Already certain regions – northern China, the western United States, North Africa and western Asia – are pumping water faster than aquifer sources can be replenished. Some of the world’s largest and best-known rivers – the Indus and the Nile, the Yellow River and the Ganges, the Colorado and the Rio Grande – no longer reach the sea in any volume for part of the year. All are being exhausted by the demands of irrigating water-hungry crops and taps in burgeoning cities.
Among other examples, Lake Chad has decreased in size by four-fifths in the last 40 years. Wells too are emptying as we pump out underground reserves that have survived for thousands of years. The loss of these resources is a hidden holocaust on a par with the destruction of rainforests; yet it is barely remarked upon. Worldwide, we are ‘mining’ some 200 cubic kilometres of water a year. Half a billion people are consuming wheat and rice irrigated with water reserves that are not being replenished.
Can science come to the rescue? This is highly unlikely. True, ever-bigger engineering projects can move water round the planet. In 2003 at the World Water Forum a coalition of governments and industry leaders called for a doubling in the number of large dams across the world. But many would be on rivers already running dry.
Another idea is to move water between river basins. China is currently spending tens of billions of dollars on three giant transfer schemes to take water from its great southern river, the Yangtze, to relieve the artery of northern China, the Yellow River. India has an even bigger plan, currently under discussion, to divert part of the flow of its great northern monsoon rivers, like the Ganges and Brahmaputra, to its arid south and west – at a cost some believe could reach US$200 billion. There are schemes too to divert Congo River water into the Sahara and divert Australia’s northern tropical rivers into its desert interior.
But these schemes are hugely costly, and cheaper solutions are available. One way of relieving local water crises is by moving water in the form of food. There is a huge hidden trade in what is being called “virtual water”, defined as the water needed to grow crops or produce other products that would have used large amounts of water if grown at home.
“In recent years, water has become a hidden part of world trade,” says Arjen Hoekstra, until recently at UNESCO’s Institute for Water Education, in Delft, the Netherlands. “Whenever we buy a T-shirt made of Pakistani cotton, or eat Thai rice or burgers made of meat from Central America, we are influencing the hydrology of those countries – taking a share of the River Indus, the Mekong or the Costa Rican rains.”
Hoekstra estimates the global virtual water trade at around 1,000 cubic kilometres a year, mostly in crops like grains, vegetable oil, sugar and cotton. “About 15% of the water used in the world for human purposes is not used for domestic consumption but for export in virtual form,” he adds.
This trade is essential for the survival of some countries, especially in the Middle East. Iran, Egypt and Algeria could starve otherwise. Water-stressed Jordan effectively imports between 60 and 90% of its water in the form of food. More water flows into the Middle East each year as a result of imports of “virtual water” than flows down the River Nile.
The price of virtual water
But, he says, virtual water is sold as a virtually free resource: “Water is generally priced far below its real economic, social and environmental cost.” Pakistan, for instance, consumes a third of the flow of the River Indus in order to grow cotton for export. When the Soviet Union transformed the deserts of Central Asia into a vast cotton plantation, it sowed the seeds of the destruction of the Aral Sea. Hoekstra estimates the European market for cotton alone is responsible for a fifth of the emptying of the sea.
If on the contrary virtual water were properly priced, it could act as a global market to help the world make better use of its limited supply of water. And it would be much more efficient than moving water round in bulk. But, besides this route towards the globalisation of water supplies, UNESCO’s water scientists have taken more interest in the subtler and cheaper arts of reviving traditional water systems – water systems that give communities greater control over their own water supplies.
Often these have the advantage of being cheaper, and of making better and more sustainable use of local water resources. They represent one route towards solving water crises. We need to find others, to help prevent water from becoming a luxury available only to a privileged few
UNESCO Water Portal
UNESCO-IHE Institute for Water Education