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The American Geophysical Union and the University of Colorado on July 20 released a study concluding that the reservoirs along the Colorado River could dry up by the middle of the century due to temperature increases. The likelihood is high unless water management policies are changed, researchers suggest.
The warning is significant considering that approximately 30 million people depend on the Colorado River for drinking and irrigation water. The Colorado River Basin runs from Wyoming and Colorado through Utah, Arizona, Nevada, New Mexico and Lower California. The largest reservoirs within the basin are Lake Mead and Lake Powell.
The study entitled “Water Supply Risk on the Colorado River: Can Management Mitigate?” examined scenarios of flow reductions in the Colorado River. The researchers say that changes in water management are crucial to avoiding a drastic reduction of reservoir storage that could occur under severe drying due to climate change. The study suggests more aggressive management practices involving reduction of downstream releases when reservoirs are in short supply.
Lead study author Balaji Rajagopalan of the University of Colorado at Boulder said, “This study, along with others that predict future flow reductions in the Colorado River Basin, suggests that water managers should begin to re-think current water management practices during the next few years, before the more serious effects of climate change appear.”
The Colorado River system has suffered under drought for the past ten years; though, at the onset of the drought the reservoirs were near full capacity. Now, the system is at 59 percent capacity, the researchers say. For the next 16 years, the risk of depleting the reservoir storage in any particular year due to warming is fairly low and the storage level could increase from the current low level, they said. However, a reduction of 10 or 20 percent due to climate warming poses the risk of depletion rises as time goes on.
Rajagopalan warns that should climate change cause a 20 percent reduction in flow, “the chances of fully depleting reservoir storage will exceed one in two by 2057.”
On average, drying caused by climate change would increase the risk of fully depleting reservoir storage by nearly ten times more than the risk we expect from population pressures alone,” he says. “By mid-century this risk translates into a 50 percent chance in any given year of empty reservoirs, an enormous risk and huge water management challenge.”
The study is slated for publication in the journal Water Resources Research, published by the American Geophysical Union. The study was conducted with support from the Western Water Assessment, a joint venture of University of Colorado at Boulder and the National Oceanic and Atmospheric Administration (NOAA), as well as Center for Advanced Decision Support for Water and Environmental Systems and the University’s Bureau of Reclamation.
