Upper Salmon Basin

The Upper Salmon basin in central Idaho is the easternmost range for the oceangoing fish. This is where they come to spawn and rear the next generation of wild salmon and steelhead.

The basin is a tributary of the Columbia River and includes four large watersheds with more than 7,000 miles of waterways—the Lemhi, the Pahsimeroi, the East Fork and the headwaters of the Salmon River.

These waters once provided remarkably productive spawning and rearing habitat for millions of salmon and steelhead. Now, only thousands of fish return. Threats such as loss of habitat, diverted and reduced water flows and increased stream temperatures keep remaining fish populations at risk.

The basin is known for huge wilderness areas and vast public land, but over half of critical spawning habitat for salmon is located on private land.  

With a diverse team of partners, TNC is leading efforts in the Upper Salmon to balance the needs of salmon and steelhead with the needs of human communities in Idaho. Taking a collaborative approach that unites stakeholders around recovery efforts, TNC Idaho is facilitating strategic land transactions that result in the protection of important stream habitat and increased flows in rivers and streams.

The collective efforts of many in restoring this habitat have been a lifeline for the fish but we remain perilously close to losing our salmon and steelhead. They continue to return in critically low numbers and additional protections and habitat improvements are urgently needed. While actions within Idaho are important and necessary, many of the solutions to recovering Idaho salmon lay well beyond Idaho’s borders. With a focus on supporting an Indigenous-led vision for salmon recovery across the basin, TNC has launched the Columbia Basin Salmon Program across Idaho, Montana, Oregon and Washington to support comprehensive solutions for salmon and steelhead in the region

On the Pahsimeroi River, TNC purchased the Moen Ranch, located on a stretch of river that contains as many as 40% of the salmon spawning areas of the entire river. The river corridor was sold to the Idaho Department of Fish and Game, which manages it as a public fishing and recreation area. Public access to the river is limited along the Pahsimeroi and this partnership opened access to one of Idaho’s gems.

TNC also worked with partners to remove a key fish barrier on the Pahsimeroi River, allowing salmon to reach the Big Springs Creek tributary for the first time in 60 years. The first year after the barrier was removed, 60 fish completed the nearly 900 mile journey from the ocean to spawn in the newly reopened creek. Ongoing restoration, protection and water savings practices have resulted in more water in stream and more habitat for fish.

Since 2012, TNC and the Page family have worked together to place conservation easements on the majority of their nearly 6,000 acres of land in the Pahsimeroi River valley. Today, after years of work, nature is thriving. The sage grouse populations have stabilized in this critical breeding habitat and long-billed curlew began breeding in places they never had before. Additionally, the Pages, agencies and neighbors, have restored water to a once-dry tributary of the Pahsimeroi River for the return of chinook salmon and steelhead trout. In 2020, TNC worked with the Page family to complete another conservation easement on their ranch to protect important cold water spring sources that contribute to flows in Big Springs Creek, a stream that provides critical habitat for salmon and steelhead. 

Ranchers are deeply invested in the land they work, relying on its health and productivity to provide for their livelihood. It’s with that philosophy that Phil F. Moulton entered a multi-year deal with TNC that resulted in the restoration and protection of two historic steelhead and salmon streams in the Upper Salmon Basin.

Moulton collaborated with TNC to purchase the ranch and place a conservation easement on more than 2,300 acres across both properties.

Moulton expanded his cattle operation while also restoring access to important salmon and steelhead habitat, improving irrigation practices, and hauling off the remnants from a decades-old feedlot polluting a downstream river. A coalition of nonprofits and government agencies worked with him on the project.

TNC worked with valley landowner Merrill Beyeler on a ranch exchange, which resulted in two conservation easements protecting more than 2375 acres. The project reconnects tributary streams and ensure more water in the Lemhi for salmon. The early efforts of the Conservancy to protect these properties continues to provide opportunity for additional restoration work to occur there. Installation of in-stream wood and log structures is occurring in Lee Creek to mimic beaver activities, and larger scale work is scheduled in the coming years on the Lemhi River and Canyon Creek.

The Lemhi Valley in Central Idaho is one of the strongholds for Idaho's wild Chinook salmon and steelhead populations. In 2015, the Conservancy and Trout Unlimited began a project to protect and restore two streams important to ocean-going fish: Pratt Creek and Wimpey Creek. Both have been degraded over the years by poor grazing practices and low water flows. Thanks to the cooperation of three willing landowners, TNC is employing creative conservation financing, better grazing management and teaming with Trout Unlimited and others to implement restoration to improve stream conditions on both creeks.

In  2025, TNC secured a conservation easement on the 181-acre Peterson Ranch. Owners of the ranch agreed to restrict development on their property and committed to engage in significant river restoration efforts on Hayden Creek and the reach of the Lemhi River located on the ranch.

One of the top salmon spawning tributaries in the state, the Lemhi River meanders 60 miles through central Idaho before joining the Salmon River. According to research, a key limiting factor influencing fish productivity in the Lemhi system is the lack of overwintering and summer rearing habitat downstream of current spawning areas. In addition to quality habitat, juvenile fish need specific conditions further downstream to grow strong for their 850-mile journey to the Pacific Ocean. This project is increasing habitat for juvenile fish where they can linger and grow robust before migration, increasing their chances of a successful journey.

The Peterson Ranch easement is part of a larger project identified by TNC and partners to improve conditions for Snake River steelhead and spring/summer chinook salmon—both designated as endangered species. TNC and the Lemhi Regional Land Trust have completed additional easements on land both above and below the ranch, and active restoration is taking place on the creek and river.