Humankind’s average annual water footprint from 1996 to 2005. Arjen Hoekstra and Mesfin Mekonnen/PNAS Early Edition
By Lauren Contorno
Which country is the world’s largest consumer of freshwater? What factors lead to higher per-capita consumption of water? Which countries rely heavily on imported “virtual water”, and therefore deplete water resources beyond their borders? These are a few of the many questions scientists from the University of Twente in the Netherlands set out to answer in their new study assessing global water consumption patterns.
Agricultural is, by far, responsible for the majority of freshwater consumption worldwide, accounting for a whopping 92 percent of water usage. The water-intensive production of cereal grains like wheat, rice and corn account for 27 percent of the world’s water footprint, while meat production is responsible for 22 percent and dairy for 7 percent.
Here in the United States, our population accounts for only 5% of the world population, yet we are the third largest consumer of freshwater behind China and India. However, our per-capita water consumption is more than double of China and India’s. Comparing ourselves to other industrialized nations, the United States is also near the top of per-capita consumption statistics. While the per-capita water usage in the U.S. is 2,842 cubic meters a year, Britain has a per-capita water use rate of 1,258 cubic meters per year. What factors account for this staggering difference? The gap between the U.S. in Britain is largely due to dietary habits; Americans eat 4.5 times as much beef as the global average while the British eat only twice what is normal elsewhere. Raising cattle for beef production, especially when grain-fed, is extremely water intensive. (For a great resource detailing the water required for various types of food, visit this interactive guide from National Geographic.)
About one-fifth of the water consumed globally is “virtual water”, or water that is transported between nations. Virtual water moves between countries when, for example, rice grown in Asia using Asian water is exported to Africa. By investigating the flow of virtual water, we can determine which countries rely heavily on foreign water supplies and therefore are indirectly depleting and polluting freshwater in other countries. The biggest net exporters of virtual water are North and South America, South Asia and Australia. The biggest net virtual water importers are North Africa, the Middle East, Mexico, Europe, Japan and South Korea. On average, exported goods were found to consume and to pollute surface and groundwater more than domestically consumed goods do.
Shades of green indicate water-exporting nations; lighter shades and slimmer arrows signify smaller volumes. Other colors highlight nations importing virtual water, with red nations importing the most. Arjen Hoekstra and Mesfin Mekonnen/PNAS Early Edition
Researchers hope the publication of this study will help governments assess their nations’ water footprints and adjust unsustainable practices and inefficiencies in production accordingly.
What can you do to reduce your water footprint? Simple changes in lifestyle such as turning off the tap when brushing your teeth, installing low-flow showerheads, or reducing the amount of meat you consume can all help dramatically reduce the amount of freshwater you consume. Calculate your water footprint today and stay informed through campaigns like What our Water’s Worth to continue learning water-savvy techniques to reduce your consumption of our precious water resources.
