Arizona water managers have announced their decision to intervene in Nevada’s federal lawsuit against the United States government regarding imposed Colorado River water cuts. Both states contend that the federal government’s proposed operating framework ignores fundamental elements of river law, potentially devastating the economies of the West's fastest-growing regions and most productive farmlands.
Nevada filed its lawsuit in late August, and Arizona's intervention was announced on a Friday press call. Arizona Department of Water Resources director Tom Buschatzke stated that Arizona shares Nevada's belief that the federal government's plan could lead to cuts in state apportionment that would harm Arizona's economy.
John Entsminger, Nevada’s governor-appointed Colorado River negotiator and general manager of the Southern Nevada Water Authority, indicated that Arizona's decision reinforces Nevada's argument that the operating plan is flawed. He noted Arizona’s intervention reflects a shared commitment to ensuring decisions about the Colorado River are based on transparent, scientific, and legally sound processes, while also emphasizing his dedication to keeping discussions open. Nevada Gov. Joe Lombardo added that Arizona’s move was an important step in safeguarding Nevada’s interests. A spokesman for California Gov. Gavin Newsom confirmed the state is considering its next steps.
The Interior Department responded to Arizona's decision, calling out Arizona Gov. Katie Hobbs by name in a Friday evening statement. The department stated that Governor Hobbs was incorrect and it was "unfortunate to see Arizona playing politics" instead of pursuing meaningful solutions. They added that litigation would not generate additional water or alter the hydrological realities facing the Colorado River Basin. The Upper Basin states, which include Colorado, Utah, Wyoming, and New Mexico, did not issue comments.
In legal terms, intervention allows a third party not originally involved in a case but with a stake in its outcome to participate. This includes filing briefs, submitting evidence, presenting arguments, and appealing decisions. For Arizona, the threat of federal action is particularly severe due to the Central Arizona Project, which delivers Colorado River water from Lake Havasu to urban centers like Phoenix and Tucson. This project holds relatively junior water rights, making its supplies especially vulnerable to cuts. Under one management scenario, the federal government has suggested a cut of up to 77 percent of Arizona's available Colorado River water. Nevada, along with Arizona and California, forms the Lower Basin.
Nevada’s water managers report that while near-term cuts over the next two years are manageable within the state's planning, the federal government has asserted its authority to reduce the state's share of the river by up to 71 percent of its normal allocation within the next decade. In contrast, the Upper Basin states have primarily faced only voluntary conservation measures.
The overarching dilemma facing officials is the sharply declining water availability across the larger basin. Human-caused climate change is altering weather patterns that typically provide Rocky Mountain snowmelt, contributing to this shortage. Lake Mead, which supplies about 90 percent of Southern Nevada's water, is projected to decline as federal water managers prioritize protecting dam infrastructure above the upstream reservoir Lake Powell.
For more than a century, the 1922 Colorado River Compact has served as the foundation for all river operations. The compact allocates 7.5 million acre-feet per year to both the Upper and Lower Basins. It also stipulates that the Upper Basin cannot reduce flows to downstream states below a 10-year, 75 million acre-foot average, measured on a rolling basis at Lees Ferry in Arizona. Both Nevada and Arizona have suggested that the new river plan could push states closer to a “compact call,” which would involve the first-time litigation of the compact. However, much of the lawsuit's claims have focused on administrative procedure and standard protocols for environmental review.
Arizona’s attorneys stated in a legal filing that the Trump administration’s actions violate the series of compacts and laws governing the river, including the 1922 compact, which they assert should be the agency’s guiding principle. They wrote that the Trump administration’s plan would “guarantee violations” of the compact’s set delivery obligation, asserting that the agency had disregarded its guiding principle. While Nevada has called for a complete nullification of the operating plan, Arizona’s attorneys are instead asking the court to uphold the short-term plan for 2027 and 2028. They argue that without it, too much uncertainty would remain for the next two years, potentially pushing the Upper Basin closer to a compact violation. The federal government has not yet filed an official response to Nevada’s initial complaint, and no court dates have been scheduled.
