Britain and other rich countries depend heavily on importing hidden "virtual" water from places that regularly experience droughts and shortages, according a report published today by the Royal Academy of Engineering.
Although the UK is notoriously wet, it is estimated that two-thirds of all the water that its population of 60 million people needs comes embedded in imported food, clothes and industrial goods. The result is that when people buy flowers from Kenya, beef from Botswana, or fruit and vegetables from parts of Asia and Latin America, they may be exacerbating droughts and undermining countries' efforts to grow food for themselves, say the authors.
According to the report, the average Briton uses nearly 3,000 litres of imported water a year. One kilogram of beef needs 15,000 litres of water to produce, more than 10 times the amount required to produce the same weight of wheat. A T-shirt requires 2,700 litres.
"We must recognise how the UK's water footprint is impacting on global water scarcity. We should ask whether it is right to import green beans – or even roses – from water-stressed countries like Kenya," said professor Peter Guthrie, chair of the group of engineers who compiled the report. "The burgeoning demand for water from developed countries is putting severe pressure on areas that are already short of water. Our water footprint is critical", he said.
The report backs analysis by the UK chief scientist, John Beddington, the World Bank and others who say that water shortages are worsening, especially in developing countries. More than 700 million people in 43 countries are now regularly affected by water scarcity and this is expected to grow as a result of climate change, population growth, the switch to meat-based diets in countries such as China, rapid urbanisation in Asia and the pollution of rivers and lakes in many developing countries.
"By 2030 demand for food will increase by 30% and for water by 30%. Potentially we have a global crisis," said Guthrie.
The report said that many countries were now using water unsustainably, by turning to desalination, which demands large amounts of energy, and by drawing on "fossil" ground water laid down millions of years ago. Libya, Algeria, Saudi Arabia are taking vast quantities of fossil water from deep wells in the Sahara desert. Eventually this resource will be depleted and alternative source will be needed," it said.
"In many regions, the demand for water is already much greater than the available supply. This affects developing countries where many people do not have access to safe water, and the developed world where burgeoning demand simply cannot continue to be met," it said.
The authors called for consumers to be aware of the water they were unwittingly using, and for governments to address the international trade of commodities that required large amounts of water to produce.
In 2008, green group the WWF warned that the UK has become the sixth largest net importer of water in the world.