The Colorado River is shrinking faster than ever. Evaporation and overuse have reduced the capacity of its major reservoirs—Lake Powell and Lake Mead—to 23 % and 12 % of their normal levels, respectively. In this context, the U.S. Bureau of Reclamation is confronting a decision that pits ecological stewardship against consumer cost: should Glen Canyon Dam release cold water from its bottom tiers (a so‑called *cool‑mix* operation) to protect threatened fish species, or should it maintain maximum hydropower generation?
## What is a cool‑mix release?
Glen Canyon Dam’s power plant draws water from near the surface of Lake Powell, where temperatures can rise well above 60 °F (16 °C) in the summer. That warm water, when drawn through the turbines, flows downstream and heats the river. Fish species such as the federally protected humpback chub, which thrives in cooler waters, face mounting pressure from introduced predators like smallmouth bass that survive the turbines and thrive in the warm downstream flow.
A cool‑mix release pulls water from deeper in the reservoir, where temperatures stay around 45 °F (7 °C), and discharges it through jet tubes that bypass the turbines. This would lower downstream temperatures, limiting sweet‑spot conditions for bass spawning that threaten the chub and the world‑famous trout fishery in Marble Canyon.
During a pilot cool‑mix project in 2024, the Bureau diverted roughly 900,000 acre‑feet of cold water, diverting most of it from turbines and incurring an estimated **$19 million** in replacement energy costs. The draft cost for 2025 is projected at roughly **$25 million**.
## Ecology vs. economics
Environmental groups argue that the ecological risk of letting bass thrive outweighs the cost of the release. If the river stays too warm, we’re doomed to lose not only the humpback chub but also the entire riparian ecosystem that depends on it, said Heather Whitlaw, a U.S. Fish and Wildlife Service field supervisor. We’re giving up the future for short‑term savings.
Utilities that purchase federal hydropower—about 155 customers represented by the Colorado River Energy Distributors Association—warned that bypassing even half of the dam’s potential generation would force them to buy expensive alternative power. The association requested that remediation costs not exceed $20–30 million per year but noted that the recent pilot already reached $19 million.
Emily Brandt, an energy resource manager at Heber Light & Power in Utah, highlighted the broader impact on consumers: The ongoing loss of generation from drought, and now from this environmental experiment, has already forced us to raise rates five times in the last five years. Pricing electricity has become unsustainable for many customers.
Ann Moulton of Heber City reported her April bill rose from $86 USD in 2024 to $126 USD in 2025, a 45 % increase over a 12‑month period. The rise has spurred more late payments, from 10 % to 12 % over the past two years.
## The downstream fishing community
Guides in Marble Canyon, known for its rainbow trout, have experienced dramatic losses. In 2022 a warm‑water die‑off wiped out nearly half of the trout population that feeds the tourist economy. In the face of these losses, many guides, including Dave Foster, insist that without cool releases they will not survive:
> We’re going to lose the fishery. There’s no ambiguity about it, Foster told the AP. If the water gets too warm, we’ll have to cancel trips; the trout will die.
Cool water releases in earlier years have mitigated the 2022 die‑off, and the 2024 pilot helped keep temperatures below the breaching threshold. Critics of the program view it as an expensive “experiment” that offers limited long‑term benefit.
## Decision pending
The Bureau of Reclamation is expected to announce its stance in the next couple of weeks. It is weighing several factors: the *ecological health* of the Colorado River, the *hydropower productivity* of Glen Canyon Dam, and the *economic impact* on utilities and ratepayers. The Interior Department has declined to comment.
The decision will come at a time when the states and tribal nations that rely on the river have yet to reach a long‑term agreement on water allocation for the 2027 cycle, the guidelines scheduled to expire this year. Meanwhile, the river remains the artery of the Southwest, sustaining *more than 40 million people* across seven U.S. states, tribal nations and Mexico.
As the Colorado River braces for a hot, dry summer, the outcome of the cool‑mix debate will shape not only the river’s ecological future but also the financial burden on its human users.
