Study: Colorado River water reservoirs could be depleted by 2057

Several factors are conspiring to deplete the Colorado River water reservoirs that supply 30 million people in the western United States with drinking and irrigation water.

Those factors include a 10-year draught, current water management practices, and climate change, according to researchers at the University of Colorado in Boulder.

The reservoir system is currently at 59 percent of capacity, said lead study author Balaji Rajagopalan, associate professor in the civil, environmental and architectural engineering department. "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," said Rajagopalan.

Researchers studied the effects that different scenarios might have on reducing the Colorado River’s stream flow and the rate of depletion of the reservoirs. 

They found that if climate change leads to a 10 percent reduction in the Colorado River's average stream flow -- as some studies have predicted --  there’s a 25 percent chance the reservoir storage will be fully depleted by 2057. But the risk of fully depleting the reservoir storage increases to 50 percent if climate change causes a 20 percent flow reduction in the river.

While the study sends a warning, the researchers wanted to clarify that the reservoirs could still recover from their current low levels. Even under harsh drying caused by climate change, the large storage capacity of reservoirs on the Colorado, particularly Lake Mead and Lake Powell, might be able to maintain water supplies for a few decades, said the researchers.

"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," said Rajagopalan.

The study was supported by the Western Water Assessment, the National Oceanic and Atmospheric Administration (NOAA), Center for Advanced Decision Support for Water and Environmental Systems, (CADSWES), and the Bureau of Reclamation.

The findings are to be published in the September issue of Water Resources Research, a journal published by the American Geophysical Union.