The Colorado River Deal Died. The Lawsuits Have Started.

On Friday, October 16, Arizona announced it was moving to intervene in Nevada's lawsuit against the federal government over the Colorado River — the river that supplies water to roughly 40 million people, 30 tribal nations, and 5.5 million acres of American farmland. Two of the three Lower Basin states are now formally in court against Washington's new operating plan for the most litigated river in North America.

This was never supposed to happen. The seven basin states — California, Arizona, and Nevada in the Lower Basin; Colorado, Utah, Wyoming, and New Mexico in the Upper — spent four years negotiating a successor to the 2007 operating guidelines that expire at the end of this year. They were given a federal deadline of November 11, 2025 to produce a consensus framework. They missed it. In February, the Interior Department announced it would finish the environmental review and write the rules itself. In August, it did.

The plan nobody signed

The framework the Bureau of Reclamation finalized in August — a Final Environmental Impact Statement on July 31, followed by a Record of Decision — governs the river from 2027 through 2036, implemented through operating guidelines set in two-year increments. The first set, covering 2027–2028, adopts cuts the Lower Basin states themselves had floated: 760,000 acre-feet from Arizona (about 27% of its allocation), 440,000 acre-feet from California (about 10%), and 50,000 acre-feet from Nevada (about 17%) — roughly 1.25 million acre-feet combined per year, more than double the deepest reductions required under the current guidelines.

The Upper Basin states, by contrast, were asked for a voluntary contribution of 200,000 acre-feet over the two-year period. Mandatory cuts for the Lower Basin, a request for the Upper. That asymmetry is the core of the litigation.

And the two-year plan is the gentle part. In the framework's deepest shortage scenarios, modeled Lower Basin reductions reach as much as 3.6 million acre-feet per year — against a total Lower Basin compact apportionment of 7.5 million. After 2028, absent a new interstate agreement, the framework shifts to priority-based distribution: the most junior water rights get cut first. Arizona holds the most junior major rights in the Lower Basin.

The hydrology doesn't care about the briefs

The 1922 Colorado River Compact divided the river assuming roughly 17.5 million acre-feet of annual flow. The long-term historical average came in near 14.7 million. Between 2020 and 2024, according to figures cited in Nevada's complaint coverage, the river averaged about 11.2 million acre-feet — a quarter century of drought compounded by a warming basin.

The reservoirs tell the same story in concrete. As of October 19, Lake Mead sat at 1,037 feet — about 26% of capacity. Lake Powell sat at 3,521 feet, roughly 23% full. The federal framework designates 3,500 feet at Powell and 1,000 feet at Mead as critical infrastructure-protection triggers, where dam operations themselves come under threat. Powell is about 21 feet above its trigger. That is not a decade of cushion; depending on the snowpack, it may not be two years of cushion.

Nevada filed first, on August 24, in the U.S. District Court of Nevada — the state, its Colorado River Commission, and the Southern Nevada Water Authority against the Interior Department and the Bureau of Reclamation. Nevada argues the framework's shortage math could take its 300,000 acre-foot allocation down to as little as 86,500 acre-feet in extreme conditions — a cut of more than 70% to a supply that serves, per SNWA general manager John Entsminger, 90% of the water for about three-quarters of the state's population. "Catastrophic impacts on our economy," he called it. Governor Joe Lombardo described the suit as "a matter of survival." Nevada's complaint leans heavily on its conservation record: Las Vegas cut its Colorado River consumption more than 40% since 2002 while adding 875,000 residents.

Arizona's counsel put it bluntly in the state's filing to intervene: "The State's towns, cities, tribes, farmers, factories, and businesses cannot survive without sufficient water from the Colorado River."

So the operating rules for the water supply of the fastest-growing region in America are now, simultaneously: finalized, in effect for planning purposes, and under legal attack by two of the three states they bind most. The question that matters for capital isn't who wins the case. It's who absorbs the cuts while it's argued — and which assets are quietly repricing already.

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The rest of this briefing is free — it just requires a free AlphaBriefing account: the post-2028 priority stack and why Phoenix, not Las Vegas, is the real stress point; the "nuclear option" Supreme Court scenario and the 82.5 million acre-foot question; and where the money is already moving — homebuilders buying water rights, the Phoenix groundwater construction limits, and the muni and farmland exposure map.

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