Comparison Evaluation of Nash and Hybrid models Parameters Estimation Methods in Order to Model Rainfall-Runoff Process (Case Study: Alandchay Watershed)

Rainfall-runoff hydrologic models have been recognized as an important and essential tool for water resources management in the world. In this direction, Nash and Hybrid models have been developed as rainfall-runoff models in the recent years. In the present research, the different methods were evaluated to estimate the mentioned models parameters in Alandchay watershed in West Azarbayjan and these models were compared with each other. For this purpose, Hybrid model parameter in the base of empirical method and Nash model parameters using eight different methods were estimated. To evaluate the capability of two mentioned models, the statistical indices such as RMSE, R2 and MAE were used. The less amount of error indices and high values of determination coefficient showed the ability of two models for modeling the flood hydrographs. The comparison of the statistical indices values and calculated errors showed that Nash model had the better performance than Hybrid model. The mean error of peak discharge for Nash and Hybrid modes was obtained 5.99 and 12.07 m3/s and the mean error of flood hydrograph peak time for mentioned models was calculated 0 and 3 hours, respectively.