Arizona has joined Nevada in a legal challenge against the federal government over mandated water reductions from the Colorado River, escalating tensions surrounding the management of the river’s dwindling resources. The Arizona Department of Water Resources filed a motion on Friday to intervene in Nevada’s lawsuit, which was originally filed in August to contest the Trump administration’s 10-year water allocation plan across the Southwest.
The dispute arises amid severe water shortages caused by record-low snowpack in the Rocky Mountains and persistent drought conditions that have significantly lowered reservoir levels. The Colorado River, a critical water source for approximately 35 million people in seven states, Native American tribes, and extensive agricultural areas, is under increasing pressure as its flow continues to decline.
Under the federal plan, California, Arizona, and Nevada—collectively known as the three downstream states—are required to reduce their water consumption by a combined 3.2 million acre-feet between now and the end of 2028. Specifically, California will cut usage by about 12%, Arizona by roughly 31%, and Nevada by 28%. While Arizona officials, including Department of Water Resources Director Tom Buschatzke, have expressed commitment to these immediate reductions, they object to the plan’s provisions for potential further cuts between 2029 and 2036. During that later period, the plan could mandate reductions amounting to as much as 3 million acre-feet annually, which amounts to about 40% of the water currently allocated to the three states.
The legal challenge contends that the federal government’s plan unfairly places the bulk of the burden on Arizona and Nevada, while failing to require similar cutbacks from the four upstream states—Colorado, Utah, New Mexico, and Wyoming—that also use water from the river. This imbalance, according to Arizona officials, jeopardizes the state’s economy and water security. Arizona Governor Katie Hobbs criticized the federal plan, declaring it unacceptable to force severe cuts on Arizona’s families, farmers, and businesses without holding upstream states accountable for water deliveries mandated by the 1922 Colorado River Compact.
Arizona’s stakes are particularly high because of its reliance on water delivered through the Central Arizona Project (CAP), a canal system supplying the Phoenix and Tucson metropolitan areas. Because the CAP is newer than older water delivery systems in the basin, Arizona holds lower-priority water rights and is among the first subject to forced reductions under drought contingency plans.
Nevada has similarly warned that drastic cutbacks could devastate water availability for Las Vegas and surrounding communities. Nevada Governor Joe Lombardo welcomed Arizona’s decision to join the lawsuit, underscoring regional concerns about water security.
California, the largest user of Colorado River water, has not indicated plans to pursue legal action. The seven-state region continues efforts to negotiate equitable water-sharing agreements, but the expanding litigation could complicate these talks and potentially escalate to the U.S. Supreme Court.
The Colorado River Compact mandates that upstream dams release an average of 7.5 million acre-feet of water over any decade to the downstream states, plus an allocation for Mexico. Continued declines in river flow threaten compliance with the compact’s terms, prompting legal and political challenges as states seek to manage a deeply strained resource amid persistent drought and climate change.