This story by Allen Best appeared on BigPivots.com on August 18, 2025. We are sharing it in two parts.
The words “urgency” and “immediate action” were used by Trump administration officials on August 15 in releasing the U.S. Bureau of Reclamation 24-month study for the Colorado River Basin.
The study sees a high probability of water levels of Lake Powell falling to within 48 feet of the minimum power pool by January. That elevation, 3,490 feet above sea level, is the reservoir’s lowest level at which hydroelectricity can be produced. That has not happened since soon after Powell began filling following completion of Glen Canyon Dam in 1966.
“This underscores the importance of immediate action to secure the future of the Colorado River,” said David Palumbo, acting commissioner for the agency.
Scott Cameron, the acting assistant secretary for water and science in the Department of Interior, had similar words of warning to the seven states that share use of the river.
“As the basin prepares for the transition to post-2026 operating guidelines, the urgency for the seven Colorado River Basin states to reach a consensus agreement has never been clearer,” said Cameron. “We cannot afford to delay.”
The announcement cited “unprecedented drought” but made no mention of climate change. This seems to be a theme.
Cameron, at the Getches-Wilkinson Center’s annual water seminar in Boulder during June, talked for 24 minutes without once mentioning climate change. He even answered a question about climate change without using the phrase. He did seem to acknowledge it, saying that in the “real world” there is less water than before, “and that is probably not going to change a whole bunch.”
Might the situation be even worse than what Bureau of Reclamation has projected will be most likely?
A bias of optimism
On August 14, a day before the bureau’s release of the 24-month study, John Fleck and others posted an analysis on Fleck’s Inkstain that warned the study would likely be overly optimistic.
The problem, explained Fleck and his co-authors, is that the “assumptions underlying the study do not fully capture the climate-change driven aridification of the Colorado River Basin.”
The bureau uses a 30-year average in predicting what lies ahead. However, using the hydrology of the Colorado River Basin since the 1990s no longer provides the same usefulness in predicting what lies ahead during the next 24 months. The climate is changing too fast.
Paul Milley, then of the U.S. Geologic Survey, and others from that and other institutions, noted this problem in a 2008 paper, “Stationarity is Dead: Whither Water Management.”
In that paper, Milley and his co-authors argued that human-induced climate changes were altering the means and extremes of precipitation, evapotranspiration, and the rates of runoff in rivers. As such, they contended, using the old models to guide water management no longer worked as well.
In their posting at Inkstain, Fleck and his coauthors — Anne Castle, Erick Kuhn, Jack Schmidt, Kathryn Sorensen and Katherine Tara — noted that the Bureau of Reclamation’s 24-month study a year ago found that the “most probable” level for Powell would be 3,593 at the end of July 2025.
It was 38 feet lower than the projection. It had been another so-so or worse winter and then an early, warm spring.
This, they said, illustrated the bias toward optimism in the models used by the agency. That bias had been detailed in a 2022 study of past projections by a team led by Jian Wang of the Utah State Center for Colorado River Studies.
“Most probable” in the Bureau of Reclamation projections occupied a band of 80% likelihood. The bureau also issues maximum and minimum probable scenarios.
Fleck and his team contend that the bureau’s “minimum probable scenario has become the most valuable in providing a reliable indicator of the future” for Colorado River flows.
This past winter was mediocre, near average snowfall in some basins but among the worst in the San Juans. Spring was warm or more in many places, and rains in July were almost entirely absent.
The preliminary estimated inflow into Powell for April through July was 41% of the average from 1991 through 2020, according to the bureau’s most-probable study. During July, runoff slipped to 12% of that 30-year average.
Might fortunes soon be reversed? Not likely in months ahead, said Fleck and his team. They noted this summer’s weak monsoon for most of the upper basin coupled with the seasonal outlook by the National Oceanic and Atmospheric Administration. Together, they point to a warmer and drier than average fall.
“It’s a good bet that this trend will continue at least through winter,” they wrote.
As it stands, levels in Lake Mead, downstream from Powell, will necessitate cuts in the lower-basin as required by several agreements reached between 2007 and 2019. Arizona is to see an 18% cut and Nevada a 7% cut in their annual apportionments. Mexico is to get 5% less than its annual allotment. In acre-feet, that’s 412,000 for Arizona, 21,000 for Nevada, and 80,000 for Mexico.
A new agreement
The big story continues to be what agreements the seven basin states can achieve in recognition of the inadequacy of past agreements given reduced flows.
Drought as conventionally understood is part of the story, but only a part. A 2017 study by Jonathan Overpeck and Brad Udall, “The 21st Century Hot Drought and Implications for the Future,” concluded that between a third and a half of reduced flows in the Colorado from 2000 to 2014 could be attributed to the rising greenhouse gas emissions. They spoke about “megadrought,” a word now common in Colorado River discussions, as is “aridification.”
This year has brought more studies that strengthen the evidence. Included is a study published just last week in Nature, that identifies new ways that the warming climate has altered the hydrology of Colorado and other southwestern states. See: “Why rain and snow skip the Southwest.”
In 2018, an agreement among the states was reached regarding how to deal with drought. It was universally recognized as an interim agreement, with a final agreement to be reached in advance of a 2026 deadline. That deadline is now close at hand.
That impending deadline was alluded to in the comments of the federal officials.
“Health of the Colorado River system and the livelihoods that depend on it are relying on our ability to collaborate effectively and craft forward-thinking solutions that prioritize conservation, efficiency, and resilience,” said Cameron, Interior’s undersecretary, in the Aug. 15 announcement.
In June, Cameron had called on the Colorado River Basin states to submit details of a preliminary operations agreement by mid-November and share a final seven-state proposal by mid-February 2026. The plan would be to reach a final decision in the summer of 2026 with implementation beginning in October 2026.
Non-government organizations issued statements also calling for the states to figure out a way forward.
“This is not just a crisis. It’s also a call to action to use remaining time wisely to replace our current, reactive, emergency-based management framework with new, long-term solutions,” said John Berggren, the regional policy manager for Western Resource Advocates. “We can’t litigate our way out — we must collaborate forward.”
Allen Best publishes the e-journal Big Pivots, which chronicles the energy transition in Colorado and beyond.