Water resources drying up.

• Author: Brown, Lester R.
• Position: EYE ON ECOLOGY

AS THE WORLD'S DEMAND FOR WATER has tripled over the last half-century and, as the need for hydroelectric power has grown even faster, dams and diversions of river water have drained many rivers dry. As water tables fail, the springs that feed rivers also go dry, reducing flows. Numerous nations are overpumping aquifers as they struggle to satisfy growing water needs, including each of the big three grain producers--China, India, and the U.S. More than half of the world's people live in countries where water tables are falling.

There are two types of aquifers: replenishable and nonreplenishable (or fossil). The shallow aquifer under the North China Plain and most found in India are replenishable. When these are depleted, the maximum rate of pumping automatically is reduced to the rate of recharge. For the fossil variety, such as the vast U.S. Ogallala aquifer, the deep aquifer under the North China Plain, or the Saudi aquifer, depletion brings pumping to an end. Farmers who lose their irrigation water have the option of returning to lower-yield dryland farming--if rainfall permits. In more arid regions, however, such the Middle East or America's Southwest, the loss of irrigation water means the end of agriculture.

The U.S. embassy in Beijing reports that Chinese wheat farmers in some areas now are pumping from a depth of nearly 1,000 feet. Pumping water from this far down raises extraction costs so high that farmers often must abandon irrigation and return to less-productive dryland fanning. A World Bank study indicates that China is overpumping three river basins in the north--the Hai, which flows through Beijing and Tianjin; the Yellow; and the Huai, the next river south of the Yellow. Since it takes 1,000 tons of water to produce one ton of grain, the shortfall in the Hai basin of nearly 40,000,000,000 tons of water per year (one ton equals one cubic meter) means that, when the aquifer is depleted, the grain harvest will drop by 40,000,000 tons--enough to feed 120,000,000 Chinese.

In India, water shortages particularly are serious simply because the margin between actual food consumption and survival is so precarious. In a survey of India's water situation, New Scientist indicates that its 21,000,000 wells are lowering water tables in most of the country. In North Gujarat, the water table is falling by 20 feet per year. In Tamil Nadu, a state with more than 62,000,000 people in southern India, wells are going dry almost everywhere and...