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Groundwater continues to vanish beneath Colorado River basin

Lake Mead
Lake MeadU.S. Bureau of Reclamation

The continuing drought out west is having a devastating effect on the amount of drinkable water available for human consumption, particularly those who depend on the Colorado River Basin. According to a new study by NASA's Gravity Recovery and Climate Experiment (GRACE) and University of California, Irvine, research-scientists, have found that, more than 75% of the water loss in the drought-stricken Colorado River Basin since late 2004 originated from underground resources, posing an even greater threat to nearly 40 million people in 7 states as well as northern Mexico (which have been experiencing the ‘driest 14-year period in the last 100 years), than previously imagined according the U.S. Bureau of Reclamation, the federal water management agency. The Colorado River is the only major river in the southwestern United States.

By studying satellite images used to follow monthly changes related to water both above and below the surface, in the mass of the Colorado River Basin, scientists have determined that the basin has lost “more than 53 million acre feet of freshwater (41 million acre feet of which was groundwater) between December 2004 and last November (2013). This is amount to nearly twice the volume in Lake Mead, the largest reservoir in the US.

"This is a lot of water to lose. We thought that the picture could be pretty bad, but this was shocking, especially when we have no idea of much groundwater we have left, so we don't know when we're going to run out," stated study lead author, Stephanie Castle, a water resources specialist at the University of California, Irvine. Additional authors included scientists from NASA's Goddard Space Flight Center, Greenbelt, MD, and the National Center for Atmospheric Research, Boulder, CO.

"The Colorado River Basin is the water lifeline of the western United States," added Earth system science professor Jay Famiglietti, senior water cycle scientist at Jet Propulsion Lab, on leave from UC Irvine."With Lake Mead at its lowest level ever, we wanted to explore whether the basin, like most other regions around the world, was relying on groundwater to make up for the limited surface-water supply. We found a surprisingly high and long-term reliance on groundwater to bridge the gap between supply and demand." He also warned that the “rapid depletion rate, combined with population growth and shortage of snow, will compound the problem of short supply by leading to further declines in streamflow in the Colorado River.”

For more information on NASA's GRACE satellite mission, see: http://www.nasa.gov/grace and http://www.csr.utexas.edu/grace