The Colorado River, a critical source of water for more than 40 million people across the West, is in dire health and its users should take immediate action to keep the system from possible collapse, a new study warns.
The study, released Sept. 11 by a group of water experts across the river’s basin, warned that without rapid action to reduce usage, the “dwindling reserve” in the Colorado’s two major reservoirs may soon be exhausted.
“The river recognizes no human laws or governance structures and follows only physical ones,” the authors wrote. A warming climate has lengthened growing seasons, dried out soils and altered winter snowpack runoff, they said, reducing the amount of water flowing into the river system.
Their findings come as the seven states and 30 tribes who rely on the Colorado try to work out a new plan to share shortages on a river buffeted by a quarter-century of drought and growing demand. Those talks have stalled in recent months over differences in who should give up water.
The new study offered pointed advice to the states, arguing that the way water managers and water agencies look at storage may be lulling people into a place of complacency.
“There’s a lot of less buffer (in the reservoir storage) that a lot of people may not be aware of,” said Anne Castle, one of the study’s six authors and a former U.S. commissioner of the Upper Colorado River Commission. “So we took a simpler approach: What if next year looks like this year?”
The authors estimated that just 9.3 million acre-feet of water could flow into Lakes Powell and Mead this season, while river users will consume about 12.9 million acre-feet of water — a shortfall of 3.6 million acre-feet over the coming year if this winter’s conditions are similar to last year’s.
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The report, unusually blunt and favoring plain words over jargon, analyzed the quantity of water that is “realistically accessible” in Lake Powell and Lake Mead for use in 2026. That means only the water that can be drawn from the reservoirs before water levels drop below “deadpool” conditions, when water can no longer flow through the dams or keep hydropower turbines turning at Glen Canyon and Hoover dams.
The 12 federal reservoirs storing water in the basin had started the 21st century nearly full, the report said, but a quarter-century of overdrafts have left them just 40% full as the Southwest experiences a historic drought.
Lake Powell holds 7 million acre-feet of water as of September, and Lake Mead had 8.1 million acre-feet. But, the report said, only 41% of that water is above the levels set by Reclamation to avoid system collapse.
There’s also the dilemma caused by “assigned water” in Lake Mead. That’s water saved back when rights holders such as the Colorado River Indian Tribes and the Gila River Indian Community agreed to leave some of their allocation in Lake Mead, and a water reserve allocated to Mexico, which under treaty is owed about 1.5 million acre-feet of the river annually.
Lake Mead held about 3.5 million acre-feet of assigned water at the end of 2024, which is about the same amount of realistically accessible water.
“So long as both annual orders in the priority system (the current amount of river allocations) and desired withdrawals of assigned water can be fulfilled, there is no conflict,” the authors wrote. “But further declines in storage in Lake Mead could lead to one.”
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This winter may be warmer, drier
The coming winter season is likely to be warmer and drier than average according to the National Weather Service forecast. Reclamation has projected lower than average inflows into Lake Powell and a continuation of Tier 1 shortage protocols as well.
The report said that even with shortage cuts in place, Powell’s water could drop below the critical level of 3,500 feet in elevation by August 2026. Assuming that the river’s current operating rules will still be in effect in Water Year 2027, which begins Oct. 1, 2026, releases from Powell could not exceed what comes into the reservoir, a condition known as “run of river.”
Sending water downstream to prop up Lake Powell from Upper Basin reservoirs like Flaming Gorge could help, the authors said, but would be only a “one-time” solution. Water was moved downstream in 2022 as lake levels plunged.
“Such releases do not solve the fundamental problem of the gap between supply and use/losses,” they wrote. “Unless overall system water use is brought down to a sustainable level, using Flaming Gorge Reservoir releases simply exacerbates future shortages.”
The same group that wrote the new study proposed “seven pillars” in crafting new river guidelines to replace the rules that expire Dec. 31. Those steps, released in April, would balance usage to supply and restore reservoir storage. “These pillars can also function as guideposts for immediate action,” they said.
Castle, a former assistant Interior secretary for water and science, said water users and state negotiators have been putting a great deal of time and energy developing new river management guidelines that are scheduled to take effect after the current ones expire next year.
“They have really hard jobs and it would be hard to shift gears,” she said. Political considerations in approving and implementing additional reductions rapidly could prove difficult. “That puts an emphasis on the Interior Department to implement reductions.”
With conditions on the Colorado becoming “unforgiving,” the authors said, basin stakeholders must be realistic, as the next few years could be even worse.
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Castle also said the group was not making predictions, just describing what could happen if current conditions continue.
“If the situation we’re describing does occur a year from now, the actions needed would be really unpleasant, and worse than if we enacted changes now,” she said.
Lakes Mead and Powell have about 6.3 million acre-feet in accessible storage, the authors said. “If we continue business as usual, we will deplete nearly half that amount,” which could put the basin in a very difficult position when the new post-2026 guidelines take effect.
“Near-term actions must reflect this stark reality.”
Debra Krol reports on Indigenous communities at the confluence of climate, culture and commerce in Arizona and the Intermountain West. Reach Krol at debra.krol@azcentral.com. Follow her on X, formerly known as Twitter, @debkrol and on Bluesky at @debkrol.bsky.social.
This article originally appeared on Arizona Republic: Colorado River can’t meet demand and needs fast action, study says