The average person consumes 4000 litres of water a day; this is including all the water needed for food and other products. However, consumption varies greatly from country to country. Many countries rely heavily on water supplies from other countries where water is in fact very scarce. These are the findings of a large study into the global 'water footprint' published by researchers at the University of Twente on 13 February in the Proceedings of the National Academy of Sciences (PNAS).
The study looks at the use of rainwater, groundwater and surface water, and contaminated water, respectively the green, blue and grey water footprint (WF). Water used by the agricultural sector accounts for nearly 92% of annual global freshwater consumption, the largest proportion of which is the green WF (74%). In the period between 1996 and 2005, the average consumer used an annual total of 1385 cubic meters. However, on examining the statistics per country, startling differences emerge: one American consumes more than double the average global amount, while the inhabitants of China and India consume little more than 1000 cubic meters. The water footprint of the average consumer is determined mainly by the consumption of cereals (27%), meat (22%) and dairy products (7%).
Water shortages
The "Water Footprint of humanity" study shows in particular the 'virtual' import and export of water. A Dutch consumer buying coffee or a T-shirt uses water from the country of production. Some countries, like the U.S. and China, are both large importers and exporters of water. Research shows that the water-rich countries in northern Europe, including the Netherlands, often rely on water imports from areas struggling with severe water scarcity. The researchers also expect to see a drastic change in consumption in China as it relies increasingly on farmland in, for example, Africa. This will lead to much greater water imports. These are all clear indicators that water scarcity is not a local problem but must be seen from a global perspective. The researchers are therefore questioning whether the continued use of the limited blue WF for export is a sustainable and efficient option.
The Water Footprint not only allows us to quantify and map the consumption levels of individuals and countries, but also that of businesses and particular products. In addition to measuring consumption itself, it can also identify the origin of the water. The international Water Footprint Network brings together large organizations and companies from diverse origins with the common goal of searching for solutions to water scarcity through quantifying and mapping water consumption.
The research was carried out in the Institute of Governance Studies at the University of Twente, headed by Professor Arjen Hoekstra who is also the scientific director of the Water Footprint Network. An earlier article published in PNAS discussed the water footprint of crops grown for biomass. The article entitled ‘Water Footprint of Humanity’ by Arjen Hoekstra and Mesfin Mekonnen appears in the current issue of Proceedings of the National Academy of Sciences of the USA (PNAS).
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