EarthTrends: Featured Topic Title Will There Be Enough Water? Author(s): Carmen Revenga Editor. Pilot Anab sis of Global Ecosy stems: Freshwater Systems Date written: October 2000 Water policies in most nations are failing to protect lifes most Water Scarcity: The World's Most Pressing Resource Issue vital resource. This fact is Figure 1: Annual Renwable Water Supply per Person by River Basin, 1995 reflected in growing water scarcity and alarming decline in the health of aquatic ecosystems worldwide. More precious than oil, yet routinely wasted, water is arguably the world's most pressing resource Ensuring Water Supply Human development depend Annual Renewable Water(m"/person/year on adequate water-a fact that D No data has driven the location o 4,000-10,000 immunities the extent of 1,000-1,700 >10,000 griculture, and the shape of industry and transportation for Sources: CIESIN et al. 2000; Fekete et al. 2000 centuries. Because of its central place in our activities, water is expansion of agriculture domestic demand increases Iso the focus of much through the use of irrigation, as (WMO 1997: 9) engineering activity and well as the capability to Not surprisingly, the investment in the form of distribute water more evenly environmental impacts of our dams, canals, pipelines, and throughout the year in many water consumption are irrigation systems. Today, there areas of the world where growing rapidly as well. For are more than 45,000 large seasonal water shortages are a example, the enormous dams(dams more than 15 problem. But water demand is increase in the number of meters high) ams has fragmented and most of them built in the last the availability of the supplies seriously altered the flow of 35 years (WCD 2000: 8, 11). we would like to collect, store roughly 60 percent of the This storage capacity and use Global water world's major river basins represents a 700 percent consumption rose sixfold These fragmented rivers carry increase in the standing stock between 1900 and 1995--more nearly 90 percent of the water of water in river systems since than double the rate of flowing through these major 1950 (VOrosmarty et al population growth-and basins(revenga et al. 2000: 17) 1997:210) continues to grow rapidly as As population increases and The increase in storage agricultural, industrial, and freshwater systems are capacity has permitted the o a point whe OEarthTrends 2001 World Resources Institute. All rights reserved. Fair use is permitted on a limited scale and for educational I
©EarthTrends 2001 World Resources Institute. All rights reserved. Fair use is permitted on a limited scale and for educational purposes. Sources: CIESIN et al. 2000; Fekete et al. 2000 Water Scarcity: The World's Most Pressing Resource Issue Figure 1: Annual Renwable Water Supply per Person by River Basin, 1995 Annual Renewable Water (m3 /person/year) 10,000 No data EarthTrends: Featured Topic Title: Will There Be Enough Water? Author(s): Carmen Revenga Editor: Greg Mock Source: Pilot Analysis of Global Ecosystems: Freshwater Systems Date written: October 2000 Water policies in most nations are failing to protect life's most vital resource. This fact is reflected in growing water scarcity and alarming declines in the health of aquatic ecosystems worldwide. More precious than oil, yet routinely wasted, water is arguably the world’s most pressing resource issue. Ensuring Water Supply Human development depends on adequate water—a fact that has driven the location of communities, the extent of agriculture, and the shape of industry and transportation for centuries. Because of its central place in our activities, water is also the focus of much engineering activity and investment in the form of dams, canals, pipelines, and irrigation systems. Today, there are more than 45,000 large dams (dams more than 15 meters high) in the world— most of them built in the last 35 years (WCD 2000:8, 11). This storage capacity represents a 700 percent increase in the standing stock of water in river systems since 1950 (Vörösmarty et al. 1997:210). The increase in storage capacity has permitted the expansion of agriculture through the use of irrigation, as well as the capability to distribute water more evenly throughout the year in many areas of the world where seasonal water shortages are a problem. But water demand is growing quickly, jeopardizing the availability of the supplies we would like to collect, store and use. Global water consumption rose sixfold between 1900 and 1995—more than double the rate of population growth—and continues to grow rapidly as agricultural, industrial, and domestic demand increases (WMO 1997:9). Not surprisingly, the environmental impacts of our water consumption are growing rapidly as well. For example, the enormous increase in the number of dams has fragmented and seriously altered the flow of roughly 60 percent of the world’s major river basins. These fragmented rivers carry nearly 90 percent of the water flowing through these major basins (Revenga et al. 2000:17). As population increases and freshwater systems are modified to a point where
