Federal officials reported Tuesday that the water level in Lake Powell, one of the main water storage reservoirs for the Colorado River Basin, could fall low enough to stop hydropower generation at the reservoir by December 2026.
The reservoir’s water levels have fallen as the Colorado River Basin, the water supply for 40 million people, has been overstressed by rising temperatures, prolonged drought and relentless demand. Upper Basin officials sounded the alarm in June, saying this year’s conditions echo the extreme conditions of 2021 and 2022, when Lake Powell and its sister reservoir, Lake Mead, dropped to historic lows.
The basin needs a different management approach, specifically one that is more closely tied to the actual water supply each year, the Upper Colorado River Commission’s statement said.
The seven basin states, including Colorado, are in high-stakes negotiations over how to manage the basin’s water after 2026. One of the biggest impasses has been how to cut water use in the basin’s driest years.
“You can’t reduce what doesn’t come down the stream. And that’s the reality we’re faced with,” Commissioner Gene Shawcroft of Utah said in the statement. “The only way we’re going to achieve a successful outcome is if we’re willing to work together — and not just protect our own interests.”
Lake Powell, located on the Utah-Arizona border, collects water from Colorado, New Mexico, Utah, Wyoming, part of Arizona and tribal reservations in the Colorado River’s Upper Basin. Glen Canyon Dam releases the reservoir’s water downstream to Lake Mead, Native American tribes, Mexico, and Lower Basin states, including Arizona, California and Nevada.
Lake Powell and Lake Mead make up about 92% of the reservoir storage capacity in the entire Colorado River Basin.
The U.S. Bureau of Reclamation’s July report, called a 24-month study, shows the potential for Lake Powell to decline below two critical elevations: 3,525 feet and 3,490 feet.
It could drop below 3,525 feet in April 2026, which would prompt emergency drought response actions. That’s in the most probable scenario, but the federal agency also considers drier and wetter forecast scenarios. The dry forecast shows that the reservoir’s water levels would fall below this elevation as soon as January.
Lake Powell would have to fall below 3,490 feet in order to halt power generation.
Planning for emergency water releases
In 2021 and 2022, officials leapt into crisis management mode and released water from upstream reservoirs — including Blue Mesa, Colorado’s largest reservoir — to stabilize Lake Powell’s water levels.
The emergency releases prompted some concerns about recreation at Blue Mesa.
The July 24-month study triggered planning for potential emergency releases, called drought response operations, at Lake Powell, and Flaming Gorge, Blue Mesa and Navajo reservoirs, said Chuck Cullom, executive director of the Upper Colorado River Commission.
“The Upper Division States and Reclamation have been monitoring the risks to Lake Powell since January 2025 due to the declining snowpack and runoff, and are prepared to take appropriate actions as conditions evolve through 2025 and spring of 2026,” he said in an email to The Colorado Sun.
At-risk hydropower
Hydroelectric power generation takes a hit with lower water levels at Lake Powell and Lake Mead.
Reclamation’s dry conditions forecast says Lake Powell could fall below 3,490 feet by December 2026, and Lake Mead’s water level could fall below a key elevation, 1,035 feet, by May 2027. At that point, Hoover Dam would have to turn off several turbines and its power production would be significantly reduced, said Eric Kuhn, a Colorado water expert.
In more typical or unusually wet forecasts, neither reservoir would fall below these critical elevations in the next two years, according to the report.
Lake Powell and other federal reservoirs provide a cheap and consistent source of renewable energy. Without that, electricity providers would have to look to other, more expensive sources of energy or nonrenewable supplies. Some of those costs can get handed down to customers in their monthly utility bills.
Glen Canyon’s hydropower is normally pooled with other power sources to serve customers in Wyoming, Colorado, Arizona, New Mexico, Nevada, Texas and Utah. Its power generation has already been impacted: Fourteen of the lowest generation years at the dam have occurred since 2000.
A strong monsoon season this summer could help elevate the water levels in the major reservoirs, as could a heavy winter snowpack in the mountains this coming winter.
“If next year is below average, then we’re setting ourselves up for some very difficult decisions in the basin,” said Kuhn, former general manager of the Colorado River District and author of “Science Be Dammed,” a book about the perils of ignoring science in Western water management.
An interstate legal mire
Kuhn has also been tracking the releases from Lake Powell with big, interstate legal questions in mind.
If the river’s flow falls below a 10-year total of about 82.5 million acre-feet, it could trigger a legal mire. In that scenario, the Lower Basin could argue that the Upper Basin would be required to send more water downstream in compliance with the foundational agreement, the 1922 Colorado River Compact.
Some Upper Basin lawyers disagree about the terms of when states, like Colorado, would be required to send more water downstream. That’s a big concern for water users, including farmers and ranchers, who say they already don’t have enough water in dry years.
From 2017 to 2026, the 10-year cumulative flow is expected to be about 83 million acre-feet, Kuhn said.
“We’re OK through 2026,” Kuhn said. “But under the most probable and minimum probable [forecasts], it’s almost a certainty that the flow will drop below 82.5.”
Lake Powell’s ecosystems feel the strain
Bridget Deemer, a research ecologist for the U.S. Geological Survey, keeps her eye on how lower water levels impact ecosystems in Lake Powell.
In a recent study, she found that low dissolved oxygen zones grow larger as water levels fall and more sediment gets backed up in the reservoir over time. This sediment can spur more decomposition, which uses up oxygen in the water.
The zones can cut down on fish habitat. Fish don’t want to be in the warm surface waters of the lake, but as they search for their preferred temperature and food source, they can end up in an area with low oxygen, Deemer said.
The effect is greatest right below Glen Canyon Dam. In 2023, there were 116 days when the oxygen was below 5 milligrams per liter, which is the threshold for trout. At 2 to 3 milligrams per liter, the fish can die.
Deemer also studies how these zones are impacted by algae blooms.
Lake Powell researchers noted toxic algae blooms around the Fourth of July and last fall. They don’t know definitively what caused either bloom event, but research does show that warming water temperatures and increased nutrients are two leading causes of harmful algae blooms.
These blooms can impact fish, people, pets or anything that ingests the algae.
“In general, Lake Powell is doing well,” she said. “Its waters are really clear without a lot of nutrients and algal growth. These blooms are smaller scale and localized.”
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