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Virtual water

‘Virtual water’ is the nonevident water embedded in water intensive commodities such as food crops. A tonne of wheat, for example, requires 1,000 tonnes of water over 100- 150 days in order to reach maturity. ‘Virtual water’, if factored into the national water balance sheet, can be the most economically significant form of water in water-short (arid) countries. Rather than use valuable supplies of freshwater for producing crops such as wheat (whose price in real terms has been falling over time), a country can, by importing food, effectively import water. Thus, integrating ‘virtual water’ into economic and environmental assessments of the agricultural resource base may permit the reduction of water deficits. Around 95 million tonnes of wheat entered world trade in the mid- 1990s, reflecting a ‘water-trade’ of at least 95 cubic kilometres of ‘virtual water’ annually. The Middle East and North Africa economies imported about 40 cubic kilometres of ‘virtual water’ annually in cereals in the mid-1990s.

Further information: Water Policy: allocation and management in practice, E & FN Spon/Chapman and Hall, 1996.

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