Colorado River IMG: via Shutterstock

A newly released study by NASA and the University of California at Irvine showed shocking news for the Colorado River basin. Using a satellite which tracks changes in groundwater, the research team discovered that the basin, which supplies water to 40 million people in seven states, lost 15.6 cubic miles of freshwater in the last 10 years alone.

The study explains that over 75 percent of this loss is from excessive groundwater pumping. This is the first study of its kind to quantify how big a role the overuse of groundwater has in the dwindling water resources in the Western United States.

“We don’t know exactly how much groundwater we have left, so we don’t know when we’re going to run out,” said Stephanie Castle of UCI, the study’s lead author, in a press release. “This is a lot of water to lose. We thought that the picture could be pretty bad, but this was shocking.”

The nine-year study from December 2004 to November 2013 measured the change in water mass monthly, using data from NASA’s Gravity Recovery and Climate Experiment (GRACE) satellite mission to track changes in the mass of the Colorado River Basin. Changes in water mass are related to changes in water amount on and below the surface.

“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,” Jay Famiglietti, senior author on the study and senior water-cycle specialist at NASA’s Jet Propulsion Laboratory, said in a statement.