YAKIMA, Wash. (AP) - Slightly more than 10,000 adult sockeye salmon just arrived in Lake Cle Elum, their upstream migration diverted by a tanker truck ride courtesy of Yakama Nation Fisheries.
By introducing the fish to an area that has been blocked for a century by a dam, tribal biologists hope to rebuild a healthy population. These adults will spawn and their surviving offspring will migrate to the ocean and back, returning to help the population grow.
It’s a good plan, but there’s a big hurdle. The Cle Elum Dam doesn’t just hold back water, it holds back salmon.
The reservoir’s fluctuating levels make it impossible to use the types of fish passage typically found on the Columbia River’s hydroelectric dams, where water levels stay relatively stable.
After years of work, Bureau of Reclamation engineers are finalizing a first-of-its-kind design for a system to let juvenile fish head downstream, regardless of reservoir level. The plans will be ready for construction next year, but federal funding for the $100 million project, a key part of the Yakima Basin Integrated Plan for water management, still needs to be authorized before work can begin.
“There’s nothing like this anywhere,” said Jason Wagner, an engineer at Reclamation’s technical center in Denver. “It’s very new. It’s kind of exciting.”
The passage has three parts: a stepped inlet to let fish swim in at varying water heights, and a spiral water slide that quickly lowers the fish to a tunnel past the dam that delivers them to the river.
Plans for getting returning adults upstream are far less high-tech. Fish will be trapped below the dam, be driven around the dam in a tanker truck and then dumped in the lake.
For Wagner, the most exciting part is the novel design for the downstream passage, which he believes can be used at other storage reservoirs in the region. For Brian Saluskin, fish passage biologist for the Yakama Nation, it’s the critical step to eventually restoring self-sustaining runs of salmon and steelhead to the Yakima River’s upper tributaries, where they have been largely shut out for a century.
“With fish passage, you are opening up 41 miles of pristine habitat above Cle Elum,” Saluskin said. “We’d like to see this happen as soon as it can.”
Saluskin said the Yakama Nation wants to see the Bureau of Reclamation build fish passages at all five of the region’s storage dams, but efforts started with Cle Elum because it offered the most upstream habitat.
Before spending millions to build fish passage for a reservoir with no fish, Reclamation and the Yakama Nation decided to make sure that salmon could still use the habitat that had been empty for so long. The Yakamas began reintroducing sockeye salmon in 2009, with adults transplanted from the upper Columbia River.
In preparation, they built a temporary fish slide down the dam’s face in 2005 and tested it with leftover hatchery fish. It’s definitely better than nothing, Saluskin said, but the fish can only access it when the reservoir is full and water is spilling over.
When the reservoir fills up varies from year to year, depending on when snow melts. In drought years, the lake may never reach maximum height, said Joel Hubble, a Reclamation fish biologist. That makes things difficult for the juvenile fish, who have a specific migration window for heading downstream, he said.
This spring, for example, the juvenile sockeye were ready to leave the reservoir in April, swimming back and forth in front of the dam, Hubble said, but they couldn’t use the slide until mid-May.
Waiting can mean the fish miss their window and decide to stay in the lake or face higher temperatures in the lower Yakima River, which reduces survival, Hubble said.
“They all have their own time they want to leave; it depends on weather and temperature,” Saluskin said. “It’s just being able to get fish out when they want to as opposed to on our timetable.”
The new fish passage will almost entirely solve this problem. As long as the reservoir level is within 60 feet of full, fish will be able to access an outlet. That should be sufficient for all species in all but the worst drought years, Saluskin said.
Six intake structures, each about 10 feet tall, will be built along the sloping lake bed next to the dam, like steps. Each step will capture the top 10 feet of water, depending on the lake level, Wagner said.
From watching the sockeye in recent years, biologists know they will swim along the shore looking for a way downstream, so Wagner believes they will find the passage easily.
Once the fish swim in to the passage, biologists want to get them down to the river below as fast as possible. That’s where Wagner’s helix-shaped water slide comes in.
Inside it, the water accelerates to 30 to 50 feet per second, bringing fish to a tunnel below the dam that will carry them to the river. Extensive testing using scale models in the Denver labs helped Wagner and his colleagues figure out how to keep the flow smooth.
“We’ve spent a million-plus in hydraulic modeling, but it’s money well invested in a $100 million project for something that’s never been tried,” Hubble said.
Initial designs produced too much turbulence in the intake and in the slide, but the engineers solved those problems.
“If it’s too scary and turbulent, they may decide to stay in the reservoir and we lose the benefit of the structure,” Wagner said. “At every point from reservoir to river, we are designing this around the juvenile fish.”
It’s an expensive endeavor, but Hubble believes that the Yakamas’ work to start rebuilding a sockeye population in the lake makes the benefits apparent. Last year, 700 sockeye returned to the lake, to much fanfare.
“Ecologically, this habitat is already producing fish. Why not invest in it?” Hubble said. “It’s not like we are going to build this facility and it’s not going to produce fish.”
The construction should take five years, Hubble said. Then, Reclamation engineers will turn to the four other dams in the Yakima Basin that lack fish passage on Rimrock, Bumping, Kachess and Keechelus lakes.
Saluskin said that once the fish passage is built, the tribe plans to re-introduce other species, including steelhead and chinook, and then move on to reintroduction efforts in the other reservoirs and upstream habitat.
“We’re going to keep doing it until we can get self-sustainable runs,” Saluskin said. “We are doing this for everybody. It’s not just the tribe that we are returning fish to. It benefits everybody.”
Information from: Yakima Herald-Republic, https://www.yakimaherald.com
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