Comparison of two Calibration-uncertainty Methods for Soil and Water Assessment Tool in Stream Flow Modeling

Abstract

Hydrological models are increasingly being used as decision support tools in water resource management. It is therefore important that these models undergo calibration and uncertainty analysis before their application. This study addresses the application and comparison of two calibration-uncertainty methods for a distributed model in the Upper Tana Basin. The Generalized Likelihood Uncertainty Equation (GLUE) and Sequential Uncertainty Fitting Ver. 2 (SUFI-2) were used in this study to calibrate the Soil and Water Assessment Tool (SWAT). The performance of the GLUE and SUFI-2 was evaluated using three objective functions namely: coefficient of determination (R2), Nash–Sutcliffe Efficiency (NSE) and coefficient of determination divided by coefficient of regression (bR2). Uncertainty statistics used were the P-factor and R-factor. The study established the best method for calibration and uncertainty analysis is SUFI-2.