Higher standards of living, demographic changes, land and water use policies, and other external forces are increasing pressure on local, national and regional water supplies needed for irrigation, energy production, industrial uses, domestic purposes, and the environment. In many parts of Europe groundwater quantity and quality in particular has come under server pressures and water levels have decreased, resulting in negative environmental impacts. Rapid, and often, unpredictable changes with regard to freshwater supplies create uncertainties for water managers. At the same time, climate change adds a new level of uncertainty with regard to freshwater supplies and to the main water use sectors such as agriculture and energy, which will in turn exacerbate uncertainties regarding future demands for water.