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September 30, 2008

Virtual Water

Throughout the first two Global Innovation Outlook deep dives on Water and the Oceans, a concept known as “virtual water” has come up again and again. The idea is straightforward enough: virtual water is the amount of water used in the production of a good or service.

For example, it takes 246 liters of water to make one kilogram of potatoes. Or 10,600 liters to make one pair of jeans. In each instance, the amount of virtual water estimated in the production of these goods is a cumulative total of the entire development cycle. For potatoes most of the water is accounted for through irrigation of the crop. For jeans, the growing of cotton is taken into account, along with whatever industrial practices -- including dying and washing -- that are added into the process later on.

For some, these measurements are useful, especially when estimating the amount of virtual water embedded in different kinds of international trade. In other words, a water-scarce nation may want to reconsider exporting a water-intensive product, like beef or produce. It’s easy to see how understanding water use in various products could have an impact on trade strategies in some regions.

Many people feel that the concept of virtual water would also be useful in raising consumer awareness of water use. Some have suggested that products should come with labels that estimate their virtual water content. And that some day consumers would add virtual water to the list of things on which they base their buying decisions.

But there are a few important shortcomings to the notion of virtual water. For one thing, it doesn’t take into account the source of water that was used for the product. Wheat that was grown using 80 percent rain fed water supplies should have a different virtual water content than wheat grown using 80 percent irrigation. Desalinated water has a greater environmental toll than surface water. And so on.

Virtual water also makes the assumption that if that water had not been used to grow potatoes or make a pair of jeans, it could have been used for some other purpose. This is not always the case. Distinctions also need to be made between the use of “green” water (from rainfall), “blue” water (surface or groundwater), and “grey” water (polluted discharge.)

See how quickly a simple measure of water use can become too complicated for the average consumer to worry about? Virtual water is instructive to be sure. But it’s not clear whether it is a viable tool for shaping trade policy, or even informing consumer decisions. To do that, far more variables need to be taken into account, and distilled into easily understood, actionable metrics.

September 30, 2008 in Water and the Oceans | Permalink


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A great articulation of virtual water and the challenges of what seems to be a logical and simple metric.

It also illustrates the fundamental difference between the water issue and Global Climate Change. With Global Climate Change, the CO2 emitted is no different if emitted from Peking, Cleveland, or even Midland Michigan. Although the ultimate impacts are indeed regional in nature (sea levels, growing seasons, severe weather patterns) - it would seem to be easier from a mitigation standpoint to develop global solutions for reducing CO2.

This cannot be said for water, and "virtual water" and the challenges inherent in this simple metric are a good example.

Having said that, what could we do to make the concept of virtual water more informative and, god forbid, actionable by a consumer?

One concept may be to incorporate a "quality" function with the virtual water - a sort of "stress gallons" approach. In other words, a gallon of water conserved from a location with high stress on the environment (extreme scarcity) is more "valuable" than a gallon of water conserved from a less stressful location.

Dow is working on a metric like this for our over 140 facilities across the globe - using a Water Tool from the World Business Council for Sustainable Development (you can download the tool at:


You can enter your GPS coordinates for your production facilities and the tool maps these against World Meteorlogic Organization know areas of water stress. What is really cool is that you can also map against projected areas of stress in 2025!

So how does this relate to virtual water? What if everyone mapped out their water use this way, and we had a relatively simple weighting factor for extreme scarcity, scarcity, balanced, abundant locations. Using Life Cycle Assesment tools - we could then "add up" the stress gallons into the virtual water metric.

Are there problems with this approach? Absolutely - but this approach begins to take into account the fundamental regionalism of water - which is what distinguishes this "global challenge".

What do you think?

Posted by: Scott Noesen | Oct 4, 2008 5:37:06 AM


I think there are a number of metrics, and variables that could be effective in mapping the nature and availability of water on our globe. Local water stress is certainly one of them, and would be an important planning parameter.

Water -quality- is also a very important factor. Maybe the diamonds and water analogy deserves a closer look. After all, we do judge diamonds very strongly on their intrinsic quality. Also, submerged in this equation is the implicit knowledge that diamonds are simply carbon, an abundant and readily available resource. It is the physical -form- of diamonds that introduces their value! In the same sense, it is the physical -form- of water, it's purity, not the quantity of H2O existing in a container that introduces value.

We do, indeed, -have- markets in Water. Outfits like Merck, and maybe even Dow, will sell you reagent grade H2O, although typically laboratories produce it themselves. You can purchase bottled drinking water in most locations as well. As in the case of diamonds, this is about the form or purity of the chemical compound or element, not the -actual- physical quantity of that chemical!

This is instructive because issues surrounding chemical purity or physical state of a system are really about entropy, and altering the entropy of a system requires energy! In the end, any cost (I don't like "price") associated with water is going to be keyed to the price of energy, the energy required to purify and transport drinkable or usable water.

This allows one to establish upper bounds based on the local water stress factor you consider. As a example, an upper bound for the -cost- of water might be the cost of distilling a liter of sea water, and transporting it from the coast to where ever you are. The true cost, like the true cost of energy, really has to do with your good fortune in location within this enormous reaction vessel we call the global ecosphere.

In the end, I am fairly convinced that we can formulate a -cost- for water, or some financial quantity, by construct a dual problem in energy, physical chemistry, and local and global entropy.

As for the -price- of water? All one has to consider is the possibility of a family drinking water with industrial pollutants in it, because they can't afford the -good- water that the people in he wealthy section of town drink, and the whole idea of pricing water goes out - Way out!

Posted by: Tim Raisbeck | Oct 9, 2008 9:13:28 AM

Is it 70% of the earth covered by water ? So should be enough, we just need cheap technology to purify for the right purpose (drinking water, planting, industry use, recycling of sewage, energy generation(fuel cell).....) and for transport to the required destinations.

Posted by: Manfred Potzmann | Dec 12, 2008 5:41:45 AM

>> will sell you reagent grade H2O... You can purchase bottled drinking water in most locations as well

There ought to be a better and cheaper solution to provide this globally.

Posted by: Water Treatment | Mar 18, 2009 6:42:32 PM

Nice informaiton about cooling technologies for HVAC Industries.

Posted by: Jeyakumar | Aug 22, 2011 8:05:46 AM

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