problems in the water sector of the region can be addressed.

functions and a platform-independent structure of computational methods and interfaces has been established, by making use of the unified modelling language, an industry standard for the structuring and co-ordination of large projects in software development [Booch et al., The Unified Modelling Language User Guide, Addison-Wesley, Reading, 1999]. DANUBIA is object-oriented, spatially distributed and raster-based at its core. It applies the concept of ‘‘proxels’ ’ (process pixels) as its basic objects, which have different dimensions depending on the viewing scale and connect to their environment through fluxes. The presented paper excerpts the hydrological view point of GLOWA-Danube, its approach of model coupling and network-based communication, and object-oriented techniques to simulate physical processes and interactions at the land surface. The mechanisms and technologies applied to communicate data and model parameters across the typical discipline borders are demonstrated from the perspective of the Landsurface object. It comprises the capabilities of interdependent expert models for energy exchange at various surface types, snowmelt, soil water movement, runoff formation and plant growth in a distributed Java-based modelling environment using the remote method invocation [Pitt et al., Java.rmi: The Remote Method Invocation Guide, Addison Wesley Professional, Reading, 2001, p. 320]. The presented text summarizes the GLOWA-Danube concept and shows the state of an implemented DANUBIA prototype after completion of the first project-year (2001). 2003 Elsevier Ltd. All rights reserved.Web-based modelling of energy, water and matter fluxes to support decision making in mesoscale catchments––th