The First Global Virtual Water Network Model

Ignacio Rodriguez-Iturbe of Princeton University and Samir Suweis of the Swiss Federal Institute of Technology in Lausanne have built the first mathematical model of the global virtual water trade network using the U.N. Food and Agricultural Organization's data on trade in barley, corn, rice, soya beans, wheat, beef, pork, and poultry in 2000 (Structure and Controls of the Global Virtual Water Trade Network). 

The model shows that a small number of countries have a large number of connections to other countries, offering them a steady and cheap supply of virtual water even if some connections are compromised.  A much larger number of countries have very few connections and so are vulnerable to market forces.  Most importantly, the model illustrates that almost 80% of the water flows over only about 4% of the links, which Rodriquez-Iturbe calls the "rich club phenomenon".  In total, the model shows that in 2000, there were 6,033 links between 166 nations.  Yet 5% of global water flow was channelled through just one link between two "rich club" members - - the U.S. and Japan.

See my previous October 30, 2010 posting for an introduction to the idea of virtual water - - My Water Footprint.