Arizona has joined a lawsuit challenging the federal government's plan for Colorado River operations over the next decade. The Arizona Department of Water Resources filed a motion Friday to intervene in the case.
According to the filing, Arizona contends that the federal government's new operating framework violates fundamental principles of Colorado River law. The state argues the plan could result in cuts to Arizona's water apportionment under the Colorado River Compact, the 1922 agreement that divides water among seven U.S. states and Mexico.
The Colorado River supplies water to nearly 40 million people across the Southwest and irrigates millions of acres of farmland. The river system has faced severe stress in recent years due to prolonged drought and declining water levels in Lakes Mead and Powell, the two largest U.S. reservoirs.
The federal government has been developing new operational guidelines for the river to address these challenges. States including California and Nevada have grappled with how to manage reductions in available water as climate change and overuse strain the system's capacity.
Arizona's decision to join the lawsuit reflects the state's concerns about protecting its water rights and interests in ongoing disputes over Colorado River management. The state has been central to Colorado River politics, holding significant water rights and facing substantial agricultural and urban water demands.
The lawsuit adds to existing tensions among Colorado River basin states over how federal water management policies should evolve. These conflicts have intensified as the river's annual flow continues to decline from historical averages, creating difficult negotiations over allocations that all seven states depend on for economic and environmental needs.