Posted: Sep 24, 2010 6:09 am
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Groundwater depletion rate accelerating worldwide
AGU Release No. 10–30
23 September 2010
For Immediate Release
WASHINGTON—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.
In the new study, which compares estimates of groundwater added by rain and other sources to the amounts being removed for agriculture and other uses, the team taps a database of global groundwater information including maps of groundwater regions and water demand. The researchers also use models to estimate the rates at which groundwater is both added to aquifers and withdrawn. For instance, to determine groundwater recharging rates, they simulate a groundwater layer beneath two soil layers, exposed at the top to rainfall, evaporation, and other effects, and use 44 years worth of precipitation, temperature, and evaporation data (1958–2001) to drive the model.
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