Multi-Objective Optimization in Determine the Environmental Flows of the River

Construction of Reservoir dams on the river, in addition to change and decrease the river’s regime in downstream, cause environmental problems for ecosystems. This issue can be more severe by dumping pollution into rivers. Therefore, estimating the minimum environmental flow for river systems and other aquatic ecosystems is necessary to keep environment and water resources. In this study, the environmental flow of Dez River was determined using optimization of Dez outlet on upstream. For the purpose, a safe range of environmental flow, with 10 to 100 m3/s, was firstly defined. Then, simulation of river water quality for mentioned ranged was done by QUAL-2K model. Next, by using Nash's theory of conflict resolution, the optimization of the dam release, under three scenarios of relative weights for quantitative and qualitative aims, was determined that 66, 57, and 74 m3/s were obtained respectively, the average concentration were 2.926, 3.237, and 2.727 respectively for each scenario. Each of this value can provide different percentages of quantitative and qualitative needs, so the prioritization of these aims was given decision makers.