Parameter uncertainty, sensitivity analysis and prediction error in a water-balance hydrological model |
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Authors: | Kurt K Benke Kim E Lowell Andrew J Hamilton |
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Institution: | aPrimary Industries Research Victoria–Parkville Centre, Department of Primary Industries, PO Box 4166, Parkville, Victoria 3052, Australia;bCRC for Spatial Information, The University of Melbourne, 723 Swanston Street, Ground floor, Carlton, Victoria 3052, Australia;cSchool of Resource Management, Faculty of Land and Food Resources, The University of Melbourne, 500 Yarra Boulevard, Richmond, Victoria 3121, Australia |
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Abstract: | Analysis of uncertainty is often neglected in the evaluation of complex systems models, such as computational models used in hydrology or ecology. Prediction uncertainty arises from a variety of sources, such as input error, calibration accuracy, parameter sensitivity and parameter uncertainty. In this study, various computational approaches were investigated for analysing the impact of parameter uncertainty on predictions of streamflow for a water-balance hydrological model used in eastern Australia. The parameters and associated equations which had greatest impact on model output were determined by combining differential error analysis and Monte Carlo simulation with stochastic and deterministic sensitivity analysis. This integrated approach aids in the identification of insignificant or redundant parameters and provides support for further simplifications in the mathematical structure underlying the model. Parameter uncertainty was represented by a probability distribution and simulation experiments revealed that the shape (skewness) of the distribution had a significant effect on model output uncertainty. More specifically, increasing negative skewness of the parameter distribution correlated with decreasing width of the model output confidence interval (i.e. resulting in less uncertainty). For skewed distributions, characterisation of uncertainty is more accurate using the confidence interval from the cumulative distribution rather than using variance. The analytic approach also identified the key parameters and the non-linear flux equation most influential in affecting model output uncertainty. |
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Keywords: | Complex systems Error propagation Hydrological model Monte Carlo simulation Risk Sensitivity analysis Uncertainty 2C 2CSalt |
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