A review of hydroacoustic studies for estimation of salmonid downriver migration past hydroeiectric facilities on the Columbia and Snake Rivers in the 1980s

Hydroelectric development on the Columbia and Snake Rivers substantially impacted salmonid populations. The 1980 Pacific Northwest Electric Power Planning and Conservation Act mandated development of a program to mitigate these impacts. Hydroacoustics was one of the techniques that were applied to study the temporal and spatial characteristics of the downstream salmonid migration. Over 60 hydroacoustic studies were conducted at the various hydroelectric facilities on the Columbia and Snake Rivers during the 1980s. The primary objectives were measurement of run timing, vertical distribution, horizontal distribution, diel distribution, spill efficiency, and bypass efficiency. The techniques provided a cost‐effective, nonlethal, and accurate means to study passage rates, migration paths, and efficiencies of various operational and bypass mechanisms. In at least one case, the techniques were instrumental in the development of a successful bypass procedure. The development of hydroacoustic techniques for the Columbia and Snake Rivers contributed to successful applications of these techniques throughout the world, although more widespread application is hindered by the complexity and lack of understanding of the techniques.