Stream flow modeling using SWAT model and the model performance evaluation in Toba sub-watershed, Ethiopia

Streamflow modeling is essential in developing long-term water resource management plans. Especially in the inaccessible area like Toba sub-watershed, Ethiopia, modeling is an alternative means of obtaining streamflow data. Knowing of the hydrological response of a watershed would help to resolve potential water resources problems associated with floods, droughts, and availability of water for irrigation, hydropower, domestic and industrial use, and to develop the adaptation and preparedness strategies to meet these challenges, in case of their occurrence. In the present study, the Soil and Water Assessment Tool (ArcSWAT version 2012) model was used to simulate streamflow from Toba sub-watershed located in the southwest part of Ethiopia. The model Sensitivity analysis, calibration, and validation made using a sequential uncertainty fitting (SUFI-2) method of the ArcSWAT Calibration Uncertainty program known as SWAT-CUP2012. Groundwater delay (GW_DELAY) and curve number (CN2) were the first and the second most sensitive parameters. Calibration and validation results indicated a good much between the measured and simulated streamflow data with R-2, 0.82 and 0.70 and NSE, 0.72, and 0.68, respectively. The mean monthly stream simulated at Toba station was 58.71m(3)/s and 55.91m(3)/s during calibration and validation, respectively, and the mean annual runoff of the Toba river was 434.38 mm.