GIS for regionalization and visualization in hydrology

GIS today offers a lot of multi-purpose methods for general spatial analysis but only a few GIS-tools for analysing and modelling hydrological processes. For scale invariant spatial transfers as well as up- and downscaling of hydrological information, special Tools for Hydrological Information and Modelling, "T4HIM" has been developed, using ARC/INFO as a GIS kernel. As an example, an improved GIS-tool for aggregating flow directions in river basins is discussed. The visualization of hydrological data and processes is considered as another important research problem. "HydroVIS" couples GIS techniques with cartographic methods and multimedia approaches. The growing number of GIS applications in hydrology must not obscure our view of the conceptual and practical shortcomings of GIS. Newly developed object-oriented data models, temporal and three-dimensional approaches and the promising idea of open GIS will help to clear the path from loose coupling to full integration of GIS and hydrological models.