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October 6, 2008
Volume 86, Number 40
p. 16

Water Footprints

Everyday Products Carry A Hidden Global Cost

Melody Voith

Consumers looking for the latest metric to understand their own deleterious effect on the planet can calculate their water footprint at If they log in first thing in the morning, they will find their mark has already been quite considerable: That first cup of coffee took 140 L of water to make, hundreds of times the volume of the drink itself.

A water footprint is a measure of the total volume of fresh water used to produce a certain good. Many people live in dry regions that cannot support the production of goods requiring a lot of water, so they effectively consume water in the form of imported goods. These imported goods carry with them great quantities of what King's College London professor Tony Allan calls "virtual water." If not for the ability to trade virtual water, populations living in places such as the Middle East, or even Texas, would not be able to meet their needs.


Allan received the 2008 Stockholm International Water Prize at the World Water Week conference in August for developing and communicating the theory of virtual water and illustrating water's importance to global trade, food security, climate change, and politics. His greatest legacy may be that he has inspired a new generation of researchers to further quantify the concept of virtual water and investigate its deeper trade-offs.

Arjen Y. Hoekstra, professor of multidisciplinary water management at the University of Twente, in the Netherlands, worked with a group of students to quantify the virtual water content of various products. "With the numbers that we created, we examined virtual water flows between countries, and through this research I developed the water footprint concept," he says.

In his new book, "The Globalization of Water," Hoekstra argues that, because of global trade, water is not just a local resource. "The good message is that scarce water regions can save water through trade. If countries import virtual water, they can use water resources elsewhere. So Europe imports virtual water, and the U.S. exports it."

But of course it's not that easy. "Part of the U.S. water scarcity problem is related to water export. The U.S. doesn't price its water" at market rates, "and so the rest of the world profits from the fact that they have externalized their water footprint to the U.S.," Hoekstra says. That means that exporting nations are taking on the economic, social, and environmental costs of water scarcity by exporting goods.

Hoekstra says the water footprint concept helps consumers and businesses understand they have an impact on water because of their consumption. Through product supply chains, everyone is connected to water problems throughout the world. "Bringing that connection together creates new opportunities for solutions. When supply chains are not sound, there is no guarantee for consumers that they won't buy unsustainable products—they don't know the difference," he says.

To put the footprint of one cup of coffee, 140 L, into perspective, the minimum amount of fresh water that a person needs daily for drinking, cooking, and cleaning is between 20 and 50 L, according to the United Nations. More than one in six people worldwide, or 1.1 billion, do not have access to even that amount of fresh water.

The fact that a big water footprint might make an otherwise responsibly made product unsustainable has caught the attention of industry. Scott Noesen, director of sustainability and business integration at Dow Water Solutions, was staggered by the implications of what he learned at the World Water Week conference. "We need to understand about the baggage of the products we sell, not just our operations," he says. "Rarely are our operations the major driver of water use. Instead, we have to think about the whole supply chain."

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Chemical & Engineering News
ISSN 0009-2347
Copyright © 2009 American Chemical Society

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