Evaluation of Discharge Simulation of Baghan Watershed Using Four-variable Salas Model

Water balance and flow analysis within a basin is particularly important in terms of water development and utilization programs. Therefore, the purpose of this study is to evaluate and predict the outflow rate of Baghan watershed in Bushehr province. The data required for the implementation of the rainfall and discharge models were used to obtain the precipitation data of the Baghan Meteorological Station and the discharge of Baghan Hydrometric Station from 1981 to 2010. The Salas model is derived from a number of simple sub models that characterize different flow processes in the basin such as surface runoff, infiltration, evapotranspiration, deep infiltration and base flow. Error squares were used to calibrate the function model. The results of this study showed that the highest amount of rainfall in the basin was evacuated from the basin by evapotranspiration. The results showed Relative root mean square error before and after optimization of the coefficients of the four-variable Salas model decreased from 2.18% to 1.5% and the mean absolute error from 10.13 to 0.73. and mean error of the Salas four-variable model showed that in the years when the discharge value is almost average, the simulation value is very close to the observed value, and when the discharge value is much higher than the normal years, the simulation value is the less than its observed value.