Functional similarity in landscape scale SVAT modelling

In this study, it is shown that the complexity of Soil Vegetation Atmospher e Transfer (SVAT) models leads to an equifinality of functional behaviour-m any parameterizations from many areas of the parameter space lead to very s imilar responses. individual parameters derived by calibration (i.e. model inversion) against limited measurements are, therefore, highly uncertain. D ue to the non-linear internal behaviour of SVAT models, aggregation of unce rtainly known parameter fields to parameterize landscape scale variability in surface fluxes will yield highly uncertain predictions. A disaggregation approach suggested by Beven (1995) requires that the land surface be repre sented by a linear sum of a number of representative parameterizations or f unctional types. This study explores the nature of the parameter space in t erms of a simple definition of functional behaviour. Parameter interactions producing similar predicted behaviours are investigated through applicatio n of Principal Component Analyses. These reveal the lack of a dominant glob al interaction indicating the presence of highly-complex parameter interact ions throughout the feasible parameter space.