Water Footprint – The Importance of `Virtual Water’


Water is one of our planet’s most precious resources. It is ubiquitous: we drink it, wash with it, swim in it, and sail on it. We also use it to produce things like food, paper, and cotton clothing, among others.

But what is “virtual water?” Is it invisible? Sort of. But it is equally – if not more – omnipresent.

Virtual water, or the water footprint, is an indicator of water usage that looks at both direct and indirect water use of a consumer or producer. The water footprint of an individual, community or business is defined as the total volume of fresh water used to produce the goods and services, consumed by the individual /community or produced by business.

We don’t realize it as we sit down to a meal, but most crops require huge volumes of water to grow: 65 gallons to grow a pound of potatoes; 650 gallons for a pound of rice. How about your cup of coffee? It takes far more than one 10 ounces to make it. Thirty-seven gallons of water were used from the time the bean was planted to the moment it hits your cup at Starbucks. That includes growing, harvesting, packaging, and shipping it. And that’s without adding any milk (which took another 67 gallons of water to produce).

At a national level, it becomes more complicated. Here’s the formula:

Domestic water resources used


virtual water exports


virtual water imports

equals: the water footprint of a nation

The total water footprint of a nation is an indicator of a nation’s demand for global water resources, and is tied to dietary habits of people. High consumption of meat brings along a large water footprint. Also, more the food that originates from irrigated land, larger the water footprint becomes.

Nations in warm climate zones have high water consumption for their domestic food production resulting in a larger water footprint. Increasingly, these countries are relying less on their own resources and are switching to food imports. Those imports include importing the water embodied in the crops, or virtual water. So, every ton of wheat arriving in port brings along (in virtual form) the tons of water needed to grow it.

Two-thirds of all the water drawn from nature by humans is used to grow crops. Nearly one-tenth of the water used in growing crops is traded internationally. Exchanging virtual water – from grains and vegetable oil, sugar and cotton, meat and dairy products from animals raised on crops – has kept the world fed.

The virtual water trade is not a bad thing. It allows the world’s food to be grown where it makes the most sense. It improves efficiency in the production of vital foodstuffs like grain. But our growing reliance on it creates risks, because the trade can only go so far. It requires both exporters and importers and, as water shortages emerge around the world, exporters will be in short supply.

That being said, we are not about to run out of water. Thanks to Mother Nature’s water cycle of rainfall and evaporation, water is the most renewable of all resources.

However, it is worth noting that humans are affecting that natural cycle on such a scale that some of the great rivers of the world are, indeed, running dry. And, if harvests fail because of dry river beds, it is little comfort to know that it’s raining somewhere else.

Article by Bari Faye Siegel, a technology writer and marketing consultant at Noveda Technologies, an innovative leader in real-time, web-based energy and water monitoring. For more information, visit www.noveda.com.

About Author

Walter’s contributions to CleanTechies over the past 4 years have been instrumental in growing the publications social media channels via his ongoing editorial and data driven strategies. He is the founder and managing director of Sunflower Tax, a renewable energy tax and finance consultancy based in San Diego, California. Active in the San Diego clean technology community, participating in events sponsored by CleanTech San Diego, EcoTopics, and Cleantech Open San Diego, Walter has also been a presenter at numerous California Center for Sustainability (CCSE) programs. He currently serves as an adjunct professor at the University of San Diego School of Law where he teaches a course on energy taxation and policy.


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  2. Very good post, I have been reading about virtual water and water footprint recently. Another very good one:

    http://www.deliveringdata.com/2011/05/virtual-water.html, with more examples of water needed to produce products, but this time the comparison is made with “tap running minutes”, which is quite revealing and clear. For instance, “To produce 100 grams of beef we need 10 cubic metres of water, equivalent to letting the tap run for 714 minutes (almost 12 hours!)”. Excellent to increase public awareness!

    • Absolutely agree with the post and the comment. Unfortunately, it seems to remain fashionable for opponents of water footprinting to put forward various uninformed or spurious arguments as to why it is a largely useless concept in a practical context. I made a first pass at attempting to correct matters in a recent article I wrote for Sustainabilia journal (free for reading/downloading at http://www.landscapeandlanguagecentre.au.com/Sustainabilia/Sustainabilia%20Tools%20J%20Hannan.pdf). I hope to publish a further paper in the near future that addresses and critically evaluates the validity of prevailing objections to water footprint applications. Opponents should be aware that the practical limitations of water footprinting are acknowledged recognised in the literature by the leading WF researchers. It is clear from this that opponents have failed to keep pace with research developments and continue to rely on legacy objections that no longer apply, if they ever really did.

  3. Really good points here. In addition to the water cost of manufacturing there is the cost of energy to pump that water. Water utilities spend about one third of their operating budget pumping water.