Nearly Half the World Will Live With Water Scarcity by 2025 ontaining abundant water and Figure 2: Global Renewable Water Supply per Person, 1995 and 2025 others a much more limited supply. For example, arid and emiarid regions receive only 2 Water Supply 1995 2025 percent of the worlds runoff, (m3/person/ Population 1995 Percent Population 2025 ercent even though they occup (millions) of Total of Total roughly 40 percent of the 1,700 3.091 3,494 scarcity calculated by the Unallocated 241 296 4.0 World Resources Institute in collaboration with the Total 5,665 100.0 7,274 100.0 University of New Hampshire how that some 41 percent of the Source: WRI. The 2025 estimates are considered conservative because the morld's population, or 2.3 billion re based on the United Nations' low-range projections for population growth people, line in rirer basins under which has population peaking at 7.3 billion in 2025(UNDP 1999: 3). In vater stress, "meaning that per addition, a slight mismatch between the water runoff and population data sets leaves 4 percent of the global population unaccounted in this analysis capita water supply is less than 1, 700 m /year(see Figures 1 many of their basic functions between 39, 500 kand and 2). An area in"water are affected. it becomes 42, 700 kma year(Fekete et al. stress"is subject to frequent increasingly difficult to ensure 1999: 31; Shiklomanov water shortages that there is enough water for 1997: 13) In many of these areas, both people and nature. See However, not all of this water supply is actually less related feature: Freshwater water is available to humans. than 1,000 m per capita. In Biodiversity in Crisis Much of the runoff o these "highly stressed"river flood events or is inaccessible basins, the consequences of How Scarce is Water? to people because of its remote water scarcity can be much location. In addition, part of more severe, leading to Humans now withdraw about the runoff needs to remain in problems with local food 4,000 km of water a year- waterways so that aquat production and economic about 20 percent of the base ecosystems continue to development unless the region flow(the average dry-weathe function. In fact, aroun d is wealthy enough to apply new flow) of the worlds rivers 9,000 kmis readily accessible or water use Shiklomanov 1997: 14, 69) to humans every year as conservation, or reuse. Some 1.7 Understanding what this runoff. An additional 3 500 billion people (out of the 2. 3 billia means in terms of the global km is stored in reservoirs noted abore) line in such higb water- water cycle requires some WMO1997:7 stress basins context: scientists estimate that In any case, such global Assuming that current the average amount of global aver ages fail to portray the water consumption patterns runoff (the amount of water details of the worlds water unabated projection that is available for human use situation. Water supplies show that at least 3.5 billion after evaporation or absorption unevenly distributed around people-or 48 percent of the into groundwater aquifers) is the globe, with some areas world's projected population-- OEarthTrends 2001 World Resources Institute. All rights reserved. Fair ed on a limited scale and for educational
©EarthTrends 2001 World Resources Institute. All rights reserved. Fair use is permitted on a limited scale and for educational purposes. 2 Water Supply (m3/person/ year) 1995 Population (millions) 1995 Percent of Total 2025 Population (millions) 2025 Percent of Total 1,700 3,091 54.6 3,494 48.0 Unallocated 241 4.2 296 4.0 Total 5,665 100.0 7,274 100.0 Nearly Half the World Will Live With Water Scarcity by 2025 Figure 2: Global Renewable Water Supply per Person, 1995 and 2025 (projected) Source: WRI. The 2025 estimates are considered conservative because they are based on the United Nations' low-range projections for population growth, which has population peaking at 7.3 billion in 2025 (UNDP 1999:3). In addition, a slight mismatch between the water runoff and population data sets leaves 4 percent of the global population unaccounted in this analysis. many of their basic functions are affected, it becomes increasingly difficult to ensure that there is enough water for both people and nature. (See related feature: Freshwater Biodiversity in Crisis.) How Scarce Is Water? Humans now withdraw about 4,000 km3 of water a year— about 20 percent of the base flow (the average dry-weather flow) of the world’s rivers (Shiklomanov 1997:14, 69). Understanding what this means in terms of the