Regionalisation of physically-based water balance models in Belgium. Application to ungauged catchments

More than 60 catchments from Northern Belgium ranging in size from 16 to 3160 km2 have been studied by means of a physically-based stochastic water balance model. The parameter values derived from calibration of the model were regionally mapped for the study region. Associations between model parameters and basin lithological characteristics were established and tested. The results show that the simple conceptual monthly water balance model with three parameters for actual evapotranspiration, slow and fast runoff is capable either to generate monthly streamflow at ungauged sites or to extend river flow at gauged sites. This allows a fairly accurate estimation of monthly discharges at any location within the region.