What is “virtual” or “hidden” water?

Virtual water, sometimes known as “embedded” water, is a measure of the amount of “invisible” water required to generate various foodstuffs and products. Many products require a considerable amount more water to create than might be suggested by looking at it. For example, a cup of coffe requires around around 140 litres of water and a cotton T-shirt needs around 2000 litres! This water is needed to grow, wash and process the products and refers to any water required during the product cycle.

You can discover more about the idea of virtual water here: http://news.bbc.co.uk/1/hi/sci/tech/8628832.stm

This is an increasing problem as many countries are effectively “exporting” large quantities of water in products they generate. This is occurring in many parts of the developing world where growing demand for water from increasing populations  and “thirsty” technology is combining with a decline in available water due to previous consumption of reserves, poor management and changing climatic condition.

You can listen to Prof Tony Allan of King’s College London (http://www.kcl.ac.uk/schools/sspp/geography/people/acad/allan/research.html), who developed the concept, talking about the idea here:


From a sustainable development point of view, this metrication of water required to generate the goods and services we consume allows us to create a “water footprint” which shows the impact of individuals, groups and activities on our water supply. You can find more about this here: http://www.waterfootprint.org/?page=files/home


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