 0.225 0.013 0.352 0.411 programmes, The Rajasthan State Government, Gujurat 0.565 0.002 0.673 0.009 (supported by the World Bank), is preparing a first Madhya Pradesh 0.610 0.002 1.113 0.008 phase . . . * ma e Punjab 0.170 0.114 0.091 0.595 phase intiative to uild groundwater management Tamil Nadn 1.t15 0.026 1.411 0.111 capacity. This initiative combines investments in data Uttar Pradesh 1.112 0.129 1.130 1.608 collection wit]n groundwater pilot projects to develop user-based management organisations in a series of NATIONAL TOTAL 6.110 0.475 8.743 3.43 groundwater resource conservation zones. It also Inset I: Growth in waterwells (in millions)for selected contains major public education components. Indian states (*public tubewells rarely exceed 5% of the category and are decreasing) * Where energy subsidies are concerned, Andhra Pradesh have taken bold steps to reform pricing Development of groundwater resources in India structures, which should reduce the incentive for aquifer proceeded rapidly (Inset I), and the number of energised overabstraction. Other measures include: wells has increased to more than 15 million in 1996 * the prohibition of drilling deep tubewells for irrigation (Inset II). Increases in groundwater abstraction have * the mandatory construction of streambed groundwater had a major impact on the resource base in many arid recharge structures and hard rock regions. Nationwide, the number of * the introduction of economic incentives for dryland administrative 'groundwater resource blocks' classified (as opposed to irrigated) cropping. as fully/excessively abstracted increased to 383 in 1992-93 (CGWB, 1995). The direct cost of groundwater overdraft in India to the end of the 1980s 30 - + electrical pumpsets had been estimated at US$ 300 million, (almost - - el diesel pumpsets A certainly an underestimate). N total number of al ak i energized wells A * The emerging groundwater resource problems are X A A, closely related to high government subsidies in the ° 10a A, agriculture sector. The subsidy on power-supply is r A - E * perhaps the most significant where groundwater - _ . * overdraft is concerned. In most states, power for 195's 1960'sJ1970's 1980's s 2000 agricultural pumping is provided at a flat annual rate based on pump capacity, and in some (such as Tamil Inset i': Growth in number of energised wate rwells in India 45 Groundwater Resource Sustainability Groundwater in Rural Development Figure 12: Historical development of the Deccan Traps groundwater system in Maharastra, India average well est. total YEAR no. o abstraction abstraction wells (M) (m3d) (Mm31d) 1960 0.55 70 38 ............................. .. ..... ,.IT ................. * limited groundwater abstraction (few wells/animal power/some diesel pumps) * significant baseflow to streams |1970 0.70 | 100 70 1980 0.85 150 | 128 VV .. , T1 1 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~... . .... * increased groundwater abstraction (additional wells, diesel/electric pumps) and many wells deepened * reduced baseflow to streams 1_1990 | 1.25 | 230 | 276 | max ................. ....... .. .................. ...........,..... * further major increase in abstraction (electric pumps) with all wells deepened * no baseflow discharge to streams Note: The total abstraction increased 7-fold in a 30-year period as a result of both the spread of motorized pumping plant and of well drilling, but this led to intense competition for the available groundwater resources and virtual elimination of baseflow to local streams. 46 Groundwater Resource Sustainability Groundwater in Rural Development In sum, the historical perception of groundwater as an unlimited resource and the large benefits access to groundwater brings to individual irrigation users have been major factors underlying the rapid expansion in well numbers, the emergence of organizations focused on resource development, and the related political interests. In combination they represent both a cause of groundwater management problems and an obstacle to the development of effective responses. Economic Characteristics of Groundwater. The economic characteristics of groundwater resources have also played a major role in the emergence of management problems ,and represent significant obstacles to the development of management responses. Groundwater is generally undervalued (especially where its abstraction is uncontrolled) and there is a pressing need for national governments to undertake systematic valuation of their groundwater resources and for regulatory agencies to find ways of introducing economic instruments into resource management to begin to reverse this situation. In this situation the user of the resource, in effect, receives all the benefits of groundwater development, but (at most) pays only part of the costs, usually the recurrent ccsts of pumping (although even energy supplies may be subsidized) and sometimes the capital cost of well construction (Figure 13). The economic costs associated with externalities (such as reductions in stream baseflows, impacts on wetlands, saline intrusion, loss of the strategic value of groundwater storage in extreme drought) are rarely included with charges to users, although they may suffer their consequences. Moreover, in economic terms groundwaters (like fish) are a resource for which property rights are not readily and obviously defined in a legal sense (Foster, 1992). Thus, except in those nations where clear rights systems have been implemented, groundwater would still be termed a common-property (or common -pool) resource, which is to significant degree local in distribution. In this situation individual users have little ability to conserve groundwater for their own future use, and exploitation is notoriously difficult to control. It may even be subject to accelerated depletion, when individual users become aware of trends towards over- abstraction and attempt to recover their development investment while resources still remain. The perception of groundwater as an infinite resource clearly contributes to undervaluation. Even where the finite nature of the resource is fully recognized, users often lack clear understanding of resource dynamics, aquifer boundaries and potential contamination, which further contributes to the problem of undervaluation. Undervaluation is a key factor leading to economically-inefficient patterns of groundwater allocation and use (Young, 1992). In many cases groundwater is allocated to low value uses (such as the production of grain or fodder crops in arid regions), while higher value uses (such as provision of safe drinking water) are only partially met. In addition, because the in-situ values associated with groundwater are rarely reflected in its cost, undervaluation creates a strong incentive for over-abstraction. This incentive is often further increased by direct subsidies and/or by indirect subsidies (such as crop price supports) that encourage allocation to lower value uses. At the same time, undervaluation reduces incentbves for investment in water conservation and, more generally for resource management. Issues of Resource Scale and Variability. Rural groundwater use for irrigation is organized predominantly at the level of individuals or small groups, while aquifers range in scale from less than 10 km2 up to major regional systems (that occupy areas of more than 1,000 km2 and even. 100,000 krn2). Management tensions result from the fact that state and local administrative units, settlement patterns and cultural groupings rarely correspond to the boundaries of aquifer systems. In many cases there is a particular gap at the intermediate level. State organizations operate at a large-scale and find it difficult to address the highly localized factors governing groundwater use. At the sarne time, village and corrmunity groups lack the regional perspective and influence essential to understand aquifer management needs. 47 Groundwater Resource Sustainability Groundwater in Rural Development Figure 13: Measuring the costs of groundwater abstraction Water Supply Costs Social Opportunity External Costs Costs U) O OPRTON& wU FOREGONE IN-SITU E | MOAPIENRTAETNIAONNCE | ez O | VALUE OF VALUE O CAPITAL MAINTENANCE m C. ALTERNATIVE (cost of saline ro COSTS (O & M) 0 USES intrusion, land X CSTS (present/future) subsidence, COSTS OF 2 drought buffer etc.) GROUNDWATER LL ABSTRACTION - - __ _ _ 0 t~~~~~~~~~~~n uJ CAPITAL O&M O : COSTS COSTS s X (credit (energy j I| c normally normally im .t o subsidised) subsidised) | = E * frequently not t levied or do not < _ j cover real costs Note: No relative scale of full economnic costs is implied, but it is evident that in the typical situation the costs paid by the user represent only a part of the full economic cost. Highly dispersed use patterns can have significant aggregate impacts but the problems often arise at substantial distance from many users. The migration of a saline water front for example, is often due to changes in groundwater flow caused by regional pumping patterns, but the only users affected are those in the specific area where saline water intrudes. In any one nation or region, there is likely to be significant variability in the hydrogeological factors controlling groundwater resource availability and the socioeconomic factors affecting their use for agricultural irrigation. These sets of factors interact and result in a groundwater resource management context that can change significantly over time and very greatly between locations. In India, for example, the national and state policies subsidizing both groundwater development and electrical energy for groundwater pumping have had little negative impact on the resource base in areas with adequate wet season rainfall and only seasonal groundwater use. But in the more arid areas these policies have greatly exacerbated aquifer overexploitation and lie at the root of unsustainable development