Global socio-hydrology: An overview of virtual water use by the world economy from source of exploitation to sink of final consumption

To reflect a key aspect of global socio-hydrology, this paper explores global virtual water use from source of exploitation to sink of final consumption via interregional trades within the world economy as reflected by world input-output database for 2014. An embodiment accounting model is developed, which takes full account of virtual water feedbacks related to primary inputs. Global total trade volume of virtual water is estimated to be in magnitude around 30% of the global direct freshwater withdrawal. Moreover, it is revealed that global virtual water transfer in intermediate trade is in magnitude around 1.4 times that in final trade. In intermediate trade of virtual water, China, Japan and the United Kingdom turn out to be the three leading net importers, while India, Russia and the United States are revealed as the leading net exporters. In final trade of virtual water, the United States, Japan and Russia are the major net importers, in contrast to China, India and Mexico as the leading net exporters. Trade connections and imbalances of major economies in terms of virtual water are quantified and analyzed. Two new indicators in terms of water self-sufficiency rate by source and that by sink are devised. It is found that around 40% of the use of China's freshwater withdrawal finally sinks into foreign economies while only 20% of China's virtual water use originates from other regions. With regard to Germany, Canada and France, they behave like active pumps driving vast virtual water inflows and outflows, demonstrating their high involvement in the global supply chain in terms of virtual water. With the increasingly frequent virtual water transfer within the world economy, nations and regions ought to assess their behaviors in intermediate and final trades of virtual water for sustainable use of freshwater resources.