Colorado River Law Struggles with Water Supply Discrepancy

Colorado River Water Supply Dwindles, Demands New Framework

The water supply of the Colorado River, which serves nearly 40 million people and irrigates about 5.5 million acres across a larger than 246,000 square miles basin, is under strain. An updated Congressional Research Service (CRS) report from Oct. 1 reveals that from 2000 to 2024, the river’s average natural flows fell to around 12.4 million acre-feet (MAF) per year. This is significantly less than the total commitments of 7.5 MAF each year designated to each basin under the Colorado River Compact of 1922, as well as the added 1.5 MAF assured to Mexico by the 1944 U.S.-Mexico Water Treaty.

The Bureau of Reclamation, a part of the Department of the Interior, implemented a new 10-year operating framework on Oct. 1, after finalizing it on Aug. 21. This framework, which covers 2027 through 2036, was put into action following separate proposals from both Upper and Lower Basin states in
2024 that failed to result in an agreed-upon basin-wide approach.

Under the new framework, Lower Basin reductions may reach up to 3.6 MAF each year. The CRS report also indicated potential needs for additional federal authority, more appropriations, settlements for tribal water rights, and changes to infrastructure, which might include alterations to Glen Canyon Dam.

The Current Scope of the Issue

The Compact’s allocations were based on assumed average flows of 16.4 MAF per year. However, actual natural flows averaged around 14.6 MAF per year from 1906 to 2024. Furthermore, combined storage at Lake Powell and Lake Mead fell dramatically from 42.7 MAF in 1996 to just 12.0 MAF in 2026. To keep Lake Powell above the minimum power pool elevation, the Bureau of Reclamation reduced Glen Canyon Dam releases to 6.0 MAF per year and transferred 1.0 MAF from Flaming Gorge. These cuts, according to the report, may result in the basin’s first-ever “compact call.”

The federal government led drought-response agreements in 2003, 2007, 2019, and 2024. The latest required the three Lower Basin states to collectively conserve 3.0 MAF from 2023 through 2026, largely compensated with $4.0 billion allocated under P.L. 117-169, also known as the Inflation Reduction Act.

The Bureau of Reclamation’s new framework employs a flexible “sideboards” structure implemented in two-year increments. For 2027-2028, the plan accounts for U.S. shortages totaling 1.25 MAF per year, divided among Arizona, California, and Nevada, with Mexico absorbing an extra 250,000 acre-feet as per Minute 334, signed on Sept. 2. However, the report does not identify a funding source for the voluntary Lower Basin conservation of 700,000 acre-feet per year as assumed by the plan.

Adding to the complexity, Nevada filed a lawsuit 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 known as Nevada v. Burgum, No. 2:26-cv-02665 (D. Nev. filed Aug. 24). There are also unresolved tribal water rights issues, with 11 basin tribes holding unquantified claims, and tribes held diversion rights of approximately 3.4 MAF per year as of December 2020.

The Key Takeaways

The CRS report indicates that the central challenge now is not merely temporary water conservation, but a permanent reconciliation of water use with lower and increasingly variable supplies. Therefore, the basin’s allocation framework, developed under hydrologic assumptions that no longer reliably hold, needs reconsideration. Congress may be asked to approve new or modified authorities, fund tribal settlements and ecosystem programs, and authorize modifications to Glen Canyon Dam that Reclamation is actively studying. Whether and how quickly Congress acts will dictate if the administration can implement the new framework on its existing legal basis or if it must seek further authority and funding from Capitol Hill.

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