DESCRIPTION
The Mid-Columbia Fisheries Enhancement Group (MCFEG) will use this grant to assess and produce a final design for a restoration action that will reduce fish stranding and mortality in the Yakima River mile 153 side channel and Wilson Creek. A river-spanning rock weir was installed in the late 1990s, as an enhancement project that allowed Yakima River fish to access a 0.6 mile left bank side channel at RM 153. The structure was damaged by a combination of factors, and currently requires annual maintenance in order to divert flow. Fish are stranded in the side channel when Yakima River flows drop. The Bull Canal Company diverts Yakima River water from the side channel for irrigation. When flow is insufficient in the side channel, they rely on their Wilson Creek water allocation instead. Withdrawing water from Wilson Creek significantly decreases flow in the lower 8 miles of the creek, reducing the quality of off-channel habitat in this system. MCFEG proposes to create a final design for a restoration action which may replace the need for annual maintenance of the rock structure, reduce fish stranding and mortality in the side channel and Wilson Creek, increase availability of Yakima River water for Bull Canal Company, and increase the limited availability of off channel habitat. MCFEG will assess existing conditions, perform an alternatives analysis, model hydraulic function, perform cultural resource surveys, and produce a final design.
Off-channel habitat availability is reduced throughout the length of the Yakima River. In the late 1990s, an enhancement project near Ellensburg allowed Yakima River fish to access a 0.6 mile left bank side channel. The project installed a river-spanning rock structure in the Yakima River to divert flow into the side channel. The structure was damaged by a combination of factors, and currently requires annual maintenance in order to divert flow. Fish are stranded in the side channel when Yakima River flows drop. The Bull Canal Company diverts Yakima River water from the side channel. When flow is insufficient in the side channel, they rely on their Wilson Creek water allocation instead. This can significantly decrease flow in the lower eight miles of Wilson Creek, reducing the quality of off-channel habitat in this system. Mid-Columbia Fisheries Enhancement Group (MCF) worked with local stakeholders and engineers from Herrera, Inc. to create a preliminary design to reduce the need for annual maintenance of the rock structure, reduce fish stranding and mortality in the side channel, increase flow in Wilson Creek in September and October, increase availability of Yakima River water for Bull Canal Company, and increase availability of off channel and stream edge habitat. MCF and its partners assessed existing conditions, completed a two-year alternatives analysis, modeled hydraulic function, performed the cultural resource survey, and produced a preliminary design. The preliminary design includes replacing two small gated culverts with a larger arch culvert, regrading the side channel to increase conveyance, installing two wood structures on the left bank of the Yakima River, and improving fish passage at the lower end of the side channel. The project is intended to benefit Chinook and Coho salmon, steelhead, Rainbow Trout, and Cutthroat Trout.
