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Lake Powell and Lake Mead, the two largest reservoirs in the United States, have fallen to their lowest combined level on record, according to a recent report, marking what Colorado River experts describe as a significant moment in the West’s deepening water supply crisis.
Record Low for Combined Storage
The report found that, on July 12, the combined live storage in Lake Powell and Lake Mead dropped to 12,675,509 acre-feet, breaking the previous record low of 12,677,161 acre-feet set on March 14, 2023.
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An acre-foot is the amount of water needed to fill an acre to the depth of one foot.
The report said Lake Powell’s surface elevation stood at 3,524.32 feet above sea level on July 12, equal to 5,505,869 acre-feet of live storage, while Lake Mead stood at 1,042.77 feet, equal to 7,169,640 acre-feet.
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The authors said the last time the two reservoirs held so little combined usable water was May 23, 1957, when 12,668,000 acre-feet was stored entirely in Lake Mead, before Lake Powell began filling.
Although the reservoirs are often treated separately, the report argued that they should also be understood as one connected storage system. Lake Powell is administered in the Upper Colorado River Basin and Lake Mead in the Lower Basin, but together they sit downstream of major Upper Basin water uses and upstream of major Lower Basin uses, it said. The report added that they "essentially comprise one gigantic reservoir," separated by the Grand Canyon, "where there are minimal consumptive uses."
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Storage Losses Accelerated in 2026
The decline appears to have accelerated through 2026. Since March, the report said combined storage in the two reservoirs has been depleted by about 16,000 acre-feet per day, except in May, when the rate slowed to about 11,000 acre-feet per day as Rocky Mountain snowmelt and supplemental releases from Flaming Gorge Reservoir flowed into Lake Powell.
Monthly depletion averaged 2,626 acre-feet per day in January, 6,494 in February, 15,733 in March, 16,861 in April, 11,001 in May, 16,230 in June and 16,661 from July 1 to July 13, according to the report.
The report warned that, until runoff from the 2026-27 winter snowpack begins next spring, "every day going forward" is likely to set a record low for combined storage.
"This is a significant moment in the evolving Colorado River water supply crisis," the authors said.
Why the Colorado River Matters
The Colorado River is one of the most important water systems in North America. The Bureau of Reclamation says that it provides water supply, hydropower, recreation, fish and wildlife habitat and other benefits across Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming, as well as Mexico. Agriculture accounts for about 70 percent of Colorado River water use, while 35 million to 40 million people rely on it for at least part of their municipal supply, according to the agency.
"The lowest snowpack on record for the Colorado River Basin has now resulted in the lowest spring inflow into Lake Powell. The Department of the Interior and Bureau of Reclamation remain committed to reducing the collective risk of both Lake Powell and Lake Mead falling below critical elevations to protect critical infrastructure to continue to meet the water and hydropower needs of the basin," a Reclamation spokesperson told Newsweek.
"Collaboration and stewardship remain essential as we strive to optimize every drop of available water to best meet the needs of the 40 million people who rely on the Colorado River."
Scientists have warned that by 2028, reservoir levels could fall so low that normal operations—including water deliveries and hydropower generation—may no longer be possible.
The threshold effectively defines what the report describes as a "system crash," where the multibillion-dollar infrastructure underpinning the Colorado River can no longer function as intended, threatening millions of people and vast agricultural economies that depend on it.
Agreements Near Expiration
The new storage low comes as the federal government weighs the next phase of Colorado River management. Reuters reported that a U.S. plan is expected to require Arizona, California and Nevada to cut their Colorado River use by about one-fifth in 2027 and 2028, with deeper reductions possible later, citing a state water official. Arizona Governor Katie Hobbs, meanwhile, has said that "unreasonable cuts" to her state’s Colorado River allocation are "unacceptable."
Several operating agreements expire are set to expire at the end of the year, making the coming decisions central to how the shrinking river is shared.
As of Sunday, Lake Mead was 27 percent full, with 7,061,904 acre-feet in storage, according to Bureau of Reclamation data. Lake Powell was 22 percent full, with 5,424,836 acre-feet.
Update, 7/29/26, 12:26 p.m. ET: This article was updated with comment from the Bureau of Reclamation.
Contact Newsweek editors on this story: Matthew Robinson and Dave Siminoff.
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