Assessment of Selective Withdrawal and Inflow Control on the Hydrodynamics and Water Quality of Ilam Reservoir.

The hydrodynamics and water quality of Ilam reservoir, consisting of three main inlet branches and two outlets, was simulated with the CE-QUAL-W2 model. After calibrating and verifying the numerical model, effects of various management scenarios (selective withdrawal, controlling water inflow, and their combinations) were investigated on thermal stratification and water quality. The total reduction of nutrient loads derived from the Chaviz and Ema rivers decreased the total phosphorus concentration. The chlorophyll a concentration of this scenario increased less than in other scenarios. Variation of the withdrawal elevation from the surface to the bottom significantly facilitated the heat conduction of the water column, therefore, the thermal and dissolved oxygen stratification was weakened. The best management scenario was a combination of water withdrawal from the bottom and surface and total reduction of nutrient loads derived from Chaviz and Ema rivers because of improving eutrophication, thermal, and dissolved oxygen stratification in Ilam reservoir.