Arizona joins Nevada lawsuit challenging federal Colorado River cuts

Arizona announced Friday that it intends to join Nevada’s lawsuit challenging the federal government’s new operating plan for the Colorado River, arguing that the framework unfairly burdens Lower Basin states and threatens Arizona’s water supply.

The Trump administration’s plan calls for Arizona, California and Nevada to collectively reduce their river use by 1.25 million acre-feet in both 2027 and 2028. Arizona would absorb the largest reduction, at 760,000 acre-feet annually, while California would lose 440,000 and Nevada 50,000 acre-feet. The Upper Basin states — Colorado, New Mexico, Utah and Wyoming — would face no federally mandated cuts.

Arizona Gov. Katie Hobbs said the federal government was failing to hold the Upper Basin accountable while threatening reductions beyond a voluntary conservation agreement among the three Lower Basin states. Arizona Department of Water Resources Director Tom Buschatzke said joining Nevada’s case was necessary to protect Arizona’s legal rights while preserving the possibility of a negotiated agreement with California and Nevada.

The seven Colorado River states have been unable to agree on long-term rules after years of negotiations amid declining water availability and historically low levels at Lake Mead and Lake Powell. Under the federal framework, the states would negotiate new terms every two years over the following decade. Lower Basin states have also committed to conserving an additional 700,000 acre-feet through 2028, subject to an agreement that must be approved by their legislatures.