Arizona hires high-powered law firm, setting the stage for a legal battle over Colorado River water
Arizona is preparing for a legal battle over its rights to Colorado River water.
Following an extraordinarily dry winter along the river basin and what’s expected to be an exceptionally hot and dry spring across the West, where high temperatures in March have already blown past records, the pressure to maintain access to the state’s fair share of river water is growing.
The Colorado River is a vital source of drinking water for 40 million people in the seven basin states, Mexico and 30 Native American tribes, and provides water for farming operations and hydroelectricity.
Reaching a water usage agreement is imperative to the basin states as the river’s water supply continues to decline, as it has done for the past 25 years due to a persistent drought spurred on by climate change.
On Monday, the Arizona Governor’s Office announced that it had retained the law firm Sullivan & Cromwell to represent the state in possible litigation among the Colorado River Basin states and the federal government.
Sullivan & Cromwell is an international firm based in New York City that has represented big names like Microsoft, BP, Goldman Sachs and JPMorgan Chase. The state is using some of the $3 million it put into its Colorado River legal defense fund last year to retain the law firm.
The Governor’s Office doesn’t expect to take any legal action until June at the earliest, but wants to be prepared for the possibility, especially if the dispute ends up before the U.S. Supreme Court.
The Lower Basin states — Arizona, Nevada and California — and the Upper Basin states — Colorado, New Mexico, Utah, and Wyoming — have been negotiating an updated water usage agreement for more than two years.
But so far the states have blown past two deadlines to do so — one in November and one in February — and are quickly approaching October, when the existing usage agreement expires.
If the states can’t reach an agreement before that, the federal government will implement one of its draft plans, all of which would place an outsized burden on the Grand Canyon State.
Hoover Dam on the Colorado River Drought © iStock - ngc4565
That’s because the Central Arizona Project, a series of canals that supplies Colorado River water to the Valley and the Tucson area, is one of the newest users of the river water, making it legally one of the first to be cut.
But so far, the Upper Basin states have refused to agree to any water usage cuts of their own, while the Lower Basin states insist that every state take their fair share.
Arizona has offered to reduce its Colorado River allocation by 27 percent, California by 10 percent, and Nevada by nearly 17 percent.
Negotiators for Arizona also insist that the Upper Basin states be held to the original 1922 Colorado River Compact that requires them to release a 10-year rolling average of at least 75 million acre-feet of water to the Lower Basin, in addition to one-half of the annual allotment owed to Mexico, for a total of about 80.2 million acre-feet.
An acre-foot of water represents enough to cover an acre of land to a depth of one foot, or about 325,851 gallons. That’s enough to provide three homes in Arizona a year of water, on average.
So far, the Upper Basin states have held to the original release agreement. But as water levels in the two major reservoirs on the river, Lake Mead and Lake Powell, continue to decline, it’s expected that the Upper Basin states will be unable to meet that requirement as early as 2027.
When the states entered into the original Colorado River Compact in 1922, they allocated 7.5 million acre-feet of water each year to be shared by the Upper Basin states and another 7.5 million to be used among the Lower Basin states.
Since then, the states have updated their water usage guidelines several times, even though the apportionments remain the same. But Lower Basin states face mandatory cuts during times of drought and Upper Basin states do not. In 2025, for the fifth year in a row, the federal government imposed drought-based cuts, and Arizona’s amounted to a loss of 512,000 acre-feet of water for the year.
© artzenter - iStock-509493427
Under current allocations, Arizona has rights to 2.8 million acre feet of water per year, and has implemented 800,000 acre feet in reductions per year. In contrast, Colorado gets 3.6 million acre feet a year, but has said it can’t handle cutting 50,000 acre-feet during dry years.
However, Colorado doesn’t always get that full allotment, because it relies mostly on melted snowpack for its water, which varies from year to year. This year’s snowpack levels are historically low.
The Lower Basin states have undertaken significant conservation efforts for Colorado River water since 2014 and have reduced their consumption from 7.4 million acre-feet in 2015 to just over 6 million in 2024.
The Upper Basin states have increased their usage in the past five years, from 3.9 million acre-feet in 2021 to 4.4 million in 2024. The federal government’s draft plans allow for the Upper Basin states to use even more water.
Governor Katie Hobbs’s proposed budget for this year would put another $1 million toward the Colorado River Legal Defense fund, and lawmakers earlier this month gave preliminary approval to doing just that.
Even as Arizona prepares for a legal battle, the state plans to continue attempting to reach an agreement with the other river basin states, according to the Governor’s Office.