patterns. It is thus necessary to develop management approaches that can be tailored closely to specific situations which will vary with hydrogeological diversity. It also necessitates the development of adaptive management which can respond effectively as the larger econormic or social contexts change. These needs conflict with the macro nature of many key policy tools. They also greatly reduce the chance of success for attempts to develop uniform management models or regulatory structures. Limitations of Regulatory Agencies. National and regional regulatory agencies are all too often under- resourced and weakly empowered when it comes to controlling groundwater abstraction. Moreover, all too often groundwater resource management remains under the administration of professional engineers who have been trained mainly in surface water resource development and tend to think in terms of major hydraulic structures rather than influencing large numbers of small stakeholders. Simply increasing funding and empowerment, however, will not necessarily enable them to regulate groundwater abstraction effectively. A change of attitude and perspective is needed. There are also inherent factors which weaken their ability to introduce effective controls: 48 Groundwater Resource Sustainability Groundwater in Rural Development * The highly dispersed nature of groundwater abstraction, comlbined in many countries with deeply entrenched traditions giving individual landowners the right to abstract * The uncertainty of most groundwater resource evaluation due to natural hydrogeological complexity and meteorological variability, and to inadequate monitoring of system response to abstraction * The strong pressure for resource development (regardless of long-term consequences) sometimes exerted by the politically powerful lobby of land owners and/or plantation enterprises * The high incidence of corruption of regulators during consideration of new abstractions or sanctions on illegal abstractions * The lack of public and political awareness of the potentially irreversible consequences of excessive groundwater abstraction, and thus the absence of an adequate consensus for action. The existence of traditional methods of aquifer development, often involving large numbers of small abstractors with shallow wells and limited pumping capacity in aquifer discharge areas, works in the contrary direction. Implicit prior rights held in perpetuity by such abstractors can make it difficult to introduce more rational use of groundwater and this tends to sterilize valuable storage resources against future development (Foster, 1992). Institutional Framework for Resource Management To make effective progress groundwater resources management requires the effective integration of the key hydrogeologic and socioeconomic elements that determine and control the interaction between water/land- use and groundwater systems (Figure 14). For the purpose of groundwater management, the institutional framework is fundamental and consists of a set of organizations, social processes and legal agreements that enable management functions to occur. Perhaps the most important set of questions to ask in framing approaches to groundwater management are: * What set of functions need to occur to address management needs within the specific context of concern? - Are those functions already enabled adequately, either through formal institutions or through informal social processes? * If not, how might the capacity of existing systems be strengthened, or new institutions be created, to enable these critical functions to be performed? These questions can also be used as a starting point for framing institutional reform programs. Tiered Institutional Arrangements Groundwater management needs and options vary widely between locations, and thus have to reflect local hydrogeologic and socioeconomic conditions. However, local conditions often cannot be addressed in the absence of a higher-level enabling framework. In particular the need for adequate legal and/or social definition of groundwater abstraction rights (Feitelson and Haddad, 1998; Salman, 1999) will be a key provision in many instances. Furthermore, many functions critical to groundwater management--such as determination of agricultural or energy subsidies-are a function of national-level policy decisions. As a result, institutional arrangements for groundwater management inherently involve multiple levels, and need to be tiered or "nested." Local management contexts are shaped by the dynamics of regional economic and institutional systems. Local institutions also draw legitimacy and authority for specific courses of action from a "higher level" or from social norms. Key management functions are enabled by a chain of arrangements that connect basic principles (such as state ownership or trust responsibilities over groundwater) with the authority to act (for example by limiting 49 Groundwater Resource Sustainability Groundwater in Rural Development Figure 14: General conceptual framework for the management and protection of groundwater resources HYDROGEOLOGIC FACTORS SOCIOECONOMIC FACTORS l YIELD POTENTIAL STRATEGIC PLANNING AQUIFER RESOURCE INSTITUTIONA l SYSTEMS/ SUSTAINABILITY lFRAMEWORK WATER & GROUNDWATER LAND USERS RESOURCES SUSCEPTIBILITY STAKEHOLDER I TO SIDE-EFFECTS PARTICIPATION POLLUTION ECONOMIC VULNERABILITY INSTRUMENTS NAote: The key hydrogeologic and socioeconomic elements that determine the level of impact and potential control of water/land use activities on groundwater are indicated schematically. pumping from individual wells). These chains can evolve upward as management needs drive communities to develop higher-level enabling frameworks (such as legislation to create aquifer management comnmittees) or they can evolve downwards from basic social principles to specific implementation policies (such as highly subsidized domestic water supply). In general, the institutional framework shaping groundwater management options can be viewed as comprising four possible levels: - The macro high-levelframework comprising social norms, fundamental rights and legal principles * State organizations, rights structures and market institutions operating at regional level * Intermediate level organizations operating at the level of hydrological units (catchments or aquifers) * Local institutions operating at the level of groups of users or communities. Enabling groundwater management to occur requires institutional arrangements at several of these levels. As a result, it is essential to think through the relationship between each level and their importance in relation to the specific management functions needed. In doing this it is important to recognize the several issues which are discussed below. First, agencies at different levels can have a range of functional roles depending on their capabilities. There is no inherent reason, for example, why regulations must be implemented and enforced by state agencies rather than local organizations. The appropriate level for regulation to occur depends on both the object of the regulation and the capacity of organizations at given levels. Second, macro frameworks matter, providing the ultimate legal authority for action. Constitutional provisions specifying groundwater as owned by the state but subject to private appropriation or as the common property of all users, play a major role in shaping management options and public attitudes (Salman, 1999). In Yemen, for example, groundwater is treated as common property under one interpretation of the Islamic code and many view water markets or water charging as inherently unethical. Recently attention has 50 Groundwater Resource Sustainability Groundwater in Rural Development focused on the public trust concept as a mechanism for balancing public and private interests in water resources (Koehler, 1995). This enables the state to initiate management while leaving room for private use rights and water market operations. Furthenmore, because water is being held in trust for the people (rather than being either private or sovereign property), the concept enables public participation in management. Third, in most situations there is a major gap at the intermediate institutional level. National water laws generally exist and in many cases articulate basic principles clearly (Salman, 1999). State regulatory agencies also often exist, though their capabilities vary greatly. There is., however, often a major gap between these organizations and the level of community groups and local users. This gap is of critical importance because most state organizations do not have the implementation capability essential to manage at aquifer scale. At the same time existing local organizations generally cover too little area to be effective in groundwater management and generally lack the necessary financial, technical and administrative resources. Intermediate institutions, such as aquifer management committees, will thus be needed in many instances. The establishment and operation of aquifer management comrinittees has a number of critical aspects: * Defining a sound legal basis for their operation and relationship with the regulatory agency and local government * Providing an element of financial support for meeting facilities,, at least in their initial stages * Promoting balanced representation of the groundwater user community, bearing in mind that even the agricultural user sector may be heterogeneous in tenns of dependence on groundwater, cultivation regime and income status * Developing and funding a technical information and communication system with the regulatory agency * Ensuring that the macro level water resources framework does not distort the agenda of the committee and accidentally convert them into a policy lobby group on other water resource issues (such as subsidized surface water transfer schemes) or even agricultural issues (such