Mapping water footprints across the globe

By Tierney Smith

With the Earth’s freshwater resources under increasing pressure from global changes, researchers argue that water issues must be addressed on a global scale.

Pollution, climate change and increased consumption are all putting increased pressure on water resources, and as countries continue to trade in water-intensive commodities, one study aims to track consumption globally.

Published in the, Proceedings of the National Academies of Science, the latest study looked at global consumption of water between 1996 and 2005.

It aimed to study the flow of “virtual water” – water used to, for example, grow rice in Asia, using Asian water, which is then exported to the UK – across the world.

Virtual water balance per country and direction of gross virtual water from related to trade over the period 1996-2005 (source: PNAS Early Edition)

It found the biggest net exporters of virtual water to be the US, China, India, Brazil, Argentina, Canada, Australia, Indonesia, France and Germany.

With many of these countries under water stress, the researchers pose the question of whether the choice to consume the limited water – particularly surface water (known as blue water) – for exports is the most sustainable pathway.

The major importers of water are once again the US, China, Germany and France, along with Japan Italy, Mexico, the UK and the Netherlands.

The largest share of international water flows relate to trade in oil crops, for example cotton, soybean, oil palm, sunflower, rapeseed and others as well as derived products – accounting for 43% of water flows.

This figure is unsurprising as the study also found that around 92% of the global water footprint – imported, exported and domestic – comes from agricultural production.

Within this 27% comes from cereal grains like wheat, rice and corn, meat production accounts for 22% and dairy for 7%, according to the study.

Industrial production accounts for 4.4% and domestic use just 3.6% of global consumption.

The study also examined water consumption per country. When looking in overall terms, the US, China and India come out top – not surprising that the countries with large populations would have large footprints.

The water footprint of humanity in the period 1996-2005 (source: PNAS Early Edition)

When breaking this down into consumption per head, however, the researchers found different results. While industrialised countries had a footprint ranging from 1,250-2,850 m3 per capita the developing countries footprint varied much more widely from 550-3,800 m3 per capita.

The researchers say this can be traced back to both differences in consumption patterns and difference in products consumed.

In the developing world the wide range has more to do with low water productivity than large consumption patterns – although water-intensive meat consumption could play a role – the researchers said.

The aim of the study was to help governments evaluate various factors contributing to national water footprints and take a more global approach when it comes to sustainable water use.

Contact the author on [email protected] or @rtcc_tierney.

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