It's a 50 percent possibility, a new Scripps study finds, which would squeeze water supplies in Arizona, California, Nevada, and New Mexico.
Lake Mead and Lake Powell, which supply water and power to millions in the American Southwest, stand a 50 percent chance of running dry by 2021 unless dramatic changes take place in how the region uses water, according to a new study.
Causes include growing population, rising demand for Colorado River water, which feeds both lakes, and global warming, according to scientists at the Scripps Institution of Oceanography in La Jolla, Calif., who conducted the study.
The results underscore the importance of water-conservation measures that many communities throughout the region are putting into place. Other studies, some dating back nearly 20 years, have projected that Lake Mead could fall to virtually useless levels as climate warmed, but they lacked a sense of the timing. The new results, the Scripps scientists say, represent a first attempt to answer when lakes Mead and Powell would run dry, squeezing water supplies in Arizona, California, Nevada, and New Mexico.
"We were stunned at the magnitude of the problem and how fast it is coming at us," notes Tim Barnett, a research physicist at Scripps who led the effort. By "dry," the team means that water levels fall so low behind the Hoover and Glenn Canyon Dams that the water fails to reach the gravity-fed intakes that guide it through turbines or out through spillways. In addition, the report estimates that the lakes stand a 50 percent chance of falling to the lowest levels required to generate electricity by 2017.
Last week, Dr. Barnett published additional work in the journal Science attributing 60 percent of the reduction in snowpack, rising temperatures, and reduced river flows over the past 50 years to global warming.