Analysis of hydrological processes with semi-distributed model

The Soil and Water Assessment Tool (SWAT) model is widely used to simulate streamflow in the basin by integrating complex interactions between climate, geography, soil, vegetation, land use / land cover, and other human activities. The SWAT model, a semi-distributed physically based hydrological model, was applied to analyze the hydrological processes in Göksu Himmetli, Zamanti-Ergenuşağı, Göksun Poskoflu ve Hurman-Gözler Üstü sub-basins in the upper region of Seyhan and Ceyhan watersheds located in the south of Turkey. Model sensitivity analysis, calibration and validation were performed using SWAT-CUP automatic calibration program and SUFI-2 algorithm. According to the model sensitivity analysis results, the most sensitive parameters in these basins have been seen as CN2 (SCS Flow curve number), ALPHA_BNK (Base flow alpha factor for storage), CH_K2 (Effective hydrological conductivity of main channel) and GW_DELAY (Groundwater delay time). In this study, 11-years (1994-2004) meteorological and 8-years (1997-2004) observed flow data were used, 3-years for model warm-up period, 5 years (1997-2001) for calibration and 3 years (2002-2004) for validation. Nash Sutcliffe Efficiency (NSE) was used as the objective function to evaluate the statistical performance of the model. As the result of the model calibration and validation, the NSE value in the considered 4 sub-basins varied between 0,70 - 0,90. The results obtained in the study showed a relatively high correlation between the observed and simulated discharge data.