Thursday, November 11, 2010

Groundwater depletion rate accelerating worldwide

American Geophysical Union: In recent decades, the rate at which humans worldwide are pumping dry the vast underground stores of water that billions depend on has more than doubled, say scientists who have conducted an unusual, global assessment of groundwater use. These fast-shrinking subterranean reservoirs are essential to daily life and agriculture in many regions, while also sustaining streams, wetlands, and ecosystems and resisting land subsidence and salt water intrusion into fresh water supplies. Today, people are drawing so much water from below that they are adding enough of it to the oceans (mainly by evaporation, then precipitation) to account for about 25 percent of the annual sea level rise across the planet, the researchers find.

Soaring global groundwater depletion bodes a potential disaster for an increasingly globalized agricultural system, says Marc Bierkens of Utrecht University in Utrecht, the Netherlands, and leader of the new study. “If you let the population grow by extending the irrigated areas using groundwater that is not being recharged, then you will run into a wall at a certain point in time, and you will have hunger and social unrest to go with it,” Bierkens warns. “That is something that you can see coming for miles.”

He and his colleagues will publish their new findings in an upcoming issue of Geophysical Research Letters, a journal of the American Geophysical Union.

… The new assessment shows the highest rates of depletion in some of the world’s major agricultural centers, including northwest India, northeastern China, northeast Pakistan, California’s central valley, and the midwestern United States. “The rate of depletion increased almost linearly from the 1960s to the early 1990s,” says Bierkens. “But then you see a sharp increase which is related to the increase of upcoming economies and population numbers; mainly in India and China.”…

Global map of groundwater depletion, where 1000 on the legend is equal to one cubic kilometer of depletion per year. From the AGU website


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