Nevada sues Interior over Colorado River water reduction plan

Aug. 24, 2026, 10:29 p.m. ET

LAS VEGAS – Nevada filed a federal lawsuit against the Department of the Interior on Aug. 24 over new rules that manage how water from the Colorado River is distributed among seven states.

The lawsuit challenges an Interior plan, released Aug. 21, that calls for a 21% reduction in water from the river to California, Nevada and Arizona for two years starting in 2027. The states that draw from the Colorado River were unable to agree on how to share the water after more than three years of talks to replace a plan that expires this year.

Nevada would see cuts to the state’s 300,000-acre-foot allocation of water from the river by up to 213,556 acre-feet, according to a news release announcing the lawsuit.

Officials from the Southern Nevada Water Authority officials, who are a part of the lawsuit, say that the remaining allotment is not enough to supply Southern Nevada’s basic water needs.

The rules established by the Department of Interior could leave southern Nevada, home to Las Vegas, with less than 86,500 acre-feet a year. The news release states that Las Vegas and its surrounding cities used under 212,500 acre-feet of water in 2024. The lawsuit states that the Colorado River supplies 90% of all water used in the Las Vegas Valley.

“Over the past 25 years, southern Nevada has become a global leader in water efficiency, reducing our Colorado River consumption by about 40 percent even as the community added 800,000-plus residents, so we have clearly demonstrated our ability to adapt and do more with less,” John Entsminger, the water authority’s general manager, said in the news release. “However, conservation has its limits.”

The lawsuit alleges that Interior failed to analyze the impact of the cuts on the Southern Nevada’s economy or consider alternatives. It also alleges that the rules violate environmental law and the Law of the River, a group of treaties, agreements and court rulings that have guided river water management.

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Water cuts split states

Under the rules issued by Interior, four states – Colorado, Utah, New Mexico and Wyoming – are allowed to implement voluntary water reductions instead of mandatory cuts. The so-called Upper Basin states refused to take mandatory cuts to their water supply from the river, arguing they already face steep reductions due to the decades-long drought in the western United States.

Nevada Gov. Joe Lombardo said in the news release that the rules solved the water shortage “on the backs of the Lower Basin states” that include Arizona, California and Nevada.

“We’ve already shown that we’re willing to do our part, but the Colorado River is a shared resource, so the solution needs to involve everybody. Until that happens, we are prepared to fight for as long as it takes,” Lombardo said.

The lawsuit is the first legal challenge to the rules, though experts warn that other lower-basin states are likely to file their own. Arizona issued a letter on Aug. 10 voicing objections to the plan and accusing Interior of violating the 1922 Colorado River compact.

The battle comes as decades of increasing water demand and drought in the West have caused a continual decline in water levels along the river, especially in reservoirs such as Lake Mead and Lake Powell. Both have fallen to record lows in August.