The Colorado River basin has lost huge volumes of groundwater over the past two decades according to a new report from researchers at Arizona State University. Researchers used NASA satellite data to map the rapidly-depleting resource.
The region, which includes seven Western states, has lost 27.8 million acre-feet of groundwater since 2003. That's roughly the volume of Lake Mead, the nation's largest reservoir.
The findings add a layer of complication for the already-stressed Colorado River. As demand for its water outpaces supply, more users may be turning to groundwater instead, which is often less regulated than water from above-ground rivers and streams.
The majority of water conservation work throughout the Colorado River basin has been focused on cutbacks to surface water use. Some river experts say the focus should be broader.
Brian Richter analyzes water policy and science as president of Sustainable Waters. He was not an author of the study but said its findings show the need for a "holistic perspective" on water management from the region's leaders.
"It suggests that we have to become more aggressive and more urgent in our reduction of our overall consumption of water," he said.
The study found that groundwater losses in the Colorado River basin were 2.4 times greater than the amount of water lost from the surfaces of Lake Powell, Lake Mead, and a number of other smaller reservoirs that store Colorado River water. The study highlights agriculture's outsized water use in the Colorado River basin, and said that industry could suffer some of the greatest consequences if the region keeps sapping limited water supplies.
Most of the losses happened in the river's Lower Basin states of Arizona, California and Nevada. The study says Arizona's "Active Management Areas," which the state set up to regulate groundwater withdrawal, may have helped slow depletion.
Kathleen Ferris, an architect of Arizona's groundwater laws, said much more work is needed to protect groundwater.
"We are not on track," said Ferris, who was not involved in the study. "We are way behind the eight ball, and I'm really sad that nothing seems to get done. We should have been thinking about this issue 25 years ago."
Ferris is now a senior research fellow at Arizona State University's Kyl Center for Water Policy.
As experts call for more robust groundwater management policies, Richter said this study presents a small silver lining: scientists are producing better data than ever before, giving policymakers a better sense of the region's water problems.
"From a public policy standpoint, this is bad news," he said. "This tells us that it's worse than we thought, because now we understand what's going on underground as well. From a science perspective, this kind of study is good news, because it says that we are now much more capable of accurately describing a water problem like what we're experiencing in the Colorado River system."
This story is part of ongoing coverage of water in the West, produced by KUNC in Colorado and supported by the Walton Family Foundation. KUNC is solely responsible for its editorial coverage.
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