WASHINGTON -- Overpumping is sucking out too much of the world's underground fresh water, with a stable world food supply now dependent on an increasing global water deficit, the Worldwatch Institute says.
Annually, the study estimates, 160 billion cubic meters of water are lost to thirsty cities and farms that are not returning it to underground aquifers.
The biggest known losses are in India, China, the United States, North Africa, and Saudi Arabia. The lost water would be enough to grow 10 percent of world grain, said Worldwatch, a nongovernment research group funded by grants and sales of its publications.
The use of giant pumps to extract water from ever-deeper in the earth was once viewed as a boon for farmers worldwide. Now, according to water expert Sandra Postel, the report's author, massive pumping intensifies water shortages that threaten to reduce the global food supply, spread hunger, and increase social conflict.
``A few years ago, the practice was confined to certain parts of the world and seemed manageable,'' she said. ``Now, we see it occurring across very wide areas over the most important food-producing regions, including in India and China.''
The large pumping projects are often subsidized by governments to get needed water to farmers and thirsty cities, she said. Unlike more visible dam projects, they have rarely been controversial.
But what they are doing underground is beginning to hurt, with wells running dry and parts of some cities such as Bangkok and Mexico City showing signs of literally sinking because of groundwater pumping, Postel said in an interview.
With world population set to surpass 6 billion in October, the problem of dropping water tables is bound to worsen, she said. Her Worldwatch book, Pillar of Sand: Can the Irrigation Miracle Last? says irrigation accounts for two-thirds of global use of fresh water, but less than half the water actually reaches the roots of plants.
Methods are needed to double the efficiency of water use, she said, citing several steps that are working:
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