River Restoration Project Triggers Massive Fish Kill on the Rio Grande

Development on a federally funded canal enchancment close to Del Norte, Colorado, dewatered 7.2 miles of the river, killing trout and native fish throughout all age courses in numbers too massive for a nine-person crew to gather. Biologists say restoration will take three to 5 years. Photos courtesy of CPW

Colorado Parks and Wildlife has confirmed a “large-scale fish kill” alongside the Rio Grande beneath Del Norte after a river restoration mission dried up 7.2 miles of channel throughout a winter chilly snap. The kill worn out brown trout and rainbow trout from 2-inch fingerlings to 24-inch adults, together with native species which have inhabited the higher Rio Grande for millennia.

The catastrophe stems from the Farmers Union Canal Diversion and Headgate Improvement project, which received $1.27 million by way of a Bureau of Reclamation WaterSMART grant. The mission—led by the Rio Grande Headwaters Restoration Project and the San Luis Valley Irrigation District—was designed to exchange an getting older diversion dam and headgates on the Farmers Union Canal, which bifurcates the Rio Grande into its north and south channels downstream of Del Norte. The brand new infrastructure was supposed to enhance irrigation effectivity for 140 water customers throughout roughly 43,000 acres whereas including fish and boat passage.

As an alternative, a development choice dewatered the river’s north department.

What Occurred

A landowner contacted CPW on February 3 to report that the north department of the Rio Grande east of Del Norte was going dry and fish had been dying. CPW investigators confirmed the dewatering was linked to the canal mission. On February 16, a nine-person CPW crew walked the affected channel to gather useless fish. They ran out of capability earlier than they ran out of carcasses.

“There have been too many useless fish for the staff to gather all of them,” stated John Livingston, CPW’s southwest area public data officer.

Farmers accustomed to the mission instructed the Alamosa Citizen {that a} “hasty choice” was made to push development ahead throughout a chilly spell this winter, drying the river by way of non-public corridors of the Rio Grande. Speedy dewatering in subfreezing circumstances left fish stranded in shrinking swimming pools, the place they froze or suffocated. CPW stated scavengers—birds, raccoons, skunks, foxes—moved in earlier than biologists may tally the total toll.

Harm Past Trout

The kill extends properly previous the sportfish that draw anglers to this stretch. CPW’s investigation documented useless brook stickleback, longnose dace, fathead minnow, and white sucker. Northern leopard frogs and aquatic invertebrates—mayflies, caddisflies, stoneflies—additionally perished.

The attain harbors an aboriginal inhabitants of Rio Grande chub (Gila pandora), a Tier 1 Species of Greatest Conservation Need below Colorado’s State Wildlife Motion Plan and a state Species of Particular Concern. Traditionally the most typical fish within the Rio Grande basin, the chub has declined dramatically resulting from habitat loss, water diversions, and predation by nonnative species. CPW and its companions have spent many years working to prevent federal listing of the chub and the associated Rio Grande sucker — stocking almost 1.2 million chub into 11 waters since 2002. Dropping an aboriginal inhabitants in the principle stem undercuts that effort.

The affected stretch additionally serves as nesting and rearing habitat for 2 federally protected fowl species: the endangered southwestern willow flycatcher and the threatened western yellow-billed cuckoo. Neither overwinters within the attain, however each rely upon its riparian hall every spring and summer season.

Restoration Timeline

CPW aquatic biologists estimate the fishery on this 7.2-mile part will want three to 5 years to recuperate. The kill eradicated a number of year-classes of trout, and brown trout eggs deposited within the riverbed gravel throughout final autumn’s spawn had been almost definitely misplaced. That loss compounds the harm: the attain gained’t start producing its personal wild brown trout recruits till surviving or recolonizing fish full a full spawning cycle.

The affected attain lies simply downstream of the Rio Grande’s Gold Medal section between South Fork and Del Norte—water CPW has designated for its trophy-caliber trout density and dimension. Fish transfer between the 2 stretches, and the lack of a number of age courses beneath Del Norte may gradual recruitment into the Gold Medal hall as properly. Anglers planning journeys to the San Luis Valley this spring or summer season ought to count on diminished fishing in and across the affected attain and will wish to give attention to water properly upstream of Del Norte till the inhabitants rebuilds.

A Restoration Challenge’s Unintended Consequence

The Rio Grande Headwaters Restoration Challenge has a powerful observe document. Since its founding in 2001, the nonprofit has replaced aging diversions, stabilized eroding streambanks, and restored fish passage alongside dozens of miles of the higher Rio Grande. Its 5 Ditches mission, accomplished in 2020, improved habitat and irrigation infrastructure for a number of ditch firms between Del Norte and Alamosa.

The Farmers Union Canal mission was constructed on the identical mannequin: modernize infrastructure, profit each irrigators and the river. The Bureau of Reclamation awarded the $1.27 million WaterSMART grant in late 2023, and development was scheduled throughout the 2025–2026 window.

What went improper was timing. Diverting flows throughout a winter freeze—when fish are physiologically confused and have nowhere to go—turned a routine development step into an ecological disaster. CPW has not but publicly launched an in depth discovering on accountability or enforcement actions associated to the incident.

The Alamosa Citizen reported that it was searching for remark from Daniel Boyes, government director of the Rio Grande Headwaters Restoration Challenge. Neither the group nor the San Luis Valley Irrigation District had issued a public assertion addressing the fish kill as of this writing.

“CPW needs to thank the landowners alongside the river for his or her cooperation and for offering entry to the river for this investigation, and CPW shares their issues concerning this incident,” Livingston stated.