global water cycle requires some context: scientists estimate that the average amount of global runoff (the amount of water that is available for human use after evaporation or absorption into groundwater aquifers) is between 39,500 km3 and 42,700 km3 a year (Fekete et al. 1999:31; Shiklomanov 1997:13). However, not all of this water is available to humans. Much of the runoff occurs in flood events or is inaccessible to people because of its remote location. In addition, part of the runoff needs to remain in waterways so that aquatic ecosystems continue to function. In fact, only around 9,000 km3 is readily accessible to humans every year as runoff. An additional 3,500 km3 is stored in reservoirs (WMO 1997:7). In any case, such global averages fail to portray the details of the world’s water situation. Water supplies are unevenly distributed around the globe, with some areas containing abundant water and others a much more limited supply. For example, arid and semiarid regions receive only 2 percent of the world’s runoff, even though they occupy roughly 40 percent of the terrestrial area (WMO 1997:7). In river basins with high water demand relative to the available runoff, water scarcity is a growing problem. New estimates of water scarcity calculated by the World Resources Institute in collaboration with the University of New Hampshire show that some 41 percent of the world’s population, or 2.3 billion people, live in river basins under “water stress,” meaning that per capita water supply is less than 1,700 m3 /year (see Figures 1 and 2). An area in “water stress” is subject to frequent water shortages. In many of these areas, water supply is actually less than 1,000 m3 per capita. In these “highly stressed” river basins, the consequences of water scarcity can be much more severe, leading to problems with local food production and economic development unless the region is wealthy enough to apply new technologies for water use, conservation, or reuse. Some 1.7 billion people (out of the 2.3 billion noted above) live in such high waterstress basins. Assuming that current water consumption patterns continue unabated, projections show that at least 3.5 billion people—or 48 percent of the world’s projected population--
Agriculture Dominates Water Use, But Its share Will Decline Adding to the problem of Figure 3: Water withdrawals by sector, various years(1982-1997) inefficient irrigation techniques is the fact that farmers usuall 1009 pay low prices for irrigation 809o water, giving them little 609o incentive to conserve 409 Government water subsidies 19o that artificially lower water Africa South prices are the primary culprit In the western United States for example, water subsid otal some $2-2.5 billion per year. Throughout the world 冒 Domestic日 Industria囗 Agricultural government support typically allows water utilities to sell Source: WRI et al. 2000: 276-277(Table Fw.1) irrigation water for far less than the cost of supplying it. In will live in water-stressed river Growth in food production in arid Tunisia, farmers basins in 2025(see Figure 2). the last 50 years has been more than one-seventh the Even regions where per capita roughly matched by a cost of their water(de moor proportional increase in water and Calamai 1997: 14-15). Such sufficient when averaged over use, with grain yields rising 2.4- low prices and subsidies the year may actually face water fold between 1950 and 1995 hostages in the dry season and irrigation water use rising The results of this analysis 2. 2-fold( Postel 1999: 165). At water-saving technology like make it clear that many of the present, irrigated agriculture drip irrigation (ohnson et al most populous river basins will accounts for 40 percent of 2001:1072; Postel1999:228 ip into water stress global food production, even 231) (with water per capita falling though it represents just 17 Water pollution add below 1, 700 m per year)over percent of global cropland enormously to existing the next quarter century as (WMO 1997: 9). As a problems of local and regional water consumption rises. consequence, agriculture is water scarcity by ng societys major user of water, large volumes of water from Wasting Water withdrawing some 70 percent the available supply. In many Inefficiency, Overuse, and of all water(WMO 1997: 8)(see parts of the world, rivers and Pollution Figure 3) lakes have become so polluted Unfortunately, most that their water is unfit even Global food production must irrigation systems are relatively for industrial uses(WMO Increase in the years ahead to ine fficient and result in massive 1997: 11; UNEP/GEMS accommodate population water waste. Global estimates 1995: 6). (See related feature growth. United Nations of irrigation efficiency show Dirty W ater: Pollution Problems projections put global that around 60 percent of Persist.) population at nearly 8 billion in irrigation water never reaches 2025--up 1.7 billion from the crop and is lost to Groundwater Is scarce. Too today(UNPD 2001: vi). This evaporation and runoff (postel means the world's farmers will 1993: 56; Rosegrant 1997: 4; Global concerns about water need more water for irrigation. Seckler et al. 1998: 25) scarcity include not only OEarthTrends 2001 World Resources Institute. All rights reserved. Fair use is permitted on a limited scale and for educational I
