Upstream Hydraulics of a Run-of-the River Hydropower Facility for Fish Entrainment Risk Assessment

Abstract

Run-of-the-river hydropower is a typical form of power generation in mountainous regions. This study investigates the velocity field upstream of Aberfeldie dam, a run-of-the river facility on the Bull River near Wardner, British Columbia, Canada. As is typical for these types of run-of-the river facilities, the headpond of this dam is very shallow (approximately 1 m deep) because of long term sediment deposition. Near the facility’s power intakes, a large scour hole has been created because of increased velocities induced by the intakes. This study conducted field measurements and developed a computational fluid dynamic (CFD) model to investigate the velocity field under various flow conditions. The CFD solver shows in a simplistic way that flow-induced bed shear stress likely causes a fluctuating, dynamic bed form that varies by season and the distance upstream, so that a consistent velocity pattern is seen across the entire headpond. The velocity field generated by the CFD solver is used to evaluate the entrainment risk of mountain whitefish and westslope cutthroat trout based on swimming mechanics and life stage. The unique habitat conditions generated by the scour hole act as an attractant to the high risk zone, greatly increasing fish density adjacent to the intakes at this facility.