The hydraulics of a vertical slot fishway: A case study on the multi-species Vianney-Legendre fishway in Quebec, Canada

This paper presents an overall assessment of the hydraulics of a vertical slot fishway, the Vianney-Legendre vertical slot fishway on the Richelieu River in Quebec, Canada, which has been shown to be successful for passing a variety of fish species, including lake sturgeon. The fishway has a number of features that combine for a unique design. This includes two turning pools, shorter and narrower than recommended regular pools, and a low overall gradient. Detailed field measurements of the water levels and velocity patterns were obtained and a computational fluid dynamics modeling study was conducted. The model study evaluates the performance of various regular pool geometries based on fishway hydrodynamics. Low overall fishway gradient was shown to result in a fishway hydraulically suitable to fish passage, overcoming non-optimal pool dimensions. The relationship between discharge and corresponding average water depth in the pools, under both uniform and non-uniform flow conditions, using the discharge coefficient enabled us to simulate the distribution of water levels in a vertical slot fishway. Two distinct flow patterns were observed in a regular pool depending on the shape ratios between the pool's length and width. This study also assessed the spatial variation of velocity magnitude in the vertical plane to reveal regions of upwelling, downwelling, and the formation of eddies and dead flow zones that have potential importance for fish migration.