Environment

Colorado River managers propose plan to protect Grand Canyon fish, but some say it's not enough

KUNC | By Alex Hager

Published February 12, 2024 at 7:26 PM MST

The humpback chub is native to the Colorado River, and conservationists worry that dropping reservoir levels may introduce predators to its habitat.

Federal water managers proposed a new plan to protect native fish species in the Grand Canyon, but conservation groups say it doesn’t go far enough.

Water levels in Lake Powell, the nation’s second-largest reservoir, have been dropping to historic lows as the region struggles to rein in demand in response to dry conditions fueled by climate change. Those low water levels have allowed non-native fish to pass through the Glen Canyon Dam, which holds back Lake Powell, and eat native fish that live on the other side, in the portion of the Colorado River that runs through the Grand Canyon.

The native species at issue is the humpback chub, which is found nowhere on earth besides the Colorado River and its tributaries. It was previously considered “endangered,” butwas downlisted to “threatened” in 2021. The fish still receives protections under the Endangered Species Act.

Lake Powell, which began filling in the 1960s, was stocked with non-native fish such as smallmouth bass for recreational fishing in 1982. Smallmouth bass prefer warm water near the reservoir’s surface. Now that the surface of the reservoir is dropping, the fish are able to move low enough to enter the tubes inside Glen Canyon Dam that allow water to pass from one side to the other.

The Bureau of Reclamation, the federal agency which manages the West’s dams and reservoirs, released a draft plan for water releases from the dam in northern Arizona. It proposed five new ways to manage releases from the dam in an effort to keep native fish thriving in the Colorado River below Lake Powell — four of which involve attempts to make the water cooler and disrupt the spawning patterns of non-native fish.

This 2023 diagram shows the tubes through which Lake Powell's fish can pass through to the section of the Colorado River that flows through the Grand Canyon.

Taylor McKinnon, Southwest director for the Center for Biological Diversity, takes issue with two components of the draft plan. The first, he said, is a tangible change.

McKinnon encouraged federal water managers to consider making physical changes to the dam intakes themselves — like adding screens — to prevent fish from passing through.

“The Bureau of Reclamation has lots of very smart engineers on staff,” he said. “The fact that they have not figured out how to do this to date shows that they have not made it a priority.”

The second issue McKinnon described is more of an ideological one. He said federal water managers are not doing enough to look at the long-term viability of the reservoir in the face of a drying climate.

“Federal agencies need to become proactive,” he said. “They need to look at the science. They need to look at the forecasts for future Colorado River flows in one decade, two decades. All that information indicates that Glen Canyon Dam is facing climate-inevitable deadpool and climate-inevitable obsolescence.”

Deadpool is the point at which water in Lake Powell drops too low to pass water through Glen Canyon Dam. A number of conservation groups are encouraging water managers to consider a future where the dam and reservoir are taken out of use.

The Bureau of Reclamation’s draft plan is now in a 45-day public comment period, which begins on February 9, 2024.

This story is part of ongoing coverage of the Colorado River, produced by KUNC in Colorado and supported by the Walton Family Foundation. KUNC is solely responsible for its editorial coverage.