©EarthTrends 2001 World Resources Institute. All rights reserved. Fair use is permitted on a limited scale and for educational purposes. 3 will live in water-stressed river basins in 2025 (see Figure 2). Even regions where per capita water availability appears sufficient when averaged over the year may actually face water shortages in the dry season. The results of this analysis make it clear that many of the most populous river basins will gradually slip into water stress (with water per capita falling below 1,700 m3 per year) over the next quarter century as water consumption rises. Wasting Water: Inefficiency, Overuse, and Pollution Global food production must increase in the years ahead to accommodate population growth. United Nations projections put global population at nearly 8 billion in 2025—up 1.7 billion from today (UNPD 2001:vi). This means the world’s farmers will need more water for irrigation. Growth in food production in the last 50 years has been roughly matched by a proportional increase in water use, with grain yields rising 2.4- fold between 1950 and 1995 and irrigation water use rising 2.2-fold (Postel 1999:165). At present, irrigated agriculture accounts for 40 percent of global food production, even though it represents just 17 percent of global cropland (WMO 1997:9). As a consequence, agriculture is society’s major user of water, withdrawing some 70 percent of all water (WMO 1997:8) (see Figure 3). Unfortunately, most irrigation systems are relatively inefficient and result in massive water waste. Global estimates of irrigation efficiency show that around 60 percent of irrigation water never reaches the crop and is lost to evaporation and runoff (Postel 1993:56; Rosegrant 1997:4; Seckler et al. 1998:25). Adding to the problem of inefficient irrigation techniques is the fact that farmers usually pay low prices for irrigation water, giving them little incentive to conserve. Government water subsidies that artificially lower water prices are the primary culprit. In the western United States, for example, water subsidies total some $2-2.5 billion per year. Throughout the world, government support typically allows water utilities to sell irrigation water for far less than the cost of supplying it. In arid Tunisia, farmers pay no more than one-seventh the cost of their water (de Moor and Calamai 1997:14-15). Such low prices and subsidies encourage inefficient use and discourage the adoption of water-saving technology like drip irrigation (Johnson et al. 2001:1072; Postel 1999:228- 231) Water pollution adds enormously to existing problems of local and regional water scarcity by removing large volumes of water from the available supply. In many parts of the world, rivers and lakes have become so polluted that their water is unfit even for industrial uses (WMO 1997:11; UNEP/GEMS 1995:6). (See related feature: Dirty Water: Pollution Problems Persist.) Groundwater Is Scarce, Too Global concerns about water scarcity include not only Source: WRI et al. 2000:276-277 (Table FW.1) Agriculture Dominates Water Use, But Its Share Will Decline Figure 3: Water withdrawals by sector, various years (1982-1997) 0% 20% 40% 60% 80% 100% Asia Europe Africa North America, Central America, and the Caribbean South America World Domestic Industrial Agricultural
surface water sources but oblems(UNEP 1996: 4-5), than 70 times more economic omprehensive data on value than the same water used than 1 billion people in Asian groundwater resources and in agriculture(Postel cities and 150 million in Latin pollution trends are not 1999:114) American cities rely available at the global level. To a certain extent the groundwater from wells or transfer of water from low springs(Foster et al. 1998: xi). Wiser Management Means value uses to higher-value uses In addition, although there are More Water is already well under way, no complete figures on especially where individuals roundwater use by the rural Better management of water hold legal water rights that they population, many countries are resources is the key to can sell to others. Farmers increasingly dependent on this mitigating water scarcities in up ur in resource for both domestic and the future and avoiding further southern India, for example, agricultural uses(Foster et al. damage