Determination of the Surface water Balance Parameters in Ag Chai Basin Using SWAT Model and Uncertainty Analysis with SUFI-2 Algorithm

Water balance analysis is the base of streams management. Because the results like changes in surface water reserve can be used efficiently in decisions and water resources optimum usage. One of the models that is used widely to simulate catchment hydrological ingredients, around the world recently quantitatively and qualitatively, is SWAT hydrological model. This model operates continuously on a daily scale. In this study, surface water balance parameters were evaluated using the SWAT model over the Agh Chai basin. The algorithm SUFI-2 by the SWAT-CUP software package for calibration and validation based on monthly river discharge and uncertainty analysis was used. The results showed that due to the calibration period Nash coefficient is 0.86 in very good level. The p-factor in the calibration period, equivalent to 17% and the r-factor is equal to 0.1. These low values, indicating high uncertainty in runoff prediction and good calibration in the basin. The values ​​for validation period are 0.52, 29% and 0.14 respectively when considering Nash coefficient was obtained in a satisfactory level. Other values confirm the results obtained in the calibration period also.