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Uncertainty analysis for nonpoint source pollution modeling: implications for watershed models
Shen, Z.; Xie, H.; Chen, L.; Qiu, J. & Zhong, Y.
Abstract
Uncertainty is inherent in watershed modeling
but it is not fully acknowledged in model applications. This
review focuses on uncertainty issues related to the Soil and
Water Assessment Tool (SWAT) model, which is one of
the most useful tools for simulating nonpoint source (NPS)
pollution processes. We considered numerous studies that
addressed three types of uncertainty in detail, i.e., the
model inputs, parameters, and model structure. It has been
shown that rainfall data, in terms of the spatial rainfall
variability and the accuracy of the measured data, play a
key role in the accuracy of the SWAT model. Geographic
information system inputs, including the digital elevation
model, land use map, and soil type map, have also been
identified as key sources of input errors. With respect to the
parameter uncertainty and model structural uncertainty, it
is anticipated that the complex, nonlinear structure, and
numerous parameters included in the SWAT model may
lead to a failure to identify parameters, as well as equifinality
phenomenon. We also compared some widely used
uncertainty analysis methods, such as the generalized
likelihood uncertainty estimation and first-order error
analysis, to provide reliable guidance for the application of
the SWAT model. This study benefits a wide range of
researchers, who are concerned with uncertainty issues in
NPS pollution modeling, and it provides insights into the
application of watershed models in the development of
watershed programs.
Keywords
Model input; Model parameter; Model structure; Soil and Water Assessment Tool; Uncertainty; Uncertainty analysis methods
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