The river that supplies 40 million Americans is down to 23% — and about to make a $25 million bet on one fish

With the Colorado River and its extensive reservoirs diminishing due to factors such as overuse and climate change, authorities are confronted with a challenging choice that juxtaposes environmental conservation against the economic impact on electricity ratepayers.

In order to combat the threats posed by non-native predators to the humpback chub, a fish species that is endangered and indigenous to the river, the Glen Canyon Dam in northern Arizona would need to implement a strategy known as "cool mix flow." This involves releasing cooler water from deeper sections of the reservoir to lower temperatures in the river downstream. However, this approach would not utilize the hydropower turbines situated in the cooler depths, resulting in a significant reduction in power generation.

This proposal emerges in the wake of the Colorado River Basin experiencing its worst recorded snowpack, impacting farmers, industries, wildlife, and over 40 million residents across seven U.S. states, tribal nations, and parts of Mexico. Furthermore, there is an ongoing failure among those states to establish a long-term agreement detailing how to distribute the dwindling resources of the river beyond the current year, which sees existing guidelines set to expire.

"There is a limited water supply. It's getting even lower. And with that, a lot of hard decisions need to be made," remarked John Berggren, regional policy manager for the environmental nonprofit Western Resource Advocates.

Utilities that procure hydropower express concern that these cooler water releases could prove to be financially burdensome, as they would need to invest millions into purchasing alternative energy sources, thus imposing additional financial strain on consumers. Conversely, advocates for the cool water releases argue that failing to implement this measure would create warm conditions conducive to the spawning of non-native predatory fish, further endangering the humpback chub and jeopardizing a renowned trout fishery in the vicinity.

The Bureau of Reclamation, expected to make an announcement in the coming weeks, stated that it is carefully considering several factors, including the ecological integrity of the river and the hydropower output from the dam. The Interior Department, which oversees the Bureau, has opted not to provide further comments. Should the cool water release be sanctioned, it is anticipated to occur from June to October via jet tubes, which would divert water away from the turbines located at the surface.

How mixing cool water protects fish

Lake Powell, one of the two significant reservoirs on the Colorado River, stands at just 23% capacity, a consequence of prolonged overuse and evaporation exacerbated by increasing average temperatures attributed to climate change. An unprecedented low inflow is predicted for the upcoming summer. Given the low water levels, warmer water close to the surface is directed through the generators and released downstream.

Smallmouth bass, a species introduced to Lake Powell in the 1980s for recreational fishing, thrive in these warmer surface waters and are also drawn into the hydropower generators, subsequently finding their way into the river below. This presents a serious issue for the humpback chub and other fish protected under federal law in the Grand Canyon, a renowned 278-mile stretch further along the river known for its geological wonders. Recent studies indicate that approximately half of the bass survive transit through the turbines. If the temperature of the river downstream is sufficiently warm, spawning can occur.

The upper reaches of the river have seen smallmouth bass already preying on the humpback chub, prompting agencies to invest millions annually in efforts to manage the invasive species. While native fish have historically enjoyed greater protection below the Glen Canyon Dam—due to the barrier it creates to the Grand Canyon—this advantage may soon diminish.

Recent forecasts predict that water temperatures just downstream of the dam could surpass records previously set in 2022, when smallmouth bass were first detected in that area. Officials anticipate that temperatures will consistently exceed 60 degrees Fahrenheit (15.5 Celsius) by mid-June, as warm water from Lake Powell is integrated into the river system. Should temperatures rise beyond this threshold, non-native predatory fish that traverse the dam may begin to reproduce.

Officials assert that cool water releases from Lake Powell in 2024 and 2025 effectively thwarted spawning incidents.

Heather Whitlaw, field supervisor with the U.S. Fish and Wildlife Service, underlined the importance of considering the ramifications of not proceeding with the cool mix. "We are certainly just giving up on the future for any kind of recovery for the humpback chub and all of the other pieces of the system that rely on those cooler water temperatures," she stated during a recent meeting focused on this issue.

Given the lack of a long-term strategy to prevent the passage of predators through the dam, refraining from cool water releases would compel officials to depend solely on manual removal methods downstream.

More hydropower loss could further impact utilities

Utilities that depend on hydropower generated from federal sources have expressed concerns about the potential implications of these cool water releases.

Approval for these releases may lead to bypassing nearly half of the generation capacity at Glen Canyon Dam, thereby compelling utilities to source power from alternative, more expensive avenues, as noted by the Utah utility group Heber Light & Power.

"We keep hearing comments that we must continue Cool Mix because the cost of not doing it will be even greater," the Colorado River Energy Distributors Association, which advocates for the interests of approximately 155 customers who purchase federal hydropower from the river and opposes the releases, stated in a recent correspondence to Interior Secretary Doug Burgum. "We would like to understand what remediation would consistently cost more than $20 to $30 million per year."

The association further articulated that these releases do not present a sustainable solution for controlling the reproduction of smallmouth bass, thus endangering a critical fund dedicated to the operation, maintenance, and investment in hydropower and transmission infrastructure.

During the cool water releases in 2024, nearly 900,000 acre-feet of water bypassed the generators, incurring $19 million in replacement energy costs, according to the Bureau of Reclamation. Although the precise amount of water expected to bypass generators this year remains uncertain, the projected cost of replacement is estimated to reach approximately $25 million—akin to the total financial impact on hydropower users from the prior two years combined.

The ongoing decline of hydropower due to Lake Powell's receding water levels has resulted in challenges for Heber Light & Power as population demands increase, as highlighted by Emily Brandt, the utility's energy resource manager. The persistent decrease in available power has contributed to rate escalations over the past five years.

Residents, such as Ann Moulton from Heber City, have observed a continuous rise in their electricity bills, with her residential bill for April reaching $125.98, an increase from previous years that saw bills of $103.24 and $86.14 for the same month. This rise has begun to impact household budgets.

Moreover, many customers are facing financial difficulties, as the utility reported an increase in late payments this year, rising from 10% to 12%.

Brandt emphasized the utility's commitment to supporting fish conservation efforts, asserting, "but this particular experiment seems unnecessary."

"We're already seeing reduced generation from drought, and now we're seeing even further reduced generation because of this environmental experiment," Brandt remarked.

Fisheries downstream are also in limbo

Dave Foster retains vivid memories of the 2022 trout die-off in Glen Canyon, a remote section of river located between the dam and the entry to the Grand Canyon. Warm water conditions resulted in the death of nearly half the rainbow trout population the renowned fishery depends on, according to Foster, who has dedicated much of his career to working in that river stretch since he was 13.

He and fellow guides continue to recover from the aftermath of the die-off, as "the population has simply not rebounded." However, past cool water releases have helped mitigate other negative impacts, and additional releases this year would support their fishery throughout the fall and winter months.

Foster has cautioned clients booking trips past mid-June that cancellations may be necessary should water temperatures rise excessively, as warmer water can induce stress in fish populations. He firmly stated, "Without cool water releases this year, that's it for the trout fishery. There's no ambiguity about it. It will destroy it."