BioEd Online

One-third of the world's population is living in water-scarce areas, say scientists behind a 5-year analysis of global water resources. The finding is a worrying update to an older study by the same team, who had previously predicted that such a situation would not arrive until 2025.

"This won't be in decades: it's here now," says Frank Rijsberman, director general of the International Water Management Institute in Battaramulla, Sri Lanka. Rijsberman launches the report today at the 2006 World Water Week in Stockholm, Sweden.

Hundreds of scientists from more than 100 different institutions contributed to the study. The work improves upon a similar assessment from 2000, which looked primarily at the use of water for crops. The new study also includes water use for cattle and fisheries, and integrates new data on individual river basins, and satellite measurements of irrigated land area.

Agriculture consumes a vast amount of our water, accounting for about 74% of the total water withdrawn from rivers, lakes and aquifers. In 2000, 7,200 cubic kilometres of water were used to grow food; by 2050, population growth is expected to see that increase to 11,000-13,500 cubic kilometres. That will require some changes in how water is used, say the report's authors, from desalinating sea water for use in irrigation to switching diets so that people rely more on less water-intensive crops.

Not a drop to drink

Developing nations are, not surprisingly, revealed to be the hardest hit by water shortages, but for differing reasons. Large parts of sub-Saharan Africa have potential access to groundwater, for example, but lack the technology to exploit it. In Gujarat in India, by contrast, decades of over-extraction of groundwater for dairy farming has "destroyed" local resources, says Rijsberman.

Some of these problems could be fixed through financial initiatives and sustainable use of basic technologies, says David Molden, a colleague of Rijsberman's. Access to 'micro-credit' initiatives would allow African farmers to invest in human-powered pumps and small-scale dams, for example, which could be used to see crops through unpredictable but frequent dry periods.

But the authors also call for a more radical change in the way that water is thought about. "People need to focus on getting more value from water," says Rijsberman. He argues that water is usually seen as a free resource, but needs to be treated as a limited commodity, and valued accordingly.

In Australia's Murray-Darling River basin, for instance, water scarcity has been caused by intensive agriculture, much of which is used to produce crops for export. Rijsberman says that the area is not necessarily water-scarce, and that local shortages could be alleviated by switching to crops that produce a greater financial return for each litre of water used - such as horticultural products instead of cereals.

Such action needs to come from national governments, say Rijsberman and Molden, who hope that the report's political backers, which include the UN Food and Agriculture Organization, will help translate its recommendations into policy. There are already some encouraging signs: a strategy for investment in African water resources, released last year and backed by the World Bank, included substantial input from the authors.

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