Hydraulic Performance of Fish Bypass-Pools for Irrigation Diversion Channels

This paper presents the results of an exploratory study on the hydraulics of a fish bypass-pool that is built to facilitate successful fish passage through an irrigation diversion channel. The hydraulic performance of the bypass-pool was investigated by performing two major experimental runs to evaluate the flow recirculation patterns within the pool when two different outlet configurations were used. This was to determine which outlet design prevents or minimizes the presence of "stagnant" regions within the pool, where fish could rest until ensnared by a predator. These experiments show that the flow from the forebay area of the irrigation diversion structure, entering the pool as a jet, diffuses because of the circulation and turbulence within the bypass pool. The diffusing jet impinges upon the back-wall of the pool and dives into the pool creating several recirculation patterns within the pool. The results collected in this study provide useful information about the jet velocity decay through the pool, the eddy length scale within the pool, the velocity contours, and the level of energy dissipation within the pool. A rational basis was developed for evaluation of the hydraulic performance of a bypass-pool by considering the recirculation pattern and turbulent flow microstructures formed within the pool.