Application of variance decomposition approach in the uncertainty analysis of a hydrological model

Abstract

Decomposition of uncertainty into individual sources is important for understanding the risks of decisions made under the modelling uncertainty. This paper has applied the predictive uncertainty analysis and variance decomposition (VD) approach for quantifying hydrological modelling uncertainty. The VD analysis is used for quantifying the contribution of various sources of uncertainty to total modelling uncertainty. The goal is to increase the reliability of predictive uncertainty analysis by the inclusion of the results of VD analysis. The approach is evaluated by analyzing uncertainty of the Soil and Water Assessment Tool (SWAT) model for a watershed of Southwestern Ontario, Canada. Three uncertainty analyzing frameworks are employed for quantifying modelling uncertainty by both predictive uncertainty analysis and VD approach. The contribution of parameter uncertainty to total error variance is expressed by the percentage of total variance explained by parameter uncertainty and this contribution is quantified for three uncertainty analyzing frameworks. The contributions of other uncertainties excluding model parameters and precipitation uncertainties to total error variance are quantified by applying the VD approach. The results obtained from predictive uncertainty and VD analyses are observed to be consistent. The underlying hypotheses of each uncertainty framework are also verified for the reliability of the uncertainty analysis.