Water levels at Lake Mead are now the lowest they've been since the nation's largest reservoir filled about 90 years ago.
It's a striking new milestone for the reservoir held back by Hoover Dam, which straddles the Arizona-Nevada border. More than two decades of drought and climate change have cut back on water supply in the Colorado River system, and policymakers have struggled to rein in demand accordingly. As a result, the massive reservoir that stores water for Phoenix, Los Angeles, Las Vegas and a sprawling agricultural industry has been left about a quarter full.
Water is expected to keep safely passing through Hoover Dam for use downstream despite the low levels, but the shrinking reserves could soon harm hydropower production inside the dam.
"Right now the complications are really with reservoir recreation, marinas, things like that," said Jack Schmidt, a longtime Colorado River researcher at Utah State University. "But we're only 5 feet above genuine conflicts with the production of electricity. It's not a good situation."
The federal government is soon expected to release the details of a plan to cut back on downstream water deliveries and keep more water in Lake Mead. Early outlines of the plan give the Interior Department the ability to cut up to 40% of the Colorado River water that flows to Arizona, California and Nevada.
The specific size of water cutbacks in 2027 and 2028 is expected to be released soon.
"In the near term, there is only one way to maintain water elevations in Lake Mead," Schmidt said, "And that is to reduce consumptive use."
Water in Lake Mead is mostly Rocky Mountain snowmelt, which pools in Lake Powell, a different reservoir upstream. Powell, the nation's second-largest reservoir, is also at record low levels. It is also tiptoeing towards impacts to hydropower generators within the dam that holds it back, and further drops could seriously jeopardize its ability to send water downstream through the Grand Canyon into Lake Mead.
Hoover Dam has long stood as a symbol of American engineering might, and the perilously low levels in the reservoir it creates, Schmidt said, speak to the seriousness of the Colorado River crisis.
"The fact that that reservoir is now hitting record lows," Schmidt said, "Really tells us that it's time to scratch our heads and say, 'This whole edifice of how we've arranged the engineering and the geography of water storage in the basin, is it time to begin to rethink that?"
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