Modeling the rainfall-runoff using MIKE 11 NAM model in Shaya catchment, Ethiopia

In the present study, the rainfall-runoff modeling was carried out using MIKE 11 NAM model at the Shaya catchment in Ethiopia. The nine parameters of the model were optimized using observed rainfall, evaporation and observed streamflow during calibration (1990-2008) of the model. The validation of the model was done using an independent data for the period from 2009 to 2015. The model performance was evaluated using statistical performance indicators, such as correlation coefficient (R), Nash-Sutcliffe Efficiency coefficient (NSE), Root Mean Square Error (RMSE) and Percentage of Bias (PBAIS). The model performance was showed a good agreement between the observed and simulated runoff during the calibration (R = 0.93; NSE = 0.86; RMSE = 3.16 and PBIAS = - 1.58) and validation (R = 0.92; NSE = 0.83; RMSE = 4.04 and PBIAS = - 0.88). The results revealed that there is a very good agreement between the observed and computed runoff, particularly the low runoff compared to the high runoff in the Shaya catchment. High flow phenomena are often not caught by hydrological models but the low and average flows do. Therefore, this indicates that the model can be used for future hydrological modeling in the area successfully.