HR: 17:30h
AN: H14A-07 INVITED     [Abstracts]
TI: Incorporating observational uncertainties more explicitly within GLUE: Examples using the rainfall-runoff model Dynamic TOPMODEL including predictions of fuzzy water table levels
AU: * Freer, J
EM: j.freer@lancaster.ac.uk
AF: Environmental Science Department Lancaster University, Bailrigg, Lancaster, LA1 4YQ United Kingdom
AB: The Generalised Likelihood Uncertainty Estimation (GLUE) procedure is underpinned by the equifinality thesis. This thesis maintains that for a given modelling problem, errors associated with the model structure and the observational data result in multiple acceptable representations that cannot be easily rejected and that should be considered in assessing the uncertainty associated with predictions. In this form errors in fitting observations are then treated as 'measurement error', even though the total model error derives from many different sources and is often larger than any conceivable real measurement error. An alternative approach is proposed, as a more rigorous implementation of the GLUE methodology. Arguments are developed to define an effective observation error, prior to the application of the model. The effective observation error may need to account for scale, heterogeneity, non-stationary error properties and other sources of incommensurability between model output variables and observables. Models that then fall outside of this allowable range are rejected. Models that fall inside the allowable range are used in prediction. The effects of input error, model structural error and effective observation error can, in principle, be separated. This modified GLUE approach is explored with examples using the rainfall-runoff model Dynamic TOPMODEL applied to discharge and fuzzy estimates of water table depths for 2 locations at Maimai catchment, New Zealand. The results have implications for how we, as modellers, consider observational uncertainties in the assessment of our model predictions.
DE: 1829 Groundwater hydrology
DE: 1860 Runoff and streamflow
DE: 1866 Soil moisture
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting