Whether jeans or breakfast eggs — manufacturing products and producing food consumes water. Professor Arjen Hoekstra explains how the virtual water footprint is calculated in this interview. The image gallery shows everyday products and the associated water consumption.
Mr Hoekstra, what does the term "virtual water footprint" mean?
The actual consumption for washing, flushing toilets, showering, cooking, etc. only makes up two per cent of the overall water consumption in private households in Germany. We are usually aware of this consumption. But the percentage made up by our groceries or articles of daily use is much larger. Ultimately, every product "costs" water during its production. However, because this consumption is not directly visible, we call it the "virtual footprint". When added to direct consumption, we can calculate the overall water footprint.
About Mr Hoekstra
Arjen Y. Hoekstra is Professor in Water Management at the University of Twente (Netherlands) and is one of the most internationally renowned experts for water consumption.Learn more
Why is it important to be aware of the virtual aspect?
Many of our products — meat, sugar, clothing — consume vast quantities of water during production. And they are often produced in regions where water is already scarce, and it then becomes even more scarce and is simultaneously polluted. Conscientious consumers can put pressure on companies and demand improvements in the supply chain. Of course, they can also change their consumer behaviour accordingly.
How do you measure the water footprint in general?
We distinguish between three types of water consumption here: the green water footprint describes the amount of rain water a product requires. On the other hand, blue stands for the ground and surface water, which is extracted for irrigation, for example. The grey water footprint is very problematic: it is calculated based on the amount of water needed to treat the water contaminated by the production process. The sum of all three categories results in the water footprint for a specific product.
Read more under the image gallery.
Classic blue jeans have an average water consumption of 8,000 litres. Nearly three quarters of their footprint is due to the water-intensive cultivation of cotton. For an item of clothing like a pair of trousers, a large percentage of water consumption occurs through washing during its useful life. For a pair of blue jeans, this is the second-largest line item after the cotton at around 1,840 litres.
This article appeared in the autumn/winter 2016 issue of CHANCEN magazine focusing on the power of water.To German edition
In the global comparison of countries, the water consumption per capita deviates dramatically — particularly in Africa. Why is the daily per capita water consumption of an arid country like Niger so high at 9,600 litres?
There are two reasons for high water consumption. One is a high level of consumption — especially for goods that require a lot of water — and a high level of water consumption per production unit, in other words, inefficient water use. The consumption in Niger is due to the second reason: the efficiency of local grain farming is extremely low.
And how can someone lower their own water footprint in everyday life?
Become a vegetarian! On average, 28 per cent of total water consumption in Germany is due to the consumption of meat. An additional 17 per cent could be saved by foregoing animal products like eggs, leather or animal fats. So, everyone can do something!
Published on KfW Stories: Tuesday, 21 March 2017