LAS VEGAS (KLAS) — Setting the course for a Colorado River with less water is an enormous challenge that’s not likely to satisfy everyone. And climate change has created a collision course with wildlife.

The river isn’t just managed to accommodate people. Governments are also responsible for the ecosystems that sustain fish, birds and other animals. The U.S. Fish and Wildlife Service (USFWS) is an important player in the battle that’s ahead. A letter submitted by USFWS to the Bureau of Reclamation has as many questions as answers.

Four fish species are at the forefront: “The endangered Colorado pikeminnow, razorback sucker, and bonytail, along with the threatened humpback chub, evolved in the Colorado River basin and exist nowhere else on earth,” according to the U.S. National Park Service. According to USFWS, the Lower Basin is home to 27 Endangered Species Act “listed and sensitive species.”

Humpback chub. (Photo: Arizona Game & Fish Department)

As agencies weigh in on how to manage the river in the future, they are asking Reclamation to tell them precisely the water conditions they might have to deal with in protecting wildlife. It’s uncharted territory.

Reclamation is working to build a new agreement as a set of rules from 2007 nears expiration. The agency has released a segment of the comments submitted by government agencies, tribes and environmental advocates, indicating that more will come “on a rolling basis.” So far, more than 700 pages of comments have been posted on Reclamation’s website. This is the third article in a series as 8 News Now looks at some of those comments.

The eight-page letter from the Fish and Wildlife Service is a glimpse at how the enormous decisions ahead will affect fish and migratory birds. Many conservation organizations including the Audobon Society, the Nature Conservancy and the Sierra Club have lined up to fight for wildlife.

In Las Vegas, Lake Mead is an important recreation area where people fish and enjoy boating and swimming. But below the biggest reservoir in the U.S., the river is home to four national wildlife refuges, along with a fifth in California at the Salton Sea. They are:

  • Havasu National Wildlife Refuge
  • Bill Williams National Wildlife Refuge
  • Cibola National Wildlife Refuge
  • Imperial National Wildlife Refuge
  • Sonny Bono Salton Sea National Wildlife Refuge

“Refuge management relies in part on water that passes through and that is diverted from the Colorado River and the four NWRs in Arizona serve as integral components of the LCR MSCP (Lower Colorado River Multi-Species Conservation Program),” the USFWS letter says.

“These five NWRs are vital to the ecology of the region. These refuges provide breeding grounds for migratory birds and other wildlife, and the protection of natural resources and conservation of several federally listed species. The four river refuges are some of the only large tracts of natural terrestrial vegetation remaining on the lower Colorado River,” the USFWS letter says.

As an example of the detail needed to respond to Reclamation, here’s one of eight requests in USFWS’s letter:

“Please ensure models also examine and predict how water reductions will affect the amount of water draining from Imperial Irrigation District and Coachella Valley Water District irrigation drains. The analysis should include the location and acreages of existing marshes at the end of those drains and how water reductions may change the size and location of the marshes and how that could impact resident Desert pupfish (Cyprinodon macularius) and Yuma Ridgway’s rail (Rallus obsoletus yumanensis) as existing marsh areas dry.”

While wildlife officials try to protect native species, one part of the job is to control non-native fish. An ongoing program to stop the spread of “predatory” smallmouth bass below Glen Canyon Dam involves several federal agencies.

Juvenile smallmouth bass sit at a National Park Service laboratory near Page, Ariz., July 1, 2022. Confirming their worst fears for record-low lake levels, NPS fisheries biologists have discovered that smallmouth bass, a non-native predator fish, has made its way through Glen Canyon dam and appear to have spawned in the lower Colorado River, where it can prey on humpback chub, an ancient native fish they have been working to reestablish. (Jeff Arnold/National Park Service via AP)

As the temperature of the river has warmed during climate change and the drought, smallmouth bass have thrived in some areas. Comments to Reclamation include many references to the bass and how various proposals — including those suggesting that Glen Canyon Dam be decommissioned — might affect efforts to control the fish.

The “emergency” release at Glen Canyon that sent a massive amount of extra water out of the dam in late April had many purposes, one related to controlling the bass population. The release simulates natural flooding and helps to rebuild sandbars below the dam.

NEXT: The Salton Sea is California’s largest lake, and it could become an environmental disaster as the drought continues.