A “shocking” 75 percent of the water relied on by California and other western states over the last decade has come from underground reserves of the drought-stricken Colorado River Basin, according to a new study.
Researchers at UC Irvine and JPL found that seven western states are relying too heavily on groundwater to supply about 40 million people.
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"This is a lot of water to lose,” said Stephanie Castle, a water resources specialist at UC Irvine. “We thought that the picture could be pretty bad, but this was shocking."
The basin lost nearly 53 million acre feet of freshwater between December 2004 and November 2013, almost twice the volume of the nation’s largest reservoir, Lake Mead. About 41 million acre feet lost was from groundwater.
"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.
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Rapid depletion of the basin comes as California struggles to find ways to conserve water during one of the worst droughts in the state’s history.
"Combined with declining snowpack and population growth, this will likely threaten the long-term ability of the basin to meet its water allocation commitments to the seven basin states and to Mexico," said Jay Famiglietti, senior water cycle scientist at JPL.
The study noted that individual states regulate the pumping of groundwater, which is “often not well documented.”