as subsidies for a given crop). Flexible Management Schemes The context for groundwater management is dynamic. This implies that institutional frameworks must be able to adapt to change. The contrast between an enabling adaptive famework and more rigid structures for groundwater management can be illustrated by the different approaches currently followed in India and the western states of the USA (Moench, 1994). In India, model legislation authorizing government control over groundwater has been in place since the mid-1970s. This bill (versions of which have recently been passed in several states) essentially creates a highly centralized government groundwater authority and provides it with a limited array of regulatory and enforcement powers. The top-down regulatory focus provides relatively little flexibility for adjusting to local conditions. In contrast legislation enabling the formation of groundwater management districts in parts of the USA authorizes a wide variety of functions and places their implemrentation under the control of locally-elected boards of directors. These boards, however, rarely have sole authority, their scope of action being limited: * On one side by private rights and the ability of individuals to enforce these through the courts * On the other side by state and federal laws, and the powers these laws give to government agencies. A system of checks and balances emerges in which the elected groundwater district boards often have broad authority but adapt courses of action to local conditions and changing circumstances. The effectiveness of groundwater management is (at best) partial, but the adaptive approach has facilitated substantial improvements (Kromm and White, 1990). In whatever manner they are achieved, flexible and alaptive institutions are central to effective groundwater management. As a result, in evaluating existing institutional frameworks (or designing new 51 Groundwater Resource Sustainability Groundwater in Rural Development ones), the degree to which they enable implementation to be adapted to local conditions and to evolve as circumstances change should be a major concern. Stakeholder Participation and Governance The importance of user participation is increasingly recognized for effective water management (World Bank, 1994). User participation is particularly important in the groundwater case due to the highly dispersed nature of resource use and the role individual decisions play in determining management outcomes. Substantial literature is available on water-user organizations and will not be reiterated here. The distinction between low levels of user participation and roles for users in governance of institutions is, however, important to emphasize in the context of groundwater resources. In most cases, addressing groundwater over-abstraction requires demand-side management-changes of individual use for irrigation that reduce total abstraction. These changes need to occur in activities that take place daily and affect both livelihoods and lifestyles. Users must, as a result, play a paramount role in management and groundwater regulators need to work with them "collaboratively on analysis, collaboratively in setting objectives, collaboratively in creating strategy and collaboratively in formulating project tactics" (World Bank, 1994). Collaboration must involve a dialogue between groundwater regulators and local stakeholders in which both parties have power to determine courses of action, and not one in which regulators encourage communities to participate by acquiescing to predetermined courses of action. This distinction is of fundamental importance, since in many cases a gulf exists between the approaches advocated by government authorities and the perceptions of local users. This gulf can become a continuing source of tension and needs to be bridged if it is not to undermine the effectiveness of management initiatives. Key Management Functions Groundwater management is inherently complex. This complexity can, however, be greatly reduced by systematically identifying what needs to be done for effective management. Once this is clearer, then identifying who should undertake what is generally more straightforward. This section, thus focuses on the key functions that institutions must undertake or enable (Table 13). An indication of the most appropriate level (or levels) at which the corresponding function should be promoted and implemented (within the institutional framework introduced previously) is also given in Table 13. The functions listed should not be reviewed as mandatory, but more as a check list. An underlying need behind many of the key functions is that of education. The characteristics of groundwater resources are often poorly understood by policy makers and water users alike. Moreover, the social, economic, political and institutional factors governing groundwater use and the effectiveness of different institutional arrangements for resource management may not be adequately appreciated by policy makers and technical specialists. Resources Evaluation A realistic assessment of the status of groundwater utilization and resources provides the essential background against which the need for, and focus of, groundwater management activities can be judged. This assessment will vary widely in its degree of sophistication from preliminary evaluation of the groundwater balance and state of storage reserves (in cases where only reconnaissance data are available) to detailed numerical aquifer modeling (in cases where the necessary input parameters can be reasonably estimated and adequate water level monitoring is available for calibration). 52 Table 13: Summary of groundwater resource management functions Institutional roles Key functions Potential activities NPM RRB AMC WUA * assessment of status of groundwater resource pro (imp)/inv inv inf Resource Evaluation exploitation (including use of numerical models) * targeted monitoring of groundwater levels and pro/imp imp/inv inf quality * integrated analysis of socioeconomic pro/imp inv inv inf Strategic Planning and roles/interactions of groundwater Coordination * coordination with government/private sector pro/imp inv inv inf institutions directly/indirectly relating to groundwater Li, * assessment of susceptibility to degradation pro imp inv inf > Identification of * identification of resource conservation zones pro/imp inv inf Management Priorities * groundwater valuation and pricing review pro imp inv inf * establishment/consolidation of register of pro/imp inv inv abstractors, abstraction rights and water Resource Regulation charges/markets * water (re)allocation and dispute resolution pro pro/imp inv * demand management support pro pro pro/imp imp * compliance monitoring and enforcement measures pro/imp imp inv NPM: national planning ministry RRB: regionally-based regulatory body AMC: aquifer management committee WUA: water-user associations pro: promote imp: implement inv: involve inf: inform Note: The need for a tiered institutional framework will be evident from the respective roles identified, although it is not the intention to imply that a top-down as such is preferable; it may be better for components of the resources evaluation function not to be under regulatory agency leadership, since this may compromise their credibility in the eyes of water-users, although this will often prove difficult to avoid in practice. Groundwater Resource Sustainability Groundwater in Rural Development Groundwater Recharge. Quantification of the current rate of groundwater recharge to an aquifer is one basic prerequisite for efficient resources management. Groundwater recharge may be defined in a general sense as the downward flow of water that reaches the water table and forms an addition to the groundwater reservoir. A clear distinction should be made between the potential recharge from the soil zone and the actual recharge to the aquifers. These quantities may differ significantly due to interception by deep-rooted vegetation or by perched water tables. At any location two distinct components of natural aquifer recharge can be recognized: * Direct (or diffuse) recharge from rainfall (excess to soil moisture deficits and short- term vegetation requirements) which infiltrates directly * Indirect (or localized) recharge, resulting from infiltration through the beds of perennial and ephemeral surface watercourses, and other forms of runoff. In practice, a spectrum of processes between these two end members occurs (Lerner and others, 1990; Simmers and others, 1997). In Figure 15 a broader conceptualization of groundwater recharge processes is introduced, distinguishing those that occur locally within the rural development area underlain by an aquifer system (be they as a result of natural direct/indirect processes or artificial causes) from those that occur at greater distance, especially in situations where the aquifer system extends into neighboring hilly terrain. Figure 15: Schematic representation and classification of aquifer recharge and discharge processes DISTANT RECHARGE LOCAL RECHARGE regular and/or intermitent NATURAL ARTIFICIAL infiltration in adjacent regular intermittent regular or intermittent permeable hills seasonal minor excess excess irrigation run-off infiltration in excess rainfall rainfall on irrigation distribution piedmont areas rver & lake unegetated losses bed seepage lekg rr, infiltration of overlying flash run-off artificial recharge works t t * aquiTers _ : DISCHARGE -_ O + FRESH U_ *011 SURFACE 7I7.\. . WATER BODIES V V. - ~~~~~discrete spring flow riverbed seepage VIA NATURAL | 0 i-- _ \ * * 4 x- ,-, --.-. . + ~~vEGETATION SATURATED AQUIFER.discrete wetlands (large storage) : . . .:.extensive riparian \ t.0 (/arge storage) . . : . . . . . . . . . vegetation (natural or agricultural) 8 t semi-permeable base . SAUNE AREAS DISCHAbRGE coastal waters OTHER ~~~~~~~~~~~~~~~~~salt lakes/playas I OTHER GROUNDWATER BODIES leakage to deeper aquifers Note: Artificial discharge through pumping wells is omitted for simplicity; other geological structures will change the distribution and scale of recharge and discharge components. 