Comparison of two Calibration-Uncertainty Methods for Soil and Water Assessment Tool in Stream Flow and Total Suspended Solids Modeling

Estimation of total suspended solids in upland watershed of reservoirs using simulation models is a vital key to manage reservoirs water quality. It is consequently essential that these models undergo calibration and uncertainty analysis before their application. In this study, Soil and Water Assessment Tool model was applied to estimate stream flow and total suspended solids for Sofichai Watershed upstream of the Alavian Reservoir located in East-Azarbayjan province. The Generalized Likelihood Uncertainty Equation (GLUE) and Sequential Uncertainty Fitting (SUFI-2) were used in this study to calibrate and analyze the uncertainty of SWAT model. The performance of the GLUE and SUFI-2 was evaluated using four objective functions namely: Nash–Sutcliffe Efficiency (NS), coefficient of determination (R2), RMSE-observations standard deviation ratio (RSR) and the adjusted R2 coefficient (bR2). Uncertainty statistics used were the P-factor and R-factor. SUFI-2 proved to be a very efficient optimization algorithm for Calibration and uncertainty analysis. The model calibrated with SUFI-2 can therefore be applied confidently for water resources management, for quantification of scenarios of climate and land use change, and for estimation of the Best Management Practices efficiencies in the watershed.