Water is one of the most important natural resources covering 75 percent of the Earth's surface. It is a major component of living organisms contributing to about 60 percent of the human body. Different European environmental monitoring programmes confirm that the current land and water resources in Europe are extremely vulnerable and subject to a range of external pressures. Water management needs to be implemented with caution following thorough evaluation. Therefore, it is crucial for the current generation to manage and preserve water resources for future generations in a sustainable way. Current human development patterns suggest that in the future there will be an increase in population, population density and an increase in agglomerations. These global change patterns (of land use and climate) add additional pressures on water resources and it might increase probability of flood events.
This problem has been recognized in recent years not only by scientists, but also by policy makers. Therefore in October 2000, the European Parliament adopted the Directive 2000/60 /EC (the EU Water Framework Directive-WFD).The WFD defines the water management objectives that need to be reached in the near future by the different member states of the EU. Since the use of natural resources in a sustainable way is one of the priorities of the European environmental agenda, sustainable exploitation and use of water resources is a key objective of the WFD. The WFD adopts a holistic approach to river water management and envisages the involvement of different actors in the design of future water management plans. Furthermore, the principles of future water management plans should be based on state-of-the-art knowledge of the functioning of the hydro-system and should be based on the sustainable exploitation of water resources. Unfortunately, the hydro-system is complex, involving many compartments, processes, and boundary conditions which vary in space and time. This makes the description of the evolution of the hydro-system for alternative potential management scenarios a difficult task. In such a context, the design of water resource management plans must inevitably adopt a multidisciplinary, multi-participatory approach, considering the pressures exerted by global change drivers and will be based strongly on the use of hydrological models.