The Concepts of Water Footprint and Virtual Water


  • Water Footprint

    A water footprint is quite simply the volume of water used. At the individual level, this is expressed in litres. But at the national level, this becomes complex - The water footprint of a nation is equal to the use of domestic water resources, minus the virtual water export flows, plus the virtual water import flows.

    The total ‘water footprint’ of a nation is a useful indicator of a nation’s call on the global water resources. The water footprint of a nation is related to dietary habits of people. High consumption of meat brings along a large water footprint. Also the more food originates from irrigated land, the larger is the water footprint. Finally, nations in warm climate zones have relatively high water consumption for their domestic food production resulting in a larger water footprint. At an individual level, it is useful to show the footprint as a function of food diet and consumption patterns.

    Ten litres of orange juice needs a litre of diesel fuel for processing and transport, and 220 litres of water for irrigaton and washing the fruit. The water may be a renewable resource, but the fuel is not only irreplaceable but is a pollutant, too.
    Behind that morning cup of coffee is 140 litres of water used to grow, produce, package and ship the beans.
    1 cup of coffee needs 140 litres of water.
    1 litre of milk needs 1000 litres of water.
    1 kg of wheat needs 1350 litres of water.
    1 kg of rice needs 3000 litres of water.
    1 kg maize needs 900 litres of water.

    • The production of one kilogram of beef requires 22 thousand litres of water.
    • To produce one cup of coffee we need 140 litres of water.
    • The water footprint of China is about 775 cubic meter per year per capita. Only about 3% of the Chinese water footprint falls outside China.
    • Japan with a footprint of 1100 cubic meter per year per capita, has about 60% of its total water footprint outside the borders of the country.
    • The USA water footprint is 2600 cubic meter per year per capita.
    Source: UNESCO-IHE - Water Footprint

  • Virtual Water

    Virtual water is the amount of water that is embedded in food or other products needed for its production. Trade in virtual water allows water scarce countries to import high water consuming products while exporting low water consuming products and in this way making water available for other purposes [World Water Council].

    For example, the virtual water content (in m3/ton) for potatoes is 160. Others examples - maize=900; milk=900; wheat=1350; soybean=2300; rice=3000; poultry=2800; eggs=4700; cheese=5300; pork=5900; and beef=16000.

    Showing people the 'virtual water' content of various consumption goods will increase the water awareness of people.

    People consume water not only when they drink it or take a shower. In 1993, Professor John Allan (2008 Stockholm Water Prize Laureate), strikingly demonstrated this by introducing the "virtual water" concept, which measures how water is embedded in the production and trade of food and consumer products.

    Behind that morning cup of coffee are 140 litres of water used to grow, produce, package and ship the beans. That is roughly the same amount of water used by an average person daily in England for drinking and household needs. The ubiquitous hamburger needs an estimated 2,400 litres of water. Per capita, Americans consume around 6,800 litres of virtual water every day, over triple that of a Chinese person.

    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.

    National, regional and global water and food security, for example, can be enhanced when water intensive commodities are traded from places where they are economically viable to produce to places where they are not. While studying water scarcity in the Middle East, Professor Allan developed the theory of using virtual water import, via food, as an alternative water "source" to reduce pressure on the scarcely available domestic water resources there and in other water-short regions. [SIWI -]