Simulation-Optimization of Pollutant Source Allocation in the Küçük Menderes River Basin

Abstract

Water quality models are important tools in supporting river basin scale decision-making and exploration of pollutant loading effects on the water quality of the receiving waterbody. Contemporary river basin management studies rely on the intensive use of modeling to evaluate pollutant source control strategies. To ensure that water quality standards are met in the receiving waterbody, a viable strategy is to appropriately allocate loadings to all point sources in the river basin such that good quality water status is achieved. The problem of source allocation can be effectively solved using a simulation-optimization approach. The objective of this study is to develop an approach to allocate pollutant point sources in a river basin. We present the interim results of a simulation-optimization approach to set effluent limits for the Küçük Menderes river basin which is located in Western Turkey. The approach is demonstrated on a sub-basin that receives discharges from three industrial sites, one domestic wastewater treatment plant and one tributary. The water quality model AQUATOX is used to determine time-variant concentrations in the main reach. The model is set up using arbitrary yet realistic values for hydraulic variables and point source loadings of one decaying pollutant. The optimum allocation of pollutant loadings to maintain a certain water quality standard is determined using the generalized-reduced-gradient method (GRG). We demonstrate that the simulation-optimization process simplifies when response coefficients and the principle of superposition are used to calculate the cumulative effect of pollutant loadings. We present also an example calculation of optimum source allocation. © 2019, IAHR.