As defined by the Global Water Partnership (GWP) Integrated Water Resources Management refers to the coordi-nated development and management of water, land and related resources for optimising economic and social welfare without compromising the sustainability of vital environmental systems. It is obvious that this is a complex issue where we need new approaches to the assessment, development and management. To assist processes in IWRM so-cio-technical tools as for instance Decision Support Systems (DSS) can be very helpful. A DSS for IWRM can be understood as a socio-technical instrument which is a machine, a tool and a medium which promotes better under-standing and handling of such complex system as river basins in a coherent and transparent management process with mutual learning.