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 perennial rivers, lakes, and groundwater, so called blue water in the hydrological cycle. Little attention is paid to the role of green water, or vapour flows, in sustaining the generation of terrestrial ecosystem services, including biomass production. Ecosystem services (such as carbon sequestration, nutrient retention, pollination and pest control) are generated by ecological processes in different biomes of the World and essential for socio-economic development. In this paper we critically assess the limitations of the past blue water bias for future ecohydrological landscape management. We present results from an effort of quantifying continental green water fluxes for major terrestrial biomes indicating that the large biomes, generating essential ecosystem services depend on more than 90 % of the total average terrestrial return flow of green water to the atmosphere. The paper discusses the future implications of such large dependence on green water fluxes, and options of improving efficiency in water resources management. It points at the need of avoiding sectoral management and calls for an ecohydrological landscape management based on both ecological and hydrological knowledge.