At Glen Canyon Dam in northern Arizona, a quiet act of hydrology is becoming one of the Colorado River's most difficult choices: whether to sacrifice millions of dollars in electricity to save a small fish fighting for survival in the Grand Canyon's 278-mile stretch.
The humpback chub, a federally protected native fish with a hump-shaped head and a deep orange belly, has thrived in these waters for millennia. But now it faces an enemy that arrived by accident: smallmouth bass, introduced for sport fishing in the 1980s, have started moving downstream toward the Grand Canyon, where they devour the humpback chub. The solution is technically simple but economically painful. The Bureau of Reclamation is considering "cool mix flows," where cold water is released from deep in Lake Powell's reservoir, bypassing the hydropower turbines entirely and cooling the river downstream. Without these cold releases, water temperatures are expected to exceed 60 degrees Fahrenheit by mid-June—the threshold at which non-native predatory fish spawn and reproduce.
The crisis comes as Lake Powell sits at just 23 percent full, drained by decades of overuse and climate change. With the worst snowpack on record for the Colorado River Basin, the situation has become urgent. Officials project water temperatures that would shatter records set in 2022, when smallmouth bass were first discovered below the dam. Cool water releases in 2024 and 2025 successfully prevented spawning, proving the method works—but at a cost that utilities and power customers say they can no longer bear.
The dilemma pits conservation against immediate financial hardship. Releasing water from the deep, cold sections of the reservoir means bypassing turbines, forcing utilities to spend millions buying alternative electricity. Ratepayers downstream could see higher bills. Yet supporters of the releases, including officials at the U.S. Fish and Wildlife Service, point out the cost of inaction: losing an iconic trout fishery world-famous among anglers, and potentially watching a species edge closer to extinction. "There is a limited water supply. It's getting even lower. And with that, a lot of hard decisions need to be made," said John Berggren, regional policy manager for the environmental nonprofit Western Resource Advocates.
The Colorado River system itself—relied upon by farmers, industries, wildlife and more than 40 million people across seven U.S. states, tribal nations, and Mexico—hangs in the balance. The region's seven states have failed to reach a long-term agreement on how to share the river's dwindling resources beyond this year, when current guidelines expire. Every decision about water allocation now carries ripple effects far beyond the Grand Canyon.
The Bureau of Reclamation is expected to announce its decision within weeks, weighing ecological health against hydropower production. If approved, cool water releases would likely operate from June through October via jet tubes that bypass the surface generators entirely. The decision will reveal whether the region is willing to pay a steep price for an ancient fish, or whether economic pressures will outweigh conservation. Either way, it marks a turning point: a moment when the Colorado River's scarcity forces a choice between competing visions of what the region values most.