The drama engulfing the seven states in the Colorado River Basin could take another, more perilous, turn in a few weeks.
Water experts are warning that by October, the river’s flow may cross a critical threshold at Lee’s Ferry, a bend in the river in Arizona that has been a bellwether of the river’s health for decades. The 1922 Colorado River Compact — the river’s foundational agreement — states that the river’s flow must stay above a certain level at Lee’s Ferry in order to provide enough water for downstream states.
If the flow falls below that point, which some experts equate to a “tripwire,” it could trigger prolonged and expensive litigation at the Supreme Court, a turning point that could have terrible consequences for basin states.
“I can’t imagine what the Front Range of Colorado would look like at that point,” said Darren Beck, a water program supervisor for Boulder County Parks and Open Space, of the prospect of huge cuts to their Colorado River water.
“It would just be dry fields and weeds and decimated economies and families.”
Tensions along the Colorado River have already run high this year — a historic drought, following record-breaking winter temperatures, has threatened water supplies for communities across the West that rely on the river and its tributaries.
For more than three years, the seven states in the Colorado River Basin have been unable to reach a deal to share increasingly scarce water. In August, the federal government issued its own plan to save water, which foisted massive water cuts on Arizona, Nevada and California.
Nevada officials called the cuts draconian, and the state has already sued the Bureau of Reclamation over the plan.
A Supreme Court case and ruling could impose even more dire cuts and lead to bitter disputes for decades. A ruling could, for instance, force cities, farmers and ranchers in Colorado to slash their water use, leading to painful decisions.
“We’re talking about a really significant portion of this state’s water supply being unavailable for five or 10 or 15 years to make up [for] a bad court decision,” said Andy Mueller, general manager of the Colorado River Water Conservation District, during a June hearing to state lawmakers.
Both upper and lower basin states are lawyering up. Colorado Attorney General and gubernatorial candidate, Phil Weiser, said his office would defend the state’s rights, and has insisted his lawyers are now the “best … water law firm in the state.”
But Michael L. Connor, who led the Bureau of Reclamation under President Obama, said a Supreme Court case would create more headaches and not solve the river’s fundamental problem: There is less water to go around.
“If there is Supreme Court litigation over the compact, everybody loses,” he said.
At stake is who decides how to divide up an ever-shrinking pool of water. Will it be state negotiators, who represent millions of people and could still one day reach an agreement?
Or will it be nine justices in black robes?
“Handing the ability to decide really important questions about the operation of the Colorado River to nine people — who don’t know much about it — is very risky business,” said Anne Castle, a scholar at CU-Boulder Law School and former chair of the Upper Colorado River Commission, which represents the Upper Basin states.
Lawsuits over the river’s management are already flying in federal court.
In August, the Bureau of Reclamation finalized its two-year plan to release water from Lake Mead and Lake Powell, the country’s two largest reservoirs. The plan is a short-term attempt to deal with a long-term reality: since 2000, the river’s flow has declined by about 20%, and Mead and Powell are at their lowest levels since the 1950s.
Besides states, tribes could also sue over Reclamation’s plan.
The entire river basin is home to 30 federally recognized tribes, who are legally entitled to more than 25% of the river’s water. But many of those rights have never been fully recognized, and many tribes can’t access all of their water because they lack the expensive infrastructure to redirect it.
Still, “the feds absolutely have a duty to tribes to protect their water interests,” said Heather Tanana, a tribal water law expert at the University of Denver. That stems back to a 1908 Supreme Court decision, which ruled that tribal reservations should have enough water to function.
While that has hardly been achieved, some tribes downstream could argue that Reclamation’s latest plan violates the government’s responsibility by slashing their water supplies, Tanana said.
Arizona is poised to take the lion’s share of water cuts, which would affect the Gila River Indian Community, near Phoenix.
Gila River Governor Stephen Roe Lewis said the tribe is poised to sue if water cuts become too extreme, even though litigation is not their first choice.
“The community … will not hesitate to turn to the courts to protect our interests and our future,” he said at a CU-Boulder water conference in June.
A tripwire in an unsettled document
The 1922 compact allocates an equal amount of water between the Upper Basin and Lower Basin — 7.5 million acre-feet per year. One acre-foot is roughly enough water for two households a year.
The compact is an inherently incomplete document — it took more than a dozen new laws, agreements and settlements over the next 50 years to build out the River’s complicated system of dams, diversions and reservoirs, and even include tribes and Mexico in the process.
The compact clearly states that the Upper Basin will not cause the river’s flow at Lee Ferry (now called Lee’s Ferry) to drop below 75 million acre-feet of water over any 10-year period.
The Upper Basin also has to kick in roughly half of what’s owed to Mexico, based on the compact and a 1944 treaty. That brings the 10-year total to between 82.5 and 81.5 million acre-feet, depending on how much water is being sent to Mexico, according to Castle and Eric Kuhn, a river historian and former general manager of the Colorado River District. (The Upper Basin, for their part, strongly disputes they owe this much).
Flows at Lee’s Ferry have dipped below that amount before, in the 1960s and ‘70s, but in much different circumstances. During that period, Reclamation was filling Lake Powell, and the river still had plenty of water to go around, according to Kuhn.
For decades since then, flows have steered well clear of that range. But officials at the Upper Colorado River Commission and the Arizona Reconsultation Committee, which advises state officials, estimate that by October, the river’s 10-year flow will dip below 82.5 million acre feet.
“We call that the first tripwire,” Kuhn said. “That’s when the flows are below the upper bookend of how much the upper division states might owe.”