to aquatic ecosystems. have begun to abandon 2000:1 n the short term. more farming so that they can sell Currently humans withdraw efficient use of water could their groundwater at a approximately 600-700 km of dramatically expand available premium to water-hungry resources. This is particularly industries and urban users 20 percent of global water true in the agricultural sector, (Postel 1999: 114). Such"water withdrawals( Shiklomanov where experience shows that markets"are becoming more 1997: 53-54). Some of this drip irrigation systems common in arid regions of water is fossil water(ancient outinely cut water use 30-70 western United States and water that isn't routinely percent, while simultaneously Australia replenished) that comes from increasing crop yields 20-90 An important key to using deep sources isolated from the percent. Although the use of and allocating water more normal runoff cycle, but much drip irrigation has grown more efficiently is phasing out groundwater comes from than 50-fold over the last 20 subsidies and allowing water shallower aquifers that draw years, it is still used in only 1 prices to re flect the true cost of from the same global runoff percent of the worlds irrigated ly. Price reforms in Chile that feeds freshwater areas(Postel 1999: 174) reduced irrigation water use ecosystems. Indeed More efficient water 22-26 percent and saved $400 overdrafting of groundwater technology alone will not be nillion in costs for developing sources can rob streams and sufficient to fully address the new water supplies. In Bogor, rivers of a significant fraction looming water crisis. It will Indonesia, price increases cut of their flow. In the same way, also require difficult policy domestic consumption by 30 pollution of aquifers by choices that reallocate water to percent ( ohnson et al nitrates, pesticides, and the most economically and 2001:1072). However industrial chemicals often socially beneficial use. This effective water pricing, affects water quality in adjacent may mean diverting water from particularly of irrigation water, freshwater ecosystems agriculture to commercial or remains a highly sensitive issue Although overdrafting and household uses. In China, for in low-income countries, wher contamination of groundwater example, planners estimate that agriculture still dominates the aquifers are known to be a given amount of water used economy and most farmers widespread and growing In industry generates more have limited incomes OEarthTrends 2001 World Resources Institute. All rights reserved. Fair use is permitted on a limited scale and for educational I
©EarthTrends 2001 World Resources Institute. All rights reserved. Fair use is permitted on a limited scale and for educational purposes. 4 surface water sources but groundwater sources. More than 1 billion people in Asian cities and 150 million in Latin American cities rely on groundwater from wells or springs (Foster et al. 1998:xi). In addition, although there are no complete figures on groundwater use by the rural population, many countries are increasingly dependent on this resource for both domestic and agricultural uses (Foster et al. 2000:1). Currently humans withdraw approximately 600–700 km3 of groundwater per year—about 20 percent of global water withdrawals (Shiklomanov 1997:53–54). Some of this water is fossil water (ancient water that isn’t routinely replenished) that comes from deep sources isolated from the normal runoff cycle, but much groundwater comes from shallower aquifers that draw from the same global runoff that feeds freshwater ecosystems. Indeed, overdrafting of groundwater sources can rob streams and rivers of a significant fraction of their flow. In the same way, pollution of aquifers by nitrates, pesticides, and industrial chemicals often affects water quality in adjacent freshwater ecosystems. Although overdrafting and contamination of groundwater aquifers are known to be widespread and growing problems (UNEP 1996:4–5), comprehensive data on groundwater resources and pollution trends are not available at the global level. Wiser Management Means More Water Better management of water resources is the key to mitigating water scarcities in the future and avoiding further damage to aquatic ecosystems. In the short term, more efficient use of water could dramatically expand available resources. This is particularly true in the agricultural sector, where experience shows that drip irrigation systems routinely cut water use 30-70 percent, while simultaneously increasing crop yields 20-90 percent. Although the use of drip irrigation has grown more than 50-fold over the last 20 years, it is still used in only 1 percent of the world’s irrigated areas (Postel 1999:174). More efficient water technology alone will not be sufficient to fully address