Colorado River Groundwater Disappearing at 'Shocking' Rate

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A ring of light-colored rock shows how much the water level has dropped at Nevada's Lake Mead.
Credit: U.S. Bureau of Reclamation

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Between December 2004 and November 2013, more than 75 percent of the water lost in the Colorado River Basin was from groundwater, according to the study. The region has been in a drought since 2000, according to the U.S. Drought Monitor.

The results show that groundwater is already being used to fill the gap between the demands of the region's millions of residents and farmers, and the available surface water supply, the researchers said.

"We found a surprisingly high and long-term reliance on groundwater," study co-author Jay Famiglietti, senior water cycle scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, said in a statement.

For example, the amount of land irrigated by groundwater increased since the study began in December 2004, the researchers reported July 24 in the journal Geophysical Research Letters.

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The Colorado River Basin stretches across seven states: from Wyoming across Colorado, Utah, Arizona, New Mexico, Nevada and California. Its groundwater is stored in underground aquifers and is sucked from the ground by wells. If water is removed from an aquifer faster than it can be replaced, eventually the wells will go dry.

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Since December 2004, the basin of the Colorado River lost nearly 53 million acre feet (65 cubic kilometers) of freshwater, almost double the volume of the region's largest reservoir, Nevada's Lake Mead, the researchers reported. About 75 percent of the total — about 41 million acre feet (50 cubic km) — came from groundwater, the study found.

"We don't know exactly how much groundwater we have left, so we don't know when we're going to run out," Castle said. "This is a lot of water to lose."

http://www.livescience.com/46998-colorado-river-groundwater-loss.html?cmpid=514627_20140725_28422246