Consistent assessment of global green, blue and virtual water fluxes in the context of food production: regional stresses and worldwide teleconnections

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Global food production relies on both blue water (available in rivers, lakes and aquifers, and used e.g. for irrigation) and green water (soil water transpiring through plants). Conventional indicators of water stress, however, are based upon blue water only, despite the dominant role of green water in agriculture. These indicators also ignore the mitigation potential of virtual water (the amount of blue or green water transpired to produce a unit of crop yield) that is associated with international crop trade. The proposed project will derive for the first time a model-based, global yet geographically explicit assessment of green, blue and virtual water flows for the present and for scenarios of climate change and atmospheric CO2 enrichment. To achieve this project goal, we employ two macroscale hydrological process models-the well-established dynamic global vegetation and water balance model LPJ and the state-of-the-art global model of water availability and water use WaterGAP-, and compare their results to estimate model-specific uncertainties. New water stress indicators-which consistently account for the combination of blue, green and virtual water balances-are calculated and used to identify hotspot regions of water scarcity. In addition, effects of agricultural management practices on the diverse water flows are studied for selected regions.