Water Resources Research Report



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Assessment of climate change impact on hydrology at watershed scale incorporates downscaling of global scale climatic variables into local scale hydrologic variables and computations of risk of hydrologic extremes in future for water resources planning and management. Atmosphere-Ocean General Circulation (AOGCM) models are designed to simulate time series of future climate responses accounting for enthropogenically induced green house gas emissions. The climatological inputs obtained from several AOGCMs suffer the limitations due to incomplete knowledge arising from the inherent physical, chemical processes and the parameterization of the model structure. This study explores the methods available for quantifying uncertainties from the AOGCM outputs by considering fixed weights from different climate model means for the overall data lengths and provides an extensive investigation of the variable weight nonparametric kernel estimator based on the choice of bandwidths for investigating the severity of extreme precipitation events over the next century. The results of this study indicate that the variable width method is better equipped to provide more useful information of the uncertainties associated with different AOGCM scenarios. This study further indicates an increase of probabilities for higher intensities and frequencies of events. The applied methodology is flexible and can be adapted to any uncertainty estimation studies with unknown densities.

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Department of Civil and Environmental Engineering, The University of Western Ontario


London, Ontario, Canada


Civil and Environmental Engineering


Report no.: 070

Quantifying Uncertainties in the Modelled Estimates of Extreme Precipitation Events at the Upper Thames River Basin