The megadrought that’s lasted 25 years so far could continue parching Utah and the Southwest until 2050. Or maybe even the end of the century.
New research from the University of Texas indicates global warming may disrupt a key atmospheric pattern that brings winter precipitation to the West — and could do so for decades to come.
“Instead of saying that we've just been really unlucky the past few decades,” said researcher Victoria Todd, “what we're hypothesizing is that this could actually be a shift in the climate state. That this could be basically the new normal.”
Utah is already strapped for water. Drought conditions cover all of Utah — the only Western state where that’s the case — which increases water demand. Statewide reservoir levels dropped 10% in June, according to the Utah Division of Water Resources. The average decline during that month is just 2%. That prompted a plea from the governor to save water.
It’s a similar story across the Colorado River Basin, where thirsty farms and growing cities have strained the river’s shrinking supply. The nation’s largest reservoirs, Lake Powell and Lake Mead, could both face historic lows within the next two years.
So, a prolonged drought would lead to some tough choices. Regional water managers are already trying to plan for that worst-case scenario, said Colorado River Authority of Utah Executive Director Amy Haas.
“The study tracks with what we're seeing, which is something that is certainly more attenuated than just what we consider to be drought,” she said. “What I think we're seeing on the Colorado River is more in line with what we've coined ‘aridification,’” referring to the term that describes the long-term transition to a more water-scarce environment.
The Colorado River’s average flows have diminished by a quarter since the original multistate water use agreements were negotiated more than a century ago. Now as the river basin’s seven states negotiate updated rules for splitting that water, they can’t count on the flows remaining steady.
“As water managers, we've got to respond to that,” Haas said. “And I think that we are, and we have been responding.”
One strategy that could help would be to give each basin state a percentage of the water that’s actually in the river, rather than basing their allocations on a fixed number, a reservoir level or a forecast. The idea is gaining support, Haas said, but everyone involved isn’t on the same page yet.
The basin states need to come up with a new Colorado River agreement by August 2026, she said, so it can be implemented by the Oct. 1 deadline.
There are still details to work through. The negotiators are figuring out exactly how to measure the river’s natural flow and deciding whether or not it should be a rolling average across a few years. They’re also considering a plan that would allocate higher percentages to states in good water years and lower percentages in bad ones.
Another element Haas hopes to see would be a provision that allows states to come back to the table in the event of an “Armageddon-like hydrology” year.
“We would have to have some sort of a process whereby we would address the unknowns,” she said. “Things that we just simply can't plan for.”
The University of Texas research team based its megadrought hypothesis on a prehistoric comparison.
First, they examined sediment samples taken from beneath the Rocky Mountains to get a clearer picture of a widespread, long-lasting drought that hit the Southwest more than 6,000 years ago. The idea was to quantify how big the drought was and why it happened.
This ancient drought lasted for thousands of years and was more intense than previously thought, said Timothy Shanahan, an associate professor at The University of Texas who also worked on the study.
“When I saw [Todd’s] results, it was really surprising,” he said. “Because they suggest a really big drought, and that is not what traditional climate models predict” happened during that period.
It had profound impacts on life in the Southwest, Shanahan said, from drastic drops in lake and river levels to the formation of dune fields.
That prehistoric drought appears to have been caused by warming temperatures across the Northern Hemisphere, according to the study. At that time, Africa’s Sahara Desert was covered with grasslands and lakes — a dark surface that soaked up the sun’s heat much more than the light, reflective sand there today.
“It's like wearing a black T-shirt out on a hot summer day,” Todd said. “You're going to heat up really fast under those kinds of conditions.”
The heat set off a chain reaction that forced other atmospheric conditions out of rhythm. That included weather patterns that bring precipitation to the Southwest from the ocean, like the Pacific Decadal Oscillation. Todd’s model estimates it led to a 20% decline in winter precipitation.
That’s where the team found similarities between the ancient drought and the changing climate of today.
“It seems that this response in the North Pacific is related to warming,” Shanahan said. “It doesn't require vegetation change. It just requires warming.”
So, climate change that’s driven by fossil fuel emissions could still potentially produce enough heat to mess with the ocean’s atmospheric cycles. The Pacific Decadal Oscillation has already been in a historically negative phase in recent years, which also coincided with the record dry winter in southwest Utah in 2025.
Warmer temperatures can also set off a snowball effect that amplifies drought. Extreme heat can accelerate evaporation and cause snowpack to melt earlier. It dries the soil, too, which then soaks up water before it even gets to rivers or lakes.
It all means Utah and other Western states need to get ready for the possibility of more dire water years. But it’s hard to prepare when even the experts don’t know exactly how bad things could get.
If the drought of 6,000 years ago was in fact worse than climate models had previously thought, Shanahan said it’s likely current scientific simulations are also underestimating the future of this megadrought.
“We should expect the drought to continue, and we should expect it to get more severe,” he said. “Current projections are not getting how big this drought is going to be as we go into the future, because they're underestimating the magnitude of this [warming] effect.”
The good news, he said, is that the ancient drought finally ended when the planet cooled. So, curbing current warming trends should also limit how bad the megadrought becomes.
