- Water use exceeds natural flow in the Colorado River Basin.
- Reservoirs could lose nearly half their accessible storage by late 2026.
- Lake Powell may dip below safe operating levels by next summer.
- Current rules leave few options before new guidelines take effect in 2026.
- Experts call for immediate, enforceable reductions in water use.
Wednesday, September 17, 2025 — An analysis released September 11, 2025
, by researchers from several universities and policy centers warns that consumptive water use in the Colorado River Basin continues to exceed the natural flow of the river. For decades, this imbalance has been offset by drawing down storage in major reservoirs such as Lake Powell and Lake Mead. The report concludes that this reserve is nearly exhausted and that urgent reductions in water use are needed to avoid dire outcomes.
According to the Bureau of Reclamation’s August 2025 forecast, 7.48 million acre-feet will be released from Lake Powell in Water Year 2026, and the Lower Basin will remain in a Tier 1 shortage. This condition requires reductions in deliveries to Arizona, Nevada, and Mexico, but the cuts are not expected to close the gap between supply and demand.
Reservoirs Near Critical Thresholds.
On September 1, 2025, Lake Powell held 7.0 million acre-feet of active storage, but only 2.7 million acre-feet was above the 3,500-foot threshold considered necessary to safely operate Glen Canyon Dam. At Lake Mead, 8.1 million acre-feet of active storage was reported, yet just 3.6 million acre-feet was above the 1,000-foot mark set to protect Hoover Dam. In total, the two reservoirs had 15.1 million acre-feet of active storage, but only 6.3 million acre-feet was realistically accessible
If conditions mirror last year, consumptive use is projected to exceed inflows by 3.6 million acre-feet. Most of this shortfall would be absorbed by Lakes Powell and Mead, reducing their combined accessible storage to about 3.6 million acre-feet by late summer 2026. That reduction would occur just as the system enters its annual drawdown period, which typically continues through early spring.
Forecasts and Hydrologic Limits.
The natural flow at Lees Ferry for 2025 was about 8.5 million acre-feet. Adding smaller inflows from the Grand Canyon and Virgin River, researchers assume a repeat of 9.3 million acre-feet for 2026. By contrast, water uses in the United States and Mexico are projected at 12.9 million acre-feet, creating the 3.6 million acre-foot deficit.
The report emphasizes that the Colorado River follows physical laws, not legal ones. A warming climate is lengthening growing seasons, drying soils, and reducing the efficiency of snowpack runoff. While the reservoirs can store excess water in occasional wet years, they cannot increase the overall supply. The system has already lost 60 percent of its storage since 1999.
Engineering Constraints at Powell and Mead.
Even within active storage, not all water is available for release. At Lake Powell, Reclamation has identified elevation 3,500 feet as the practical lower limit for safe operations, restricting access to roughly 400,000 acre-feet that lies above the dead pool but below this threshold. Concerns include cavitation damage, reduced hydropower efficiency, and maintenance risks if low-level outlets are used extensively.
At Lake Mead, federal policy aims to protect the reservoir from dropping below 1,000 feet. If elevations fall under 1,035 feet, only five of Hoover Dam’s seventeen turbines can operate due to safety risks. These physical and operational constraints mean that “realistically accessible storage” is less than reported active storage.
The Role of Upstream Reservoirs.
The 2019 Drought Response Operations Agreement (DROA) allows for releases from upstream reservoirs such as Flaming Gorge, Blue Mesa, and Navajo under certain conditions. These emergency measures were triggered in 2021 and 2022 when Lake Powell fell near critical levels. While Flaming Gorge could provide as much as 3.7 million acre-feet, the current storage is closer to 3.0 million, and only a fraction of that is likely available. Blue Mesa and Navajo face their own constraints, limiting their role as backup supplies.
The report notes that such releases are temporary stopgaps. They cannot resolve the fundamental imbalance between inflows and consumptive use. Future releases would only be possible if wet years refill upstream reservoirs, and any water shifted downstream reduces inflows available in later years.
Implications for Post-2026 Guidelines.
The researchers caution that continuing “business as usual” could deplete nearly half of the currently accessible storage in Powell and Mead before new operating rules take effect in 2026. That scenario would severely constrain management options.
They argue that immediate, enforceable reductions in both the Upper and Lower Basins are the only way to preserve operational flexibility. Without action, the Department of the Interior may be forced to impose drastic cuts. As the authors conclude, near-term conservation steps can slow reservoir decline and create space for long-term solutions. Delay, however, could leave the basin with little room to maneuver when the post-2026 regime begins.
Citation.
This article is based on the September 11, 2025, analysis authored by Jack Schmidt, Anne Castle, John Fleck, Eric Kuhn, Kathryn Sorensen, and Katherine Tara, published through the University of Colorado Boulder Getches-Wilkinson Center.
