Colorado Parks and Wildlife (CPW) has confirmed a “large-scale fish kill” along a 7.2-mile stretch of the Rio Grande below Del Norte after the river channel was dried during a restoration project.
The incident occurred in connection with the Farmers Union Canal Diversion and Headgate Improvement project, part of the Rio Grande Headwaters Restoration initiative. According to CPW, a construction-related decision resulted in rapid dewatering of the north branch of the river, leading to significant ecological damage.
Thousands of fish affected
Officials from Colorado Parks and Wildlife said multiple species were impacted, including brown trout, rainbow trout, brook stickleback, longnose dace, fathead minnows and white suckers.
“A significant number of fish across all age classes died,” said John Livingston, CPW’s southwest region public information officer. Trout ranging from two inches to 24 inches were found dead.
Additional losses include northern leopard frogs and aquatic invertebrates such as mayflies and stoneflies. Brown trout eggs laid in autumn are also believed to have been destroyed.
Investigation and recovery concerns
CPW teams collected dead fish, though officials acknowledged that many were scavenged or trapped in frozen pools. Biologists estimate it could take three to five years for the fishery to recover.
The affected stretch is also habitat for the federally endangered southwestern willow flycatcher and the federally threatened western yellow-billed cuckoo, raising further ecological concerns.
The diversion project reportedly received nearly $1.3 million in funding from the U.S. Bureau of Reclamation and involves collaboration with local irrigation authorities.
CPW stated it is continuing its investigation and assessing long-term impacts on the riparian ecosystem. Landowners along the river have expressed frustration over the incident, calling for accountability and remedial measures.