What Happened?

If you drink tap water in the Southwest, water your lawn in Phoenix, or buy produce from California's Imperial Valley, the Colorado River is part of your daily life. The river supplies nearly 40 million people and irrigates roughly 5.5 million acres of farmland, but it is delivering far less water than the legal agreements governing it assumed.

A Congressional report updated this month finds that average natural river flows from 2000 to 2024 ran about 12.4 million acre-feet (MAF) per year, 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, the federal water agency within the Department of the Interior, finalized a new 10-year operating framework on Aug. 21, covering 2027 through 2036, which took effect last week.

Why Does it Matter to Me?

The new framework could require Lower Basin reductions of as much as 3.6 million acre-feet (MAF) per year, according to the Congressional Research Service report. For 2027 and 2028, the plan assumes 1.25 MAF per year in U.S. shortages split among those three states, with Mexico absorbing an additional 250,000 acre-feet under Minute 334, an agreement signed Sept. 2.

Combined storage at Lake Powell and Lake Mead dropped from 42.7 MAF in 1996 to 12.0 MAF in 2026. To keep Lake Powell above its minimum power pool elevation, the Bureau of Reclamation cut Glen Canyon Dam releases to 6.0 million acre-feet (MAF) per year, according to the Congressional Research Service report.

Both Sides, Now

The Congressional Research Service (CRS) report says the basin's allocation framework was developed under hydrologic assumptions that no longer reliably hold, and that 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. The federal government backed a recent conservation agreement requiring Lower Basin states to conserve 3.0 MAF from 2023 through 2026, with much of the conservation compensated by $4.0 billion from the Inflation Reduction Act.

Nevada, the Colorado River Commission of Nevada, and the Southern Nevada Water Authority sued the Interior Department on Aug. 24 to block the federal shortage framework, which would reduce deliveries from Lake Mead, according to the Arizona Republic. The lawsuit alleges violations of the National Environmental Policy Act, the Administrative Procedure Act, and the Law of the River. The Department of the Interior did not respond to a request for comment on the litigation.

The CRS report also flags that the framework does not identify a funding source for the 700,000 acre-feet per year of voluntary Lower Basin conservation the plan assumes, and that 11 basin tribes hold unquantified water-rights claims.

What Happens Next?

Congress may be asked to approve new legal authorities, fund tribal water-rights settlements, and authorize modifications to Glen Canyon Dam that the Bureau of Reclamation is actively studying. The Bureau of Reclamation is actively studying possible modifications to Glen Canyon Dam, but the 2026 environmental impact statement did not include them as options.

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