Water Quality methods have been added to Reservoirs, Reaches and Computational Subbasins to model Total Dissolved Gas (TDG) in both Simulation and Optimization. High TDG concentrations can reduce the population of some fish species. These effects are most pronounced in the tailwater of reservoirs during spill operations. The TDG concentrations are increased by spills; the turbulent nature of the spill creates air bubbles that are then forced deep into the tailwater. The deep water has higher pressure which cause gases in the bubbles to dissolve in the water. Once dissolved, the gas propagates downstream.

For more information, see Outflow TDG using Tailwater Depth in Water Quality.