Climate change is stealing rain and snow from the Colorado River, and it might be the basin’s new permanent condition, according to a report released this week.
Leading scientists from around the Colorado River Basin, which spans parts of Colorado, six other Western states and Mexico, released Tuesday a collection of essays on the future water supply for 40 million people. In many ways, it’s bleak. Rainfall is low, river flows are down, reservoir storage is on the brink of depletion and groundwater is struggling, according to several authors in the Colorado River Research Group.
“We still don’t have a crystal ball, but the future is pretty dark,” Brad Udall, a member of the research group and a Colorado-based climate scientist, told The Colorado Sun.
The group, formed in 2014, includes leading scientists from around the basin and aims to share scientific insights into Colorado River system management.
Reservoirs that once held four full years of river flows are now more than two-thirds empty, one essay said.
A single dry year or two could push those massive reservoirs, Lake Powell and Lake Mead, into critically low levels where hydropower production, water deliveries, and physical conveyance of water downstream can no longer be assured — a scenario called deadpool.
The good news is people can still do something about it. The essays, collectively named in “Colorado River Insights 2025: Dancing with Deadpool,” offered some solutions, like creating a basinwide management entity. They emphasized that the basin has the resources it needs to take action — if basin officials can agree on what to do.
The dealings among states in the basin, however, have been strained. Federal, state, tribal and other officials have been working on new, post-2026 reservoir storage and release guidelines. But their talks have been stalled for months.
Basin water watchers are hoping to get updates next week at the biggest Colorado River gathering of the year, the Colorado River Water Users Association conference in Las Vegas.
“This report underscores that the basin is out of time, the crisis is no longer theoretical,” said Doug Kenney, with the University of Colorado Law School and chair of the Colorado River Research Group. “Post-2026 negotiations must produce durable, equitable, climate-realistic solutions — and they must do so urgently.”
Where has the rain gone?
One key challenge for the Colorado River Basin? Rainfall — or the lack thereof.
Since 1999, precipitation in the basin has dropped by 7% compared with the 20th-century average.
In some years, parts of the basin receive near-normal precipitation during the winter, but come spring only about half the usual amount of water makes it into springs and rivers.
Flows in the Colorado River have fallen, too. The 26-year average flow is 12.2 million acre-feet. That’s well below the 16.5 million acre-feet of water the states and Mexico have agreed to share on paper. One acre-foot roughly equals the annual water use of two to four households.
It’s not the basin’s first dry period. Historically, long periods of lower precipitation in the basin have swapped irregularly with periods of more rain and snow. Over the past 2,000 years, some of the basin’s drought periods have lasted as long as 80 years.
Some researchers point to these swings to say that periods of greater precipitation could be coming back to the Colorado headwaters.
Udall and co-author Jonathan Overpeck disagree.
“This new science tells us … these flows are not going to rebound,” Udall said. “Also on the table are future flow declines as it continues to warm and as precipitation potentially goes down.”
There’s natural variability, but human actions are also tipping the scales, studies show.
Human-caused greenhouse gas emissions lead to warmer temperatures. A warmer atmosphere holds more water. Snow melts earlier, and soils and vegetation lose more water during hotter seasons. Thirstier soils suck up more water before it can reach springs, rivers, reservoirs, farms and homes.
New studies also show that human-caused emissions are behind the decline in precipitation.
One study, published in the journal Nature in August, shows that these emissions are the main factor behind higher sea-surface temperatures, in places like the tropical Pacific Ocean. Those temperatures drive weather patterns over Colorado, called El Niño and La Niña. Typically, warmer water equals a La Niña season, which is associated with a dry southwestern U.S., Udall and Overpeck said.
In another study, researchers looked at a warmer period from about 11,000 to 6,000 years ago caused by changes in Earth’s orbit. The Pacific Ocean warming during that time locked in a multimillenia dry phase in the western U.S., Udall and Overpeck wrote in their essay.
So with no end in sight for those emissions, precipitation in the basin is more likely to flatline or fall than increase, Udall said. It’s a long-term drying process called aridification.
There is a silver lining: Having more clarity around future rain forecasts helps water managers.
For the last two decades, short-term climate forecasts have run the basin — dictating how and when large reservoirs, like lakes Mead and Powell, store and release water.
While temperature forecasts have been more certain, precipitation has always been harder for climate forecasters to predict.
“What we need to plan for is either more of the same or, as I’ve suggested, potentially even an additional 20% decline in flows,” Udall said.