Abstract
Abstract. The calibration of hydrologic models is a worldwide challenge due to the uncertainty involved in the large number of parameters. The difficulty even increases in a region with high seasonal variation of precipitation, where the results exhibit high heteroscedasticity and autocorrelation. In this study, the Generalized Likelihood Uncertainty Estimation (GLUE) method was combined with the Soil and Water Assessment Tool (SWAT) to quantify the parameter uncertainty of the stream flow and sediment simulation in the Daning River Watershed of the Three Gorges Reservoir Region (TGRA), China. Based on this study, only a few parameters affected the final simulation output significantly. The results showed that sediment simulation presented greater uncertainty than stream flow, and uncertainty was even greater in high precipitation conditions (from May to September) than during the dry season. The main uncertainty sources of stream flow came from the catchment process while a channel process impacts the sediment simulation greatly. It should be noted that identifiable parameters such as CANMX, ALPHA_BNK, SOL_K could be obtained with an optimal parameter range using calibration method. However, equifinality was also observed in hydrologic modeling in TGRA. This study demonstrated that care must be taken when calibrating the SWAT model with non-identifiable parameters because these may lead to equifinality of the parameter values. It was anticipated this study would provide useful information for hydrology modeling related to policy development in the Three Gorges Reservoir Region (TGRA) and other similar areas.
Highlights
Watershed hydrology and river water quality models are important tools for watershed management for both operational and research programs (Quilbeand Rousseau, 2007; Van et al, 2008; Sudheer and Lakshmi, 2011)
A hydrological station is locate9d in Wuxi County, and this study focused on the watershed controlled by the Wuxi hydrological station, which has an a1r0ea of approximately 2027 km2 (Fig. 1)
The Generalized Likelihood Uncertainty Estimation (GLUE) method was employed to assess the parameter uncertainty in the Soil and Water Assessment Tool (SWAT) model applied in the Daning River Watershed of the Three Gorges Reservoir Region (TGRA), China
Summary
Watershed hydrology and river water quality models are important tools for watershed management for both operational and research programs (Quilbeand Rousseau, 2007; Van et al, 2008; Sudheer and Lakshmi, 2011). The modification of parameter values reveals a high degree of uncertainty. Overestimation of uncertainty may lead to expenditures in time and money and overdesign of watershed management. Underestimation of uncertainty may result in little impact on pollution abatement (Zhang et al, 2009). In order to apply hydrological models in the practical water resource investigations, careful calibration and uncertainty analysis are required (Beven and Binley, 1992; Vrugt et al, 2003; Yang et al, 2008)
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