Assessment of green water flows to sustain major biomes of the world: Implications for future ecohydrological landscape management

Global freshwater assessments tend to focus primarily on water flow in pere nnial rivers, lakes, and groundwater, so called blue water in the hydrologi cal cycle. Little attention is paid to the role of green water, or vapour f lows, in sustaining the generation of terrestrial ecosystem services, inclu ding biomass production. Ecosystem services (such as carbon sequestration, nutrient retention, pollination and pest control) are generated by ecologic al processes in different biomes of the World and essential for socio-econo mic development. In this paper we critically assess the limitations of the past blue water bias for future ecohydrological landscape management. We pr esent results from an effort of quantifying continental green water fluxes for major terrestrial biomes indicating that the large biomes, generating e ssential ecosystem services depend on more than 90 % of the total average t errestrial return flow of green water to the atmosphere. The paper discusse s the future implications of such large dependence on green water fluxes, a nd options of improving efficiency in water resources management. It points at the need of avoiding sectoral management and calls for an ecohydrologic al landscape management based on both ecological and hydrological knowledge . (C) 2001 Elsevier Science Ltd. All rights reserved.