There is a growing concern over the future of the world’s water resources. A series of world water assessments, starting with the classic work of L’vovich (1979) and the fundamental work by Falkenmark (Falkenmark and Lindh, 1976) onwards to the latest freshwater assessments (Raskin, 1997; Shiklomanov, 1997, 2000; UN, 1997; Cosgrove and Rijsberman, 2000), have convincingly shown that humankind is, through increased pressure on finite water resources, heading towards a water resources scarcity.