R45546 — Management of the Colorado River: Water Allocations, Drought, and the Federal Role

The Colorado River Basin covers more than 246,000 square miles in seven U.S. states (Wyoming, Colorado, Utah, New Mexico, Arizona, Nevada, and California) and Mexico. Pursuant to federal law, the Bureau of Reclamation (Reclamation, part of the Department of the Interior) manages much of the basin’s water supplies. Colorado River water is used primarily for agricultural irrigation and municipal and industrial (M&I) purposes; it is also important for tribal uses, hydropower production, fish and wildlife, and recreational uses. Dating to the early 2000s, reservoir storage levels throughout the basin have fallen. Pursuant to existing authorities, the Secretary of the Interior, through Reclamation, is currently leading a process analyzing potential “long-term” (post-2026) operational changes to the Colorado River system. River Management A collection of compacts, treaties, statutes, and other authorities govern Colorado River allocations and apportionments. The foundational management document, the Colorado River Compact of 1922, established a framework to apportion water supplies between the river’s Upper and Lower Basins, divided at Lee Ferry, AZ. The compact allocated 7.5 million acre-feet (MAF) annually to each basin, and a 1944 treaty made an additional 1.5 MAF in annual flows available to Mexico. A Supreme Court case and related decrees inform the Secretary of the Interior’s management of the delivery of all water below Hoover Dam. Consumptive use plus other water losses (e.g., evaporation) on the Colorado River typically exceed the basin’s flows. This imbalance, coupled with a long-term drought dating to 2000, has stressed basin water supplies. Reclamation closely tracks the status of two large reservoirs—Lake Powell in the Upper Basin and Lake Mead in the Lower Basin—as indicators of basin storage conditions. Since the onset of dry conditions in the early 2000s, storage levels at these reservoirs have fallen. To alleviate these trends, water releases from both lakes have been tied to specific water storage levels. Since 2020, Reclamation has conserved Lower Basin storage in Lake Mead through reduced water deliveries to Arizona, Nevada, and Mexico. In the Upper Basin, dwindling supplies in Lake Powell could jeopardize hydropower generation and Lower Basin releases from Glen Canyon Dam. As a result, Reclamation has transferred water from upstream reservoirs to Lake Powell while also reducing releases to the Lower Basin. Efforts to Address Drought The federal government has led multiple efforts to improve the basin’s water supply outlook, resulting in collaborative agreements in 2003, 2007, 2019, and 2024 that reduced water use and increased operational flexibilities, among other things. In the most recent agreement, the three Lower Basin states (Arizona, California, and Nevada) agreed to “near-term” (i.e., 2023-2026) conservation of 3.0 MAF, with 2.3 MAF of these reductions compensated with federal drought mitigation funds approved by Congress in P.L. 117-169 (commonly referred to as the Inflation Reduction Act). Despite these efforts, storage levels throughout the basin have continued to fall and pose widespread concerns among observers and stakeholders. With previous agreements set to expire at the end of 2026, Reclamation is currently leading an effort to study and implement post-2026 operations that account for the realities of the basin’s hydrology. Upper and Lower Basin state leaders proposed their own long-term actions in 2024, but have yet to agree on a basin-wide approach. In January 2026, Reclamation published a draft environmental impact statement (DEIS) with four potential action alternatives for post-2026 operations, and plans to identify a preferred alternative in the summer of 2026. Three of the four DEIS alternatives require action by Congress for implementation, and all of the action alternatives would reduce water supplies beyond current levels (and without compensation). In May 2025, Lower Basin states submitted a short-term operations proposal as an alternative to the DEIS. Congressional Role Congress funds and oversees management of the basin’s federal water and hydropower facilities, and has previously approved legislation affecting water supplies and authorizing water shortage plans and drought mitigation funding. In considering basin operations, Congress may weigh whether or not to act on secretarial requests for new or modified authorities, or whether to issue other authorities and/or directives for river management. If the Secretary recommends an operations option that relies on congressional enactment of new or modified authorities and Congress does not act, the Secretary may be forced to limit post-2026 activities to those available under existing authorities and funding.

Curated by CRS — every bill listed in this report's relatedMaterials. Edge type cited_in_report, gold confidence.

• HR 7078 — To amend the Colorado River Basin Project Act to provide for the equitable distribution of Colorado · 119th Cong
• HR 2025 — Northeastern Arizona Indian Water Rights Settlement Act of 2025 · 119th Cong
• S 953 — Northeastern Arizona Indian Water Rights Settlement Act of 2025 · 119th Cong
• HR 831 — Lower Colorado River Multi-Species Conservation Program Amendment Act of 2025 · 119th Cong
• S 291 — Lower Colorado River Multi-Species Conservation Program Amendment Act of 2025 · 119th Cong
• HR 231 — Colorado River Basin System Conservation Extension Act of 2025 · 119th Cong
• S 154 — Colorado River Basin System Conservation Extension Act · 119th Cong