A fish passage project on a tributary to the North Platte River near Encampment will make it easier for fish to move upstream to spawn without obstacles.

The Big Creek Fish Passage project involved installing a rock ramp “fishway” to help trout and native fish species move upstream past the existing Henry and Casteel Diversion Dam on Big Creek. The diversion dam, located on privately owned Big Creek Ranch, is a concrete structure that spans the stream channel and has two headgates, with one on each side of the river.

Big Creek is a wild trout fishery, containing brook, brown and rainbow trout, as well as native white sucker and longnose dace. It’s also an important spawning tributary for brown trout and rainbow trout from the North Platte River, which move up the stream to lay their eggs. A 2014 study on Big Creek showed that in good flow years, adult brown trout may pass over the dam, but on low flow years there is not enough water for fish to swim up the steep surface of the dam.

In an effort to improve fish passage and increase spawning habitat availability, Aquatic Habitat Biologist Christina Barrineau worked with Big Creek Ranch, Green Watershed Restoration and WWC Engineering to design a structure that allows fish to pass while still meeting the ranch’s irrigation needs. Left Hand Excavating was contracted to implement the project. The Wyoming Wildlife Natural Resource Trust was a major funder and other partners include Big Creek Ranch, A Bar A Ranch, Trout Unlimited, U.S. Forest Service, Saratoga Encampment Rawlins Conservation District, Wyoming Governor’s Big Game License Coalition, and the Bureau of Land Management.

The project involved constructing a grouted rock ramp on the downstream side of the dam. The new ramp has a slope of 40 percent compared to the previous steep slope of 10 percent. The flatter slope makes it easier for fish to pass over the structure. Strategically placed rocks along the ramp provide important resting areas for fish on their way upstream. A large boulder grade control structure was placed downstream of the rock ramp fishway to assist in making the flatter stream slope. The project will also allow trout to re-colonize areas impacted by last year’s Beaver Creek Fire.

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