Arizona has joined Nevada's legal challenge against new federal rules for the Colorado River, bringing the state facing the deepest short-term cuts into the dispute over how water is managed. Governor Katie Hobbs of Arizona and the Arizona Department of Water Resources announced Friday that the state intervened in the lawsuit Nevada filed in August against the U.S. Department of the Interior. This action integrates Arizona, which is set to experience significant water reductions, into the ongoing legal battle concerning the division of mandatory cuts among the seven states of the Colorado River basin.
Arizona officials stated that the federal plan does not adequately require Upper Basin states—Colorado, Utah, Wyoming, and New Mexico—to deliver their due water contributions to Lake Mead. They indicated this oversight could lead to annual cuts of up to 3 million acre-feet for the Lower Basin states. Governor Hobbs affirmed Arizona's position, saying the state is “drawing a line in the sand.” She added that Arizona intends to continue collaborating with Nevada and California to implement their own two-year agreement for the Lower Basin as the court case proceeds. Tom Buschatzke, director of Arizona's water department and lead negotiator for the state on Colorado River matters, explained that intervention was necessary to protect Arizona’s legal rights to the river while maintaining the possibility of reaching a negotiated agreement with California and Nevada.
Nevada, along with the Nevada Colorado River Commission and the Southern Nevada Water Authority, initiated the lawsuit on August 24. This made Nevada the first state to challenge the Department of the Interior's final plan, which was published on August 21. Governor Joe Lombardo of Nevada stated Friday that Arizona's decision is “an important step to challenge a federal plan that unfairly burdens the Lower Basin.” Governor Lombardo also noted Nevada's continued commitment to a negotiated solution but emphasized that the state would not accept a framework that jeopardizes its water supply.
Under the federal framework, Nevada's allocation of 300,000 acre-feet could be reduced by as much as 213,556 acre-feet, representing nearly 71 percent, if the Lower Basin reductions reach the maximum limit outlined in the framework. This potential reduction would leave southern Nevada with less than 86,500 acre-feet annually. The Southern Nevada Water Authority reported that southern Nevada utilized approximately 198,000 acre-feet in 2025. An acre-foot is equivalent to about 326,000 gallons, an amount sufficient to cover a football field with one foot of water or supply two to three homes for a year.
John Entsminger, General Manager of the Southern Nevada Water Authority, indicated that Arizona shares Nevada's concerns regarding deficiencies in the federal environmental review and the process used to develop the post-2026 framework. Entsminger also noted that his agency continues to work with California and Arizona to finalize a Lower Basin agreement aimed at reducing short-term demand on Lake Mead. The three Lower Basin states proposed this agreement in May, committing to conserve over 3.2 million acre-feet of water until 2028.
The Department of the Interior adopted the distribution of short-term cuts for 2027 and 2028 based on this proposal. Under this distribution, Arizona is required to reduce its water usage by 760,000 acre-feet per year, California by 440,000 acre-feet, and Nevada by 50,000 acre-feet. Officials in Arizona highlighted that the stakes are particularly high for their state, largely because the Central Arizona Project, which delivers river water to Phoenix and Tucson, holds more recent water rights. These authorities further explained that without the Lower Basin agreement, the Colorado River allocation for the Central Arizona Project could decrease by 77 percent over the next two years.
Arizona's intervention plans include challenging specific parts of the federal government's final environmental review and the definitive plan itself. The state contends that the federal plan unlawfully omits requirements for water releases from Upper Basin reservoirs into Lake Mead. Following the initial filing of Nevada's lawsuit, the Speaker of the Utah House of Representatives criticized the legal action, stating that it exacerbated an already complex situation.
