Analysis of parameter uncertainty in hydrological and sediment modeling using GLUE method: a case study of SWAT model applied to Three Gorges Reservoir Region, China

摘要

The calibration of hydrologic models is a worldwide challenge due to theuncertainty involved in the large number of parameters. The difficulty evenincreases in a region with high seasonal variation of precipitation, wherethe results exhibit high heteroscedasticity and autocorrelation. In thisstudy, the Generalized Likelihood Uncertainty Estimation (GLUE) method wascombined with the Soil and Water Assessment Tool (SWAT) to quantify theparameter uncertainty of the stream flow and sediment simulation in theDaning River Watershed of the Three Gorges Reservoir Region (TGRA), China.Based on this study, only a few parameters affected the final simulationoutput significantly. The results showed that sediment simulation presentedgreater uncertainty than stream flow, and uncertainty was even greater inhigh precipitation conditions (from May to September) than during the dryseason. The main uncertainty sources of stream flow came from the catchmentprocess while a channel process impacts the sediment simulation greatly. Itshould be noted that identifiable parameters such as CANMX,ALPHA_BNK, SOL_K could be obtainedwith an optimal parameter range using calibration method. However,equifinality was also observed in hydrologic modeling in TGRA. This studydemonstrated that care must be taken when calibrating the SWAT model withnon-identifiable parameters because these may lead to equifinality of theparameter values. It was anticipated this study would provide usefulinformation for hydrology modeling related to policy development in theThree Gorges Reservoir Region (TGRA) and other similar areas.