Surface Runoff Simulation Based on SWATCUP Sensitivity Analysis Method (Case study: Ghareh-Chay River )

The purpose of this study was to simulate surface runoff of the Ghareh-Chay River that was modeled using SWAT hydrological model. In this regard, GIS software version 10.4, DEM and waterways and river network characteristics were first extracted. The statistics used for the 2003-2016 Ghareh-Chay Basin Pole Doab Khondab, Joshiravan, and Sarouq stations were considered. Soil curve number (CN) method was used to calculate basin mortality. Model calibration and validation were performed by SWAT-CUP software with SUFI-2 algorithm. To evaluate the model's ability to simulate runoff discharge, Nash-Sutcliffe, R2, p-factor and r-factor indices were used. Eight years of measured data (2004-2011), precipitation, temperature and daily discharge were used to calibrate the model. And model validation with residual data (2012–2016). The model validation results with Nash-Sutcliffe, R2, p-factor and r-factor indices for the Khondab station were 0.65, 0.66, 0.35, 0.07%, and for the Pole Doab station, respectively, the results were 0.57, 0.72, 0.07, 0.05. The model evaluation confirms the SWAT model's ability to simulate surface runoff of the Ghareh-Chay River. Finally, the comparison of simulated hydrographs and monthly observations showed that the model modeled well the peak discharge and base discharge times but estimated the peak discharge values more than the actual values.