Arizona water managers say they will intervene in Nevada's federal lawsuit over Colorado River cuts tied to Lake Mead

What happened

Arizona water managers said they will intervene in Nevada's lawsuit against the federal government over its imposition of Colorado River cuts, the Las Vegas Review-Journal reported. The move puts a second Lower Basin state alongside Nevada in the legal fight over how the shrinking river is shared.

Tom Buschatzke, director of the Arizona Department of Water Resources, explained the decision on a Friday press call. "Like Nevada, Arizona believes the federal government's new operating framework ignores basic elements of the law of the river," he said, according to the Review-Journal. He added that the framework could lead to cuts "that would devastate Arizona's economy."

Why Nevada went to court

The Review-Journal reported that the federal plan to cut the allocations of Nevada, California and Arizona remains unpopular amid historic drought. The threat of litigation had hung over years of talks among the seven Colorado River states that did not produce results. Even so, Nevada water managers surprised much of the water world when they filed their federal lawsuit in late August.

Short-term cuts versus the 10-year outlook

Nevada water managers say the near-term cuts over the next two years can be handled within their planning. Their concern is the longer horizon. According to the Review-Journal, the federal government has asserted it could reduce Nevada's share of the river by up to 71 percent of its normal allocation at some point over the next 10 years. Readers can find more on the cut that took effect this water year.

How the Upper Basin was treated

The Upper Basin states of Colorado, Utah, Wyoming and New Mexico faced only voluntary conservation, the Review-Journal reported. The Lower Basin is made up of Nevada, Arizona and California, the three states whose allocations the federal plan would cut.

Arizona's stake in the fight

The Review-Journal described the threat to Arizona as similarly existential. The outlet reported that the federal cuts could hamstring some of the West's fastest-growing economies and most productive farmland.

Junior rights on the Central Arizona Project

Much of Arizona's risk comes from the Central Arizona Project, which carries Colorado River water from Lake Havasu to cities such as Phoenix and Tucson. The project holds relatively junior water rights, which leaves its supplies especially exposed to reductions, according to the Review-Journal.

A possible cut of up to 77 percent

Under one management scenario, the federal government has floated cutting up to 77 percent of available Colorado River water in Arizona, the Review-Journal reported. Buschatzke said cuts to the state apportionment could devastate Arizona's economy.

What it means for Southern Nevada

The dispute is unfolding as water availability across the larger basin declines sharply. The Review-Journal reported that human-caused climate change is shifting the weather patterns that normally deliver Rocky Mountain snowmelt to the river.

Lake Mead's role

Lake Mead provides about 90 percent of Southern Nevada's water supply, according to the Review-Journal. The reservoir is projected to plunge as federal water managers prioritize protecting dam infrastructure at Lake Powell, which sits upstream. More Southern Nevada water coverage is available on our water page.

What to watch next

• Arizona's planned intervention in Nevada's federal lawsuit, which state water managers have announced while the case remains unresolved.
• Whether the federal government moves toward the larger cuts it has floated, up to 71 percent of Nevada's normal allocation over the next 10 years and up to 77 percent of available water in Arizona under one scenario.
• Lake Mead levels, which are projected to plunge as federal managers prioritize protecting dam infrastructure at Lake Powell.