A nice article posted in DnaIndia by R. N. Bhaskar.
If the next wars would be fought for water, it is time to look at how countries manage their own water resources. Savvy countries augment their water needs by importing goods which otherwise would have necessitated additional water consumption. For instance, a country may choose to import rice, and thereby actually save on 1,670 litre of water for every kg of import.This is where a more serious look atwater footprints on a global scalebecomes all the more imperative.
As Arjen Y Hoekstra (who originally promoted this concept) states in his paper titled Virtual Water: Measuring Flows around the World, "International trade of 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 can be estimated from statistics on international product trade and estimates of the virtual water content of products. The global volume of virtual water flows related to the international trade in commodities is 1,625 Gm3/year (GM3 means a billion cubic metres - or a trillion litres -- of water)."
Currently, the global volume of water used for crop production, including both effective rainfall and irrigation water, is 6,390 Gm3/year. The global water footprint is 7,450 Gm3/year, which is 1,240 cubic metres per capita per year.
You can see detailshttp://www.dnaindia.com/money/report-policy-watch-india-splurges-51-of-water-it-could-have-otherwise-saved-1995733