On Aug. 21, 2026, the U.S. Department of the Interior (Interior) adopted a new decision framework for operating Lake Powell and Lake Mead through 2036 and simultaneously issued operating guidelines for 2027 and 2028 (Operating Guidelines). The actions are intended to replace the 2007 Interim Guidelines and other Colorado River water management agreements that expire at the end of 2026.
The Aug. 21, 2026, Record of Decision cites ongoing drought, historically low reservoir levels, concerns about the reliability of infrastructure at Lake Powell’s Glen Canyon Dam, and the inability of the seven Colorado River Basin states to reach a cooperative agreement as the reasons for unilaterally adopting the new decision framework. The decision framework establishes general operational principles, “sideboards,” and the process for developing and issuing operating guidelines in two-year intervals through 2036. The operational principles emphasize protection of critical infrastructure, reliable water system operations, flexibility to respond to changing hydrologic conditions, continued stakeholder consultation, and the incorporation of conservation and other water management tools where appropriate. The sideboards establish the operational ranges and thresholds within which future operating guidelines must be developed, including parameters for Lake Powell releases, Lower Basin shortages, reservoir operations, and conservation and water storage programs.
The 2027 and 2028 Operating Guidelines are designed to respond to the shortage conditions and protect infrastructure at Glen Canyon Dam and Hoover Dam. The Operating Guidelines list objective criteria to release water from Lake Powell to maintain a minimum elevation of 3,510 feet elevation at Glen Canyon Dam. For Lake Mead, the guidelines establish a shortage condition for both 2027 and 2028 and require the Lower Basin States to reduce consumptive use to 6.25 million acre-feet annually, a reduction of 1.25 million acre-feet to the allocation under “Normal Conditions” pursuant to the Supreme Court decree in Arizona v. California, 376 U.S. 340 (1964). The Operating Guidelines would allocate the consumptive use as follows: 2.04 million acre-feet to Arizona, 3.96 million acre-feet to California, and 250,000 acre-feet to Nevada; these allocations represent decreases of Colorado River water of 27.1%, 10%, and 16.7%, respectively, compared to the original allocations under the Colorado River Compact. The Operating Guidelines also require the Lower Basin States to conserve and store at least 700,000 acre-feet in addition to the cuts and establish a federally managed pool to offset up to 25% of reductions to Tribes in Lower Basin States. The Operating Guidelines also continue, with modifications, certain water conservation programs and the “Intentionally Created Surplus” program.
On Aug. 24, 2026, just two days after Interior issued the Record of Decision, the state of Nevada, the Colorado River Commission of Nevada, and the Southern Nevada Water Authority jointly filed a lawsuit in the U.S. District Court for the District of Nevada challenging the Record of Decision, the associated Final Environmental Impact Statement (EIS), and the Operating Guidelines. The plaintiffs allege that the federal actions violate the Administrative Procedure Act, the National Environmental Policy Act, and the “Law of the River,” which is a compilation of laws and agreements governing use of Colorado River water, including the 1922 Colorado River Compact and treaties with Mexico. In part, the plaintiffs alleged that Interior did not correctly interpret and apply the Law of the River, and further, failed to consider a reasonable range of alternatives, correctly assess environmental effects, or analyze mitigation measures. The plaintiffs ask the court to enjoin implementation of the Record of Decision and Operating Guidelines and vacate those actions and the Final EIS.
The lawsuit marks the first — but potentially not the only — judicial challenge to Interior’s newly adopted post-2026 Colorado River operating framework and introduces additional uncertainty during a time of historic drought, as the Colorado River Basin transitions to new reservoir operating rules beginning Oct. 1, 2026.