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24th March 2022
How low can the Colorado River go? Drought forces states to face tough choices about water

Brandon Loomis
Arizona Republic
March 21, 2022

SALT LAKE CITY — Water managers from across the Colorado River Basin are preparing to negotiate new rules for allocating the river's dwindling flow and sharing the pain of a deepening shortage.

They’re adapting the 100-year-old Colorado River Compact to a river that little resembles the bountiful gusher that negotiators from seven states and the federal government in 1922 thought — or hoped — would bless the Southwest forever. The stakes rise with every foot that Lake Mead and Lake Powell fall, as the states and the water users within them recognize they’re due for a tighter squeeze.

Arizona gets more than a third of its water from the river, growing abundant crops around Yuma and homes around Phoenix and Tucson. The Las Vegas area gets most of its water from the river and has built a deeper pipe in Lake Mead to assure its continued access. Late-developing states like Wyoming use water for ranching and energy development, and are hoping to continue growing on it.

“We’re all going to lose,” Southern Nevada Water Authority General Manager John Entsminger told his counterparts from across the watershed on Friday at a river law symposium at the University of Utah’s Wallace Stegner Center for Land, Resources and the Environment.

His warning was less a lament than a call to action on behalf of a river that some 40 million people from the headwaters in Wyoming and Colorado to the delta in Mexico are using up.

“We’re up to the challenge because we don’t have a choice,” said Entsminger, whose agency in Las Vegas has embraced water austerity by banning most new grass lawns and golf courses and restricting new pool sizes.

Re-thinking the river's flow

Before the states, Indigenous communities and water districts can agree on a new plan to more conservatively divvy the water, they’ll need to agree on how low the river might go.

The 1922 negotiators asserted that the river could supply more than the 15 million acre-feet distributed among the seven states that share it, with some left over to flow into Mexico. The 2022 negotiators are debating whether they should plan for just 11 million acre-feet, as Entsminger’s Nevada agency already has penciled into its water security plans.

Today in Arizona, a 326,000-gallon acre-foot is about enough to supply three households for a year.

Since 2000, the river has delivered on average 12.3 million acre-feet a year, which is generally a couple of million less than the region has used. Consequently, the giant reservoirs that were full back then have tanked, Lake Mead to about a third of capacity, Lake Powell to a quarter.

Although the compact assigned specific shares to the upper and lower basins of the 1,450-mile river, the U.S. Interior Department’s Bureau of Reclamation in 2007 agreed with the states on an adaptive plan that reduces some users’ deliveries when reservoirs dive past certain thresholds. States including Arizona have built on those rules, sometimes paying tribes and other users to keep water in Lake Mead. But the guidelines expire at the end of 2025, and the states, tribes and water districts will spend the next few years debating a new, likely harsher, blueprint.

A federally declared shortage based on the 2007 rules already has fallen hard on some users who aren’t high on the river’s list of first-in-time, first-in-right appropriations, such as central Arizona farmers.

Planning for a regular supply of just 11 million acre-feet would obliterate long-held assumptions about how much water some or all of the users thought they were entitled for future growth. Contingencies for that level could severely limit growth potential in the Upper Basin, where Wyoming, Colorado, New Mexico and Utah are far from fully developing their collective 7.5 million acre-foot share outlined by the compact.

Those states are required to send on average another 7.5 million acre-feet downstream to the Lower Basin states of Arizona, Nevada and California, with another 1.5 million acre-feet promised to Mexico. If the states and water users agree, the Lower Basin could cut deeply into its already developed share, which many observers believe would spread the suffering more fairly. Failure to agree would leave the decision solely to the U.S. Interior secretary, or to the courts if states sue each other.

'We have to plan for less'

While the water experts who gathered in the S. J. Quinney College of Law’s moot courtroom know they must plan on less water, some aren’t ready to publicly commit to a number that will alarm water users back home. Arizona Department of Water Resources Director Tom Buschatzke, for instance, needs legislative approval for any deal he might make.

“I won’t say 11,” Buschatzke quipped from the symposium stage, “because I might get arrested when I get off the plane in Phoenix tonight.”

Climate scientists who study and project the Colorado’s flows as the region warms believe even 11 million acre-feet could be wishful thinking. Some studies suggest heat’s toll on the water supply will drop the river to just 9 million acre-feet in coming decades, said Brad Udall, a Colorado State University researcher who has focused on the river for 20 years.

“I could live with 11” as a planning guideline, even if it’s optimistic, Udall said. That projection is stark enough to require bold action that water managers could later build upon. It would follow the trajectory that scientists like Udall say represents the region’s heat-induced aridification, as opposed to temporary drought.

Others think it would be wise to plan contingencies to protect a river that might deliver only 9 million acre-feet. Without adjustments to the Lower Basin’s guaranteed deliveries, a river that’s routinely that small would leave the Upper Basin less than half what it currently takes out.

“We have to plan for less,” said Colorado River District General Manager Andy Mueller, who represents water users in western Colorado. “You don’t plan a system on hope or politics.”

The expanded role of tribes

Tribal representatives and attorneys said federal and state negotiators must include Indigenous perspectives in these talks, far more than in past rounds. The original compact, in particular, did not consider the needs of tribes who now hold or, in some cases, expect to hold sufficient water rights to make critical contributions to climate adaptation and conservation of reservoir storage.

Everyone who shares the river must use it responsibly and in a way that protects a semblance of nature and harmony, said Nora McDowell, a member of the river’s Water and Tribes Initiative and former chairwoman of the Fort Mojave Tribe on the Lower Colorado.

“We have a responsibility to change what we’ve learned in the past hundred years of this compact being in place,” McDowell said. Tribes need a voice to ensure that the river itself is no longer an afterthought, she said. “It is time.”

Whatever volume the parties pick and plan for, those in the Upper Basin will want to alter the hard requirement that they deliver a set amount of water to the states below Glen Canyon Dam near the Arizona-Utah state line. And some in the Lower Basin concede they’ll likely have to bend on that provision to reach a deal.

Entsminger told The Arizona Republic that water users in both the upper and lower regions will have to bend, or they won’t reach an agreement. Asked if that meant the Lower Basin might have to cut back enough to allow for an even split of future flows with the Upper Basin, he said he was not ready to discuss how to allocate the water.

“A 50-50 split would go a long way to solving problems,” said Amy Haas, who directs the Colorado River Authority of Utah.

That’s certainly true for her state, but an even split would likely deepen the pain in Arizona, where the state has already maxed out its use of the river and would have to cut further to allow upstream development. Arizona’s Buschatzke, like Nevada’s Entsminger, has not put numbers on a preferred rationing plan, but said all of the river’s users must share the benefits and the pain.

“We need a discussion about equitable shares of the river,” said Udall, the Colorado State researcher. The Upper Basin states are still using less than two-thirds of what they were promised in 1922, and could not have foreseen back then how climate change would penalize them for their slower development.

Still, he told The Republic, the states will likely need to agree on a deal that doesn’t force an even split on the Lower Basin, where California and Arizona have the watershed’s largest populations.

The Bureau of Reclamation in coming weeks will invite suggestions for what the new guidelines should consider, and it will launch a formal environmental review next year. The agency must balance the needs of seven states and 30 tribes while honoring treaty obligations with Mexico during, the agency’s program manager Carly Jerla said, and will need those partners to pull together.

“Our job here has never been harder,” Jerla said.

Brandon Loomis covers environmental and climate issues for The Arizona Republic and Reach him at or follow on Twitter brandonloomis.