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.