The revered and provider role of Nature from the ancient times was arguably on account of its most ubiquitous resource, water. Humanity understood its life sustaining importance in the antiquity and man’s approach to it as a commodity and a treasure is documented in archeology and history in the form of water retaining structures, water distribution systems, public bathrooms and tons of literature. This relationship with Nature’s most abundant resource was however philosophically rooted in a deep belief that supply of water is limit less. Traditionally global and regional water resources were thought of as an everlasting supply to furnish the needs of human societies and thereby assisting in socio-economic development. It is only recently and with advancement of science and technology, we started to grasp the limitedness of usable freshwater in nature and the Water Paradigm changed with a underlining of the issue of sustainability.
The new water paradigm started with the ground-breaking work of Professor John Anthony Allan, a British geographer and an emeritus of the School of Oriental and African Studies of King’s College London under University of London when he was awarded 2008 Stockholm Water Prize for creating the concept of Virtual Water. To a common man the rapport of John’s work may not be as popular as celebrity scientists like Einstein or Stephen Hawking, but I feel confident to say that his foresight and approach to water will continue to influence human future in a profound way in years to come. It is important and almost a necessary element of understanding and practice for any Water activist.
So what is Virtual Water?
Virtual Water, also loosely referred as embedded water, embodied water or hidden water, is the water used in the production of a good or service. Hoekstra and Chapagain have defined the virtual-water content of a product (a commodity, good or service) as “the volume of freshwater used to produce the product, measured at the place where the product was actually produced”. It refers to the sum of the water use in the various steps of the production chain. This is a concept similar to Carbon Footprint, only here we are dealing with Water Footprint and mostly looking at water use from a Global or Regional trade context.
An example may make it interesting. Wheat, an edible essential for two thirds of the world, has a connection with freshwater. A metric ton of wheat, on the average, requires about 1,300 cubic meters of water (the actual requirement of water may vary somewhat depending on climatic conditions and agricultural practice). !,300 cubic meter of water is approximately 1,300 metric tons so in the context of trade, import or export of 1 metric ton of wheat essentially mean 1,300 times as much by weight of unseen water crossing geo-political boundaries. This is interesting because in a global scale, for a water-deficient country it makes better sense to import wheat from a water-abundant country both from long term economy of the country and the smart utilization of water as a key natural resource. Many countries are starting to realize this and such realization is expected to make tremendous impact on global trade and hopefully, a better management of water use.
“Virtual water has major impacts on global trade policy and research, especially in water-scarce regions, and has redefined discourse in water policy and management. By explaining how and why nations such as the US, Argentina and Brazil ‘export’ billions of litres of water each year, while others like Japan, Egypt and Italy ‘import’ billions, the virtual water concept has opened the door to more productive water use.”
-Professor John Anthony Allan at SIWI (Stockholm International Water Institute).
Following are some Virtual Water equivalence for few daily consumer products (a commodity, good or service)
Agricultural Products 
•the production of 1 kg eggs costs 3,300 L water
•the production of 1 kg broken rice costs 3,400 L water
•the production of 1 kg beef costs 15,500 L water
Household Products 
•Jeans (1000g) contain 10,850 liters of embedded virtual water
•A cotton shirt (medium sized, 500 gram) contains 4,100 liters of water
•A disposable diaper (75g) contains 810 liters of water
•A bed sheet (900g) contains 9,750 liters of water
•1.1 tonne passenger car has about 400,000 liters of water embedded in it 
•Construction of a house, using a combination of methods, requires about 6 million litres of water 
For a more detailed list or to buy a poster of Virtual Water World check this site. For a poster like one below you will need to pay Euro 10 roughly.
Being a futuristic and new concept Virtual Water is not beyond some criticism. Some think that there is significant risk in relying on this concept while deriving policy conclusions. Australia’s National Water Commission considers that the measurement of virtual water has little practical value in decision making regarding the best allocation of scarce water resources. I find this hesitation and skepticism quite like US Conservatives, who view anything new with suspicion and do not bother to get down to critical understanding of the aspects of a theory. In my opinion this hesitation will eventually go away and policies will be based on this very smart and practical approach to water management.
For a common person to understand and react about present day water crisis, it is essential to know the Virtual Water and unlimited-supply dichotomy. Our traditional water usage attitude has propagated on three dead end avenues:
3.Expansion of irrigated agricultural
I call these dead-end because these aspects of development of societies have an element of linearity incompatible in a cyclic natural setting and therefore anti-sustenance approaches. The corresponding water demand and use patterns bear the sad signs of similar anti-sustenance attitudes.
Contrary to mainstream academics, I do not see Virtual Water Paradigm as a socio-economic theory, rather, in my opinion, it contains a sustainability oriented worldview which has the potential to develop into a meme and make the effort to manage Global water crisis manageable by active participation of one and all. It removes the ignorant luxury of a common man/woman of assuming the daily consumption of water as negligible. Our requirements of physical water that we drink, shower with and use for sanitation is a puny percentage of the total water that we, by our daily life consumption, withdraw from global hydrological cycle. So, a sense of responsibility and restraint towards our life-styles seem imperative if we have to be sincere in combating water crisis.
“The contrast in water use can be noticed between continents. In Asia, people consume an average of 1,400 litres of virtual water a day, while in Europe and North America, people consume about 4,000 litres. About 70 per cent of all water used by humans goes into food production. [...]
“Among the biggest net exporter countries of virtual water are the U.S., Canada, Thailand, Argentina, India, Vietnam, France and Brazil. Some of the largest net import countries are Sri Lanka, Japan, the Netherlands, South Korea, China, Spain, Egypt, Germany and Italy.”
-Daniel Zimmer, Director of the World Water Council, in his presentation at the session on “virtual water trade and geopolitics” at the 2003 World Water Forum in Kyoto
If you are a young man on a tight budget and your girlfriend is not impressed with a cup of coffee in the neighborhood restaurant, tell her that her cup of coffee has a history of 140 liters of water in its genesis.
Update as on 28 February 2011
Professor John Anthony Allan is now with King's College of London, which is not under School of Oriental and African Studies, as appeared in my post. This error was pointed out to me by Hussam Hussein, fellow blogger and ex-SOAS student.
 Chapagain AK, Hoekstra AY (2004). “Water footprints of nations”. Value of Water Research Report Series (UNESCO-IHE)
 Chapagain AK, Hoekstra AY, Savenije HHG, Gautam R (2006). “The water footprint of cotton consumption: An assessment of the impact of worldwide consumption of cotton products on the water resources in the cotton producing countries”. Ecological Economics 60 (1): 186–203. doi:10.1016/j.ecolecon.2005.11.027. http://www.waterfootprint.org/?page=files/Publications.
 Virtual water and water footprint database [Link presently not working]
 McCormack MS, Treloar GJ, Palmowski L, Crawford RH (2007). “Modelling direct and indirect water consumption associated with construction”. Building Research and Information 35 (2). http://www.informaworld.com/smpp/content~db=all~content=a773360717.