Restoring Cold-Water Pathways for Idaho’s Salmon and Steelhead

Snake River Chinook and steelhead are the ultramarathon runners of the salmon family. They undertake the longest and highest migration in the lower 48 states, traveling about 900 miles and reaching elevations up to 7,000 feet. To return to their spawning grounds in the Idaho mountains, they must climb fish ladders over eight major dams, navigate warming reservoirs, and evade a host of predators.

But even after passing those obstacles, some fish never reach their final destination. Small, human-made barriers, such as poorly designed road culverts, can block migration. Even if adult fish make it through, their tiny offspring-which can spend several years in freshwater before migrating to the ocean-may not. Juvenile salmon and steelhead need to move up and down streams as temperatures change.

To ensure these fish can successfully migrate, NOAA Fisheries' Office of Habitat Conservation is funding multiple salmon habitat restoration projects in the Snake River basin. The Idaho Office of Species Conservation is improving fish passage at four sites along tributaries of the Salmon and Clearwater rivers. Meanwhile, the Shoshone-Bannock Tribes and Trout Unlimited are restoring salmon habitat on Yankee Fork, a tributary of the Salmon River impacted by historic dredge mining.

"The Snake River Basin holds important cold-water habitat" says Larissa Lee, NOAA marine habitat resource specialist. "These projects help ensure more salmon and steelhead reach cool water tributaries ideal for spawning and rearing juveniles."

Historically, the Snake River Basin accounted for 40 to 50 percent of the salmon in the Columbia River Basin. Wild runs that once numbered in the millions have declined by more than 90 percent in the last 60 years. Today, Snake River spring/summer Chinook salmon and steelhead are listed as threatened under the Endangered Species Act.

Despite those declines, the basin remains critical. The Snake River Basin still contains about half of the remaining cold-water salmon habitat in the lower 48 states. When water temperatures reach 68°F or higher, salmon and steelhead experience physiological stress and can die without access to cooler refuge.

"Migration barriers and high temperatures are two of the biggest threats to Snake River salmon and steelhead," said Mike Edmondson, administrator of the Idaho Governor's Office of Species Conservation. "It's arid here. Summertime air temperatures can reach the high 80s and 90s. As temperatures warm, salmon need access to smaller tributaries where the water stays much cooler."

Reopening Cold-Water Tributaries

With $4.2 million in NOAA funding, the Idaho Office of Species Conservation is replacing or upgrading four failing road culverts on tributaries to the Salmon and Clearwater rivers:

• Poison Creek
• Kinnikinic Creek
• George Creek
• Big Cedar Creek

Together, these projects will restore access to nearly 25 miles of high-quality habitat.

"There are a lot of culverts that were just poorly installed," Edmondson said. "They're either perched or massively undersized. At higher flows, they can become velocity barriers, and for juvenile fish moving up and down the system to find the best habitat, they just reduce the amount of available habitat."

The benefits are especially important during the hottest months of the year. For example, Poison Creek runs about 14 degrees cooler than the Salmon River in summer while Kinnikinic Creek is typically 12 degrees cooler.

"If you were to snorkel around the mouth of Poison Creek [where the culvert still blocks fish passage], you'll find fish sheltering in the cool water," said Edmondson. "When the culvert is replaced, fish can use the entire 6.7-mile creek as a cold water refuge."

These upgrades also reduce flood risk. In 2019, the narrow culvert at Big Cedar Creek backed up, flooding nearby property. A new, larger culvert allows the stream to flow naturally.

"The larger culvert is a much better situation," said Edmondson. "It's got natural substrate at the bottom of it. It's got passage for juveniles and adults, both upstream and downstream, year-round. If we hadn't replaced it, the next flooding event probably would have taken out the road."

Partnering with Landowners to Support Fish and Communities

Collaboration with local landowners is key to opening up spawning habitat.

"Eighty to ninety percent of spawning habitat in our two-county area is on private land," said Chad Fealko, a NOAA fish biologist based in Salmon, Idaho. "Without landowner collaboration and permission, these projects simply wouldn't happen."

He noted that working with landowners demonstrates that habitat restoration can support fish recovery without harming agricultural production. "When people see that recovery work doesn't negatively affect their bottom line-and can even improve it-that opens the door for broader participation," he said.

Restoration investments also support local economies. Contractors hired for on-the-ground work are largely local.

"Restoration dollars stay in the economy three to four times longer than recreation dollars," said Edmondson. "Those dollars go to people who live in the community, and they spend that money locally again and again."

Tribal-Led Salmon Habitat Restoration

Farther upstream in the Salmon River Basin, the Shoshone-Bannock Tribes and Trout Unlimited are restoring habitat on the Yankee Fork. These projects will help rebuild populations of Chinook salmon, steelhead, and bull trout.

For the Tribes, this work is personal. Yankee Fork supported robust tribal fisheries for millennia. Today, the Tribes take only three fish per year for ceremonial purposes.

"Our hope is to get numbers higher so we can increase that harvest limit and actually have a meaningful fishery," said Joe Snapp, biology specialist for the Shoshone-Bannock Tribes. "We want to give families opportunities to go to this special place and fish as we once did."

The upper part of Yankee Fork still contains relatively intact salmon habitat, with no irrigation withdrawals and no cattle grazing. Downriver, however, a 6-mile stretch still bears the scars of large-scale gold dredge mining that occurred in the 1940s and early 1950s.

The Legacy of Dredge Mining

Before dredging began, bulldozers cleared trees along the river corridor. Crews built earthen dams to create ponds so a massive floating dredge could excavate the floodplain. The machine dug more than 30 feet deep in places, scraping across the valley floor and cutting the channel to bedrock.

The operation destroyed natural stream complexity, left mountains of mining tailings along the river, and flushed spawning gravels and fine sediment downstream into the Salmon River.

"There are written accounts of people who were floating down the Middle Fork of the Salmon River in the 1940s," said Cassi Wood, Upper Salmon program manager for Trout Unlimited. "Where the Middle Fork joined the main Salmon, the water looked like chocolate milk because of all of the sediment in it."

Restoring Yankee Fork

The Tribes and Trout Unlimited have partnered on Yankee Fork restoration since 2010. With NOAA funding, they are reconnecting a series of dredge ponds to the main channel.

The project will reconnect off-channel habitat where juvenile salmon can survive the winter. When temperatures drop in fall, young salmon seek slow-moving areas with cover where they can conserve energy and avoid freezing.

The restoration includes:

• Replacing an undersized and perched culvert
• Regrading channels to prevent stranding
• Removing barriers between ponds
• Adding large wood for cover
• Replanting vegetation

When complete, more than 1,640 feet of side-channel habitat will reconnect to the mainstem Yankee Fork.

Past projects on Yankee Fork show how quickly salmon respond.

"Chinook salmon moved right into a glide we had just constructed," said Wood. "It was shock and awe to watch fish building redds [salmon nests] in spawning gravel that an excavator placed there just 3 weeks earlier."

This project should be complete later this year. In the meantime, the Shoshone-Bannock Tribes are developing designs for future projects.

"We're going to continue to do restoration work as long as needed to give our members an opportunity to catch fish," Snapp said.

These projects are part of a broader, long-term effort to recover Snake River salmon and steelhead. Habitat restoration alone cannot offset all the pressures the fish face, but each mile of reconnected habitat brings them closer to recovery.