HR: 14:10h
AN: H53H-03    [Abstracts]
TI: Improving model structure and reducing parameter uncertainty in conceptual water balance models
AU: * Son, K
EM: son@cwr.uwa.edu.au
AF: Centre for Water Research in the University of Western Australia, 35, Stirling Highway, , Crawley, WA 6009 Australia
AU: Sivapalan, M
EM: sivapala@uiuc.edu
AF: Department of Geography University of Illinois, Urbana-Champaign 220 Davenport Hall, MC-150 607 South Mathews Avenue, Urbana, IL 61801 United States
AB: The use of uncertainty analysis is gaining considerable attention in catchment hydrological modeling. In particular, the choice of appropriate model structure, identification of parameter values, and the reduction of model predictive uncertainty are deemed as essential elements of hydrological modelling. The chosen model structure must be parsimonious, and the parameters used must either be derivable from field measured data or inferred unambiguously from analysis of catchment response data. In this research, a long-term water balance model for the Susannah Brook catchment in Western Australia has been pursued using the ›r­’downward approach›r­_, which is a systematic approach to determine the model with the minimum level of complexity, with parameter values that in theory are derivable from existing physiographic data relating to the catchment. Through analysis of rainfall-runoff response at many different timescales, and exploring the climate, soil and vegetation controls on the water balance response, an initial model structure was formulated, and a priori model parameter values estimated. Further investigation with the use of additional data such as Deuterium concentration in the stream and groundwater level data exposed inadequacies in the model structure. Two more model structures were then proposed and investigated through formulating alternative hypotheses based on the underlying causes of observed variability, including those associated with the absence of a contribution of deep groundwater flow to the streamflow, which was indicated by Deuterium concentration and internal dynamics characterized by the observed groundwater levels. Along the way, the resulting models were evaluated in terms of their performance (ability to reproduce observations), predictive uncertainty, and physical realism. The final model, which included an efficient but detailed representation of unsaturated zone time delay, was deemed to be superior on all three counts: improved performance, reduced predictive uncertainty and improved physical realism.
DE: 1804 Catchment
SC: Hydrology [H]
MN: Fall Meeting 2005