The 27-year-long drought in the Southwestern U.S. — the longest dry period in the last 1,200 years — is taking a serious toll on the flow of the Colorado River. Climate change is shrinking the snowpack in Colorado’s Rocky Mountains, the source of roughly 80 percent of the river’s annual flow, and higher temperatures are melting the snowpack earlier in the year, which saps runoff in late summer and fall. Warmer weather is also increasing evaporation from the river’s 40 reservoirs, including its two largest — lakes Powell and Mead.
Last month, Lake Powell, on the Utah-Arizona border, reached a record low, at less than 150 feet above dead pool, the point at which water can no longer flow through the Glen Canyon Dam’s bypass tubes to reach Lake Mead, behind Hoover Dam, 300 miles downstream. The low water levels reduced the generation of hydropower from both reservoirs, complicated how riverine ecosystems are managed, and slashed deliveries of water to the Lower Basin states of Arizona, California, and Nevada.
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