Nevada filed a federal lawsuit on Monday to block the Trump administration’s plan to slash water allocations from the Colorado River to California, Nevada and Arizona by 21% over two years starting in 2027.
The lawsuit, filed in U.S. District Court in Las Vegas, names the Department of the Interior, Interior Secretary Doug Burgum and the U.S. Bureau of Reclamation as defendants. The state’s Colorado River Commission and Southern Nevada Water Authority joined as plaintiffs. The plan, finalized by the department on Friday, would replace an expiring agreement and is subject to review every two years.
Under the proposal, lower basin states would face mandatory reductions for the first time, while upper basin states—Colorado, Utah, New Mexico and Wyoming—would avoid mandatory cuts despite ongoing drought conditions. The four upper basin states have resisted mandatory reductions, arguing they already bear disproportionate impacts from prolonged water scarcity.
Nevada’s legal challenge argues the administration violated administrative law and environmental statutes, including the Law of the River, a framework of treaties and court rulings governing the river. The lawsuit contends the plan fails to consider reasonable alternatives, economic impacts or mitigation measures, and does not adequately respond to public comments.
The Interior Department’s plan would reduce water deliveries to lower basin states by 21% for two years beginning in 2027, with potential near-doubling of cuts after 2028. The Colorado River supplies water to one in 10 Americans and generates hydropower for 6 million people.
The lawsuit marks the first legal challenge to the administration’s Colorado River management strategy, which follows more than three years of unsuccessful negotiations among the seven basin states. The dispute underscores deepening tensions over water rights amid worsening drought conditions in the western United States.
