Reclamation told stakeholders in an email that the cool-mix operation would not proceed because of “significant hydropower generation concerns under already strained system conditions,” according to the Associated Press report published August 13, 2026.

The immediate effect is on river-temperature management and endangered-fish protection below the dam. The decision does not announce a new direct water-allocation cut for households.

Why the cool-water release mattered

A cool-mix flow releases colder water from deeper in Lake Powell through Glen Canyon Dam’s bypass tubes and river outlet works, which are below the hydropower penstocks. That can cool the Colorado River downstream, but it also reduces the amount of water passing through generating equipment.

The biological goal is to disrupt spawning by invasive smallmouth bass and reduce threats to the federally threatened humpback chub and other native fish in the Grand Canyon. Smallmouth bass were introduced into Lake Powell for sport fishing and can prey on federally protected native fish if they become established below the dam.

Reclamation’s trigger for recommending cooler releases is an average river temperature above 60 degrees Fahrenheit for three consecutive days at a monitoring point below Glen Canyon Dam. The river downstream was about 69 degrees when officials made the decision, AP reported.

Reclamation said cool-mix operations in 2024 and 2025 successfully prevented smallmouth bass spawning. For 2026, the agency said it will rely on expanded rapid-response removal, additional backwater modifications, evaluation of innovative tools and longer-term structural solutions.

Why officials withheld the release

Lake Powell ended June at an elevation of 3,525.17 feet, with 5.60 million acre-feet of storage, or about 24% of live capacity, according to Reclamation’s operating data updated July 17, 2026.

The agency’s most-probable water-year 2026 forecast calls for 3.50 million acre-feet of unregulated inflow, or 36% of average. That is a forecast for water flowing into Lake Powell during the 2026 water year, not a measurement of all Colorado River Basin supplies.

Using that forecast, Reclamation projects that Lake Powell will end water year 2026 near an elevation of 3,516.18 feet, with approximately 5.05 million acre-feet in storage, or 22% of capacity. That is a model projection, not a final result. The projection remains above the agency’s cited minimum-power-pool elevation of 3,490 feet.

Reclamation’s operating data set the water-year 2026 Lake Powell release volume at 6.0 million acre-feet under the current operating framework. Utilities that buy Glen Canyon hydropower told AP that a cool-mix operation would have required millions of dollars in replacement electricity, potentially increasing customer costs. That is a utility warning about a possible consequence, not evidence that the 2026 decision directly raises household electricity rates.

Who is affected

The immediate ecological concern is the river below Glen Canyon Dam, where warmer water may make it easier for smallmouth bass to establish and threaten humpback chub habitat. Conservation advocates also warned AP that elevated temperatures could harm the nearby rainbow trout fishery.

The power tradeoff reaches beyond the Grand Canyon. The Colorado River supplies water and supports hydropower, agriculture, wildlife and recreation for more than 40 million people in seven U.S. states, tribal nations and Mexico, according to Reclamation. Hydropower customers, river managers, recreation interests and native-fish advocates all have a stake in how the system’s limited operating cushion is used.

What happens next

The 2026 decision is an operational choice, not a permanent abandonment of cool-mix flows. Future decisions will depend on river temperatures, reservoir conditions, fish monitoring and available power.

Reclamation’s next steps include fish-removal work, backwater modifications and evaluation of longer-term structural solutions. Readers should also watch updated Lake Powell storage and inflow data, as well as negotiations over the Colorado River operating rules that are scheduled to expire at the end of 2026. Those decisions will help determine how water, electricity and endangered-species protections are balanced from 2027 onward.

Sources

• Associated Press: Officials will not release cool water from a Colorado River reservoir to protect threatened fish
• Bureau of Reclamation: Glen Canyon Dam Water Operations