Friday, May 11, 2012

Groundater pumping is causing seas to rise

LiveScience: People around the world are pumping so much water out of the ground, and releasing it back into the environment, that it's causing oceans to rise, a new study reveals. The effect is bigger than you might expect. The research estimates that by 2050, seas will rise about one-third of an inch (0.8 mm) per year due to groundwater pumping, and it may rival melting glaciers as a primary cause for rising seas.

Groundwater pumped for irrigation, drinking water and industrial uses does not typically end up back underground. Instead, it flows into streams or rivers or evaporates into the atmosphere, eventually finding its way to the ocean.

Other studies have shown that many aquifers — natural underground lakes that have built up water over millions of years — are being pumped dry. The ground tends to compact when the water is extracted, and once pumped dry, often an aquifer can never store as much water as it once did — sort of like a sponge that’s lost its sponginess.

“Other than ice on land, the excessive groundwater extractions are fast becoming the most important terrestrial water contribution to sea level rise,” said Yoshihide Wada, with Utrecht University in the Netherlands and lead author of the study, detailed in Geophysical Research Letters, a journal of the American Geophysical Union.

...In the coming decades, Wada said groundwater contributions to sea level rise are expected to become as significant as those of melting glaciers and ice caps outside of Greenland and the Antarctic. Already rising seas are causing some islands to disappear. In March, a study found that 4 million Americans are threatened by rising seas....

Image from the US Geological Survey

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