Robustness of river basin water quality models

In this paper the concept of robustness is introduced and applied to a model for the analysis of the impacts of spatially distributed policy measures on the surface water quality on a river basin scale. In this model the influence of precipitation on emissions and resuspension of pollutants in the river sediment are taken into account. The major sources of uncertainty can be found in the transport model and the emission data. The uncertainty in the prediction of future pollutant loads is dominated by the stochastic character of the precipitation. The uncertainty in the spatial representation of the emission sources seems to be of minor importance relative to the other sources of uncertainty. Evaluation of the robustness of the model conclusions on the basis of these results led to useful guidelines about how to improve the model effectively.