The Ministerial Declaration of the Second World Water Forum in the Hague, Netherlands, (March 2000) set water security as a principal concern for sustainable development in the twenty first century. The global statistics speak for themselves. Approximately one in three people live in regions of moderate to high water stress and it is estimated that two thirds of people will live in water stressed conditions by 2025 (WBGU 1999, UNEP 1999). Human demand and the misuse of water resources continue to grow. Intensive irrigation is placing steadily increasing pressure on aquifers and their ability to recharge, and reported incidences of groundwater and surface water contamination continues to rise. In large cities, total municipal and industrial uses of water have grown by 24 times in the last century and urban populations are expected to grow to 5 billion people by 2025. Some large-scale water infrastructure projects and an intensification and greater frequency of natural threats, such as flooding and droughts, are having a devastating impact on people’s livelihood and access to water. These pressures are also placing freshwater ecosystems and their associated species under enormous strain. The critical issues for water security, in terms of the causes and the resultant impacts, are particular to each locality and region of the world (Table 1).