CAP joins lawsuit against US over Colorado River cuts

"CAP has spent years negotiating with the federal government. Our goal has been to stay out of court, but not at the expense of our rights and the health of the river," said Brenda Burman, CAP's general manager, at a news conference Tuesday announcing it is joining the litigation.

"Saving the river should not fall disproportionally on the CAP and its water users," Burman said, referring to the decision by the U.S. Bureau of Reclamation to not require water use cuts by any of the four Upper Colorado River Basin states while cutting deliveries to Arizona and the other two Lower Basin states.

Tucson Water customers living in the city and in some suburban areas get most or all of their drinking water from the Colorado River water brought via the CAP canal.

CAP is seeking to intervene in a lawsuit already filed in U.S. District Court by the Southern Nevada Water Authority and two other Nevada-based water agencies. The Arizona Department of Water Resources has filed a separate motion seeking to intervene in the same lawsuit.

Officials with Reclamation and its parent agency the Interior Department "have said they could reduce CAP supplies possibly to zero," Burman said. 

"These federal cuts will dry up the canal, cutting off supplies to major communities and 11 tribes; with no cuts required of the Upper Basin states," said Burman, who was commissioner of the bureau during the first Trump administration.

One of the key allegations in the lawsuit is that Interior and the Bureau of Reclamation are violating the 1922 Colorado River Compact, which divided river water rights among the seven river basin states.

It sets minimum levels of water releases over a 10-year period from the Colorado River's four Upper Basin states to the three Lower Basin states of Arizona, Nevada and California. The Upper Basin states are New Mexico, Colorado, Utah and Wyoming.

Burman said at the news conference that for the first time, the Upper Basin states have failed to meet the compact's minimum requirements that they release at least 82.5 million acre-feet of water to the Lower Basin over 10 years. 

For 100 years, the Upper Basin states met that requirement. But in the "water year" ending Sept. 30 of this calendar year, the water delivery fell so low that the total 10-year delivery failed to meet that requirement, Burman said. Her comment was the first public statement by an official that this requirement wasn't met this past year.

A "water year" is a technical term used by water officials and scientists to describe the period of Oct. 1 of one year through Sept. 30 of the next year.

This year's inter-basin water releases put the 10-year total release below the federal minimum because this past year was extraordinarily dry and warm, dramatically reducing river flows. That came on top of another very subpar year of flows in 2025.

The Upper Basin states' officials, however, have said they don't believe they're in violation of the compact because it is climate change, not their water uses, that reduced the river flows so dramatically. Under the 1922 Colorado River Compact, the Upper Basin states aren't supposed to deplete river flows below the 10-year minimum, and those states' officials say they haven't depleted the river — the weather has.

At a news conference last week at newly formed Chiricahua National Park in southeast Arizona, Interior Secretary Doug Burgum criticized Arizona's earlier decision to intervene in Nevada's lawsuit.

He predicted Nevada’s lawsuit would get tossed out because the state is claiming hypothetical future damages, not actual damages.

He also said the last thing Arizona should be doing is going to court, because as the junior-most water rights holder on the Colorado, the state shouldn't want its future river allocations decided by a judge. Burgum said Arizona should stick to the negotiating table instead.

Other Interior officials have also criticized the litigation, saying it won't put any more water back into the depleted river. The river has lost at least 20% of its average annual flow since 2000 due to drought and climate change.

But Kathryn Sorensen, an Arizona State University water researcher, countered, "I think litigation is going to determine who gets what little water there is left."

The federal law that authorized CAP's construction back in 1968 did give Arizona lower priority for river water than California during shortages. It says CAP must give up all its water during shortages before California gives up anything, although California has since agreed in interstate negotiations to give up some of its river water supply before CAP gives up all of its supply.

But Burman told the news conference that legally, "CAP is not a junior user to the Upper Basin and the compact delivery obligation must be met. CAP can’t be cut while the U.S. is illegally withholding millions of acre-feet in Upper Basin reservoirs."

Arizona has contributed more water savings than any other state to stabilize the river, Burman said.

"We're experts at tough water conservation. Arizona uses less water than in the 1950s, while our population has grown five times larger. Just look at our economy. Yet the Upper basin refuses to commit to a single cut of water," she said. 

Over the past year, water users in Arizona and other Lower Basin states have put considerable pressure on the federal government to release more water into the river from its Upper Basin reservoirs, the largest of which is the Flaming Gorge reservoir at the Utah-Wyoming border. 

Although the bureau is releasing some water from those reservoirs, Upper Basin states have sought to keep a lid on those releases because they want that water for use within their states' boundaries.