|Toward Sustainable Management of Water Resources (World Bank, 1995)|
Carnet water management practices and policies have resulted in stark and terrible failures. But the problems we witness today are only an indication of what may lie ahead. Current trends in the growth of population, urbanization, industrialization and income will not allow us to continue current practices without crippling our health and our economies as well as causing irrevocable damage to the environment one-third of the projected population. In the Middle East, nine out of fourteen countries are already facing water-scarce situations, and populations in many countries of the region are expected to double in less than thirty years.
Population pressure will increase the demand for food. Some 40 percent of the world's food supply already comes from irrigated land. Since 1950, irrigated area has grown more than 2 percent a year, a key factor in allowing food production to keep pace with the growth in food demand. Half of the growth in food supply in the past thirty years has come from the expansion of irrigated agriculture, and an estimated half to two-thirds of the increment in food production in the future will have to come from irrigated land. However, it is becoming increasingly difficult to sustain the expansion of irrigation. The investments with the lowest cost and highest benefit have already been made (see below). There are also serious environmental concerns about irrigation projects and the dams that serve them. Salinity and water logging may now take as much old land out of irrigation as is added through new development. The overexploitation of ground water is another serious problem. Given the share of water going to agriculture, many countries are under pressure to reallocate water from irrigation to other uses. All these factors suggest that the increased demand for food will have to be met by increasing cropping intensities and achieving higher yields using less water. Currently only 45 percent of irrigation water is actually used by the crop (figure 4).
Rapid urbanization and industrialization will substantially
increase pressures on the supply and quality of water. Between 1950 and 1990,
the number of cities with populations of more shall 1 million nearly quadrupled
from 78 to 290. They are expected to more than double and exceed 600 by 2025
(figure 5). In the next few years, fully half the world's population will live
in cities. By 2025, 90 percent of population
growth will have taken place in urban areas, increasing the demand for water of suitable quality for domestic, municipal, and industrial use and for treatment of waste.
Today in the industrial world, industry uses more than 40 percent of total water with drawls; the comparable figure in developing countries is less shall 10 percent. This figure can be expected to grow significantly. Greater industrial use will also lead to more water quality problems, especially if there are no clear and enforceable rules for controlling pollution. Income growth will also put pressure on household water use, as people who are well off use more water than those who are not.
The pressure on water resources does not come only from the demand side. Even with measures to contain the growth of demand in agriculture and to improve the efficiency of existing systems, new water supplies will be needed, especially in urban areas. However, the lowest-cost, most reliable, and least environmentally damaging sources of water have already been developed in many countries. As a result, the financial and environmental costs of tapping new water supplies are increasing dramatically, and they will rise even further when adequate facilities, especially in drainage and sanitation, are included as essential parts of investments.
Beijing must already consider drawing water from a source that is more than 1,000 kilometers away, while Mexico City may be forced to build schemes to pump water over a height of 2,000 meters.
· In Mexico City, water is being pumped over an elevation of 1,000 meters into the Valley of Mexico from the Cutzamala River. The average incremental cost of $0.82 per cubic meter is about 55 percent greater than the cost of water from the Valley of Mexico aquifer. Use of the aquifer has been restricted as a result of the falling water tables and water quality problems.
· In Amman, Jordan, the water supply system was, for the most part, based on groundwater. The average incremental cost was estimated at $0.41 per cubic meter. But constant shortages of groundwater resulted in the increased use of surface water, which raised the incremental cost to $1.33 per cubic meter.
· In Shenyang, China, the cost of new water supplies will increase from $0.04 to $0.11 per cubic meter from 1988 to 2000 due to problems with the quality of the current source of water. The ground water from the Hun Valley Alluvium is not suitable for use as potable water. As a consequence, water will have to be conveyed by gravity from a source that is 51 kilometers away.
These kinds of investments are expected to make the average cost of most new projects two to three times that of existing investments (figure 6).
Proper management of international watercourses will also present an increasingly important challenge as water becomes more scarce. Downstream countries are beginning to recognize their vulnerability. The problem is that fragmented planning and development of transboundary rivers, lakes, and coastal basins remain the rule rather than the exception. There are also no clear and enforceable international laws governing the resolution of disputes. And, although more than 300 treaties have been signed by countries to deal with specific concerns about international water resources and more shall 2,000 treaties have provisions related to water, countries have not devoted funding to manage surface and subsurface water jointly, scientific data are not freely shared, and the requisite spirit of cooperation is often lacking. The results are economic losses in downstream countries that are greater than the potential benefits to countries upstream, further environmental degradation, and continued conflict.
Note: Cost excludes treatment and distribution. Current cost refers to cost at the time data were gathered. Future cost is a projection of cost under a new water development project. Source: World Bank 1992.