Evaluation of a Fish Passage Site in the Walla Walla River Basin, 2009 Annual Report : September 2008 - August 2009.

Abstract

In 2009, Pacific Northwest National Laboratory (PNNL) evaluated the Touchet Consolidated Facility to determine if it is designed, constructed, operated, and maintained to effectively provide juvenile salmonids with safe passage past the diversion and back to the Touchet River. Completed in 2008, the Touchet Consolidated Facility combined two irrigation diversions with an existing intake for the Touchet Acclimation Facility. The consolidated facility includes a separate fish screen and intake for each user, a pool and chute fishway, and an adult fish trap. The fish screens portions of the facility were evaluated on April 20, 2009, using underwater videography, acoustic Doppler velocimeter measurements, and visual observations while water was diverted to the acclimation facility alone and again as water was diverted to the irrigation system and pond together. The facility is in good condition and is well maintained, although water velocities within the site do not meet the criteria set by the National Marine Fisheries Service (NMFS). Approach velocities above 0.4 ft/s at the upstream end of the facility and decreases in sweep velocity toward the bypass are likely caused by the proximity of the upstream screen to the spill over stoplogs that control flow at the upstream end of themore » forebay. We recommend working with Touchet Acclimation Facility staff to try different configurations and heights of forebay stoplogs while PNNL staff measure water velocities, allowing real-time monitoring of changes in approach and sweep velocities resulting from the configuration changes. It may be possible to bring approach and sweep velocities more in line with the NMFS criteria for juvenile fish screens. We also recommend evaluating the facility later in the year when river levels are low and the irrigation district is the only water user. During the site visit, it was noted that the upstream end of the fishway has relatively closely spaced louvers that point downstream. During higher river levels such as on April 20, the orientation of the louvers causes a headloss of up to 1 ft or more. Fish must maneuver through this hydraulic jump and between the louvers. The Washington Department of Fish and Wildlife is considering alternatives to this configuration; if needed, we would be available to offer technical assistance.« less