Interior Finalizes Colorado River Rules, Mandates 2027–28 Cuts; Arizona Faces Largest Reduction

The federal government has finalized the first Colorado River operating rules that will take effect after 2026, requiring mandatory water cuts in 2027 and 2028 for Arizona, California and Nevada, with Arizona absorbing the largest reduction. The move marks the first concrete two-year implementation of a broader federal framework adopted after the seven basin states failed to agree on long-term river operations.

Under the final 2027-2028 operating guidelines, total Lower Basin consumptive use will be capped at 6.25 million acre-feet a year for calendar years 2027 and 2028, down from the Lower Basin’s normal 7.5 million acre-feet apportionment. The new annual allocations are 2.04 million acre-feet for Arizona, 3.96 million acre-feet for California and 250,000 acre-feet for Nevada. That translates to cuts of 760,000 acre-feet for Arizona, 440,000 acre-feet for California and 50,000 acre-feet for Nevada.

The mandatory cuts apply to the three Lower Basin states. The Upper Basin states — Colorado, Utah, New Mexico and Wyoming — do not face mandatory cuts for now, according to contemporary reporting on the federal action.

The U.S. Department of the Interior, acting through the Bureau of Reclamation, finalized the broader post-2026 operating plan after interstate negotiations failed to produce a basinwide deal. Reclamation published the Final Environmental Impact Statement on July 31, 2026, and the department adopted its preferred Decision Framework in an August 2026 Record of Decision, making it the governing framework for river operations from 2027 through 2036. The newly issued 2027-2028 Operating Guidelines are the first implementation step under that framework and begin with the 2027 water year starting Oct. 1, 2026.

The old operating regime, including the 2007 Interim Guidelines and 2019 Drought Contingency Plans, expires at the end of 2026, requiring a replacement. Interior has authority to manage the major federal reservoirs on the river, including Lake Powell and Lake Mead, and stepped in after the seven states did not reach consensus. The Record of Decision says the secretary convened the governors multiple times before adopting the federal framework when no basinwide agreement emerged.

The decision carries broad consequences across the West because the Colorado River supplies water for more than 40 million people, supports about 5.5 million acres of farmland, and serves about 30 Tribal Nations and two Mexican states, according to Reclamation. The agency also said the combined contents of Lake Powell and Lake Mead have not been this low since before Lake Powell began filling in 1963.

“The Department has a responsibility to ensure the Colorado River system remains reliable and resilient for the millions of Americans, communities and industries that depend on it,” Secretary of the Interior Doug Burgum said in a Bureau of Reclamation news release on July 31, 2026.

In addition to the mandatory Lower Basin cuts, the 2027-2028 guidelines call for 700,000 acre-feet of additional Lower Basin system conservation across 2026, 2027 and 2028. Interior said that conservation is to be achieved through voluntary agreements or implementing agreements.

The wider 2027-2036 framework gives federal managers flexibility to respond to changing river conditions over time. It allows annual releases from Lake Powell to range from 5.0 million acre-feet to 12.0 million acre-feet and contemplates Lower Basin shortages of as much as 3.0 million acre-feet depending on hydrology.

“This plan strikes a balance between flexibility and predictability for the Colorado River system that is vital to the 40 million people who rely on it given unprecedented hydrologic conditions and the potential for considerable impacts on water users,” Assistant Secretary for Water and Science Andrea Travnicek said in the same release.