Virtual Water

Water Footprint

Virtual water (also known as embedded or embodied water) refers to the hidden flow of water if food or other commodities are traded from one place to another. For instance, it takes 1,600 cubic meters of water on average to produce one metric ton of wheat.

The precise volume can be more or less depending on climatic conditions and agricultural practice. Hoekstra and Chapagain have defined the virtual-water content of a product (a commodity, good or service) as ‘the volume of freshwater used to produce the product, measured at the place where the product was actually produced.’

It refers to the sum of the water use in the various steps of the production chain. Professor John Anthony Allan from King’s College London and the School of Oriental and African Studies introduced the virtual water concept, to support his argument that countries in the Middle East can save their scarce water resources by relying more on import of food. Israel, for example, discourages the export of oranges (relatively heavy water guzzlers) precisely to prevent large quantities of water from being exported to different parts of the world.

Allan stated: ‘The water is said to be virtual because once the wheat is grown, the real water used to grow it is no longer actually contained in the wheat. The concept of virtual water helps us realize how much water is needed to produce different goods and services. In semi-arid and arid areas, knowing the virtual water value of a good or service can be useful towards determining how best to use the scarce water available.’ There are, however, significant deficiencies with the concept of virtual water that mean there is a significant risk in relying on these measures to guide policy conclusions. Accordingly, Australia’s National Water Commission considers that the measurement of virtual water has little practical value in decision making regarding the best allocation of scarce water resources.

Virtual water has several issues. First, it relies on an assumption that all sources of water, whether in the form of rainfall or provided through an irrigation system, are of equal value. Also, it implicitly assumes that water that would be released by reducing a high water use activity would necessarily be available for use in a less water-intensive activity. For example, the implicit assumption is that water used in rangeland beef production would be available to be used to produce an alternative, less water-intensive activity. As a practical matter this may not be the case, nor might the alternatives be economic. Virtual water also fails as an indicator of environmental harm, nor does it provide any indication of whether water resources are being used within sustainable extraction limits.

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