---
[AP coverage on the Colorado River](https://apnews.com/article/colorado-river-drought-water-snow-record-west-d204acb04bdac2524071b6bd627e4665),
[Joint Texas‑Wyoming water agreement discussions](https://apnews.com/article/colorado-river-lake-mead-lake-powell-d94d5a36398d2a34be7e2c4d10ef1bf6),
[Study on smallmouth bass survival](https://digitalcommons.usu.edu/etd2023/288/),
[Trout die‑off in Marble Canyon](https://apnews.com/article/travel-lakes-colorado-river-canyons-0d2fa09dc285d4a7aafee9402565dde3)
## What is a cool‑mix release?
Glen Canyon Dam’s power plant draws water from near the surface of Lake Powell, where temperatures can rise well above 60 °F (16 °C) in the summer. That warm water, when drawn through the turbines, flows downstream and heats the river. Fish species such as the federally protected humpback chub, which thrives in cooler waters, face mounting pressure from introduced predators like smallmouth bass that survive the turbines and thrive in the warm downstream flow.
A cool‑mix release pulls water from deeper in the reservoir, where temperatures stay around 45 °F (7 °C), and discharges it through jet tubes that bypass the turbines. This would lower downstream temperatures, limiting sweet‑spot conditions for bass spawning that threaten the chub and the world‑famous trout fishery in Marble Canyon.
During a pilot cool‑mix project in 2024, the Bureau diverted roughly 900,000 acre‑feet of cold water, diverting most of it from turbines and incurring an estimated **$19 million** in replacement energy costs. The draft cost for 2025 is projected at roughly **$25 million**.
## Ecology vs. economics
Environmental groups argue that the ecological risk of letting bass thrive outweighs the cost of the release. If the river stays too warm, we’re doomed to lose not only the humpback chub but also the entire riparian ecosystem that depends on it, said Heather Whitlaw, a U.S. Fish and Wildlife Service field supervisor. We’re giving up the future for short‑term savings.
Utilities that purchase federal hydropower—about 155 customers represented by the Colorado River Energy Distributors Association—warned that bypassing even half of the dam’s potential generation would force them to buy expensive alternative power. The association requested that remediation costs not exceed $20–30 million per year but noted that the recent pilot already reached $19 million.
Emily Brandt, an energy resource manager at Heber Light & Power in Utah, highlighted the broader impact on consumers: The ongoing loss of generation from drought, and now from this environmental experiment, has already forced us to raise rates five times in the last five years. Pricing electricity has become unsustainable for many customers.
Ann Moulton of Heber City reported her April bill rose from $86 USD in 2024 to $126 USD in 2025, a 45 % increase over a 12‑month period. The rise has spurred more late payments, from 10 % to 12 % over the past two years.
## The downstream fishing community
Guides in Marble Canyon, known for its rainbow trout, have experienced dramatic losses. In 2022 a warm‑water die‑off wiped out nearly half of the trout population that feeds the tourist economy. In the face of these losses, many guides, including Dave Foster, insist that without cool releases they will not survive:
> We’re going to lose the fishery. There’s no ambiguity about it, Foster told the AP. If the water gets too warm, we’ll have to cancel trips; the trout will die.
Cool water releases in earlier years have mitigated the 2022 die‑off, and the 2024 pilot helped keep temperatures below the breaching threshold. Critics of the program view it as an expensive “experiment” that offers limited long‑term benefit.
## Decision pending
The Bureau of Reclamation is expected to announce its stance in the next couple of weeks. It is weighing several factors: the *ecological health* of the Colorado River, the *hydropower productivity* of Glen Canyon Dam, and the *economic impact* on utilities and ratepayers. The Interior Department has declined to comment.
The decision will come at a time when the states and tribal nations that rely on the river have yet to reach a long‑term agreement on water allocation for the 2027 cycle, the guidelines scheduled to expire this year. Meanwhile, the river remains the artery of the Southwest, sustaining *more than 40 million people* across seven U.S. states, tribal nations and Mexico.
As the Colorado River braces for a hot, dry summer, the outcome of the cool‑mix debate will shape not only the river’s ecological future but also the financial burden on its human users.
---
[AP coverage on the Colorado River](https://apnews.com/article/colorado-river-drought-water-snow-record-west-d204acb04bdac2524071b6bd627e4665),
[Joint Texas‑Wyoming water agreement discussions](https://apnews.com/article/colorado-river-lake-mead-lake-powell-d94d5a36398d2a34be7e2c4d10ef1bf6),
[Study on smallmouth bass survival](https://digitalcommons.usu.edu/etd2023/288/),
[Trout die‑off in Marble Canyon](https://apnews.com/article/travel-lakes-colorado-river-canyons-0d2fa09dc285d4a7aafee9402565dde3)