54 Groundwater Resource Sustainability Groundwater in Rural Development A number of general observations can be made in relation to aquifer rec:harge: * There is no doubt that recharge occurs, to some extent, even iTI the most arid regions, although areas of increasing aridity will be characterized by much decreasecl downward flux to the water table of much greater temporal variability (Figure 16). * As aridity increases, direct recharge will become less important in terms of total replenishment than indirect recharge, and the artificial (or incidental) components of recharge arising from human activity also become increasingly significant. * Estimates of direct recharge are always likely to be more reliable than those of indirect recharge. For most practicable purposes it would be sufficient initially to estimate recharge rates in the more arid regions within two of the scale increments indicated in Figure 16, but even this will sometimes prove difficult. More precision can only be achieved through the analysis of carefully-monitored aquifer response to significant medium-term abstraction. The actual frequency of infiltration events, and the vadose (unsaturated) zone transit time until recharge reaches the water table, are also important considerations. Figure 16: Categorization of aquifer recharge in the more arid regions for practical groundwater resource evaluation and development DIRECT (DIFFUSE) RECHARGE (D) frequency 1 in 1 3 10 30 100 300 years EXAMPLES Botswana Kalahari ....... ....... ........... ..0 .i (rainfall 300-500 mm/a, 100 1 ------------------------little surface water) 1* 00t. .LJO eivdt ar ieywt ILr..< o stablPeruvian Atacama .......0- - 5--- x . (rainfall <20 mm/a, but with E 100 30 1 3tm 0co important Andean rivers) LUJ -.0 CZ: 'I believed to varyideywt Note: In 2he exarnplesshown,thePeruvianAtacarnadesertisahyperaridregion thatiri vegetation type which numrou peena 20er flw weesteBtwnKaaaider,lhog cevgcnidependbupo widheraifly, withnetesv _J depends uponthickness of sU plai a) stable sand cover over caicrete; LL Q)~~~~~~~~~~~~~~~ 0) (outcrop calcrete and recent 10 1-------0....... .....dunesoffer improved prospects a)dt ofrecharge) L3) cc includes recharge from irrigated WU o E agriculture 100 30 1 0 3 I 0.3, %time INDIRECT (LOCALISED) RECHARGE (L) frequency Note: In the examples shown, the Peruvian Atacama desert is a hyperarid region that fringes a major mountain chain from which numerous perennial rivers flow, whereas the Botswana Kalahari desert, althouigh receiving considerably higher rainfall, is an extensive sand-covered plain covered with well established deep-rooted vegetation withi signlificant soil infiltration but very low rates of groundwater recharge Source: Foster, 1987. 55 Groundwater Resource Sustainability Groundwater in Rural Development Major, but very infrequent, recharge is a totally different proposition in resource management terms to more regular, if smaller, replenishment. This is because the negative side effects of excessive abstraction (albeit temporary) may have already occurred prior to replenishment. Further, the existence of an aquifer hydraulic gradient is no guarantee of recent recharge, since there may be "fossil gradients" reflecting historical recharge from past periods of much wetter climate, with natural recession of groundwater levels continuing to the present day. The quantification of groundwater recharge is fraught with uncertainty and it is necessary to apply and compare a number of independent approaches (Foster, 1987). The main techniques that can be employed specifically to estimate current groundwater recharge rates may be divided into those for which the required data are often available or can readily be collected, and those for which more specialized and expensive facilities are needed (Table 14). Table 14: Principal direct techniques used for groundwater recharge estimation Technique Applicability Typical costs Specialist needs Time step Conventional Methods Hydrometerological Data Processing (soil water balance) D(L)O c** . ESYH Hydrological Data Interpretation - water table fluctuations D(L) c* . YH - differential stream/canal flow L c** * I/E Chermical and Isotopic Analyses D+L c-b* * (-) HG from Saturated Zone Modem Techniques Chemical and Isotopic Profiling of Vadose (Unsaturated) Zone DO# b-a* * HG Soil Physics Measurements DO a SY D/L diffuse (direct)/localized (indirect) recharge distribution O only suitable for relatively uniform soil profiles inappropriate for irrigated agricultural areas * isotopic analyses increase cost substantially ** excluding construction and operation of basic data collection network a = >US$50,000; b = US$10-50,000; c = \ A A Inset II: Leaching of the insecticide Carbofuran from N irrigated cultivation to shallow groundwater in vulnerable aquifer on Sri Lankan coast 0J |F |M |A |M |J |J |A|5O °|N| J Fo M IAIM 1990 systems. It is, however, not possible to make a realistic assessment of the risk of contamination of deeper InsetI: GroundwateratrazineconcentrationsinBarbados groundwater in less vulnerable aquifers (Foster & catchments under sugarcane cultivation Chilton, 1998). * Research has also been undertaken on the * Given the widerange of pesticide compounds in use northwestern coast of Sri Lanka on the fate of in agriculture, and their many toxic metabolites, an carbofuran (Foster & Lawrence, 1995), which was approach to groundwater pollution risk assessment applied at 6 kg (ai)/ha to horicultural crops. The parent based on the key properties of the pesticide compounds compound is highly mobile and was rapidly leached (mobility, solubility) and of the geological media from the soil with concentrations of 200-2000 pg/l in (propensity to preferential flow in vadose zone) is the soil drainage of a lysimeter and peak concentrations needed to target monitoring. in excess of 50 pg/l in the underlying shallow igroundwater within 20 days of application (Inset II). * In general terms, a significant additional element of Carbofuran was, however, subject to rapid degradation protection for drinking water-supplies will be provided and in part transformed to its more persistent (but less if their intake is at a considerable depth below the mobile) metabolite, carbofuran-phenol. This remained water-table, and the sanitary integrity of upper section in the shallow groundwater for more than 50 days. of solid well casing is sound. This will generally provide additional aquifer residence time for pesticide Although available research and monitoring is very degradation before entry to the waterwell concerned. sparse, there is sufficient to demonstrate the risk of Those wells most vulnerable to contamination by leaching of agricultural pesticide to shallow agricultural pesticides will be shallow dug wells groundwater in highly vulnerable aquifers, and the providing domestic supplies to isolated rural farmsteads potential persistence of toxic compounds in these in areas of intensive cultivation. The hydraulic characteristics of many aquifers are, however, such as to present high probability of the development of so-called preferential flow in the vadose zone, especially (although far from exclusively) in consolidated fractured formations. Preferential flow is of major importance in the consideration of pesticide transport into aquifers (Foster and Chilton, 1998). Where developed, it would provide routes for deeper penetration of readily-leached pesticide compounds and would be characterized by much more rapid 80 Protecting Groundwater Quality in Rural Areas Groundwater in Rural Development pollutant transport, providing less opportunity for retardation through molecular diffusion into the microporous matrix and associated adsorption, chemical reaction, and biodegradation. If preferential flow in fissures of larger aperture occurred, the possibility of transport of less mobile pesticide compounds adsorbed on colloidal material would also arise. There has, as yet, been very little research and monitoring of the leaching of agricultural pesticide residues and derivatives under tropical conditions, but some limited available data are given in Box 13. Controlling the Leaching of Agrochemicals The preceding sections demonstrate that agricultural cultivation can have a significant impact on groundwater quality and, under some conditions, seriously compromise its value as a primary source of potable water supply. In a qualitative sense Table 17 indicates the relative influence of hydrogeologic and agronomic factors in this process. It also indicates in a general way (through bold type) those factors which to some degree can be controlled by changing cultivation type or practice. In more general terms a rational strategy for the control of diffuse groundwater pollution from agricultural cultivation practices would include the following measures (Foster and Chilton, 1998): * Recognize that incremental changes in the intensification of agricultural cultivation can run high risk of adverse impact on groundwater quality, while offering rather marginal returns to farmers * Adopt major aquifer recharge areas as a separate unit in glii(lelines for agronornic practice, taking account of the need to reduce leaching to groundwater * Introduce groundwater leaching assessment in cropping trials before new agronomic practices are recomrnended and pesticide compounds approved * Accept that more positive control over land use may havre to be taken in groundwater source protection areas. Table 17: Summary of the relative impact of agronomic factors on groundwater quality SOIL LEACHATE DETERMINING FACTORS SOIL LEACHATE CONCENTRATION* CONCENTRATION* RANGE lesser ---- greater Nitrate Pesticides Nitrate Pesticides soil permeability + + ++ ++ soil thickness + excess rainfall + ++ ++ irrigation efficiency** . ++ + control of applications - 0 pesticide (type) mobility 0 ++ ++ continuity of cultivation + + frequency of plowing ++ - 0 grazing intensity** ++ 0 Note: It is difficult to be more prescriptive than this due to the wide range of agricultural regimes and hydrogeological conditions under potential consideration. * concentration not load since latter also requires consideration of recharge volume ** where applicable (+)+ tends to increase concentration 0 minimal effect (-)- tends to decrease concentration Source: Foster and Hirata, 1988. 