New water warning: 50% chance Lakes Mead and Powell will run dry by 2021

Lake Mead and Lake Powell, which helps supply water to millions, stands 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. Other studies, some dating back nearly 20 years, have projected Lake Mead could fall to virtually useless levels as climate warms, 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.

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