Humans consume water directly for drinking, cooking and washing, but much more for producing commodities such as food, paper, cotton clothes, etc. The amount of water that is used in the production processes of commodities during their entire life cycle is referred to as the virtual water contained within them (Hoekstra, 2003). Virtual water can be further divided into ‘blue’ water (which evaporates from rivers, lakes or aquifers in production processes such as irrigation), ‘green’ water (rainfall that evaporates during crop growth), and ‘grey’ water (polluted after agricultural, industrial and household use).
The water footprint of an individual, community or business is defined as the total volume of freshwater that is used to produce the goods and services consumed by that individual or community or produced by the business. Some sample water footprints are set out below (Source: www.waterfootprint.org):
• The production of 1 kilogram of beef requires 16,000 litres of water.
• To produce one cup of coffee we need 140 litres of water.
• The water footprint of China is about 700 m3 per year per capita. Only about 7 percent of the Chinese water footprint falls outside China.
• Japan with a footprint of 1,150 m3 per year per capita, has about 65 percent of its total water footprint outside the borders of the country.
• The US water footprint is 2,500 m3 per year per capita.
Since the per capita consumption of virtual water contained in our diets varies according to the type of diet (from 1 m3/day for a survival diet, to 2.6 m3/day for a vegetarian diet and over 5 m3/day for a US-style meat-based diet) it is clear that the moderation of diets (reducing meat consumption) can have a big impact on virtual water use. However, the precise impact of a water footprint depends entirely on where water is taken from and when. An increased footprint in an area where water is plentiful is unlikely to have an adverse effect, but an increase in an area experiencing scarcity could result in the drying up of rivers, the destruction of habitats and livelihoods, and the extinction of species – in addition to affecting agricultural prices, supplies and local economies. Some proponents of virtual water argue for the need for a labelling scheme, with the water footprint of a product clearly set out so as to encourage demand management. This would help consumers and policy-makers recognize links between production and consumption.
On the policy level, a water-scarce country can import products that require a lot of water in their production (import of virtual water) to relieve pressure on its own resources. This is a strategy first adopted by Israel, which imports almost all cereals. Conversely, arguments are made that dry countries such as Spain should not be exporting tomatoes with a high virtual water content to wet Northern Europe. Exports of paper pulp, soybeans or ethanol from Latin America to Europe or China imply large exports of virtual water. This type of global virtual water trade has geopolitical implications: it induces dependencies between countries.
Virtual water proponents believe insufficient attention is placed on demand management in comparison to supply management. In their opinion, consumer demand management through education/information, labeling schemes has been overlooked, because consumers and policy-makers do not recognize links between production and consumption. One problem with virtual water labeling is that water content should be considered bearing in mind its geographical and temporal importance (50 litres of water taken from England is not the same as from the Sahara, or from Valencia in summer – high tourist season when water is scarce). Similarly, an agricultural product grown with rainwater is not comparable with one grown with irrigated water extracted from non-renewable ground water. Thus, virtual water gives no indication if water is being used within sustainable extraction limits, which can change annually based on rainfall. Finally, the virtual water argument can also have consequences politically, particularly regarding equity. Water released from one use will not necessarily be used more efficiently, or distributed more equitably. If water is released from agriculture, and farmers grow lower-value crops with less water requirements, the released water could easily be absorbed by urban users, or by the industrial sector instead of being distributed more equitably among the rural poor.
Hoekstra, A.Y. (ed) (2003) Virtual water trade: Proceedings of the International Expert Meeting on Virtual Water Trade.
http://www.waterfootprint.org/Reports/Report12.pdf Last viewed November 11, 2012
For further reading:
Allan, T. (2011). Virtual Water: Tackling the Threat to Our Planet’s Most Precious Resource. IB Tauris.
Water Footprint Network [www.waterfootprint.org]
Water Footprint Network: Your water footprint calculator [http://www.waterfootprint.org/index.php?page=cal/waterfootprintcalculator_indv]
World Water Council [www.worldwatercouncil.org]
This glossary entry is based on contributions by Leah Temper and Mariana Walter
EJOLT glossary editors: Hali Healy, Sylvia Lorek and Beatriz Rodríguez-Labajos