Why It Matters

Colorado River water supplies nearly 40 million people and irrigates approximately 5.5 million acres across a basin spanning more than 246,000 square miles, yet the river is delivering far less water than its foundational legal framework assumed. A Congressional Research Service (CRS) report updated Oct. 1 finds that average natural flows from 2000 to 2024 ran approximately 12.4 million acre-feet (MAF) per year, well below the combined commitments of 7.5 MAF annually allocated to each basin under the Colorado River Compact of 1922 and the additional 1.5 MAF guaranteed to Mexico under the 1944 U.S.-Mexico Water Treaty.

The Bureau of Reclamation, part of the Department of the Interior, finalized a new 10-year operating framework on Aug. 21, covering 2027 through 2036, after Upper and Lower Basin states submitted separate proposals in 2024 but could not agree on a basin-wide approach. The framework took effect Oct. 1.

The new framework could require Lower Basin reductions of as much as 3.6 MAF per year, and the report identifies potential needs for new federal authority, additional appropriations, tribal water-rights settlements, and infrastructure changes, including possible modifications to Glen Canyon Dam.

The Big Picture

The Compact's allocations assumed average flows of 16.4 million acre-feet (MAF) per year, but actual natural flows averaged about 14.6 MAF from 1906 to 2024. Combined storage at Lake Powell and Lake Mead fell from 42.7 MAF in 1996 to 12.0 MAF in 2026. To keep Lake Powell above minimum power pool elevation, the Bureau of Reclamation transferred 1.0 MAF from Flaming Gorge and cut Glen Canyon Dam releases to 6.0 MAF per year, reductions the report says could lead to the basin's first-ever "compact call."

The federal government led drought-response agreements in 2003, 2007, 2019, and 2024. The most recent required the three Lower Basin states to conserve a combined 3.0 MAF from 2023 through 2026, much of it compensated with $4.0 billion appropriated under P.L. 117-169, commonly known as the Inflation Reduction Act.

The Bureau of Reclamation's new framework uses a flexible "sideboards" structure implemented in two-year increments. For 2027-2028, the plan assumes 1.25 MAF per year in U.S. shortages, split among Arizona, California, and Nevada, with Mexico taking an additional 250,000 acre-feet under Minute 334, signed Sept. 2, though the report does not identify a funding source for the 700,000 acre-feet per year of voluntary Lower Basin conservation the plan assumes.

Nevada filed suit against the Department of the Interior in August alleging violations of the National Environmental Policy Act, the Administrative Procedure Act, and the Law of the River, in a case captioned Nevada v. Burgum, No. 2:26-cv-02665 (D. Nev. filed Aug. 24). Tribal water rights add further complexity: 11 basin tribes hold unquantified claims, and tribes held diversion rights of approximately 3.4 MAF per year as of December 2020.

The Bottom Line

The CRS report says the central issue is no longer simply how to conserve water temporarily, but how to permanently reconcile water use with lower and more variable supplies, and it finds that the basin's allocation framework was developed under hydrologic assumptions that no longer reliably hold. Congress may be asked to approve new or modified authorities, fund tribal settlements and ecosystem programs, and authorize Glen Canyon Dam modifications that Reclamation is actively studying but that the 2026 environmental impact statement did not include as options. Whether Congress acts, and how quickly, will shape whether the administration can implement the new framework on its existing legal footing or must return to Capitol Hill for additional authority and funding.

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