The digital terrain model (DTM) is one of the basic data sets for the characterisation of the process pixel of the DANUBIA model. It is fundamental for describing vertical and lateral processes in the study area. Its accuracy is of utmost importance for the modelling and the exchange of water flow between the DANUBIA model objects, Soil, Rivernetwork and Groundwater. To assemble a hydrologically consistent DTM for the catchment area of the Upper Danube, difficulties due to differences in the resolution and the data quality of the input data sets from the various national sources had to be resolved. The initially derived 50 m resolution DTM was aggregated step by step to the model’s 1,000 m resolution. It was found that retaining the minimum elevation of river network pixels at each step reduced the undesired smoothing effects during aggregation. The river network was subsequently derived using the software TOPAZ. The resultant 1,000 m resolution DTM and river network had a good accuracy. The generated river network correlated well with the actual river network of the Upper Danube.