The Upper Baker River Dam utilizes a combination of a floating surface collector (FSC) and a guide net to facilitate the downstream migration of anadromous juvenile fish. The FSC generates attraction currents by withdrawing water from the forebay, upstream of the guide net. The withdrawn water is discharged at the rear of the FSC by two pumps. A three-dimensional (3D) computational fluid dynamics (CFD) model of the forebay of the dam is presented in this paper. The objective was to investigate forebay hydrodynamics generated by the FSC and operation of the powerhouse. The CFD model, consisting of approximately one million computational cells, was validated against field data. Model results were analyzed, using a recently proposed strain-velocity-pressure (SVP) hypothesis, to identify hydrodynamic cues responsible for attracting juvenile fish to the FSC. The CFD model indicates that the FSC pumps generated high velocity jets dominate the circulation pattern downstream of the guide net. Upstream of the guide net, the velocities are weak, except in the region impacted by attraction currents. The sweeping and normal velocities on the guide net are smaller than those suggested by regulatory agencies for designing screens at juvenile fish collection facilities.