Lemhi RM32 Habitat Enhancement Project, Confluence Phase

The Confluence Phase of the RM32 Habitat Enhancement Project will improve 1.19 miles of habitat on the Lemhi River and Hayden Creek. Hayden Creek is the most productive tributary of the Lemhi River, containing up to 40 percent of the spawning Chinook Salmon in the basin each year along with populations of Steelhead and Bull Trout. This section of the Lemhi River is currently a single channel system with high gradient and little to no rearing and overwintering habitat. This project includes raising riffles in the existing Lemhi River, grading inlets to relic side channels, grading new channels and floodplains along side channels, and installing instream wood structures which will improve and expand the riparian corridor and create off channel habitat and a side channel network allowing juvenile salmonids the opportunity to stay in the Lemhi basin longer before moving downriver. The project will also improve the L-40 diversion to reduce maintenance of the existing wing dam and headgate infrastructure and improve operational functionality. Fencing will protect the project from cattle after completion, and both plants and seeds will be installed. The site will be treated for noxious weeds. Trout Unlimited is the project sponsor and is working in partnership with the U.S. Bureau of Reclamation, Lemhi Soil and Water Conservation District, The Nature Conservancy, and the Upper Salmon Basin Watershed Program.

Expanding and enhancing side channel habitat will improve habitat capacity for juvenile Chinook Salmon and steelhead. Reactivating relic side channels and grading new channels will widen the riparian corridor and provide more habitat for fish, while wood structures will add habitat complexity. Constructing riffles in the existing Lemhi River channel will lead to more floodplain activation which will increase the amount of fish habitat and improve the current riparian vegetation. The project’s location downstream of spawning grounds on the Lemhi River and Hayden Creek provides an opportunity to provide habitat for rearing parr and overwintering pre-smolts, keeping them in the Lemhi River longer.