Bohannon Creek #3 Diversion Removal-PCSRF

Bohannon Creek, tributary to the Lower Lemhi River, is seasonally dewatered in its lower segments due to surface irrigation water withdrawals. Water rights decreed from Bohannon Creek exceed the base flow capacity of the tributary. Some of the most senior priority water rights are served from the lowermost diversion, Bohannon Creek #3. Extraction of these rights results in the disconnection of this tributary from the Lemhi River, and adult and juvenile Chinook salmon are unable to access good quality spawning and rearing habitat. To address this condition, the Idaho Department of Fish and Game (IDFG) completed a project to substantially improve stream flow over existing conditions. The goal of this project was to establish a functional connection for fish in the previously dewatered stream segment in lower Bohannon Creek. To accomplish this goal, IDFG implemented a project that “spilled” the previously extracted water to the mouth of Bohannon Creek. Two separate irrigation systems were then installed for the water users to recapture this flow from the Lemhi River and deliver it to the historic place of use.

Project actions included the following:

Worksite 1-Bohannon Creek #3 Diversion –
1. Physically removed the Bohannon Creek #3 diversion.
2. Removed an existing IDFG-managed fish screen.

Worksite 2, Water User #1 –
1. Completed water right transfers to ensure the delivery of irrigation water down Bohannon Creek to the Lemhi River, and the extraction of equal amounts of this spilled water from the Lemhi River to the Place of Use.
2. Installed irrigation system infrastructure to extract irrigation water from the Lemhi River, which included more than 10,000 feet of irrigation line to serve two primary irrigation pivots and hand and wheel lines, a new diversion/check structure, and a pump station.
3. Established a water rights agreement through the Idaho Water Board that ensures the waters rights will be extracted from the Lemhi River through 2038 and provide compensation for operations costs (e.g. commercial power) related to the project.

Worksite 3, Water User #2 –
1. Completed water right transfers to ensure the delivery of irrigation water down Bohannon Creek to the Lemhi River, and the extraction of equal amounts of this spilled water from the Lemhi River to the Place of Use.
2. Installed irrigation system infrastructure to extract the irrigation water from the Lemhi River, which included approximately 7,000 feet of irrigation line, installation of three irrigation pivots, a pump station, and diversion structure.
3. Established a water rights agreement through the Idaho Water Board to ensure the water rights will be extracted from the Lemhi River through 2038 and provide compensation for operation costs (e.g. commercial power) related to the project.

Idaho Power installed a new power line to provide commercial power to both water users 1 and 2. Additionally, a water gauge was installed at worksite 2 and worksite 3.

IDFG completed this project in collaboration with the upper Salmon Basin Watershed Program Technical Team. IDFG coordinated directly with two private landowners for their acceptance and approval of the project, and also partnered with Idaho Department of Water Resources, Natural Resources Conservation Service, and Idaho Power to implement critical components of the project. IDFG worked directly with the National Marine Fisheries Service, U.S. Fish and Wildlife Service, Bonneville Power Administration, and the U.S. Army Corps of Engineers to secure necessary permits and resource compliance. Match funding was provided by the Bonneville Power Administration. Non-match funding was provided by Natural Resources Conservation Service EQIP funds.

This project will address the tributary reconnection objective prescribed in the Lemhi Framework that supports the comprehensive water rights settlement in the SRBA. Bohannon Creek is one of the most prioritized tributaries identified for reconnection in the lower Lemhi River because of its biological importance in providing critical spawning and rearing habitat for anadromous fish. Removal of BC3 will maintain continuous flow throughout Bohannon Creek, substantially improving rearing condition for steelhead. Salmon and steelhead produced in other areas of the basin will be able to access cooler water in the watershed for rearing during summer, adult salmon will have access to the tributary for spawning, and adequate flow will be available for seaward migrating smolts.