Large-scale fish kill on the Rio Grande

Restoration project dries up 7.2-mile stretch, killing trout and other species

Published on Feb. 23, 2026

Got story updates? Submit your updates here. ›

Colorado Parks and Wildlife has confirmed a 'large-scale fish kill' along the Rio Grande below Del Norte, Colorado, that was the result of a 7.2-mile stretch of the river being dried up as part of a river restoration project. Biologists say it could take 3-5 years to recover the fishery.

Why it matters

The fish kill has impacted a diverse range of aquatic species, including endangered and threatened wildlife, and threatens the overall health of the Rio Grande ecosystem. The incident has raised concerns about the oversight and planning of the restoration project.

The details

During construction on the Farmers Union Canal Diversion and Headgate Improvement project, a decision was made that caused the ecological disaster. A significant number of fish across all age classes, including brown and rainbow trout, were found dead. Other impacted species include brook stickleback, longnose dace, fathead minnow, white sucker, northern leopard frogs, and aquatic invertebrates. CPW faces challenges in determining the full extent of the fish kill due to scavenging by wildlife.

  • On Feb. 3, a landowner notified CPW that the north branch of the Rio Grande east of Del Norte was being dewatered and fish were dying or dead.
  • On Monday, a team of nine CPW staff walked stretches of the river channel and collected as many fish as they could.

The players

Colorado Parks and Wildlife

The state agency responsible for managing and protecting Colorado's wildlife and natural resources.

Rio Grande Headwaters Restoration Project

The organization overseeing the Farmers Union Canal Diversion and Headgate Improvement project that led to the fish kill.

San Luis Valley Irrigation District

The district partnering with the Rio Grande Restoration Project on the canal diversion project.

Got photos? Submit your photos here. ›

What they’re saying

“There were too many dead fish for the team to collect them all.”

— John Livingston, Southwest region public information officer for CPW (Alamosa Citizen)

“A significant number of the fish populations in that stretch died across all age classes. Brown and rainbow trout as small as two inches and up to 24 inches have been found, along with all sizes in between.”

— John Livingston, Southwest region public information officer for CPW (Alamosa Citizen)

What’s next

CPW is concerned about the impacts to other species and the overall riparian corridor, and is working with landowners to investigate the incident further. Aquatic biologists estimate it could take 3-5 years to recover the fishery.

The takeaway

This fish kill highlights the need for thorough environmental impact assessments and careful planning when undertaking major river restoration projects, to avoid unintended ecological disasters that can take years to recover from.