The global virtual water trade network

While some countries have substantial supplies of freshwater, others need to import water to sustain their populations. Because food products contain significant amounts of water, global trade in food effectively moves water from one country to another in a “virtual water trade.” Konar et al. consider the global virtual water trade as a weighted complex network. The nations that participate in international food trade correspond to the nodes, and the links represent the flow of virtual water; weights are assigned to the links based on the volume of virtual water traded. They found that the number of trade connections follows an exponential distribution. There is a global hierarchy in which nations that trade large volumes of virtual water are more likely to link to other nations that trade large volumes of water. Several nations play a critical role in this network. For instance, the United States is the dominant exporter of virtual water, and Japan is the dominant importer. Furthermore, trade volume follows a power law relationship with the number of trade partners of each nation: The more trading partners a country has, the more virtual water it trades. The study could help in global water resource management; for instance, water‐scarce nations could consider increasing their access to virtual water resources by increasing the number of nations with which they trade food. (Water Resources Research, doi:10.1029/2010WR010307, 2011)