Impacts of entrained air bubbles on dissolved gas concentrations below spillways

Oxygen is crucial to fish survival, and hydraulic structures regenerate much oxygen through the entrainment of air bubbles and the tremendous surface area of the bubbles.  These bubbles can also create difficulties for the fishery, because bubbles driven to depth by a hydraulic structure will supersaturate the water with gas, and when the fish rise towards the surface they get nitrogen narcosis (diver's bends).  This is a big issue in the Northwest USA, because of salmon passage through multiple dams.  We are working to predict nitrogen and oxygen concentration below damsusing unsteady computational fluid dynamics to predict bubble paths and velocities, which expose the bubbles to different rates of gas transfer.