Crossing the tripwire could be a watershed moment — Arizona’s top river negotiator said it could be the basis of a Supreme Court lawsuit, one that argues that their upstream neighbors are violating the compact.
Potential decades in a black box
If history is any guide, Supreme Court water cases move at a glacial place — often taking decades to resolve — and can end with clear winners and losers.
In 1952, Arizona sued California to secure more water and question aspects of the compact. It was the last time that the compact’s fundamental questions came anywhere close to being litigated between states.
Arizona eventually triumphed, which paved the way for the construction of the Central Arizona Project, which now provides water to farms, tribes and desert metropolises, including Phoenix. The case, though, took 11 years to get to a ruling — additional decrees were issued more than 50 years later.
It took more than five years just to decide which other parties should join Texas v. New Mexico and Colorado, a 2013 suit about the Rio Grande River, according to Castle. It took more than 12 years for the Supreme Court to approve a settlement.
John Berggren, a river expert at the advocacy group Western Resource Advocates, said that litigation wastes time and cuts off cooperation that’s needed to create long-term solutions in the basin.
“It will definitely stymie any creative thinking — or any new thinking — because all seven states are going to be very much towing their legal line,” he said. “It just locks up every conversation and you’re no longer having useful or productive negotiations.”
Plus, no one actually knows how such a case would end. Colorado has ended up at the Supreme Court to fend off claims that it overused its share of water from both the Arkansas and Republican rivers. Both those cases have taken decades — and did not always break Colorado’s way.
“Our experience in the litigation around the Arkansas River Compact and the Republican River Compact has not had happy endings for Colorado,” said Castle.
“The point is that once litigation is started, you don’t know exactly where it’s going to end,” she said.
The endgame
For years, the Upper Basin states have said that they can’t agree to mandatory water cuts, because they’re at the mercy of whatever rain or snow falls that year. Last winter, Colorado experienced record-low snowpack, which strained water supplies.
Several towns near the river’s headwaters came extremely close to running out of drinking water. On the Front Range, water supplies that are normally flush were sporadic or non-existent.
Take Hecla Lake, a small pond in Louisville, Colorado. By the early summer, the lake was “bone-dry,” because drought conditions had reduced its normal supply to a trickle, according to Beck, the Boulder County water supervisor.
By August, though, Hecla had received a much needed infusion of water from the Colorado River headwaters. But that water was only temporary, destined to flow to a small, parched farm nearby. Without it, Beck said, the farm would have gone dry.
Attorney General Phil Weiser and Becky Mitchell, Colorado’s top river negotiator, both seem confident in their approach to protect Colorado water users. Both have said the state would never agree to a “bad deal” to divide up water.
“I am not willing to offer a compromise that would leave us worse off than our worst day in court,” Mitchell told state lawmakers during a June hearing.
A worst case outcome, according to Castle and Kuhn, would be if the Supreme Court, or a court-appointed expert, made a quick decision and ordered the Upper Basin states to send more water downstream. That would lead to what’s called “mandatory curtailment,” or cutting off users with water rights that were formalized after the 1922 compact.
That is a lot of water — it includes water for Denver and other Front Range cities, water for snowmaking at ski resorts, and supplies for hundreds of communities and farms across the Western Slope.
Neither Mitchell nor Weiser have publicly detailed the particulars of the state’s litigation strategy. The AG’s office denied a CPR News public records request for recent documents about Colorado River litigation, and did not comment on questions about its strategy.
But the state is preparing. The Colorado Water Conservation Board has millions in cash in case of compact litigation, according to Lawrence Pacheco, a spokesperson for the AG’s office. Attorneys and staff in the office have also billed the state for nearly 18,000 hours of work on Colorado River issues this year, according to Pacheco.
Their approach, though, is running into some pushback from lawmakers. During a June hearing, state senator Dylan Roberts sharply questioned why the state was leaning on lawyers to defend its position, instead of working towards a compromise that avoids a courtroom.
“I don’t think Colorado fares well when we go to court … throwing our fate to the nine justices on the U.S. Supreme Court, only one of whom has any experience with Colorado at all,” Roberts told Mitchell, referring to Justice Neil M. Gorsuch.
Kuhn said the state should have agreed to a specific target of water conservation during earlier negotiations, instead of holding firm. That could have staved off the possibility of much more painful, forced curtailment later.
“My concern is that Colorado backed the basin into a corner with that position,” Kuhn said. “What Colorado’s position is doing is forcing the other states to become a little bit more aggressive.”
No one exactly knows how mandatory curtailment would even work. Last year, the state began “listening sessions” with groups of water users, to figure out what Colorado would do if the Upper Basin was ordered to comply with the compact, according to Jason Ullmann, the state’s top water engineer.
Those discussions were private, Ullmann said, and are still in their early stages. The state is still figuring out if they would need new rules or not in the case of curtailment, he said.
Supreme Court case or not, it’s clear that an exceptionally bad drought year will stress the river’s supplies. At the end of the day, there is only so much water to go around … and plenty of demand from people willing to use it.
By early September, Hecla’s water was gone, pumped downstream to irrigate the farm. The lake was once again dry.
After a record-breaking season of low snowpack, Colorado is entering summer 2026 in a deep drought.
CPR News is covering this unfolding story and its impacts on communities, the Colorado River, farmers and ranchers, outdoor recreation and the environment through a new series, Water Pressure.
Read more from the series here.
Copyright 2026 CPR News
