As negotiators fight over how to curb overuse of the depleted Colorado River for the next 20 years, the river itself is on the verge of a short-term crisis that could erupt in less than a year.
Water levels in the river and one of its biggest reservoirs, Lake Powell, are forecast under the most pessimistic federal analysis to fall low enough as soon as September 2026 to force a shutdown of power generation from the turbines at Glen Canyon Dam at the Arizona-Utah border.
Having the lake fall below that level, 3,490 feet, would also require the federal government to run the river water through the dam via a set of four attached outlet tubes, which were never designed to carry large amounts of water. The water couldn't go through its usual passage, the dam's turbines, because the turbines would be shut down at low elevations.
The outlet tubes, or outlet works as they are also known, would risk suffering major structural damage if too much water is run through them for too long, the U.S. Bureau of Reclamation has said.
Under the most pessimistic federal forecasts, Lake Powell could drop to dangerously low levels by August 2026 and stay there for at least the next 15 months.
The danger zone starts at an elevation of 3,500 feet at the lake. The bureau doesn't want the lake to go below that because it's so close to 3,490 feet, the minimum level needed to generate power. The lake currently stands at a little over 3,540 feet in elevation, nearly 40 feet lower than a year ago.
The Bureau of Reclamation finished recoating the outlet tubes at Glen Canyon Dam and Powerplant earlier this year. The outlets consist of four large steel pipes that move water from Lake Powell directly into the Colorado River, bypassing the hydropower generating units. The tubes could suffer major structural damage if too much water is run through them for too long, the U.S. Bureau of Reclamation has said, a concern for potential situations in 2026.
To prevent a drop too low, the bureau, which operates Lake Powell and the river's other reservoirs, will be faced with a difficult choice if the most pessimistic forecast pans out:
— It could drastically slash the amount of water it releases from Lake Powell to Lake Mead at the Arizona-Nevada border, cutting off some of the supplies used by Tucson, Phoenix, various suburban cities and some farms, numerous Southern California cities and farms, and the Las Vegas area.
— Or, it could drain water from reservoirs upstream of Powell, led by the large Flaming Gorge reservoir at the Utah-Wyoming border, to send its water downstream and keep Powell from falling below 3,500 feet. The river's Upper Basin states don't want to give that water up; they say they need it for recreation, tourism income and power generation.
Either action is likely to be opposed by whichever basin is negatively affected by it. That would add fuel to an already overheated conflict between the Colorado River's Lower Basin (Arizona, Nevada and California) and Upper Basin (Colorado, New Mexico, Utah and Wyoming) over how to cut water use from the river, when use is outrunning supply by an estimated 3.6 million acre-feet a year.
That deficit is nearly twice as much river water as is delivered over a year by the Central Arizona Project canal to Phoenix and Tucson and the Colorado River Aqueduct to six Southern California counties in the giant Metropolitan Water District.
"The challenge is how do you balance supply, demand and expectations?" said David Wegner, a former bureau official and congressional staffer who remains active in river water issues as a National Academy of Sciences board member. "I’m sure there is no silver bullet that’s going to solve the problem or satisfy people. Everybody’s going to have to give something up. The question is how much, how long and what are the impacts?"
After more than two years of negotiating behind closed doors, the seven states' officials and the U.S. Interior Department announced last month that they had failed to meet a Nov. 11 deadline for agreeing on how to cut water use to better protect reservoir levels and bring demand in line with supply after the river's current operating guidelines expire at the end of 2026.
The divisions were stark at the annual Colorado River Water Users Association conference this month, when speakers from both basins took turns explaining why the other basin needed to do more to conserve water.
But many scientists who study the river say cuts in water use are not only needed when the operating guidelines expire in a year — they're needed now.
"Taking steps now to decrease consumptive uses across the Basin will reduce the need to implement draconian measures next summer or in the following years," said a new paper prepared by six researchers released in early December. "Every acre foot saved now is an acre foot available for our future selves, slowing the rate of reservoir decline and creating more room for creative Colorado River management solutions."
If, on the other hand, "we delay reducing water usage and addressing reservoir drawdown, we may find ourselves in more significant distress" even after the new guidelines take effect in 2027, the paper said.
'We basically don't have a storage reservoir'
This dismal outlook for the river comes from what's known as Reclamation's "minimum probable" forecast. It's taken from the bureau's most recent monthly study, released in mid-December, that predicts reservoir levels for the upcoming two years.
The "minimum probable" forecast is supposed to have only a 10% chance of becoming reality. But in many of the river's recent dry years, it has proven to be more accurate than the bureau's "most probable" forecast, which is supposed to be accurate at least 50% of the time, scientists have said.
The latest "minimum probable" forecast has the lake falling to 3,500 feet in August 2026.
For October 2026, the same forecast puts Powell a nose below 3,490 feet. Then it's predicted to keep sinking, to as low as 3,465 feet by April 2026, before recovering to 3,490 feet in June and July 2027, then sinking below 3,490 again at least through November 2027.
