Virtual Water

"Virtual water" is a new yet fundamental concept in the world of water ecology and water economics. Essentially the concept refers to the way in which virtually all products, particularly agricultural products such as food but also cotton, require water to be grown or produced. The amount of water required, of course, varies from product to product, but it is often substantial. Therefore when a product such as wheat, beef, eggs or what have you, is exported, the export of the "virtual water" that was used to produce the product needs to be calculated and taken into account in order to fully understand the economic and ecological costs of producing then exporting the product.

Forbes has recently run a good series of articles, including a slide show, that describe this concept. Rather than repaste the artlcles I've included a link. It's well worth checking out.

Peter Huston
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http://www.forbes.com/home/2008/06/19/water-food-trade-tech-water08-cx_fp_0619virtual.html