“Ideally this is something that all seven basin states can come up with together. But I want to be real clear that we can’t accept something that continues to drain the system, that puts 40 million people at risk,” said Becky Mitchell, the fiery lead negotiator for the state of Colorado who has objected to her state accepting reductions to its water use.

The battle lines between the seven states that share the river have shifted over the past year. Last fall, the biggest conflict was between Arizona and California, which fought bitterly as water levels at the two main reservoirs were falling fast toward crisis levels. But the surprisingly wet winter last year, along with a $1.2 billion conservation deal funded by the Inflation Reduction Act, helped avert that disaster and many disagreements between those two were mended.

Now, the fight has shifted — pitting the lower river states of Arizona, California and Nevada against their upstream counterparts in Wyoming, Colorado, Utah and New Mexico.

If they can’t bridge the divide soon, the issue stands to land in the lap of the Biden administration during the heat of the 2024 election season.

Both Democratic and Republican administrations have long preferred to leave it to the states to fight out their differences. But as the river’s flows have shrunk and climate change promises to squeeze its flows further, those talks have become even more fraught. Interior Secretary Deb Haaland is ultimately responsible for managing the river and holds the power to step in to pressure parties for a deal — or impose cuts on the states herself.

The state negotiators are keenly aware of the risks of an intervention by Washington.

Brenda Burman, who runs the massive canal system that delivers water to Phoenix, Tucson and others in Central Arizona, managed to avoid those political fault lines when she served as President Donald Trump’s Bureau of Reclamation commissioner. In that post, she prodded the states into a hard-fought drought deal and shepherded a water-sharing deal with Mexico across the finish line.

“No one’s trying to make water political. We’re trying to make water work,” she said in an interview from the sidelines of the conference.

Current Bureau of Reclamation Commissioner Camille Touton has already intervened over the past year to prod Arizona and California into agreement, resulting in their May deal to avert the near-term disaster at the river’s two main dams. But whether a midlevel political appointee can continue to do so in a battle that the White House would surely prefer to leave until after November remains to be seen.

Speaking at the close of the conference Friday, Touton took a far more subdued tone than she did last year, offering broad encouragement to the states after showing the crowd a highly produced video from the Bureau of Reclamation touting the importance of the Colorado River basin.

“We are committed to you and [to] facilitating discussions, providing technical support, engaging in concepts and guiding development of alternatives” for the negotiations, she told the audience.

For the states, federal intervention — be it from the Biden administration, Congress, or the Supreme Court, where the fight is likely to ultimately land if a negotiated deal can’t be reached — is the worst-case scenario.

“Russian roulette sounds like an interesting, sometimes lucrative game until it doesn’t work out for you. That’s what the Supreme Court or Congress is to us,” said J.B. Hamby, California’s lead negotiator and a director of the Imperial Valley farm district that controls the single largest share of Colorado River water.

The state negotiators face a dire challenge that has been made infinitely harder by climate change. Even before the persistent drought that is diminishing the Colorado River, it rarely delivered as much water as expected under the 1922 compact that divvied up its supplies. Now, rising temperatures and changing precipitation patterns have walloped the sprawling river basin, shrinking flows by more than 20 percent over the past two decades — and it’s only expected to get worse.

The Upper Basin states never fully used the water that that century-old compact assigned to them, but the arid Lower Basin states have maxed out their apportionment. Now, climate change has made the situation untenable.

Much of the tension now centers on whether the Upper Basin states should share in the cuts needed to bring water use in line with the shrinking supply. Arizona, Nevada and California’s negotiators say they are close to a long-term deal that would stanch their use to bring it in line with the water that the river has delivered historically — a gap known as the “structural deficit.”

But that just deals with the century-old over-allocation problem. Those reductions will almost certainly fall short of what will be needed to deal with the pain Mother Nature is inflicting, and those Lower Basin states argue that burden should be shared by Wyoming, Colorado, Utah and New Mexico, as well as Mexico, which gets a slice of the river, too.

“The structural deficit — we’re going to own that,” said Tom Buschatzke, Arizona’s lead negotiator. But what it takes after that to stabilize the river “will be a shared responsibility. A shared responsibility for everybody in the basin — all seven states and Mexico.”

New rules to govern the river must be in place in 2026, when the current guidelines expire. The Biden administration has said it plans to release a draft environmental review for the new guidelines at the end of 2024, a key step for shoring up the legal grounds for the new rules. Touton has given the states until March to submit their proposals for that analysis, negotiators say.

If the seven states haven’t reached consensus on an approach at that point, it will be up to the Biden administration to decide how to proceed. How that could play out in the pressure cooker of an election season is an uncertainty that loomed over the discussions in Las Vegas this week.

For now, state leaders say that means they must work it out themselves.

“The most viable path for us achieving anything that remotely works for everyone is the negotiation path,” said John Entsminger, Nevada’s lead for the river. “And that requires compromise. It’s a bad word in our political discourse these days.”