Evaluation of water quantity and quality modelling in ungauged european basins

The conceptual rainfall-runoff model HBV was evaluated for predictions in ungauged basins in Sweden and in selected basins across Europe. The paper mainly stresses the impact of model parameter estimation and meteorological input data. Daily simulations for 1000 sub-basins (of which 700 are Ungauged) for the period 1961–2002 include all of Sweden, normally with a volume error <5%. When transferring the model to 18 European basins, it was concluded that modeling was normally trustworthy (i.e. R² > 0.7 and VE < 5%) if rainfall data was representative. The automatically calibrated parameter values could not easily be related to basin characteristics. However, blind-test simulations showed that a priori parameter values gave almost as good results as the calibrated model. This highlights the influence of the modeller's experience and knowledge on the results.