81 Protecting Groundwater Quality in Rural Areas Groundwater in Rural Development BOX 13: Groundwater Source Pollution Risk Evaluation & Management around Managua, Nicaragua * Groundwater is of the utmost importance for stations and waste disposal sites, only one industrial domestic, industrial and agricultural water-supply in site with underground storage tanks has been classified the region around Managua, which has a population as having high potential contaminant load. well in excess of 1.0 million. Water is extracted from deep municipal and private boreholes in the major * The capture area is more predominantly agricultural volcanic aquifer system located south of Lake and it is considered that the frequent use of mobile Managua, (deposited by eruptions of the Masaya pesticides (such as the carbamate insecticides) poses Volcano, whose crater is situated some 20 km southeast the major pollution threat, and control over agricultural of the city). activity will be needed in the interests of municipal water-supply. * The volcanic formations include lava flows from the volcano (last major eruption 1792), interbedded with pyroclastic deposits. There is little soil Inset: Groundwaterpollutionassessmentmappingfor development on the most recent flows and no surface Managua groundwater system (eastern area) run-off with high rates of rainfall infiltration/ groundwater recharge. The area is classified as highly- vulnerable, despite the relatively deep water-table (ranging from 25 m bgl to more than 100 m bgl close 5 km a to the volcano), except where alluvial-volcanic deposits nua of lower permeability occur at the surface. * The main existing wellfield abstracts some 195 Ml/d and is located in the urban fringe east of Managua ESTIMATED City, but a new wellfield at a more rural location some MUNICIPAL 10 km south of the city is under investigation and CAPTURE development. ZES * The entire area, including the groundwater capture (NEW) zone of the proposed new wellfield of 70 MIl/d, has been the subject of systematic groundwater resource risk evaluation, including aquifer vulnerability mapping and subsurface contaminant load survey (Scharp, 1994; Scharp et al 1997). In this work there was a clear Lake policy to involve all stakeholders; not only the major users but also the potential'polluters of groundwater. *The capture zone of the existing wellfield is threatened by a range of industries including tanneries, metal workshops and textile manufacturers in the Zona Franca industrial area, as well as fuel and chemical N storage at the international airport and a number of developing periurban towns with in-situ sanitation. There are also several small air strips in the area, which were historically used for storage, loading and aerial spraying of agricultural land. In the past 30 years there was intensive cotton cultivation using CONTAMINATION LOAD AQUIFER many highly persistent pesticides, such as Toxaphene low moderate high VULNERABILITY and DDT. Industrial * * low Siteslo The predicted capture zone of the new wellfield is Petrol EI moderate classified as having mainly moderate vulnerability, Filling * high but there are areas of high vulnerability due to the Stations absence of soil cover, which has been removed through Landfill erosion. While there are a number of potential point lts sources of contamination from industry, petrol filling 82 Protecting Groundwater Quality in Rural Areas Groundwater in Rural Development Agricultural pollution stems from literally millions of everyday activities and management decisions made by farmers. Individually these activities may not cause discernible environmental harm, but the aggregation of these activities over many months or years can combine to affect groundwater quality adversely, and even the productivity of the soil itself. Application of a regulatory approach to diffuse pollution has the significant problem of identifying both measurable and enforceable standards and the resources needed to monitor compliances on millions of acres of agricultural land, and is a formnidable challenge. There is thus a need to identify priorities both in terms of the more polluting aspects of agricultural practice and the groundwater resources most in need of protection. Groundwater quality protection creates the need to work with all agricultural producers, and particularly those who are motivated to care for their land. Pollution prevention strategies need to focus on improved management practices leading to contaminant source reduction or risk management. Some government programs intervene when environmental problems present direct threats to health. Such intervention is crisis management and not pollution prevention. While pollution prevention may require some investment in new technologies, more often it is a matter of improving behaviors and practices. Contaminated groundwater will threaten the farmers who pollute, as well as the community drinking water supply. There are thus incentives for farmers to practice prevention. Of course, farmers alone cannot be expected to meet the challenge of incorporating pollution prevention into agriculture, and governments must provide some incentives and support initiatives. Agriculture includes not only cropland and pastures, but alsc farm buildings and facilities. These locations also involve groundwater pollution risk. Farmsteads can have petroleu:m tanks, pesticide and fertilizer storage units, septic tanks or pit latrines, livestock yards, feedstuff and rnanure storage facilities. The concentration of potential contaminants and intensity of activities around farmsteads can generate significant pollution risks from nitrates (Figure 20), toxic chemicals and microorganisms, especially to the domestic waterwells on (and in the vicinity of) farms. Pollution Hazard Assessment and Protection Strategy General Approach Improving the protection of groundwater against serious pollution is a complex task, involving concepts that are not widely understood. Two interrelated but independent components should be recognized, namely protection of: * Groundwater resources or aquifers as a whole * Groundwater sources, that is, those parts of aquifers where the resource is exploited for potable water supply. The latter is normally considered as supplementary to the forner, but a realistic balance between the two needs to be struck, according to local circumstances (Foster and Skinner, 1995). Aquifers are naturally (but variably) protected against pollution of their groundwater by the vadose zone or the confining beds which overlie them. For groundwater protection policy not to be unnecessarily restrictive on human economic activity, this natural attenuation capacitv must be utilized. This can be achieved by zoning the vulnerability of the underlying aquifer to pollution al: the land surface, and thus enabling priorities for pollution control to be logically assigned. Controls would be sought over existing and new activities involving potential hazards to groundwater, according to their location in relation to such zones. 83 Protecting Groundwater Quality in Rural Areas Groundwater in Rural Development Figure 20: Groundwater nitrate concentrations in the weathered basement aquifer of rural areas of central Nigeria 500- 0 200 - 100- WHO drinking water * * j guidelines 50-__ 0 z0 0) 20 - * 2- UNINHABITED NEAR VILLAGES/ AREAS HOUSES SMALL TOWNS wa m ?ean of wet and dry season surveys in corresponding land-use type Note: The uninhabited areas were in use for low-intensity dryland cropping and animal grazing; the increase in groundwater nitrate concentrations near habitation is due to in-situ disposal of human and animal excreta Source: Langenegger, 1994. In areas with intensive agricultural development, the zones would serve to define the priority for establishing an inventory of hazardous chemicals, for estimating subsurface contaminant load due to soil leaching and for designing an aquifer monitoring network (Chilton and others, 1990). Such actions would be required before the implementation of pollution control measures could be rationally justified. The need to achieve maximum aquifer protection will also vary with the utilization (actual or designated) of groundwater resources. Protection measures should normally be intensified around public water supply sources. Thus in the assessment of groundwater pollution hazard and the formulation of groundwater protection policy, the basic prerequisite is both: * The ranking and mapping of aquifer pollution vulnerability * The definition of special groundwater source protection areas. These tasks are discussed further technically in succeeding sections. In socioeconomic terms they are effective vehicles for initiating the involvement of all stakeholders (including water supply interests and potential agricultural polluters), which will be essential if progress on groundwater quality protection is to be made (Box 14). 