Determination of optimal parameters of empirical area reduction method in Karaj Reservoir Dam using SCE

Dam construction on the rivers causes sediment accumulation behind them. Determination of quantity and quality of sediment deposition in reservoirs is important for their stability and operation. Area- reduction method is one of the empirical methods for reservoir sediment distribution. In this method, reservoir is divided to four types, based on its shape. Parameters are presented for each types of reservoir which is carried out based on sediment distribution. Determination of suitable parameters in operating reservoirs which have at least one period of hydrographic data, leads to increment of accuracy. The objective of this research is to determine the optimal parameters of empirical area reduction method in Karaj dam using Shuffled Complex Evolution algorithm. In this research, a computer model was developed based on area reduction method theory. Then optimization model was prepared using Shuffled Complex Evolution algorithm and these two models were combined and Simulation-Optimization model was developed. Simulation- Optimization model determined area reduction method parameters for Karaj dam so that the most compatibility occurs between computational and measured volumes. To determine optimal parameters values, objective function was defined as Root Mean Square Error (RMSE) calculation of actual values. Using prepared model, optimal parameters were obtained based on information in 1961 and hydrography in 1991. To verify simulation-optimization model, sediment distribution in 2007 was calculated using obtained optimal parameters by model and was compared to hydrographic values. Results showed that values of objective function were reduced up to 62% and 48% in calibration and verification periods, respectively. Then, sediment distributions of Karaj dam were predicted based on optimal parameters.