EVALUATION OF UNCERTAINTY ESTIMATES IN DISTRIBUTED HYDROLOGICAL MODELING FOR MICRO WATERSHED IN GODAVARI RIVER IN INDIA USING SUFI-2, AND PARASOL METHODS

摘要

Hydrological models always suffer from different sources of uncertainties. As the distributed hydrological models play vital role in water resource management, reliable quantification of uncertainty in hydrological modeling results is quite necessary. The objective of the present study is to apply two uncertainty analysis methods to a distributed hydrological modeling system, quantify the impact of parameter uncertainties, and examine their performance and capability. SWAT (Soil and Water Assessment Tool) is a comprehensive, semi-distributed river basin model that requires a large number of input parameters, which complicates model parameterization and calibration. Several calibration techniques have been developed for SWAT, including manual calibration procedures and automated procedures using the shuffled complex evolution method and other common methods. In addition, SWAT-CUP was recently developed and provides a decision-making framework that incorporates a semi-automated approach (SUFI2, ParaSol) using both manual and automated calibration and incorporating sensitivity and uncertainty analysis. In SWAT-CUP, users can manually adjust parameters and ranges iteratively between auto calibration runs. The user interaction or manual component of the SWAT-CUP calibration forces the user to obtain a better understanding of the overall hydrologic processes (e.g., base flow ratios, ET, sediment sources and sinks, crop yields, and nutrient balances) and of parameter sensitivity. When calibrating a physically based model like SWAT, it is important to remember that all model input parameters must be kept within a realistic uncertainty range and that no automatic procedure can substitute for actual physical knowledge of the watershed. The selected site of water shed is under overexploited stage according to CGWB report. BMP's should be implemented for the present case study for sustainable development. This micro watershed lies in Godavari river basin which flows through Paithan, Khuldabad villages of Aurangabad district Maharashtra state India. The soil and water assessment tool (SWAT) model was applied to estimate the surface runoff during 1985-2010 and validated by the observed data. Two uncertainty analysis methods were further conducted and compared within the same modeling framework: (1) the sequential uncertainty fitting algorithm (SUFI-2), and (3) the parameter solution (ParaSol) method. Through the comparison of a set of proposed evaluation criteria for uncertainty analysis methods in this study, including R-factor, P-factor, computation efficiency, and performance of best estimates, the SUFI-2 method was able to provide more reasonable and balanced predictive results. SWAT-CUP provides a decision-making framework that incorporates a semi-automated approach (SUFI2) using both manual and automated calibration incorporating sensitivity and uncertainty analysis.