Nevada sues Interior over Colorado River cuts, saying Las Vegas water supply is on the line
LAS VEGAS — Nevada has opened a new front in the West's water wars, filing a federal lawsuit against the Interior Department over a plan that would sharply reduce the state's Colorado River supply and leave the Las Vegas area with what officials called an unsustainable allotment.
Filed Aug. 24, the lawsuit challenges rules released Aug. 21 that would cut Colorado River deliveries to California, Nevada and Arizona by 21% for two years beginning in 2027. The seven states that draw from the river failed to agree on a new sharing plan after more than three years of talks to replace the current guidelines, which expire this year.
Nevada's allocation from the river would drop by up to 213,556 acre-feet from its 300,000-acre-foot annual allotment, according to the Southern Nevada Water Authority, which joined the lawsuit. That would leave southern Nevada—home to Las Vegas—with less than 86,500 acre-feet a year. The Las Vegas Valley used just under 212,500 acre-feet in 2024, and the Colorado River supplies 90% of the region's water.
Water authority officials said the remaining supply would not be enough to meet southern Nevada's basic needs. “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 agency's general manager, said in the news release. “However, conservation has its limits.”
The lawsuit contends that the Interior Department failed to analyze the cuts' economic impact on southern Nevada or consider alternatives. It also alleges that the rules violate environmental law and the Law of the River, the collection of treaties, agreements and court rulings that has guided management of the Colorado River for decades.
The federal rules treat the river's Upper Basin states—Colorado, Utah, New Mexico and Wyoming—differently, allowing them to make voluntary reductions rather than face mandatory cuts. Those states have resisted forced cuts, arguing that the West's long-running drought already has caused steep losses in their water supplies.
Nevada Gov. Joe Lombardo said in the news release that the federal plan solved the region's water shortage “on the backs of the Lower Basin states,” which 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 fight comes against a backdrop of dramatic decline at Lake Mead, one of the largest reservoirs in the nation. A climate change-fueled megadrought and growing demand across the Southwest have left a white “bathtub ring” of mineral deposits on the rocks around the lake, marking where water levels once stood. The reservoir's surface elevation was 1,050 feet above sea level in May—175 feet below the record high of 1,225.44 feet set in July 1983.
The lawsuit is the first legal challenge to the new rules, though experts expect other Lower Basin states to follow. Arizona sent a letter Aug. 10 objecting to the plan and accusing Interior of violating the 1922 Colorado River Compact.
The dispute is the latest sign of strain on a river system that sustains roughly 40 million people and millions of acres of farmland across the Southwest. Lake Mead and Lake Powell, the two largest reservoirs in the basin, both have fallen to record lows in August, and the legal fight over who should bear the burden of a shrinking river is likely to continue as the region tries to secure its water future.