the looming water crisis. It will also require difficult policy choices that reallocate water to the most economically and socially beneficial use. This may mean diverting water from agriculture to commercial or household uses. In China, for example, planners estimate that a given amount of water used in industry generates more than 70 times more economic value than the same water used in agriculture (Postel 1999:114). To a certain extent, the transfer of water from lowvalue uses to higher-value uses is already well under way, especially where individuals hold legal water rights that they can sell to others. Farmers outside the city of Tirupur in southern India, for example, have begun to abandon farming so that they can sell their groundwater at a premium to water-hungry industries and urban users (Postel 1999:114). Such “water markets”are becoming more common in arid regions of the western United States and Australia. An important key to using and allocating water more efficiently is phasing out subsidies and allowing water prices to reflect the true cost of supply. Price reforms in Chile reduced irrigation water use 22-26 percent and saved $400 million in costs for developing new water supplies. In Bogor, Indonesia, price increases cut domestic consumption by 30 percent (Johnson et al. 2001:1072). However, effective water pricing, particularly of irrigation water, remains a highly sensitive issue in low-income countries, where agriculture still dominates the economy and most farmers have limited incomes
REFERENCES de moor, A and P Calamai. 1997. Subsidizing Unsustainable Development Undermining the Earth with Public Funds. San Jose, Costa Rica: The Earth Council Fekete, B, C.J. VOrosmarty, and W. Grabs. 1999. Global, Composite Runoff Fields Based on Observed River Discharge and Simulated Water Balance. World Meteorological Organization Global Runoff Data Center Report No 22 Koblenz, Germany: WMO-GRDC Foster, S, A. Lawrence, and B Morris. 1998. Groundwater in Urban Development: Assessing Management Needs and Formulating Policy Strategies. World Bank Technical Paper No 390 Washington, DC: The World Bank Foster, S.,J. Chilton, M. Moench, F Cardy, and M. Schiffler. 2000. Groundwater in Rural Development: Facing the Challenges of Supply and Resource Sustainability. World Bank Technical Paper No 463. Washington, DC: The World Ban Johnson, N, C. Revenga, and J. Echeverria. 2001. "Managing Water for People and Nature, Science292:1071-1072. Postel, S. 1993. Water and Agriculture, Pp 56-66 in Water in Crisis: A Guide to the World's Fresh Water Resource, P Gleick, ed. New York, New York and Oxford, U. K. Oxford University P Postel, S. 1999. Pillar of Sand: Can the Irrigation Miracle Last? Washington, DC: Worldwatch Institute Revenga, C.,J. Brunner, N. Henniger, K. Kassem, R. Payne. 2000. Pilot Analysis of Global Ecosystems: Freshwater Systems. Washington, DC: World Resources Institute Rosegrant, M. W. 1997. Water Resources in the 21 Century: Challenges and Implications for Action. Food, Agriculture, and the Environment Discussion Paper 20. Washington, DC International Food Policy Research Institute Seckler, D, U. Amarasinghe, D Molden, R de Silva, and R. Barker. 1998. World Water Demand and Supply, 1990 to 2025: Scenarios and Issues. Research Report 19. Colombo, Sri Lanka International Water Management Institute Shiklomanov, I A. 1997. Comprehensive Assessment of the Freshwater Resources of the World Assessment of Water Resources and Water Availability in the World. Stockholm, Sweden: World Meteorological Organization and Stockholm Environment Institute OEarthTrends 2001 World Resources Institute. All rights reserved. Fair use is permitted on a limited scale and for educational I
©EarthTrends 2001 World Resources Institute. All rights reserved. Fair use is permitted on a limited scale and for educational purposes. 5 REFERENCES de Moor, A. and P. Calamai. 1997. Subsidizing Unsustainable Development: Undermining the Earth with Public Funds. San Jose, Costa Rica: The Earth Council. Fekete, B., C. J. Vörösmarty, and W. Grabs. 1999. Global, Composite Runoff Fields Based on Observed River Discharge and Simulated Water Balance. World Meteorological Organization Global Runoff Data Center Report No. 22. Koblenz, Germany: WMO-GRDC. Foster, S., A. Lawrence, and B. Morris. 1998. Groundwater in Urban Development: Assessing Management Needs and Formulating Policy Strategies. World Bank Technical Paper No. 390. Washington, DC: The World Bank. Foster, S., J. Chilton, M. Moench, F. Cardy, and M. Schiffler. 2000. Groundwater in Rural Development: Facing the Challenges of Supply and Resource Sustainability. World Bank Technical Paper No. 463. Washington, DC: The World Bank. Johnson, N., C. Revenga, and J. Echeverria. 