Arizona Asks to Join Nevada's Lawsuit Against Interior Over Federal Colorado River Cuts

Arizona has gone to court against the federal government over the Colorado River, and it picked a partner. On Friday, Oct. 16, Gov. Katie Hobbs and the Arizona Department of Water Resources said the state filed a motion to intervene in the lawsuit Nevada brought against the Interior Department in August.

The target is the 10-year operating plan Interior finalized for the river and its two giant reservoirs, Lake Powell and Lake Mead. The framework took effect Oct. 1.

What the federal plan requires

Under the plan, Arizona, California and Nevada must reduce their use by a combined 1.25 million acre-feet in each of 2027 and 2028. That is more than twice the largest cut under the current guidelines, which expire at the end of this year.

The split: Arizona 760,000 acre-feet, California about 440,000, Nevada 50,000 over the two years. Arizona's reductions are scheduled to start Jan. 1, 2027.

The Upper Basin states, Colorado, Utah, Wyoming and New Mexico, face no mandatory reductions.

The plan also allows deeper cuts if conditions worsen. Nevada's lawsuit says its 300,000 acre-foot entitlement could shrink by more than 213,000 acre-feet, about 71%. Arizona's office says the federal decisions could produce cuts of up to 3 million acre-feet per year across the Lower Basin.

Arizona's argument

Hobbs, a Democrat, called the federal approach "draconian." "We are drawing a line in the sand," she said. "I am taking this legal action alongside Nevada because the federal government refuses to hold the Upper Basin accountable for the water deliveries they owe Arizona."

Her office says the federal Final Environmental Impact Statement and Record of Decision "unlawfully fail to require deliveries from Upper Basin water reservoirs to Lake Mead."

Arizona has more at stake than most. The river supplies about 36% of the state's water, much of it through the Central Arizona Project canal. The CAP is a newer system with low-priority rights, which puts it near the front of the line for cuts. Hobbs's office says that without a Lower Basin deal, forced federal cuts would slash the CAP's Colorado River allocation by 77% over two years.

ADWR Director Tom Buschatzke said intervention is needed "to protect its legal rights to Colorado River water while preserving a path forward to achieving a collaborative outcome with California and Nevada."

A bipartisan fight against a Trump agency

Nevada Gov. Joe Lombardo, a Republican, welcomed Arizona's move. He called it "an important step in challenging a federal plan that unfairly burdens the Lower Basin and fails to require the Upper Basin to make meaningful reductions." Nevada says it has already cut its Colorado River use by more than 40% since 2002 while the Las Vegas valley added 875,000 people. About 2.3 million residents depend on that supply.

So a Democratic governor and a Republican governor are suing a Republican administration together.

The Upper Basin position

The Upper Basin states reject the idea that they owe the Lower Basin more. They say they already use less water when river flows decline, and that their legal obligations differ from those of the downstream states. The Upper Basin states have also argued that the Lower Basin's overuse is responsible for the reservoirs' shortages and that the downstream states should absorb the largest cuts.

Interior stepped in after the seven states missed several deadlines for a consensus. Three years of talks ended in deadlock between the Lower and Upper Basin states. Interior did not immediately respond to a request for comment on the joint litigation.

The conditions behind it

The river supplies about 35 million people and 30 tribes, and roughly three-fourths of the water taken from it goes to farmland. This year the Rocky Mountains had the least snow on record, and reservoirs are at historic lows. The feared worst case is deadpool, where levels fall so far that water can no longer flow downstream.

The deal Arizona says it still wants

The lawsuit does not end Arizona's cooperation with its neighbors. Arizona, California and Nevada have a two-year Lower Basin Agreement to conserve more than 3.2 million acre-feet in 2027 and 2028. On the percentages, California would cut about 12%, Arizona about 31% and Nevada about 28%.

Buschatzke said Arizona is "strongly committed" to that deal and is talking with the other states to finalize the details. Hobbs said the state will keep working with Nevada and California to implement it.

Finalizing it is the open item. Arizona's motion to intervene has not yet been ruled on. The LA Times reports the dispute could reach the U.S. Supreme Court. Arizona's scheduled cuts begin Jan. 1, 2027, and no court has stayed the federal plan.