Interior sets 1.25M-acre-foot Colorado River cut for Lower Basin

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The U.S. Department of the Interior on Friday finalized rules for operating Lake Powell and Lake Mead in 2027 and 2028, cutting 1.25 million acre-feet a year from Arizona, California and Nevada while requiring no mandatory reductions from the four Upper Basin states.

Under a proposed Lower Basin sharing agreement, Arizona would absorb 760,000 acre-feet, the largest share.

Interior Secretary Doug Burgum signed the 2027-2028 Operating Guidelines and the record of decision for the Post-2026 Colorado River Operations Final Environmental Impact Statement on Aug. 21, ending a federal review that began in June 2023.

The decision also establishes a framework through 2036. Operating guidelines are expected to cover two-year periods unless the basin states reach agreements that allow longer operating periods.

Arizona’s U.S. senators, Democrats Mark Kelly and Ruben Gallego, welcomed the short-term certainty but said more work remains.

“This decision provides much-needed certainty for Arizona and the Colorado River over the next two years,” the senators said in a joint statement Friday. “The 2027 and 2028 guidelines protect Arizona from even deeper near-term cuts while giving the seven Basin states more time to reach a long-term agreement. Arizona and our Lower Basin partners have stepped up with significant conservation commitments, and now every Basin state needs to do its part.”

Upper Basin states may enter an agreement permitting releases from the Aspinall Unit in Colorado, Flaming Gorge on the Utah-Wyoming line and Navajo Reservoir on the Colorado-New Mexico line to protect Glen Canyon Dam.

Lake Powell operations

Lake Powell and Lake Mead have fallen to historically low levels after the lowest snowpack on record last winter and 26 years of drought, according to the Interior.

Reclamation’s August 24-Month Study, released Friday, projects Lake Powell will start the Oct. 1 water year between 3,510 and 3,540 feet, putting the reservoir in what the agency calls the Lower Elevation Infrastructure Protection Range.

Reclamation expects a water-year release of 6 million to 7 million acre-feet from the Glen Canyon Dam. Releases will be adjusted through April to keep Lake Powell at or above 3,510 feet, with the final water-year release volume determined in April.

The 3,510-foot operating target is 20 feet above the 3,490-foot minimum power pool at Glen Canyon Dam. The Navajo Tribal Utility Authority is a Colorado River Storage Project power customer.

Under the Lower Basin states’ proposed sharing agreement, California would give up 440,000 acre-feet and Nevada 50,000 in addition to Arizona’s 760,000-acre-foot share. If the states do not complete the necessary agreements, the Interior secretary would determine how the reduction is divided.

The guidelines also call for contractors in the Lower Basin states to conserve an additional 700,000 acre-feet total in 2026, 2027 and 2028 under voluntary agreements.

Arizona’s proposed share would be about 48% larger than its current 512,000-acre-foot Tier 1 reduction under the 2007 Interim Guidelines and the 2019 Lower Basin Drought Contingency Plan.

Tribal water impacts

The guidelines incorporate concepts from proposals submitted by the Upper Basin, Lower Basin and basin tribes, according to the Interior. Burgum thanked the 30 basin tribes, seven states and Mexico in his statement.

A federally managed pool in Lake Mead would help meet federal firming or delivery obligations under congressionally authorized tribal water-rights settlements. After those obligations are met, the pool could offset up to 25% of certain shortages affecting tribal Lower Colorado River or Central Arizona Project water entitlements.

The guidelines also provide for consultation and coordination with basin tribes on reservoir operations and specified elevation triggers.

They do not settle the larger question for the Navajo Nation. Its rights to the main stem of the Colorado River in the Lower Basin remain unquantified.

The Northeastern Arizona Indian Water Rights Settlement Act of 2025, which would resolve Navajo, Hopi and San Juan Southern Paiute water-rights claims in Arizona, remains before Congress. The legislation would provide about $5.1 billion in mandatory federal funding. Interior raised significant concerns about the cost during a Senate Indian Affairs Committee hearing in March.

Dwight Witherspoon, an attorney in the Navajo Nation Department of Justice’s Water Rights Unit, spoke with the Navajo Times Aug. 3, three days after Reclamation released the final EIS that formed the basis for Friday’s decision. He said the cuts will affect Arizona far more than the Navajo Nation.

“Since the bulk of our settlement is in the Upper Basin, the final environmental impact statement on the operations of Lake Powell and Lake Mead wouldn’t impact us nearly as much as it would the full state of Arizona,” Witherspoon said, “because we’re primarily getting the bulk of our settlement waters in the Upper Basin.”

The Navajo Nation has water interests in both basins. Its settled San Juan River rights are in the Upper Basin. Its unresolved Arizona claims include Upper Basin Colorado River water, Lower Basin mainstem water and Little Colorado River water.

President Buu Nygren told Congress in March that the Nation must be able to move its Colorado River water between Upper and Lower Basin communities in Arizona.

The settlement legislation identifies 34,100 acre-feet a year of Navajo Nation and Hopi Tribe Upper Basin water associated with water previously contracted for the Navajo Generating Station. Under the proposed conservation program, the tribes would leave 17,050 acre-feet a year in Lake Powell for 20 years. During that period, they also could lease a combined maximum of 17,050 acre-feet a year in the Lower Basin.

Witherspoon said the proposal was presented to Upper Basin attorneys at the Colorado River Water Users Association meeting in December, where the tribes asked what would be needed to gain their support.

“One of the requests was, we’d like to get a response to what you need to be able to get to a yes,” he said.

The remaining hurdles are cost, Upper Basin concerns about leasing and water accounting and obtaining congressional funding, Witherspoon said.

He said the tribes have proposed using a 1.3% population growth rate instead of the 1.8% rate used to size the pipeline in S. 953. They also have proposed building regional water projects themselves rather than through Reclamation, which he said, “has a very difficult time staying on budget.”

The Interior is reviewing the proposal, Witherspoon said.

“Getting the perfected rights or title to 44,700 acre-feet of the Upper Basin water, some of the firmest water in the Colorado River Basin, is invaluable for future generations,” Witherspoon said.

The legislation would allocate 44,700 acre-feet a year of Arizona Upper Basin Colorado River water to the Navajo Nation once the settlement’s enforceability requirements are met.

Hopi and the San Juan Southern Paiute Tribe remain on board, Witherspoon said.

The states could still reach an agreement that would be incorporated into later operations. Andrea Travnicek, the assistant secretary for Water and Science, said federal managers have flexibility to respond to changing conditions and potential consensus.

Later operating periods could bring Lower Basin shortages of up to 3 million acre-feet a year. Tom Buschatzke, the director of the Arizona Department of Water Resources, said the state remains concerned about the plan after 2028 and is preserving its ability to protect Arizona’s legal rights to Colorado River water.

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