84 Protecting Groundwater Quality in Rural Areas Groundwater in Rural Development The emphasis placed on one or other of these approaches will depend on the resource development situation and prevailing hydrogeological conditions (Foster and. Skinner, 1995). Source-oriented strategies are best suited to more uniform, unconsolidated, aquifers exploited by a relatively small and fixed number of high-yielding public water supply boreholes with stable pumping regimes. They are particularly appropriate in sparsely-populated regions where their definition can be fairly conservative without producing serious conflict with other interests. They cannot be so readily applied where there are rapidly growing numbers of individual abstractions and seasonally-variable pumping, since this will render consideration of individual sources and the definition of fixed zones impracticable. Data deficiencies and scientific uncertainties, especially in heterogenous aquifers, can also render the estimation of protection zones inadequate. Aquifer-oriented strategies are more universally applicable, but it has to be recognized that there may be limited parts of aquifers which do not justify protection because their water quality is naturally too poor or has already suffered excessive deterioration. A further complication arises where groundwater systems are thick and layered, and it will be essential from the outset to be clear about which aquifer is being considered. Mapping Aquifer Pollution Vulnerability The ability of natural subsoil profiles to attenuate many water pollutants has long been implicitly recognized. To a lesser degree, the attenuation processes continue below the soil, deeper in the vadose zone, especially where unconsolidated sediments, as opposed to consolidated fissured rocks, are present. However, not all soil profiles and underlying hydrogeological environments are equally effective in pollutant attenuation. Moreover, the degree of attenuation will vary with types of pollutants in any given environment. Concerns about deterioration of groundwater quality relate principally to unconfined or phreatic aquifers, especially where their vadose zone is thin and their water table is shallow. A significant pollution hazard may also be present even if aquifers are semi-confined and the overlying aquitards are relatively thin and/or permeable. Groundwater supplies drawn from deeper, highly confined aquifers are much less affected by pollution from the land surface, except by the most persistent pollutants in the very long term. Aquifer pollution vulnerability is a helpful concept increasingly used to indicate the extent to which an aquifer can be adversely affected by an imposed contaminant load. This is a function of the intrinsic characteristics of the vadose zone or the confining beds that separate the saturated aquifer from the land surface immediately above (Foster and Hirata, 1988). Some hydrogeological environments are inherently more vulnerable than others (Table 18). Areas of the same aquiifer system may have different relative vulnerability due to spatial variations in vadose zone thickness or the character of confining strata. Mapping of aquifer pollution vulnerability provides a simple, but consistent, set of criteria for land surface zoning. The integrated vulnerability concept is not scientifically precise, but the concept provides a general framework within which to base groundwater protection policy and pollution control measures (Table 19). Where the leaching of agricultural chemicals is the major concem, the scheme for assessing aquifer pollution vulnerability must include an element to take account of the properties of the soil zone which affect the likelihood of nutrient and pesticide leaching. Many processes causing pollutant attenuation occur at their maximum rates in this zone, as a result of its higher clay and organic content, and very much larger bacterial populations. It must be stressed that aquifer vulnerability maps are designed to provide a general framework within which to base groundwater protection policy. They should comprise a simplified, but factual, representation of the best available scientific data on the hydrogeological environment, no more or no less. Pollution control areas may include more than one vulnerability class depending on their objective. 85 Protecting Groundwater Quality in Rural Areas Groundwater in Rural Development BOX 14: Rural-Urban Competition & Conflict for Scarce Groundwater Resources in the Yemen Arab Republic * The water resource situation in the Yemen is * The situation atAl Himaand Habeercontrasts sharply extremely serious with many aquifers heavily with the water markets through which most residents overdrafted and population growing at close to 4% of Taiz meet their basic water needs (World Bank. pa, leading to escalating demand in both urban centres 1996). Well owners adjacent to the city sell water on and agricultural areas (WRAY-35, 1995). a daily basis, either directly to urban users or to tanker operators who retail to consumers. This informal water * The situation in the area around Taiz, the third largest market is highly structured with consumers paying city, is illustrative of growing competitive pressures. different rates for water of different quality (Inset). Municipal water-supply (provided by NWSA) is The intense and violent conflict that characterises Al extremely erratic, with breaks in supply often exceeding Hima and Habeer is absent, and rural populations are 10 days (World Bank, 1996). In response, informal able, at least, to increase income through water sales. water markets have evolved and many urban residents meet their needs by purchasing from tankers. WATER WHOLESALERS/ WATER PRODUCER RETAILERS CONSUMERS * Government is desperately seeking to improve the municipal water system and a new wellfield was (indicative equivalent cost) constructed in the Al Hima wadi (some 25 km Well Owners Irrigated upstream), following negotiations with a private land (US $0.004/m3 - Agriculture owner. The area was originally swampy and generated pumping costs) (US $0.030/m3) a significant baseflow, which was utilised for Well Owners Commercial Users agricultural Irimgation. (US $0.004/m3 - (with own tankers) pumping costs) (hotels, poultry * In the reconnaissance study groundwater resources farms, industrial were grossly over estimated and neither the upper premises, irrigated alluvial aquifer nor the underlying volcanic and (USl$0140/rn3) sandstone formations provided the sustainable yields . forecast. By 1995 total groundwater production had Well Owners Water Tanker Smaller Users declined to 2.6 Mm3/a from an initial yield of more (US $0.004/m3 - Operators (homeowners, than 4.0 Mm3/a, and even this was at the cost of pumping costs) (US $0.140/m3) hostels, eliminating all irrigated agriculture and eradicating restaurents, construction the lush vegetation. Most of the rural population now industry) survive through rainfed subsistence agriculture and (US $0.210/m3) casual labour in Taiz. Compensation, although promised, has not yet been paid. Well Owners Retail Shops Individual Users (US $0.004/m3 - (US $1.000/m3) (mainly purified * In 1995, the proposal for a second emergency urban pumping costs) drinking water) (up to US $ water-supply drilling program at Habeer, further Treatment Plant 2.000/m3) upstream of Al Hima, was (not surprisingly) strongly Operators opposed by the local rural population. Several women (with own tankers) (US $0.004/mn3 - were shot and injured during protests aimed at stopping pumping costs) the drilling. Nevertheless, a new wellfield was completed in 1997 and is experiencing similar Inset: Summaryoftransactionsandpricesofinformal problems; compensation has been offered. groundwater markets in Taiz, Yemen AR KEY ISSUES * should government formalise and rationalise existing water markets, which cut across strongly held cultural norms on the common nature of water rights and the interpretation of some that water sale should be forbidden * although such markets appear to represent a mechanism to reduce conflict and to maintain some income in rural areas, they will not address the deep-seated problem of groundwater overdraft and can impose a very high burden on the urban poor 86 Protecting Groundwater Quality in Rural Areas Groundwater in Rural Development Table 18: Principal hydrogeological environments and their associated pollution vulnerability Natural travel time to Hydrogeological environment saturated zone Attenuation potential Pollution vulnerability Major Alluvial unconfined weeks-months moderate moderate Formations semi-confined years-decades high low Recent Coastal unconfined days-weeks loNv-moderate high Limestone Inter-Montane unconfined years-decades moderate moderate Basins semi-confined Consolidated porous sandstones months-years imoderate moderate Sedimentary Aquifers karstic limestones days-weeks low extreme Weathered Crystalline unconfined days-weeks lowv-moderate high Basement Note: This gives a very general guide to the typical situation, and there will be much variation at local scale with detailed variations in the hydrogeology. Defining Groundwater Source Protection Areas The objective of source protection areas (called wellhead protection zones in the USA) is to provide a special additional element of protection for selected groundwater sources (boreholes or springs). This is achieved by placing tighter controls on activities within all or part of their recharge capture area. The outermost protection area that can be defined for an individual source is its recharge capture area. This is the area within which all aquifer recharge, whether derived from precipitation or surface watercourses, will be captured at the source concerned, and should not be confused with the area of hydraulic interference caused by a pumping borehole. In practice, the definition requires further specification, and it is customary to use the maximum licensed abstraction rate together with the long-term average recharge rate when calculating such areas. It is accepted that, on this basis, the actual capture area in extreme drought will be larger than that protected. The recharge capture zones of sources are significant not only for quality protection but also in resource management terms. In situations of intensive groundwater use they could be used for aquifer exploitation control also. In order to eliminate completely the risk of unacceptable source contamination, all potentially polluting activities would have to be prohibited or controlled to the required level within the entire recharge capture zone. This will often be untenable, due to socioeconomic pressure on land use for agriculture. Thus, some division of the recharge capture zone is required, so that generally the more severe constraints will only be applied closest to the source itself (Foster and Skinner, 1995). This subdivision could be based on a variety of criteria, depending on the perceived pollution threat, including horizontal distance, horizontal flow time, proportion of recharge area, saturated zone dilution or attenuation capacity. The dilution and attenuation capacity of the saturated aquifer are, in practice, difficult to quantify and predict, although the latter will in a general sense increase with increasing horizontal flow distance and flow time. Intuitively, dilution might appear to be a useiul criterion to delimit source protection perimeters; however, this is not necessarily so. Special protection of a. proportion of the recharge area may be the preferred solution to alleviate diffuse agricultural pollutioni of groundwater under certain circumstances, but even then the question of which part of the recharge capture zone ito protect inevitably arises. 