Water circulation in the hydrological cycle of evaporation, transpiration and precipitation is mainly driven by various climatic and land management factors (Falkenmark, 1997). Rockstrom, Gordon and Folke (1999) reported that about 35 percent of annual precipitation (110 305 km3) returns to the ocean as surface runoff (38 230 km3) while the remaining 65 percent is converted into water vapour flow. Moreover, major terrestrial biomes -forest, woodlands, wetlands, grasslands and croplands -consume approximately 98 percent of global green water flow and generate essential ecosystem services (Rockstrom, Gordon and Folke, 1999, Rockstrom and Gordon, 2001).