Future of Western water supply threatened by climate change

University of Colorado News: As the West warms, a drier Colorado River system could see as much as a one-in-two chance of fully depleting all of its reservoir storage by mid-century assuming current management practices continue on course, according to a new University of Colorado at Boulder study. The study, in press in the American Geophysical Union journal, Water Resources Research, looked at the effects of a range of reductions in Colorado River stream flow on future reservoir levels and the implications of different management strategies.

….The Colorado River system is presently enduring its 10th year in a drought that began in 2000, said lead study author Balaji Rajagopalan, a CU-Boulder associate professor of civil, environmental and architectural engineering.

…The research team examined the future vulnerability of the system to water supply variability coupled with projected changes in water demand. The team found that through 2026, the risk of fully depleting reservoir storage in any given year remains below 10 percent under any scenario of climate fluctuation or management alternative. During this period, the reservoir storage could even recover from its current low level, according to the researchers.

But if climate change results in a 10 percent reduction in the Colorado River's average stream flow as some recent studies predict, the chances of fully depleting reservoir storage will exceed 25 percent by 2057, according to the study. If climate change results in a 20 percent reduction, the chances of fully depleting reservoir storage will exceed 50 percent by 2057, Rajagopalan said.

"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. "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," he said….

Lake Powell in Utah is one of one of several Colorado River reservoirs in danger of depletion in the coming decades as a result of warming temperatures in the West, according to a new study led by the University of Colorado at Boulder. Image from the Bureau of Reclamation