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6 states dependent on the Colorado River have agreed to a new water sharing model

California – with the largest allocation of water from the river – is the only holdout. Officials said the state would release its own plan.

The Colorado River and its tributaries flow through seven states into Mexico, serving 40 million people and a $5 billion a year agricultural industry. Some of the country’s largest cities, including Los Angeles, Phoenix, Denver and Las Vegas, two Mexican states, Native American tribes and others depend on the river which has been severely stressed by Droughtdemand and overuse.

States missed a mid-August deadline to hear an appeal from the US Bureau of Reclamation to propose ways to conserve 2 million to 4 million acre feet of water. They’ve regrouped to reach consensus by the end of January to fall back on a larger proposal Reclamation has in the works.

Arizona, Nevada, New Mexico, Colorado, Utah and Wyoming on Monday sent a letter to Reclamation, which operates major dams in the river system, outlining an alternative that builds on existing guidelines, deepens water cuts, and takes into account ‘water that is lost through evaporation and transport.

Those states propose increasing the levels at which water cuts would be triggered at Lake Mead and Lake Powell, which are barometers of river health. The model creates more of a protective buffer for both reservoirs, the largest built in the United States. It also seeks to secure water accounting and ensure that water intentionally stored in the lower basin in Lake Mead is available for future use.

The modeling would result in approximately 2 million acre-feet of cuts in the lower basin, with smaller reductions in the upper basin. Mexico and California are factored into the equations, but neither signed Monday’s letter.

John Entsminger, chief executive officer of the Southern Nevada Water Authority, said all states had negotiated in good faith.

“I don’t consider it a failure that we don’t have unanimity at one stage of this process,” he said on Monday. “I think all seven states are still committed to working together.”

Last October California presented a proposal to cut 400,000 acre feet. One acre foot is enough water to supply two to three US households for a year.

JB Hamby, chairman of the Colorado River Board of California, said California will present a model for watershed reduction that is practical, based on voluntary action, and in line with the law governing the river and the hierarchy of water rights.

“California remains focused on practical solutions that can be implemented now to protect stored water volumes without provoking conflict and litigation,” he said in a statement Monday.

Nothing will happen immediately with the consensus reached between the six states. However, failure to reach a consensus carried the risk that the federal government would decide for itself how to eventually implement the cuts.

By not signing, California is not avoiding this risk.

Debates about how to reduce water consumption by about a third have been litigation. The upper basin states of Wyoming, New Mexico, Colorado and Utah said the lower basin states — Arizona, California and Nevada — have to do the heavy lifting. That conversation in the Lower Basin centered around what’s legal and what’s right.

The six states that signed on to the proposal on Monday acknowledged that the ideas they put forward could be left out of final plans to operate the river’s major dams. Negotiations are ongoing, they noted, adding that what they have proposed does not override existing rights states and others have to the Colorado River.

“There’s a lot of steps, commitments that need to be made at the federal, state and local levels,” said Entsminger of Nevada.

Monday’s proposal included accounting for water lost to evaporation and infrastructure losses as the river flows through the region’s dams and streams. Federal officials estimate that more than 10% of river flow evaporates, leaks or spills, yet Arizona, California, Nevada and Mexico they never realized that water leak.

The six states argued that the Lower Basin states should share those losses — essentially subtracting those amounts from their allocations — once Lake Mead’s elevation drops below 349 meters (1,145 feet). The tank was well below that Monday.

The cleanup will view the six-state deal as part of a larger proposal to overhaul how it manages Glen Canyon and Hoover Dams, the power giants on the Colorado River. The reservoirs behind the dams — Lake Powell and Lake Mead — have reached historic lows amid more than two decades of drought and climate change.

Remediation plans to publish a draft of that proposal by early March, with a goal of finalizing it by mid-August, when the agency usually announces the amount of water available for the following year. The reclamation said it will do what is necessary to ensure the dams can continue to produce hydroelectricity and supply water.

Those august annual announcements have led to mandatory cuts in the last two years for Arizona, Nevada and Mexico in the lower river basin. California has so far been spared the cuts because it has some of the oldest and most secure water rights, particularly in the Imperial Valley where much of the country’s winter vegetables are grown, along with Arizona’s Yuma region.

Without California’s participation, the six-state proposal can only go so far in meeting the hydrological realities of the river. Water managers in the Lower Basin say the scale of conservation the reclamation is seeking cannot be met without California, tribes and farmers drawing directly from the Colorado River.

It’s also unclear how much Mexico will ultimately contribute to the savings. In prime water years, Mexico receives its full allotment of 1.5 million acre feet under a treaty reached with the United States in 1944.