87 Protecting Groundwater Quality in Rural Areas Groundwater in Rural Development Table 19: Definition of aquifer vulnerability classes Integrated vulnerability class Practical significance Extreme vulnerable to most water pollutants with relatively rapid impact in many pollution scenarios High vulnerable to many pollutants except those highly absorbed and/or readily transformed Low only vulnerable to the most persistent pollutants in the very long term Negligible confining beds present with no significant groundwater flow Note: This overcomes those objections to the integrated vulnerability concept based on the need to specify individual contaminants. Source: Foster and Skinner, 1995. In practice an inner protection zone based on the distance equivalent to a specified average aquifer horizontal flow-time has been widely adopted for the prevention of pathogenic contamination of groundwater sources, from (for example) the spreading of wastewater and slurries on cultivated land. The flow-time used has varied significantly (from 10-400 days) between regulatory agencies in different countries and regions. A review of published case histories of groundwater contamination by pathogens (Lewis and others, 1982) concluded that the horizontal distance between the borehole/spring and the proven source of pollution was equivalent to no more than the distance traveled by groundwater in 20 days, despite the fact that some pathogens are capable of surviving in the subsurface for 400 days or more. A value of 50 days was thus considered a reasonably conservative basis with which to define the inner protection zone, and conforms with existing practice in many cases. Special problems arise with the definition of recharge capture areas in situations where the groundwater divide is at a great distance, the regional hydraulic gradient is very low, and/or there are surface watercourses flowing across unconfined aquifers. A further practical complication with all source protection areas is that they vary position or have complex shapes if numerous sources are in close proximity. In the case of heavily developed aquifers, it is more practical to coalesce individual source protection zones into a larger multi- source protection area. However, if a significant proportion of the abstraction is for non-potable uses (especially irrigation) a further complication arises. The definition of source protection areas can be achieved by using suitable computer models; provided these models are used properly they should give reliable results, within the limits of parameter uncertainty. A valuable first phase in the implementation of source protection areas is to estimate their extension and to consider their implications based on calculations using existing hydrogeological data, and it is strongly recomrnended that this planning exercise is undertaken by all water companies with rurally sited sources as a matter of priority. Undertaking Wellhead Sanitary Surveys While the definition of groundwater source recharge capture areas will be appropriate for higher-yielding groundwater sources used to reticulate water supply for larger villages and small towns, it is not practicable for small community and individual private domestic wells because their capture zones are very small. In these cases, however, (as with higher-yielding potable water supply boreholes) a systematic wellhead sanitary survey is strongly recommended. A standard methodology for sanitary inspection exists (Lloyd and Helmer, 1991), in which a number of direct observations on the physical condition of the wellhead area are correlated with a fecal coliform grading derived from monitoring raw water from the source concerned (Table 20). This leads to an assessment of source contamination hazard of potentially immediate impact, and simultaneously points to appropriate risk management actions. 88 Protecting Groundwater Quality in Rural Areas Groundwater in Rural Development Table 20: Systems of scoring for sanitary risk and confirmiing fecal pollution hazard for groundwater sources FACTORS IN SANITARY SURVEY Environmental Hazards (off-site) * local caves, sinkholes or abandoned boreholes used for surface drainage or sewage disposal * fissures in strata overlying water-bearing formations * nearby sewers, pit latrines, cesspools, septic tanks, drains, livestock pens or farmyards * nearby agricultural wastes discharged or spilled Construction Hazards (on-site) * well-casing leaking or not penetrated to sufficient depth, inadequate sanitary seal around casing * well-casing not extended above ground or floor of pump room, or not closed at top * leaks in system under vacuum * wellhead, pumping plant suction pipes, or valve boxes located in pits valnerable to flooding scores of 4-6 indicate intermediate-to-high, and 7+ very high, potential pollution risk GRADE FC RAW WATER COUNTS CONFIRMED POLLUTION RISK (mpn or cfu/100 ml) A 0 none B 1-10 low C 11-50 intermediate-to-high D 50-1000 high E >1000 very high Note: The combination of simple (but clearly prescribed) visual inspection coupled with microbiological surveillance provides an effective (but low cost) approach to fecal pollution hazard assessment. Source: Lloyd and Helmer, 1991. 89 5 THE R URAL- URBAN INTERFA CE: AN ADDENDUM In many senses the rural-urban interface is characterized by some of the greatest groundwater resource anomalies and conflicts. It is often the area with: * The steepest hydraulic gradient (as a result of excessive groundwater pumping in the * Periurban environment for municipal and industrial water supply) * The steepest water price gradients (as a result of the variation in groundwater abstraction charges and end-user values between the urban and rural environment) * The heaviest subsurface contaminant load and greatest risk of groundwater pollution (as a result of periurban industrial development and intensification of agricultural production by horticulture to meet urban demands). It is not the intention in this addendum to enter into detailed discussion of urban groundwater issues, nor the evolution of groundwater exploitation in urban and periurban areas, since this was dealt with in an earlier companion World Bank Technical Paper on "Groundwater in Urban Development" (Foster and others, 1998). Discussion here, therefore, is restricted to consideration of those issues which most impact upon the status of groundwater resources and/or the rural community themselves: * Competition for available groundwater resources between urban and rural users, resulting from the pressure to transfer water supplies to neighboring urban areas • Potential constraints imposed on the agricultural community by policies aimed at protecting potable groundwater quality in the vicinity of municipal wellfields * The potential impact on potable groundwater quality of the reuse of urban wastewater for agricultural irngation. Groundwater Resource Competition and Transfers Many regimes of land and water resource administration permit municipal water utilities/companies to explore for and develop new groundwater supplies well beyond current urban limits in contiguous agricultural areas. In some instances the impact of major wellfield development for the rural community can include: * Increased pumping head and energy costs, or even the need to reset/redimension/replace pumping plant and to deepen boreholes, for the owners and operators of irrigation wells * Increased rates of aquifer overdraft in situations of resource scarcity, compromnising further the long- term sustainability of groundwater resources. 