2019 CSCE Annual Conference - Laval (Greater Montreal) Conference
As fish habitats represent some of the most difficult biological, topographic and hydrodynamic phenomena to evaluate, estimation of environmental flows or instream flow needs for fish and fish habitat becomes a challenging process to assess in details. However, hydrodynamic models with habitat simulation features may now provide one tool to examine and analyze the quality and quantity of complex fish habitats in such challenging circumstances with reasonable accuracy. The purpose of this study was to estimate the instream flow needs that can be used to protect or enhance the fish and fish habitats in three sites of three low-slope Rivers in Canada. The River2D hydrodynamic model combined with fish species-specific habitat suitability criteria was used to achieve these goals. The model was used to predict channel hydraulic or physical habitat characteristics, mainly velocities, water depths and water levels. Model predictions were presented for a wide range of flows. The hydrodynamic model results, coupled with the biologically significant suitability metrics, were used to determine changes in fish habitat use areas with discharge, estimate weighted usable areas, and consequently estimate instream flow needs or environmental flows for several fish species. This ichthyohydraulic simulation process provides water management guidance to protect or enhance fish and fish habitats in these rivers.