2001. “Managing Water for People and Nature,” Science 292:1071-1072. Postel, S. 1993. “Water and Agriculture,” pp. 56–66 in Water in Crisis: A Guide to the World’s Fresh Water Resource, P. Gleick, ed. New York, New York and Oxford, U.K.: Oxford University Press. Postel, S. 1999. Pillar of Sand: Can the Irrigation Miracle Last? Washington, DC: Worldwatch Institute. Revenga, C., J. Brunner, N. Henniger, K. Kassem, R. Payne. 2000. Pilot Analysis of Global Ecosystems: Freshwater Systems. Washington, DC: World Resources Institute. Rosegrant, M. W. 1997. Water Resources in the 21st Century: Challenges and Implications for Action. Food, Agriculture, and the Environment Discussion Paper 20. Washington, DC: International Food Policy Research Institute. Seckler, D., U. Amarasinghe, D. Molden, R. de Silva, and R. Barker. 1998. World Water Demand and Supply, 1990 to 2025: Scenarios and Issues. Research Report 19. Colombo, Sri Lanka: International Water Management Institute. Shiklomanov, I.A. 1997. Comprehensive Assessment of the Freshwater Resources of the World: Assessment of Water Resources and Water Availability in the World. Stockholm, Sweden: World Meteorological Organization and Stockholm Environment Institute
United Nations Environment Program Global Environment Monitoring System/Water (UNEP/GEMS). 1995. Water Quality of World River Basins. Nairobi, Kenya: United Nations Environment Programme United Nations Environment Programme(UNEP). 1996. Groundwater: A Threatened Resource. UNEP Environment Library No 15. Nairobi, Kenya: United Nations Environment Programme United Nations Population Division(UNPD). 2001. World Population Prospects: The 2000 Revision: Highlights. New York, New York: United Nations United Nations Population Division(UNPD). 1999. World Population Prospects: The 1998 Revision. Vol 1. New York, New York: United Nations VOrosmarty, C.J., K. P Sharma, B. M. Fekete, A. H. Copeland, J. Holden, J. Marble, andJ. A Lough. 1997. The Storage and Aging of Continental Runoff in Large Reservoir Systems of the World, Ambio 26(4): 210-219 World Commission on Dams(WCD). 2000. Dams and Development: A New Framework fo Decision-Making. London: Earthscan World Meteorological Organization(WMO). 1997. Comprehensive Assessment of the Freshwater Resources of the World. Stockholm, Sweden WMO and Stockholm Environment Instituto World Resources Institute (WRD in collaboration with the United Nations Development Programme, United Nations Environment Programme, and the World Bank. 2000. World Resources 2000-2001: People and Ecosystems: The Fraying Web of Life. Washington, DC WRI World Resources Institute (WRD in collaboration with the United Nations Development Programme, United Nations Environment Programme, and the World Bank. 1998. World Resources 1998-99: A Guide to the Global Environment: Environmental Change and Human Health. New York, New York: Oxford University Pres EarthTrends 2001 World Resources Institute. All rights reserved. Fair use is permitted on a limited scale and for educational I
©EarthTrends 2001 World Resources Institute. All rights reserved. Fair use is permitted on a limited scale and for educational purposes. 6 United Nations Environment Program Global Environment Monitoring System/Water (UNEP/GEMS). 1995. Water Quality of World River Basins. Nairobi, Kenya: United Nations Environment Programme. United Nations Environment Programme (UNEP). 1996. Groundwater: A Threatened Resource. UNEP Environment Library No. 15. Nairobi, Kenya: United Nations Environment Programme. United Nations Population Division (UNPD). 2001. World Population Prospects: The 2000 Revision: Highlights. New York, New York: United Nations. United Nations Population Division (UNPD). 1999. World Population Prospects: The 1998 Revision. Vol 1. New York, New York: United Nations. Vörösmarty, C. J., K. P. Sharma, B. M. Fekete, A. H. Copeland, J. Holden, J. Marble, and J. A. Lough. 1997. “The Storage and Aging of Continental Runoff in Large Reservoir Systems of the World,” Ambio 26(4): 210–219. World Commission on Dams (WCD). 2000. Dams and Development: A New Framework for Decision-Making. London: Earthscan. World Meteorological Organization (WMO). 1997. Comprehensive Assessment of the Freshwater Resources of the World. Stockholm, Sweden: WMO and Stockholm Environment Institute. World Resources Institute (WRI) in collaboration with the United Nations Development Programme, United Nations Environment Programme, and the World Bank. 2000. World Resources 2000-2001: People and Ecosystems: The Fraying Web of Life. Washington, DC: WRI. World Resources Institute (WRI) in collaboration with the United Nations Development Programme, United Nations Environment Programme, and the World Bank. 1998. World Resources 1998-99: A Guide to the Global Environment: Environmental Change and Human Health. New York, New York: Oxford University Press