Ominous Drying Up of Groundwater that Supplies Nine States

Monday, July 28, 2014
Colorado River Basin (photo: Ethan Miller, Getty Images)

It’s easy to see the effects the prolonged drought in the Western United States is having on surface water supplies: many reservoirs have taken on a striped appearance from the difference between normal levels and the much lower levels now. But water supplies are also drying up in a place that’s not as obvious and can have more severe consequences.


The groundwater levels in the Colorado River Basin, which covers parts of Wyoming, Colorado, Utah, New Mexico, Nevada, Arizona and California, have fallen faster than they can be replenished, according a new study (pdf).


The basin has lost about 65 cubic kilometers of water over the past nine years, nearly double the volume of Lake Mead, according to The Washington Post. About three-quarters of that loss is from groundwater. “We were shocked to see how much water was actually depleted underground,” Stephanie Castle, the report’s lead author and a water specialist at the University of California at Irvine, told the Post.


The problem is that Colorado River water is strictly apportioned to each of the basin states, but the demand for water is much higher than the amount supplied by the river. So water users, particularly in agriculture, must drill for groundwater to make up the difference. But while surface water in reservoirs and rivers can be replaced after a wet season or two, groundwater can take many years to recover to previous levels, if it ever does.


“We really don’t know how much water is down there. We’ve already depleted a lot of it. There could be more, but when we have to start to dig deeper to access it, that’s a bad sign,” Castle said. “If [ground water basins] continue to be depleted, they don’t come back up.”


The study’s authors observed groundwater levels with the Gravity Recovery and Climate Experiment satellite.

-Steve Straehley


To Learn More:

The U.S.’s Western States Are Guzzling Water So Fast They Don’t Realize They’re Running Out (by Gwynn Guilford, Quartz)

Study: Colorado River Basin Drying Up Faster Than Previously Thought (by Reid Wilson, Washington Post)

Largest Reservoir in U.S. Drops to Lowest Level in its 77-Year History (by Noel Brinkerhoff, AllGov)


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