Arizona has joined Nevada in a federal lawsuit against the Trump administration over proposed Colorado River water cuts. The U.S. Department of the Interior's plan requires Lower Basin states to reduce water usage by 1.25 million acre-feet annually through 2028, with potential cuts of up to 40 percent through 2036, while exempting Upper Basin states. Arizona officials warn these reductions could dry up the Central Arizona Project and severely damage the state's economy.
Nevada lawsuit and Arizona intervention
- ▪Nevada initially filed its lawsuit in August 2026 to block the U.S. Department of the Interior's 10-year operational guidelines for the Colorado River Basin.
- ▪Arizona filed a motion to intervene in Nevada's federal lawsuit against the Trump administration on October 16, 2026, challenging federal operational plans for the Colorado River.
- ▪Nevada Governor Joe Lombardo welcomed Arizona joining Nevada's lawsuit against the federal Colorado River water reduction plan.
Interior Department response
- ▪An Interior Department spokesperson stated that litigation will not create additional water and criticized Arizona Governor Katie Hobbs for playing politics.
- ▪An Interior Department spokesperson rejected Arizona Governor Katie Hobbs's position as wrong and asserted that the department would operate in good faith.
Objections to Lower Basin cutback requirements
- ▪Arizona Governor Katie Hobbs stated she will not accept a forced federal plan that addresses the water crisis solely through Lower Basin sacrifices.
- ▪Nevada's legal complaint contends the Interior Department failed to evaluate alternatives requiring Upper Basin states to shoulder water cutbacks.
Federal mandates for Colorado River water cuts
- ▪The Interior Department guidelines require Lower Basin states to cut 1.25 million acre-feet of water use annually through 2028.
- ▪The federal operational plan exempts Upper Basin states—Wyoming, Colorado, Utah, and New Mexico—from mandatory Colorado River water cutbacks.
- ▪The federal plan allows mandatory cuts of up to 3 million acre-feet per year for Lower Basin states between 2029 and 2036, representing up to a 40 percent reduction.
Impact on the Central Arizona Project
- ▪Arizona Department of Water Resources Director Tom Buschatzke warned that proposed federal cuts could dry up the Central Arizona Project and devastate the state's economy.
- ▪The Central Arizona Project holds low-priority water rights relative to older aqueducts, making its water allocation first in line for mandatory cutbacks.
- ▪Arizona relies on the Colorado River for 36 percent of its water supply, delivering it primarily through the Central Arizona Project canal.
Interstate water negotiations
- ▪The federal government intervened to impose water restrictions after seven Colorado River Basin states missed multiple deadlines to reach a consensus.
- ▪Negotiators from the three Lower Basin states and four Upper Basin states deadlocked during three years of talks over sharing Colorado River water reductions.
Voluntary state conservation agreements
- ▪Under a two-year voluntary conservation agreement, California will reduce Colorado River water use by 12 percent, Arizona by 31 percent, and Nevada by 28 percent.
- ▪California, Arizona, and Nevada agreed to voluntarily cut 3.2 million acre-feet of Colorado River water usage total through 2028.
Drought and declining reservoir levels
- ▪State officials expressed concern that plummeting reservoir levels could reach deadpool status, blocking water from flowing downstream through Colorado River dams.
- ▪The Rocky Mountains recorded their lowest snowpack on record in 2026, leading to reduced snowmelt inflows into Colorado River reservoirs.
- ▪Lake Mead and Lake Powell have dropped to record low levels due to persistent drought, climate change, and overuse.
Colorado River water supply and usage
- ▪The Colorado River supplies water to approximately 35 million people across seven U.S. states and 30 Native American tribes.
- ▪Agricultural production across 5 million acres consumes approximately three-fourths of the water diverted from the Colorado River.
Colorado River Compact provisions
- ▪Arizona officials warned the federal government that further reductions in Lake Mead's water levels could trigger a lawsuit over Colorado River Compact violations.
- ▪The 1922 Colorado River Compact requires downstream water releases from upstream dams to average at least 7.5 million acre-feet annually over any 10-year period.
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