Will provide prime habitat for salmon, steelhead
By Ann McCreary
A meandering channel of water, interspersed with small pools and littered with a jumble of tree trunks and limbs, now runs parallel to the Methow River just north of Twisp.
The newly established channel winds its way among trees along the hillside west of Highway 20, then bends toward the Methow River and flows under the bridge just north of Twisp, emptying into the river.
While the waterway looks like a work of nature, littered with tree debris, rocks and gravel, it’s a very deliberate work of humans — created to restore a part of the valley’s environment that disappeared as a result of human activity.
Called the 1890s Side Channel Restoration Project, the restored waterway is designed to provide prime habitat for juvenile salmon and steelhead.
The channel roughly follows the path of a historic waterway that previously carried water along the valley wall parallel to Highway 20. Historic surveys indicate that this was the main channel of the Methow River in the 1890s.
Human development, including construction of Highway 20 and a large flood control levee, altered the course of the river.
“The project restores habitat that truly has been lost here,” said Hans Smith, project manager and habitat biologist for the Yakama Nation Fisheries, which developed the $2 million project.
Groundbreaking began in August with excavation of the channel route from its outlet on the Methow River just north of Twisp, extending just under a mile upstream. The side-channel bed was deepened to be in contact with the natural groundwater lying below the surface.
About 30,000 cubic feet of earth and rock were removed along the channel. The excavated material was placed in a depression in a pasture on nearby Walking D Ranch and seeded to restore the field.
Along the winding path of the channel, more than 200 large tree trunks with root wads and other pieces of wood were placed to create riffles in the stream and to form more than 40 pools of water that are essential to good salmon habitat. The placement of each tree trunk and creation of each pool was very deliberately planned, Smith said.
To provide a year-round flow of water for the channel, a groundwater collection system was installed on the east side of Highway 20 north of the upper end of the channel.
A network of perforated pipes was buried below the upper limit of the aquifer. The perforated pipes gather groundwater and feed it into a buried conveyance pipe that carries it under a bridge on Highway 20, about a mile north of Twisp, to the head of the channel.
The gravity-fed system was completed last week and water began flowing into the channel at about 3 cubic feet per second (cfs). When the Methow River is at high-water levels in spring and early summer, the pipe will carry up to 15 cfs to the channel, Smith said.
The perennial flow of groundwater is like a spring-fed creek, and means fish can access the channel year-round, Smith said.
Because groundwater stays warmer in winter and cooler in summer than the surface water in rivers, the side channel provides “thermal refuges” for fish, Smith said.
“Peak times of stress for juvenile fish rearing in their natal tributaries can occur when the river gets low and either really warm in the summer or really cold in the winter,” Smith said.
The final step in restoring the side channel is planting riparian vegetation, such as cottonwoods and willows, to provide shade, stabilize the stream banks and enhance water quality. The extensive revegetation work will take another two to four weeks, Smith said.
A net is currently in place at the outflow of the channel, where it connects with the Methow River, to prevent fish from entering. When planting is far enough along so that there won’t be any disturbance to fish, the net will be removed and fish will be able to swim up the channel.
“It’s not like they’re lined up waiting, but as soon as we pull the net they will enter,” Smith said. “We’re targeting juvenile spring Chinook salmon and steelhead, but certainly other species will be using it as well, including bull trout, Coho and resident rainbow trout.”
Upper Columbia spring Chinook are categorized as endangered under the federal Environmental Species Act, and upper Columbia steelhead are categorized as threatened.
The side channel restoration is part of the Yakama Nation Upper Columbia Habitat Restoration Project, a tribal fisheries program dedicated to restoring salmon habitat along waterways in the Methow Valley through the year 2018.
The $2 million project is funded by the Bonneville Power Administration under the Columbia Basin Fish Accords, an agreement signed in 2008 between BPA and regional tribes to promote salmon recovery as mitigation for dam impacts.