DESCRIPTION
Protecting and restoring mainstem and off-channel habitats, especially those that provide thermal refuge, is critical for upstream-migrating adults particularly during the late spring, summer and early fall, as well as out-migrating salmonids. Previous research has documented a persistent cool-water flow along the right bank of the mainstem Yakima River at RM 3.4 - 3.9. This cool-water input originates from a year-round groundwater-fed spring. Previous research also documented a persistent cool-water input at the mouth of Amon Creek at RM 2.5, which is the lowest cool water tributary upstream of the mouth of the Yakima River. The goal of this project is to build upon previous work, conduct feasibility studies and complete preliminary designs using the existing cool water inputs to create functional thermal refuge habitat at both of these locations.
Benton Conservation District (Benton CD) completed final designs, cultural resources, and initiated the permitting process for a cool water restoration project that will increase functional thermal refuge habitat for adult salmonids on the Lower Yakima River. Benton CD identified a persistent source of cool water input at the mouth of Amon Creek at RM 2.5 which is the lowest tributary in the watershed. Protecting and restoring mainstem and off-channel habitats, especially those that provide thermal refuge, is critical for upstream-migrating adults particularly during the late spring, summer and early fall when water temperatures are limiting. Benton CD completed conceptual design work using funds from the Yakima Basin Integrated Plan for the Amon Creek site and an additional site at RM 4.9 of the Yakima River near the I-182 side-channel. Stakeholder concerns arose regarding long-term stability and viability of the cool water source at RM 4.9 so further design work at that location was removed from the scope of the project. Restoration Designs at Amon Creek focused on enhancing the thermal influence and spatial extent of this cool-water input through this lower river migration corridor to support steelhead and salmon recovery goals throughout the basin. Permits will be finalized in the complimentary SRFB Implementation grant #23-1168. Minor revisions to the final designs may be needed in the process of the final permitting issuance, and those revisions will be included as part of grant #23-1168. The completed project will enhance riparian floodplain with native cottonwood plantings, increase wetland habitat, and create a cool water pool for adult migrants. Species to benefit from this project include steelhead, sockeye, spring and summer Chinook, and Pacific lamprey, as they are all obligate ocean-going species that must migrate as adults through the warm Lower Yakima River. The final design will meet SRFB Manual 18 Appendix D-3 standards.
