Native fish populations are returning more quickly than anticipated in the Colorado River Connectivity Channel near Granby.

This news is according to the latest Colorado Parks and Wildlife electrofishing survey of the trout population along the newly constructed 1-mile river channel. In May, Parks and Wildlife biologists estimated that approximately 848 brown trout and 221 rainbow trout over 6 inches in length live within the channel. 

The $33 million connectivity channel project sought to establish connectivity along the Colorado River after the construction of the 445-acre-foot Windy Gap Reservoir in 1985 disrupted flows in the region. The reservoir and dam — which were constructed to help divert water to two northern Front Range cities — impacted stream flows, caused sediment buildup and decimated fish populations. 

The Colorado River Connectivity Channel project was led by a coalition group that included the reservoir’s operator, Northern Water. It was completed in the fall of 2023. 

While the full benefits of the connectivity channel could take years to manifest, the latest fish survey, as well as one conducted in 2024, already show river health improving, Parks and Wildlife reported.

The fall 2024 survey found evidence of native sculpin — a bottom-dwelling fish — returning to the upper Colorado River and new channel after several decades of absence in nearly 30 miles of their former habitat. In a news release, Dan Kowalski, Parks and Wildlife’s aquatic research scientist, said their return was “a good indication that the channel is starting to improve the ecological health of the river.”

Jon Ewert, Parks and Wildlife’s Hot Sulphur Springs aquatic biologist, said in the release that the discovery of healthy adult trout was particularly exciting since the agency has not stocked any fish in the channel. 

According to the agency, biologists have also observed “extensive” brown trout spawning activity and “moderate” rainbow trout spawning activity in the channel. 

“Seeing such positive results with water flowing through this new river section for just over a year, we anticipate that this fish population will continue to grow,” Ewert stated in the release.

Currently, the new river section is closed to public fishing access. Parks and Wildlife expects to open it after the area has had sufficient time to fully revegetate, which it reports will take a couple more growing seasons.