If the river flows stay low, and the bureau is determined to keep Powell at 3,500, "then we basically don’t have a storage reservoir. (The states) can't draw on storage," said Anne Castle, a former assistant Interior secretary of water and science and Upper Colorado River commissioner. Instead, she said, they could only use the natural flow that comes into the lake in a given year.
That would create a "run of the river" situation, in which the only water that could leave Powell is what flows into it, minus whatever evaporates, she said. That could mean the Lower Basin states, including Arizona, get dramatically less water than they're accustomed to receiving, she said.
If the outlet tubes fail
A March 2024 bureau memo warned the outlet tubes could suffer significant damage if too much water is released through them for too long.
The memo, released after the Arizona Daily Star first reported on problems with the outlet works, said the bureau shouldn’t rely on them as the means of releasing water downstream when Powell falls below 3,490 feet.
“If any portion of the river outlet works were to fail, releases would be limited or unavailable through that individual conduit until repairs are complete," the memo said.
While the tubes could be used to a limited extent, the amount of water released would have to be limited, "to avoid cavitation," bureau official Nick Williams said in 2024.
Cavitation occurs when bubbles in moving water implode and create shock waves that travel through the liquid and damage equipment.
The outlet works at Glen Canyon Dam. If lake levels fall to low, the federal government would have to run river water through the dam via this set of four attached outlet tubes, which were never designed to carry large amounts of water.
In June this year, the Bureau of Reclamation announced it had completed a temporary fix for the outlet works. It recoated them with an epoxy solution, funded by an $8.9 million investment from the 2022 Infrastructure Investment and Jobs Act. The work repaired some minor cavitation damage in the outlets that occurred in 2023 when the bureau conducted experimental, high-flow releases through the dam to put more water into the Grand Canyon downstream.
“This is a smart, forward-looking infrastructure investment that will improve Colorado River water operations,” said Reclamation Acting Commissioner David Palumbo.
But bureau officials have acknowledged these repairs won't eliminate the risk of future cavitation, and other water experts, such as Wegner, have warned the repairs amount to only a temporary fix.
In their paper from mid-December, six outside experts reaffirmed the risk to the outlet works, writing, "If the river outlets were to be used continuously, there is significant concern that structural damage to those outlets could occur.
"Accordingly, Reclamation has determined that it will take steps to avoid Lake Powell elevation declining below 3,500 feet," the paper said.
That's considered a safe elevation for continuous withdrawal of water through the penstocks (which convey water through the dam to the turbines) without risk of harm caused by cavitation to the turbines that produce electricity, it said.
'The fundamental problem'
The other option, releasing extra water from Flaming Gorge and possibly other reservoirs, could potentially bring a lot of additional water into Lake Powell.
Flaming Gorge can store up to 3.7 million acre-feet. But currently, Flaming Gorge holds 3.0 million acre-feet, and only a portion of that is likely to be released to protect critical elevations at Lake Powell, the new paper from the research group said.
"Plus, it must be kept in mind that a release from any of the upstream reservoirs is only a one-time solution," the paper said. "Such releases do not solve the fundamental problem of the gap between supply and use or losses. The water provided from upstream reservoirs will not be available again unless wet years return and those reservoirs are refilled."
The federal government has a series of rules, regulations and guidelines that will help dictate how it should balance the two actions of reducing releases from Powell and artificially increasing flows into it.
The bureau decided in 2024 that it can reduce annual releases from Lake Powell to Lake Mead to as little as 6 million acre-feet — down from 7.48 million in 2024 and 2025 — if that's needed to keep Powell from falling below 3,500 feet. Under a different set of regulations, it can release the extra water from Flaming Gorge to prop up Powell.
The bottom line is that federal officials' ultimate decision will depend on the weather.
Right now, it's not forecast to be good for the river, although it's difficult to predict in advance how much runoff into Lake Powell will result from the coming winter's snowpack.
One of the new research paper's authors, retired Colorado-based water district manager Eric Kuhn, said the soil moisture at the Colorado's headwaters area in the state of Colorado is now below average in general.
Soil moisture is an indicator of future river flows because if it's high, the melting snowpack runs off the Upper Basin's mountains into the river in healthy quantities. But if it's low, the soils will soak up so much of the melting winter snowpack in high-elevation areas that not much will run off into rivers and streams that supply the Colorado.
Snowpack in the Upper Basin is also low, likely to be below 60% of average by the first of 2026, Kuhn said.
In addition, the National Weather Service's three-month forecast is for above-normal temperatures for most of the river basin and below-normal precipitation for all of the Lower Basin and for southern Utah and Colorado in the Upper Basin, he said.
Acting Reclamation Commissioner Scott Cameron was asked this month how his agency plans to balance the conflicting options of clamping down on water releases from Powell and increasing flows into Powell from other Upper Basin reservoirs.
"We’ll deal with that eventuality when and if it presents itself," Cameron said.
