The virtual water concept has received increased interest in policy circles, development agencies and the private sector in the past 10 years. Virtual water is the amount of embedded water in a commodity required to produce, package and ship the commodity to consumers[1]. The water footprint illustrates the total consumption of water as measured for the individual consumer, community, nation or business. Virtual water and the water footprint have helped to shed light on the role of agriculture in global water management and the role of trade to alleviate water poverty.
Origins of the concept
Virtual water was first proposed by Prof Tony Allan Kings Collage London in the 1990s, and then quantified as water footprints by Prof Arjen Hoekstra at the UNESCO Institute for Higher Education in Delft, the Netherlands. Regarding the water footprint, Hoekstra has shown that the amount of water embedded in a kilogramme of beef can be as high as 15,415 litres when produced in industrial feedlots. The metrics, however, of differently sourced beef depend on the age of the animal, the place of origin and the type of fodder. Beef production on pastures, crop residues and crop processing by-products incurs less water costs. The volume of water embedded in a kilogramme of beef can be as low as 3000 litres per kilogramme[2].[3] Furthermore, more recent analyses have highlighted the key issue of whether the virtual water embedded in production is green or blue water. Green water is root-zone water in the soil profile, while blue water is irrigation water diverted from surface sources or pumped from groundwater. If the origin of water is green water, the amount of virtual water in a commodity is significantly lower than when blue water via an irrigation system is the source.[4] [5]Additional analyses have further established that virtual water content is much lower in regions where water-use efficiency of crops is high [6].
In a nutshell, the amount of virtual water in a commodity depends on a number of variables. Consequently, the use of universal numbers for the virtual water content in a commodity can be very misleading. The main value of the virtual water concept and the water footprint metrics has been to reveal the link between food security and water security. This idea has transformed the way water security is conceptualised for a wide range of water scientists and professionals. Policy-makers are also increasingly accepting the concept and consequences of virtual water, not least its potential to affect politically stability.
Virtual water and trade
Global water resources are not evenly distributed on the planet: some regions, such as the Middle East, are highly water-scarce while other regions, such as Latin America, North America and parts of Africa, are well endowed with water resources (Water Futures 2011). As Allan [7] noted, it is possible for a water-scarce region such as the Middle East to strategically trade its way out of its water deficit if water-intensive crops, such as wheat or rice, are produced in water abundant regions and then imported, instead of grown with scarce local water. Such a strategy echoes the 19th century political economist David Ricardo’s ideas to utilise the world’s hydrological comparative and competitive advantages. World food trade is, however, subject to tariffs and restrictions and is not fully liberalised to allow free virtual water trade. Nevertheless, the virtual water concept has found application in food supply chain analyses to reflect the water footprint of the major corporates who trade the lion’s share of global water [8]. The figure below illustrates the global virtual water trade. The countries highlighted in green are ‘net exporters of virtual water’ as they provide the global economy, and the countries highlighted in yellow and red are ‘virtual water net importers’ with water embedded in food commodities imports. Most economies are net ‘importers’. About 160 out of 210 national economies world-wide are ‘net virtual water importers’. The major ‘net exporting’ economies, such as countries in North America, Latin America, Australia and Asia, are located in well-endowed hydrological regions, with the additional advantage of sound infrastructure to enable trade with other economies. The black arrows illustrate the trade flows of virtual water between countries, e.g. the importance of the US in global food commodity trade.
(Source: waterfootprint.org)
References
Policy in Prague 22nd to 26th June 2009. URL: http://amor.cms.hu-berlin.de/~h1981d0z/pdf/2009-06-prag/water-footprint.pdf (accessed 21 August 2012).
Water Footprint Network. Enschede, the Netherlands. http://www.waterfootprint.org (accessed: 20 July 2012).
GIZ, The Water Futures Partnership wins the Guardian Sustainable Business Award 2012, 2012, URL: http://www.giz.de/Themen/en/SID-4220C535-0CB6E95B/36213.htm
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