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Testing the Design at the Thurlow Diversion
The Thurlow Diversion, the lowest and oldest irrigation diversion on Beaver Creek, has been a challenge to fisheries management for many years. The diversion is supported by a concrete diversion dam that was constructed in a relatively steep section of the creek, and the combination of the creek’s fast water and the dam’s height blocked fish passage during much of the year. The fast water also frustrated efforts to create sustainable fish passage over the dam. At least four prior fish restoration projects on the site washed out within 3-4 years of their completion.
The original channel
Early this fall, MSRF worked with the Bureau of Reclamation and the Washington Department of Wildlife to develop a more durable approach. The new design called for a series of pool-and-drop structures over the two hundred feet of creek bed below the dam, creating what’s called a roughened-channel streambed. This approach has worked well on the Chewuch River below both the Fulton and the Chewuch dams, which MSRF completed with BOR between 2006 and 2009. Work on the Thurlow channel was completed in August and September of 2014 by Boulder Creek Contracting of Winthrop, with revegetation of disturbed riparian areas completed by Methow Natives. The finished channel features a series of natural-looking pools and riffles engineered to allow fish to swim from one pool to the next, not unlike a fish ladder. Sediment that naturally collects in the pools is expected to flush out each year during high water.
The revised channel
Shortly after this project’s completion, sediment from the fire-ravaged headwaters of Frazer and Beaver Creeks completely filled each of the constructed pools, obscuring the structure of the engineered channel. Modeling completed by the Burned Area Emergency Response Team estimates that sediment transport through Beaver Creek may reach more than 1700% of normal levels during the next several years until the headwaters begin to revegetate. The sediment that filled the pool structures has already started to wash through, and due to the project’s self-scouring design, we expect high water to flush the remainder out in the spring. MSRF will continue to monitor the creek below the Thurlow diversion to make certain that our project design functions better than those before it in spite of the worst creek conditions in recent history.
Projects Completed Last Fall: 3R
The work completed during the summer of 2014 at the 3R project site on the Methow River was identified by MSRF and the Bureau of Reclamation nearly seven years earlier based on the presence of cold water flowing into the Methow from a series of off-channel pools. These cold groundwater seeps can provide refuge habitat for juvenile salmon and other species. Historically, this cold water was also valuable for agricultural uses. The isolated refrigerator-like pools are thought to be the remnants of chilling ponds built when the property was home to a dairy.
The source of the cold water is probably Thompson Creek, which historically flowed through the property to the Methow River. Although the surface flows of the creek were diverted into the Foghorn irrigation ditch many decades ago, cold water still flows underground and seeps into the side channel alcove at the site.
The primary objectives of the 3R project were to restore seasonal access for salmon to the cold water alcove and side channel areas and to construct three engineered logjams to provide additional near-shore refuge habitat in the main channel of the Methow River. To anchor these jams into the riverbed with the minimum impact to the river, MSRF contracted with Palm Construction of Winthrop to drive wood piles with their new vibratory pile driver. This tool allowed them to drive the piles into the riverbed more quickly and with less environmental impact than the conventional method of digging them in with an excavator.
The restoration work at the 3R site continues a tradition of balancing environmental protection and agricultural use. The privately-owned property remains in use as active farmland with long-term environmental protections guaranteed by a Conservation Easement donated to the Methow Conservancy. MSRF worked closely with both the property owners and the Conservancy to craft a restoration approach that would be consistent with their goals and a monitoring plan to ensure that these goals continue to be met.
MSRF also worked with the landowners to expand riparian plantings along the Methow River in areas that had historically been cleared, improving the function of riparian forest and increasing shade cover for fish in the project area. Maintenance and monitoring of the revegetated areas is under the care of Camden Shaw of Plantas Nativa, who has been working on this project site for nearly a decade to restore a healthy riparian plant community. Funding for a portion of these riparian plantings as well as the on-going maintenance (critical for plant growth and survival) is provided by the Washington Department of Ecology. MSRF is pleased to work in partnership with Ecology on this and other projects that strive to improve water quality conditions in the Methow watershed.
An early indication of the project’s success occurred just two days after project completion in October, when John Crandall observed Chinook and Coho salmon spawning and holding in the newly-completed wood structures during post-construction snorkel surveys.
Just as logjams provide habitat for fish, standing dead trees provide habitat for nesting birds. Snag trees along the Methow River are a common site in mature cottonwood forests but were largely missing from the 3R site. Several mature trees at the site were toppled by a windstorm at the beginning of the restoration project. Working with the landowner, MSRF “re-planted” this 60-70’ dead conifer to provide habitat for osprey, eagles, and other species.
Our continuing monitoring of this site will include examining fish use of the wood structures and continuing our PIT tag monitoring in the side channel.
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