We used the technique of expanded General Circulation Model (GCM) downscalingto derive time series of daily weather for the analysis of potential climaticchange impact on a river catchment in Northern Germany. The derived timeseries was then fed into a spatially distributed hydrological model tosimulate various water balance components and river discharge. All componentsof this modelling approach are known to provide fairly accurate results undernormal (current) climatic conditions. Hydrological time series, theirstatistics and spatial patterns of various water balance components, resultingfrom a `business-as-usual' emission scenario, were analysed. The simulationresults showed that if everything apart from climate is held constant, asignificant increase in river discharge may be expected in the coming decadesas a consequence of increased rainfall amounts. Although the modellingapproach provides an operational way of performing watershed climate changeimpact studies, many uncertainties still have to be considered.