Officials managing the Colorado River face a difficult choice between conservation and electricity costs as reservoirs shrink due to overuse and climate change. A proposed 'cool mix flow' from Glen Canyon Dam would release cold water from deep in Lake Powell to protect the threatened humpback chub, but would bypass hydropower turbines, reducing electricity generation.
The proposal follows the worst snowpack on record for the Colorado River Basin, which supplies water to over 40 million people across seven US states, tribal nations, and Mexico. States have failed to reach a long-term agreement on sharing dwindling resources, with current guidelines expiring this year.
Utilities that purchase the dam's hydropower warn that cool water releases would force them to buy alternative energy at higher costs, increasing financial hardship for customers. However, supporters argue that without cool releases, warm downstream waters would allow non-native predatory fish like smallmouth bass to spawn, threatening the humpback chub and a world-famous trout fishery.
Lake Powell is only 23% full, and record low inflows are expected this summer. Warm water near the surface is drawn through the dam's generators, allowing smallmouth bass to pass into the river below, where they prey on native fish. Water temperatures downstream are projected to exceed 60°F (15.5°C) by mid-June, enabling bass reproduction.
The Bureau of Reclamation is expected to announce a decision soon, weighing ecological health against hydropower production. If approved, cool water releases would occur from June to October via jet tubes, bypassing turbines. Officials say similar releases in 2024 and 2025 successfully prevented spawning, but utilities remain concerned about the cost of replacing lost generation.
