Politics
Arizona backs Nevada challenge to federal Colorado River water rules
Arizona has joined Nevada’s lawsuit seeking to compel federal water deliveries to Lake Mead and challenge parts of the government’s Colorado River plan. The state says it is also pursuing a two-year conservation deal with Nevada and California to avert steep cuts to its water supply.
Arizona joined Nevada’s lawsuit against the U.S. Department of the Interior on Friday, Oct. 16, 2026, arguing that the federal government must enforce water-delivery obligations to Lake Mead and reconsider parts of its Colorado River decision.
The states are seeking to prevent potential cuts of as much as 3 million acre-feet of water annually. Arizona also plans to contest the federal environmental review, saying it does not require water from Upper Basin reservoirs to be delivered to Lake Mead, according to Gov. Katie Hobbs and the Arizona Department of Water Resources.
Arizona’s move comes as the Lower Basin states — Arizona, Nevada and California — work on an agreement to conserve more than 3.2 million acre-feet during 2027 and 2028. The states say the proposed two-year deal is intended to stabilize the river system and reduce near-term demand on Lake Mead.
Arizona says that without an agreement, federal cuts could reduce the Central Arizona Project’s Colorado River allocation by 77% over the next two years. The project supplies Colorado River water to central and southern Arizona.
“Arizona has always been willing to do our part to protect the Colorado River, but we will not accept a forced federal plan that solves this crisis on the backs of our families, farmers and businesses,” Hobbs said.
Hobbs said Arizona would continue working with Nevada and California on the Lower Basin agreement while defending the state’s water rights. Nevada Gov. Joe Lombardo welcomed Arizona’s participation, saying all seven Colorado River Basin states should share responsibility for protecting the river. He said Nevada remains open to a negotiated solution but would continue pressing for a fair deal for the state.
John Entsminger, general manager of the Southern Nevada Water Authority, said the agency is continuing to work with Arizona and California on an agreement. He said collaboration has produced results and expressed optimism that the basin states can reach a lasting solution.
The dispute places legal pressure alongside negotiations among the basin states, whose decisions will shape water supplies for communities, farms and businesses dependent on the Colorado River. Arizona says reaching the conservation agreement remains a priority even as it challenges the federal government in court.