Big Springs Lemhi River Confluence Restoration Project

This project proposed to restore 1.15 miles of instream habitat on the Lemhi River and Big Springs Creek at their confluence. Big Springs Creek is a tributary of the Lemhi River, is a spring fed channel collecting groundwater and minor surface water from the south and is entirely contained on the Leadore Land Partners Conservation Easement, held by Lemhi Regional Land Trust. The opportunity to address limiting factors on Big Springs and the Lemhi River has resulted from the easement closing. The confluence section of Big Springs and the Lemhi River is lacking riparian habitat, is over-straightened, and over widened. The project area has been heavily impacted by historic land use practices which have reduced channel complexity, floodplain connection, and riparian vegetation resulting in degraded habitat for anadromous fish.

In 2018, approximately 0.18 miles of the project area on the Lemhi River was completed rather than the entire 1.15 miles as planned due to delays in permitting. The project instream work window is July 1 – August 31 and the delay in cultural clearance did not leave time for the project to be completed in 2018. Additionally, the project timeline overall was underestimated as the level of design detail was more detailed than local contractors were accustomed to. These two factors increased the cost of the project.

The Lemhi Regional Land Trust applied for additional funding from the Idaho PCSRF program to complete the project and was awarded funds in November 2018. Phase 2 of the project, to complete the instream habitat actions on the remaining 0.97 miles of stream, will be completed through PCSRF-funded project 005 18 SA in 2019.

Project actions completed during this phase (Phase 1) included adding meanders within the 0.18 miles of stream treated and excavating 3 pools. Thirteen structures were placed in the channel including anchored individual logs, logs fastened together, stumps with roots attached, and other engineered structures. These structures included willow clumps and small wood clusters.

Riparian work included planting native grass, forbes, and tree species along both sides of the stream for 0.36 miles of streambank, which treated approximately 2.5 acres of riparian area. Livestock exclusion fencing was constructed along 0.15 mile of stream protecting 2.5 acres of riparian areas.

This project was a cooperative effort between the Lemhi Regional Land Trust, multiple private landowners, neighboring water users, Trout Unlimited, Bureau of Reclamation, Idaho Department of Fish and Game, and the Upper Salmon Basin Watershed Project. Matching funds were provided by the Bonneville Power Administration.

The goals of this project are to establish riparian vegetation to provide cover to reduce stream temperatures and to reduce erosion and sediment delivery to the stream and spawning gravels. It will also develop channel complexity in a stream that has been documented to support salmon and steelhead spawning. The project work proposed is expected to result in immediate and tangible benefits to salmon, which makes this stream a First Priority stream under the NMFS proposed recovery plan, which further directs restoration work be conducted first in streams that support salmonid spawning and rearing.