REDUCING PREDICTIVE UNCERTAINTY IN MODEL SIMULATIONS - A COMPARISON OF 2 METHODS USING THE EUROPEAN SOIL-EROSION MODEL (EUROSEM)

The simulation results from physically-based hydrology and erosion mod els contain uncertainty. This is largely the result of uncertainty ove r the value of the model's input parameters. if such uncertainties are in the form of probability distributions of model output, it becomes apparent that they are not inconsiderable. Such variation in model out put may reduce the utility of the simulations and it is therefore desi rable for it to be reduced. Two methods are considered: one which reli es on improved parameter set selection, and a second which derives phy sical parameters from observed hydrographs. Both methods are compared with a blind application of the model and observed data. The results s uggest that, while both methods may be successful in reducing the vari ation in model output, the coincidence with the observed data deterior ates. (C) 1997 Elsevier Science B.V.