How much water is in a mobile phone? A pair of jeans? You might be thinking that they don’t contain any and in a physical sense you’d be right, however in making these products huge amounts of water can be used up, taken from the local environment. Although at purchase a product may contain little or no physical water, we can assign it a virtual water value reflecting the water used up in its production.

Virtual water is defined then as the volume of water that has been used making the product that we say is virtually embedded in the product [1]. If a product is highly water intensive to produce then the mass of virtual water embedded can be orders of magnitude greater than the mass of the original product. For example 1 kg of cotton can contain 3644 kg of embedded water, so pair of jeans (0.5 kg) will have 1822 kg of water embedded in them [2].

Like all goods virtual water can also be exported and imported. If one country exports a water intensive product to another we can say the water has been virtually traded between the two countries [3]. Although there has been no physical transfer of water between the two nations the net result is the same. Countries can also export their water intensive activities to other countries creating a net import of virtual water.

You might think that it would follow that countries with more fresh water resources available would net export virtual water to those with less but this is rarely the case. In fact it is often the countries that suffer from water scarcity that produce the most water intensive crops (for example coffee or cotton) and by exporting them they too export virtual water. This can further increase global water inequality as countries suffering from water scarcity can loose even more of their precious water resources.

It is not simply a question of simply the total volume of water that has gone into making a product but we must also look at what type of water has been used. These are colour coded as blue, green and grey virtual water [4].

• Green water is the volume of water that is evaporated from the moisture stored in the soil, formed originally by precipitation.
• Blue water is the volume of fresh water evaporated that comes from ground water and surface water resources, such as lakes, ponds and rivers.
• Grey water is the volume of fresh water that is polluted at any stage of the process making a product.

Water embedded in a product can therefore be green, blue, grey or any combination of any of these three types.

Green water comes from precipitation and it is the most environmentally positive option. Using green water does not diminished long term water resources in a region as you are simply using precipitated water that would otherwise evaporate from the soil due to natural causes.

Using blue water removes water from resources such as lakes and aquifers. This reduces the volume of fresh water available for others in society as well the environment. If too much water is taken from lakes and aquifers then the available fresh water in a region may simply run out which can have devastating consequences for populations as well as the environment and biodiversity.

Creating grey water pollutes water resources. This can damage the environment as well as reducing the volume of quality water available for local populations.

Of course the methods used to make any product will have a huge effect on its virtual water composition. Beef made from cows feeding on natural rain-fed grassland will be embedded with green water, whilst beef from cows eating processed feed derived from irrigated crops will be embedded with blue water, which in turn has a huge impact on their respective environmental impacts.

To reduce our global water consumption we need to be careful about the virtual water in the products we buy and where this water has come from. Checking country of origin on a lot of products can help although even this brings up conflicting issues. If buying for example flowers from a less developed country removes virtual water it also provides much needed help to local economies.

If export of virtual water has lead to an increased global water inequity then this process could also be reversed. Water rich nations could export water intensive products to water scare nations, allowing these nations to reserve their own resources. Governments must also look at ways of “greening” the methods of production of goods, thereby reducing strain on limited water resources.

As global populations rise, individual water demands increase and global climate changes we are bound to witness a rise in demand and fall in availability of fresh water across the globe. Although itself just a concept “virtual water” may find itself increasing becoming part of a real world solution to this potential environmental and humanitarian crisis.

References

1. Allan, J.A. (1998) Virtual Water: A Strategic Resource. Global Solutions to Regional Deficits. Groundwater 36: 545-546.

2. Chapagain, A.K., Hoekstra, A.Y., Savenije, H.H.G., Gautam, R. (2006) The water footprint of cotton consumption: An assessment of the impact of worldwide consumption of cotton products on the water resources in the cotton producing countries. Ecological Economics, Vol. 60, No. 1. (2006), 186-203

3. Renault, D., Zimmer, D. (2003) Virtual water in food production and global trade review of methodological issues and preliminary results. World Water Council 2003.

4. Hoekstra, A.Y. (2003), ‘Virtual Water: An Introduction’, in A.Y. Hoekstra (ed.), Virtual Water Trade: Proceedings of the International Expert Meeting on Virtual Water Trade, 13–23.