Summary of the evaluation of fish passage through three surface spill gate designs at Rock Island Dam in 1996
design, fish passage, Rock Island Dam, passage efficiency, efficiency
Innovations in Fish Passage Technology
American Fisheries Society
In 1996, two designs of surface spill gates were chosen by Chelan County Public UtilityDistrict No. 1 (Chelan PUD) for an evaluation of fish passage efficiency of spill at Rock IslandDam. The two gate designs consisted of a 3.4 m wide by 4.3 m deep notch gate and a 9.1 mwide by 2.1 m deep overflow gate. Split-beam hydroacoustic methods were used to estimate thezone of influence of the surface spill gates, and single-beam, hydroacoustic methods used toestimate the number of fish passing the project through each spillbay and powerhouse.Hydroacoustic estimates indicated that notched gates passed significantly more fish per flow thanoverflow spill gates during spring and summer. Average fish passage per unit flow wassignificantly higher for some spillbays and seemed to be affected by the volume spilled throughadjacent spillbays. The results from this study prompted Chelan PUD to construct six additionalnotch spill gates for use during the 1997 spill period.