"Virtual water," a barometer of global water resources

When goods are produced, water is used in the process. Even though this water is "virtual," tracking its import and export gives a crucial indication of the evolution of world water resources. An international team of hydrologists has studied the global trade of virtual water, and is publishing an article this week in the journal PNAS outlining a number of striking conclusions. In 2007, the world's "virtual water trade" was 567 billion liters - more than six times the volume of Lake Geneva. This was double the 1986 volume. Every good produced at a given location, particularly agricultural goods, requires water. When the good is imported into another country, that country is also importing the water that went into its production; this is "virtual water." "This concept is very interesting when one observes it in terms of its flow between countries, particularly in terms of how the flow of virtual water evolves over time," explains Andrea Rinaldo, director of EPFL's Ecohydrology Laboratory (ECHO).