The global component of freshwater demand and supply: an assessment of virtual water flows between nations as a result of trade in agricultural and industrial products

Where the river basin is generally seen as the appropriate unit for analysing freshwater availability and use, this paper shows that it becomes increasingly important to put freshwater issues in a global context. International trade in commodities implies flows of 'virtual water' over large distances, where virtual water should be understood as the volume of water required to produce a commodity. Virtual water flows between nations have been estimated from statistics on international product trade and the virtual water content per product in the exporting country. With increasing globalization of trade, global water interdependencies and overseas externalities are likely to increase. At the same time liberalization of trade creates opportunities to increase physical water savings.