Response of a river catchment to climatic change:: Application of expanded downscaling to Northern Germany

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