Worsening climate outlooks raise the stakes for an agreement on the Colorado River

Yahoo

06-06-2025

BOULDER, CO — Everyone who's haggling or agonizing over how to split up the drying Colorado River in coming decades is painfully aware that the river's flow has dipped below what previous generations thought would water an ever-growing West.
That's now the good news.
A leading Colorado River Basin climate scientist told hundreds gathered for a conference about how to stretch, share and save the river that the current warming trajectory will seriously strain their efforts at balancing supply and demand. The world is on track to exceed 3 degrees Celsius of global warming by 2100 — 5 degrees Celsius (or 9 Fahrenheit) over land — according to Colorado State University water and climate researcher Brad Udall.
'That's a world unlike anything we currently know,' Udall said June 5 at a University of Colorado Law School conference examining the river's woes, 'and it's going to challenge us on every front.'
On the Colorado River front, warming equals reduced flows as the atmosphere, desiccated soils, thirsty forests and human irrigation demands all take their share to deplete water that could otherwise be stored in the nation's two largest reservoirs, Lake Mead and Lake Powell.
This year's snowmelt runoff outlook, projected to reach just over half of the 30-year average by the time it effectively ends in July, is complicating efforts to reach consensus on interstate cutbacks. Any future reductions in flow will only add to the pain.
Climate change is speeding faster than expected, with the likely effect of further tanking the river's bounty until it provides just two-thirds of the water that the negotiators of a century ago thought would support the growing region, according to Udall's worst-case scenario for the end of the century. And that doesn't account for water that the United States must provide to Mexico by treaty.
In the language of water managers, it means a river that the interstate negotiators of a century ago asserted could provide 15 million acre-feet to the seven states that use it could instead average just 10 million acre-feet a year. Already, the megadrought that started in 2000 has dropped the average below 13 million. Mexico's share is 1.5 million.
(An acre-foot is roughly 321,000 gallons, enough to support several households for a year, though more river water is consumed on farms.)
Measuring flows: How much water flows down the Colorado River? The right answer is more important than ever
Against today's startling water losses and tomorrow's even more frightening projections, the states are struggling to reach consensus on how to spread the pain among themselves after guidelines for navigating shortages expire next year.
The Lower Basin states of Arizona, California and Nevada fully developed their half of the 15 million acre-feet that the 1922 Colorado River Compact granted them and have had to cut back. The four states upstream of them now face the prospect of never getting their full half even as the southwestern states ask them to consider cutting back from their existing uses in the driest of years.
The Trump administration's Interior Department will likely need to step up as a moderator in a debate that to date has been left largely to the states, said Mike Connor, who led the department's Bureau of Reclamation in the Obama administration.
The new administration is showing signs that it may begin to work on bringing the states together, Connor said, and it should help that it still has more than $1 billion in funds from the last administration's infrastructure allocation to help tackle drought.
'The federal government is the key mediator and facilitator,' he said.
So far, though, the states at least publicly are far apart. The Upper Basin States of Colorado, New Mexico, Utah and Wyoming have said their cuts come in the form of dry winters that limit what farms and ranches can divert, and that it's up to the Lower Basin to cut more from what it takes out of the big desert reservoirs before they drain below useful levels.
The Lower Basin states say they are willing to give up more in future years, but that trying to fill the gap all on their own could lead to unacceptable results such as a dry Central Arizona Project Canal cutting off Phoenix and Tucson.
The rift has proved deep enough that most of the lead negotiators who normally appear together for panel discussions at this and similar annual conferences did not even show up.
Preparing for a fight: Hobbs says Arizona will defend its Colorado River water, wants other states to accept cuts
Conference attendees — the experts and advocates who work to protect the river and its various uses — must help give political cover to those negotiators who are responsible for protecting their own states' interests, said Anne Castle, a former Interior Department official and Upper Basin Commission chair who is now a fellow at the University of Colorado Law School. Their jobs are difficult, she said, and experts could help by making clear to their constituents that there's not enough water to go around, and all must use less of it.
'Some of what we thought were our legal entitlements and what we had expectations about using in the future … have to be moderated,' Castle said.
Other speakers detailed how cities have adapted by growing while using less water, and how some, such as Phoenix, are able to essentially save water by growing because homes will use less water than the farms that they displace.
But others pointed to a challenging future in which farms will likely have to cut back further to keep supplies flowing to cities. In all, according to water researcher Brian Richter of the global scarcity solutions organization Sustainable Waters, current rates of reservoir and groundwater drawdowns suggest that 15% of current use within the Colorado River Basin is unsustainable and will have to go.
And that's at today's average rate of flow. If warming and drought continue to shrink the river, more cutbacks will be needed just to balance the annual supply, let alone the roughly two-thirds of storage capacity now unfilled in Lake Mead and Lake Powell.
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To Udall, the water and climate researcher, the new 'anti-knowledge' Trump administration seems bent on worsening the problem by eliminating the science that the states and federal dam managers rely on to make informed decisions. The administration is crippling agencies that are critical to climate adaptation by 'going after anything and everything that has the word climate in it,' he said.
'It's insanity, what they're doing,' Udall said, especially given that warming is accelerating. 'There is no way this makes for a better world in which we live, a better world in which the Colorado River flows.'
A Trump administration official, Acting Assistant Interior Secretary for Water and Science Scott Cameron, was scheduled to appear on the conference's second day, June 6.
Brandon Loomis covers environmental and climate issues for The Arizona Republic and azcentral.com. Reach him at [e-mail].
Environmental coverage on azcentral.com and in The Arizona Republic is supported by a grant from the Nina Mason Pulliam Charitable Trust.
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This article originally appeared on Arizona Republic: A warming, drying Colorado River increasingly vexes water negotiators