90 The Rural-Urban Interface: An Addendum Groundwater in Rural Development In other situations the increased pressure of groundwater resources will come from private abstractors providing urban services, including the provision of tankered water supplies. The situation is frequently further complicated by inadequate characterization of the local groundwater system, and misconceptions, for example, about the degree of hydraulic independence of deeper aquifers under exploitation for urban and industrial supplies, and shallower aquifers providing the water supply for agricultural irrigation. All too often there is inadequate investigation of the potential impacts of new urban wellfield developments on existing agricultural groundwater users. Moreover, there is no acceptance of the concept of paying compensation for interference with pre-existing water rights nor existence of a transparent system by which such compensation should be estimated. On the other side, there is often a long history of not levying any charge or realistic charge for groundwater exploitation for irrigation, leading to an entrenched situation as regards the undervaluation of groundwater resources and consequently their inefficient use in agricuLture. An example of the level of resource conflict that can arise, and potential solutions in terms of resource management, is given in Box 14. What is apparent is that the way out of the more deeply entrenched rural- urban groundwater resource conflicts lies in establishing and registering groundwater abstraction rights and then using economic mechanisms to constrain and to allocate available resources more effectively. The latter may involve greatly increased abstraction charges to reflect resource scarcity, but it may be easier to introduce economic measures by establishing water rights markets for which the regulatory agency acts as broker. Municipal Wellfield Protection Issues Another potential dimension of the urban-rural groundwater resource conflict is the pressure that may arise for land-use controls in the vicinity of urban wellfields. A rational component of the development of a new municipal wellfield is to mobilize actions to protect the asset: first through the definition of a protection zone corresponding to all or part of the source capture area and seccind by controls on land-use activity within the protection zone according to the pollution vulnerability of the aquifer system involved (Box 13). Sooner or later it may be recognized that some control ever the application of agricultural fertilizers, pesticides, and slurries, or on livestock grazing densities may, in fact, be needed to protect the potability of the groundwater supply. In extreme cases more radical changes in cultivation regime may be sought. Where the latter involves actual land purchase by the municipal watier corapany, an element of compensation to those individuals in the agricultural sector is implicit. However, where constraints in agriculture are imposed following representations to the regulatory agency, conflicts may arise. This type of land-use/water quality interaction issue is, as yet, far from finding adequate institutional resolution, and introduces potential inequities between neighboring ifarmers in a relatively small land area. The question of compensation being paid to affected farmers arises, and whether the revenue should be raised from charges imposed on the municipal water-users. There is no need for the regulatory agency to act as a broker in this respect, but it is useful for the brokerage system to involve the regulator as registrar. Urban Wastewater Reuse for Irrigation Where cities have significant cover of main sewerage (as opposed to in-situ sanitation), substantial volumes of wastewater are continuously discharged, normally close to the downstream urban-rural interface. This wastewater represents both an important water resource for irrigation (the only one worldwide which is growing in volume and availability) and also a potential public health hazard, unless the WHO 1989 Guidelines for Wastewater Reuse are respected. The level of treatment varies but rarely extends beyond primary settlement. Even where it is more complete the objective is normally to reduce environmental impact in receiving watercourses (where BOD, SS and P are the main, considerations) rather than the elimination of 91 The Rural- Urban Interface: An Addendum Groundwater in Rural Development pathogens and nitrate load. As a result wastewater still normally has a major potential to pollute underlying aquifers if the local streams/rivers are influent (infiltrate to groundwater). In climates which have an extended dry season or are generally arid, urban wastewater often provides the bulk of riverflow downstream of major conurbations for many months in the year and is likely to be used for irrigation of agricultural crops on downstream alluvial tracts (Box 15). Indeed, some urban water utilities are in the process of offering partially-treated wastewater and financing improvements in irrigation technology to farmers in exchange for groundwater abstraction rights to reduce periurban groundwater resource competition and overdraft. However, given the normally high suspended solids and organic matter content of wastewater, application is by flood irrigation and results in high rates of infiltration to groundwater on permeable alluvial-terrace soils (Foster and others, 1994). The degree of groundwater pollution hazard involved varies widely with the aquifer pollution vulnerability and the characteristics of the wastewater (especially its salinity and content of toxic organic chemicals and heavy metals). At the same time it must be noted that it is possible to use some wastewaters for groundwater recharge, effecting tertiary-level treatment by infiltration through the vadose zone. This process is capable of producing groundwater of sufficient quality to allow safe irrigation of high-value horticultural crops subsequently. However, the infiltration process will not alone regenerate water of potable quality since various contaminants such as nitrates and synthetic organic (community and industrial) chemicals at least will persist and only be reduced by dilution. In less favorable circumstances there may also be residual contamination by some fecal pathogens, excessive salinity and/or other chemicals. Thus, while wastewater reuse is much needed in the urban-rural interface and around major conurbations. At whatever level it is practiced there is a need for: • Careful planning * Operational control * Systematic monitoring. At present, it rarely receives adequate attention. All too often it is practiced on an anarchical basis which threatens the well-being of agricultural workers, the health of those consuming their products and the long- term quality of groundwater in the underlying aquifer which may be an important source of potable water supply. The larger is the wastewater irrigation area, the proportion of wastewater to freshwater in the area and the salinity of the wastewater itself, the greater will be the overall impact on groundwater quality and the potential problem of locating and protecting groundwater supplies of potable quality in the area concemed. 92 The Rurat- Urban Interface: An Addendum Groundwater in Rural Development BOX 15: Wastewater Re-UseforAgricultural Irrigation in Central Mexico: Benefits, Problems and Solutions * The city of Le6n-Guanajuato (population 1.2 * It is tius not necessarily the most toxic component rmillion) is one of the fastest growing cities in Mexico, of an effluenrl which poses the main threat to and is highly dependent on groundwater for public groundwater, and this example highlights the supply. Groundwater is abstracted mainly from importance of understanding pollutant transport in aquifers downstream, including areas where city the subsurface. Future management therefore needs wastewaters are used for agricultural irrigation. Le6n to address the problem of rising salirity, while trying wastewater is of relatively high salinity and chromium to contijnue to rmaxirmise the reuse of wastewater in content because of the major leather processing and agricultre. shoe manufacturing industry. * A recent study showed (Foster, 1996; Chilton et al, 1998) that high rates of recharge from excess wastewater irrigation on alfalfa and maize southwest * wastewater lagoon N ff~ urban area of the city (coupled with no agricultural abstraction) g lan abe have helped maintain groundwater levels within lOim land abovL depth, despite intensive abstraction from deeper murlicipalsupply 0 0 horizons for municipal water supply. In adjacent subtirban areas) a areas water levels are falling at 2-5m/a. _ municpal wellield 0 extent of . 0te 0waslewater * However, salirity problems are beginning to affect irrigation LE N D a number of production wells in the wastewater irrigated area. In the most seriously affected well, . the chloride concentration rose from 100 mgAl to 230 mg/A in 2 years (even though the boreholes in this wellfield are screened from 200- 400m depth) and it is predicted that they could rise to 400mg/A by 2010 in all the neighbouring wells if no remedial action is taken. There is also evidence of increasing nitrate concentrations. * In contrast, although the wastewater also contains f roundwaereeets mann large concentrations of chromium salts, Cr desph:eheavypumping, but concentrations in groundwater remain low. Soil chlorideandnitrate risingsteadily sampling has confirmed that chromium and other heavy metals are accumulating in the soil, with very little passing below a depth of 0.3m. Neither are Inset: Location of municipal wellfields and wastewater significant levels of pathogenic micro-organisms or reuse area of Le6n-Guanajuato, Mexico. fecal coliform indicators found in the groundwater. KEY ISSUTES: * address rising salinity (more urgently than conventional wastewater treatment) through separate collection/treatment of saline industrial effluenits (altlhough substantial time-lag before benefits felt as improved groundwater quality) * shallow groundwater pumping for irrigation in existing wasl:ewater reuse area to intercept and recycle saline recharge; this may have implicationis for aLgricultural production and soil fertility, and wir also imply extending reuse area * remove affected municipal production wells from supply to reduce downward leakage of saline recharge, which will also require demand management measures (mains leakage control and private use constraints) in view of reduced supply 93 REFERENCES (Key works in relation to the development and perusal of this paper are in bold type) Ahmad, K. G. 1990. "Rehabilitation of Deteriorated Tubewells in Punjab SCARPs." Water Wells: Monitoring, Maintenance and Rehabilitation. London: Spon. 291-302. 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