Environmental advocates are looking for answers about a federal program to protect threatened fish in the Grand Canyon.
The program, which was established in 2024, releases cold water from Lake Powell into a stretch of the Colorado River when it’s particularly warm. It’s part of an effort to push out invasive fish, like smallmouth bass, that can eat federally-protected native fish like the humpback chub.
This year, the river is warm enough to trigger the releases, but Reclamation has made no announcements about whether they will take place.
The releases, which are known as “cool mix flows” took place in 2024 and 2025, and Reclamation officials heralded it as an important way to protect native fish. However, the water that would be pushed downstream is caught in the middle of a big, complicated debate about the future of the Colorado River.
The water would come from Lake Powell, the nation’s second-largest reservoir. The reservoir is less than a quarter full, and creeping toward all-time record lows. If water levels in Powell drop much lower, it could force the shutdown of hydroelectric turbines inside Glen Canyon Dam, which holds back the reservoir in Page, Arizona.
The cold water needed for fish protection must pass through a little-used set of backup pipes at the bottom of the dam that do not generate hydropower, rather than the main turbines.
At a time when federal officials are making controversial moves just to keep Lake Powell high enough to keep hydropower turbines spinning, any program to release water from Lake Powell may add stress for Reclamation, the agency responsible for keeping Glen Canyon Dam running.
Jen Pelz, water advocacy director at the Grand Canyon Trust, said monetary losses that could come as a result of lower hydropower output need to be compared to the hard-to-quantify value of a millennia-old native fishery that can’t be replaced.
“We just need to think about what it is we're willing to lose and the values that we cherish,” she said. “[The] Grand Canyon is one of the most iconic landscapes in this country, in the world. In fact, it’s a UNESCO World Heritage Site, and trying to maintain its fishery is integral to maintaining that ecological and cultural integrity of this place.”
Smallmouth bass, the main invasive species that could predate on humpback chub, start to reproduce when water rises to a temperature of 16 degrees Celsius. The cool mix flows are triggered when a certain point on the river climbs above a daily average of 15.5 degrees Celsius.
Data from the U.S. Geological Survey shows that Colorado River water temperatures at Lees Ferry appear to be above that mark. The water there has not fallen below 15.8 degrees Celsius since July 2, with some daytime highs reaching above 18 degrees Celsius.
That data, Pelz said, is likely the same information used by Reclamation as it decides if and when to begin cool mix flows. Yet, they don’t appear to have started releases yet.
Pelz said acting quickly is key to protecting native fish.
“We're at the very start of what's known as an invasion,” she said. “If you can stop that establishment from happening at the start of the invasion, it's much easier and less expensive than if you wait until those non-native fish have really gotten into every part and tributary of the Colorado River.”
A spokesman for the Bureau of Reclamation responded to KJZZ’s questions with a one-sentence written statement.
“The option for cool mix flows remains under consideration by the Department at this time,” he wrote.
This story was produced by KJZZ, the public radio station in Phoenix, and published by KNAU as part of the Arizona Public Media Exchange.