Virtual Water and Water Footprint
What is Virtual Water?
Most of the time, we tend to believe that our water consumption is limited to the water we use in its physical or ‘visible’ form for drinking, cooking, washing, bathing, etc. How many of us think of water when we look at, say, wheat, onions, a shirt, or cheese? Not many. It would surprise us, however, to know that a large amount of water goes into the production of these things. That, simply, is what we mean when we say ‘virtual water’.
If one is to define ‘Virtual water, it is the water embodied or “hidden” in the products, services, and processes people buy and use every day. Though invisible to the end-user of a product or service, virtual water has been consumed along the manufacturing life cycle of a product, thereby making its creation possible. The virtual water content of a product is the total sum of the water used along the value chain.
The concept of virtual water, a relatively recent one, was introduced by British geographer John Anthony Allan in the early 1990s. Allan formulated it as a helpful tool for water-scarce countries to feed growing populations as well as a possible answer to global conflicts over natural resources. He suggested that countries lacking domestic water resources could simply import food and other commodities containing virtual water, thereby avoid having to deal with water crises directly. 
Examples and quantum of virtual water use:
A gallon of orange juice: 272.2 gallons
A 200gm bag of potato chips: 48.9 gallons
A pair of jeans: 2,866 gallons
A pound of butter: 3,602.3 gallons
One pound of rice: 200 gallons
Direct water use, on the other hand, is the visible use of water at a given time and location, for example, direct water is used in the washing of a shirt, while virtual water is the total water used in all stages of the production of that shirt.
Virtual Water Footprint
Water Footprint is an indicator of freshwater use that looks at both direct and indirect (virtual) water consumption . The water footprint includes not only the total volume of fresh water used in the creation process of a product/service but also the category of water used, i.e. blue, green or grey water. This is important because the water footprint can be estimated to determine whether a particular production process is sustainable within the water and ecological conditions of any region. In that much, it has been recognised as a strong tool for sustainable water management and policy planning at the macro (regional or national) as well as micro (product/service) levels. The water footprint depends on agricultural practices, water use efficiency, time, place and local climatic conditions. For an example, virtual water for producing a particular quantity of crop in an arid region would be higher than in a wet or semi-arid region .
Contribution of different crops to the total global water footprint of crop production (1996 -2005).
Source: Mekonnen M. M. and Hoekstra A. Y. (2011)
Blue Water footprint: is freshwater on the land surface or within the ground. It can be easily pumped and engineered and can, with difficulty, be valued. Blue water is used for diverse purposes, namely, food production, ‘non-food’ production and other economic activities including energy generation. Blue water is usually prone to over-consumption.
Green Water: is simply rainfall that infiltrates into the soil and is incorporated by plants through transpiration. Green water consumption is limited to sustaining natural vegetation and producing local crops and therefore is used only for food production.
Grey Water footprint: is the amount of fresh water required to imbibe pollutants to meet specific water quality standards.
Above table shows the virtual water (green, blue and grey) embodied in major food crops and livestock.
Country-wise, China, India and the US have the largest total water footprints within their territory, viz., 1207, 1182 and 1053 cu. m per annum, respectively. About 38% of the global water footprint lies within these three countries. India has the largest blue water footprint within its territory at 243 cu. m. Per annum, which is 24% of the global blue water footprint. Irrigation of wheat is the process that takes the largest share (33%) in India’s blue water footprint, followed by irrigation of rice (24%) and irrigation of sugarcane (16%). China is the country with the largest grey water footprint within its borders: 360 cu.m. per annum, which is 26% of the global grey water footprint.
Why is Virtual Water Important?
Virtual water, though invisible, holds vital importance as far as water management is concerned. The analysis of virtual water can help countries determine not only how they are managing their water but also ‘who’ is consuming it, i.e., how the water resources in one country are supporting consumption in another country. In other words, virtual water helps us understand the interdependence of economies and their resources.
The notion that water can be incorporated in goods and services is very powerful when it is applied to international trade and food security. For instance, consider a country producing and exporting rice; paddy or rice is a water-intensive crop and requires large amounts of water in its cultivation. Since this country exports rice, it implies that it is also exporting the virtual water that has been consumed in cultivating that much paddy.
Combining this with the concept of water footprint enables us to work out the dependencies, and to identify risks in terms of scarcity and pollution. This has implications for food security, economy, and diplomacy.
Food and water security are vital issues for any country’s governance. Policy makers in water scarce countries or regions can use virtual water analysis to develop strategies to save water by increasing imports and restricting exports with high virtual-water content. This ‘Virtual Water Trade (VWT) is gradually changing the hydrological cycle in many ways. Several countries have begun to act early, following the VWT route to address worldwide water distress.