Hydrological and water quality modeling of Ergene River Basin

Hydrologic and water quality modeling of the Ergene River Basin has been developed by using Soil and Water Assessment Tool (SWAT). The purpose of this study is to model distributed surface flow and contaminant transport to help the management of the Ergene River Basin. SWAT model is one the few hydrologic models with water quality coupling capability that is convenient for this purpose. Most of the industrial activities, causing the water pollution in the basin, take place in the upper part of the Ergene River Basin, with about 2780 km2 and this area was modeled in this study. Daily climate data for 48 years, land use, soil properties, and contaminant point source dataset compatible with the structure of SWAT are used in the model as input data. The river basin was divided into 36 sub-basins and 205 Hydrologic Response Units (HRU). The stream flow was calibrated by considering 9 different hydrologic parameters. The water quality model was calibrated manually by adjusting the water quality default parameters in SWAT database for one year period. The streamflow was validated for 31 years. The model results for monthly streamflow was in good agreement with the observed streamflow data R2 = 0.81, however, daily streamflow (R2 = 0.57) and nutrient ( TN for R2 = 0.5041 and TP for R2=0.55 ) model results were acceptable. The monthly streamflow validation result was good (R2=0.70). The model results showed that the more data is necessary for better daily streamflow calibration. The model is convenient for monthly streamflow and water quality calibration.