The world’s thirst for water is likely to become one of the most pressing resource issues of the 21st Century. 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 .
Globally, water supplies are abundant, but they are unevenly distributed among and within countries. In some areas, water withdrawals are so high, relative to supply, that surface water supplies are literally shrinking and groundwater reserves are being depleted faster than they can be replenished by precipitation . (See Water Demand is Growing, But Supplies Are Limited.)
This situation has already caused serious water shortages to develop in some regions, shortchanging human water needs and damaging aquatic ecosystems. A 1997 United Nations assessment of freshwater resources found that one third of the world’s population lives in countries experiencing moderate to high water stress. To arrive at its estimate, the United Nations determined each country’s ratio of water consumption to water availability – its use-to-resource index – which is a good gauge of overall pressure on water resources . Moderate to high stress translates to consumption levels that exceed 20 percent of available supply .
The U.N. assessment makes clear that the global water situation will get considerably worse over the next 30 years without major improvements in the way water is allocated and used. In fact, the United Nations projects that the share of the world’s population in countries undergoing moderate or high water stress could rise to two thirds by 2025. Population growth and socioeconomic development are currently driving a rapid increase in water demand, especially from the industrial and household sectors. Industrial water use, for example, is predicted to double by 2025 if current growth trends persist .
Water use in agriculture is slated to increase as world food demand rises. Agriculture already accounts for about 70 percent of water consumption worldwide, and the United Nations projects a 50- to 100-percent increase in irrigation water by 2025 . (See Agriculture Dominates Water Use, But Its Share Will Decline.)
Much of the projected increase in water demand will occur in developing countries, where population growth and industrial and agricultural expansion will be greatest. However, per capita consumption continues to rise in the industrialized world as well.
Water pollution adds enormously to existing problems of local and regional water scarcity by removing large volumes of water from the available supply. Water quality in most of the developed countries has steadily improved in recent years, thanks to strict legislation and major investments in new water and sanitation infrastructure. Even in the developed world, however, wastewater is not necessarily treated before discharge. In the southern member states of the European Union, about 50 percent of the population is not yet connected to sewage treatment operations .
The situation is far worse in many developing countries. Water scarcity has been exacerbated and human health gravely damaged by accelerating contamination of usable water supplies, especially in rapidly urbanizing areas.
Many developing countries undergoing rapid industrialization are now faced with the full range of modern toxic pollution problems – eutrophication, heavy metals, acidification, persistent organic pollutants (POPs) – while still struggling to deal with traditional problems of poor water supply and lack of sanitation services . The pollution threat is particularly serious when it affects groundwater supplies, where contamination is slow to dilute and purification measures are costly. Ground-water reserves are estimated to provide more than 50 percent of domestic supplies in most Asian countries ; yet, these countries are currently experiencing rapid growth in the mining and manufacturing sectors – two big sources of groundwater contamination.
As clean water supplies have diminished, competition for them has been growing, usually between expanding urban areas and rural users. Where systems of water law and allocation exist, water markets can operate to transfer supplies between buyers and sellers for an agreed price. Such systems are operating with some success in an increasing number of countries, including the western United States  and Australia . However, effective water pricing, which sets water prices high enough to discourage waste, remains a highly sensitive issue in low-income countries, where most people depend on irrigated agriculture for their living. Even so, socioeconomic development in water-scarce countries may depend critically on more rational distribution of scarce supplies. Planners in China have estimated that a given amount of water used in industry generates more than 60 times the value of the same water used in agriculture .
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. In developing countries, for example, 60 to 75 percent of irrigation water never reaches the crop and is lost to evaporation or runoff . Although the use of water-efficient drip irrigation has increased 28-fold since the mid-1970s, it is still employed in less than 1 percent of the world’s irrigated areas .
In the longer term, however, the U.N. water assessment makes clear that looming water crises in many regions must be addressed through hard policy decisions that reallocate water to the most economically and socially beneficial uses. Far greater emphasis on water-efficient technologies and pollution control is also essential. However, even with measures to contain the growth of demand and use water more efficiently, new supplies will be needed. The World Bank has estimated that the financial and environmental costs of tapping new supplies will be, on average, two or three times those of existing investments, because most of the low-cost, accessible water reserves have already been exploited.
The U.N. study also highlights the potentially desperate situation of developing countries that combine high water stress with low per capita income. The majority of these countries are found in the arid or semiarid regions of Africa and Asia. Many use most of their available water supplies for farm irrigation and suffer from a lack of pollution controls. Future development in these countries appears severely constrained because they have neither the extra water nor the financial resources to shift development away from intensive irrigation and into other sectors that would create employment and generate income to import food. The figure, Low-Income Nations Are Especially Vulnerable to Water Scarcity, gives an idea of the future vulnerability of nations to water scarcity in 2025, taking into account their income level and their ability to cope with water stress both economically and socially.
Endnotes: Water: Critical Shortages Ahead?
1. World Meteorological Organization (WMO), Comprehensive Assessment of the Freshwater Resources of the World (WMO, Geneva, 1997), p. 9.
2. Ibid., p. 10.
3. Raskin et al., “Water Futures: Assessment of Long-Range Patterns and Problems,” Comprehensive Assessment of the Freshwater Resources of the World (Stockholm Environment Institute, Stockholm, 1997), p. 23.
4. Op. cit. 1, pp. 1, 14.
5. Op. cit. 1, pp. 1, 20-21.
6. Op. cit. 1, pp. 1, 21.
7. European Environment Agency, Environment in the European Union 1995: Report for the Review of the Fifth Environmental Action Programme (Office for the Official Publications of the European Communities, Luxembourg, 1995), p. 81.
8. World Health Organization (WHO), Health and Environment in Sustainable Development: Five Years After the Earth Summit (WHO, Geneva, 1997), pp. 54-55.
9. United Nations Environment Programme (UNEP), Division of Environment Information and Assessment, Characterization and Assessment of Groundwater Quality Concerns in Asia-Pacific Region (UNEP, Nairobi, 1996), p. 3.
10. Sandra Postel, “Water and Agriculture,” in Water in Crisis: A Guide to the World’s Freshwater Resources, Peter H. Gleick, ed.(Oxford University Press, New York, 1993), p. 60.
11. John Langford, “An Australian Approach to the Sustainable Use of Water,” paper presented at Workshop on Policy Measures for Changing Consumption Patterns, August 30-September 1, 1995 (Ministry of Environment, Kwacheon, Republic of Korea, 1995).
12. Op. cit. 10, p. 60.
13. Mark W. Rosegrant, Water Resources in the Twenty-First Century: Challenges and Implications for Action, Food, Agriculture, and the Environment Discussion Paper 20 (International Food Policy Research Institute, Washington, D.C., 1997), p. 4.
14. Op. cit. 10, p. 61.
15. Ismael Serageldin, Towards Sustainable Management of Water Resources (The World Bank, Washington, D.C., 1995), p. 14.