The UN has asked the politicians, economists, scientists and industry leaders who make up the forum to find ways to realise its ambitious plan to bring clean drinking water and sanitation to more than a billion more people over the coming decade.

Mahmoud Abu-Zeid, the Egyptian water minister and president of the World Water Council (WWC), the group that organised the meeting, said massive increases in spending on large construction projects such as dams, barrages, canals and sewer systems were needed. "The world will need to double its large dams," he said.

Funding for the projects will have to come from financial markets, says Michel Camdessus, a former managing director of the International Monetary Fund, whose report to the forum was widely viewed as paving the way for privatising the world's water.

A draft of the final ministerial declaration seen by New Scientist confirms that the strategy of privatisation and big-money projects is likely to be adopted by water ministers this weekend. But many scientists and UN officials condemned the strategy. They say it will never serve the billions of poor in rural communities and shanty towns who drink dirty water and have nowhere to get rid of their sewage (see "Bleeding the planet dry").

Sanitation and hygiene experts at the forum declared the strategy would not achieve the UN's goal. Instead, ministers should "reallocate finance from the big-ticket items like large dams to schemes that directly support the poor," says Richard Jolly, chairman of the Water Supply and Sanitation Collaborative Council, which promotes sustainable development.

Privatising water can never meet the needs of the poor, Jolly says. Commercially viable projects "can only deliver sanitation to a tenth of the billion-plus people targeted by the UN", he says. Most of the rest "are simply too poor to be attractive to private enterprise".

The UN Human Settlements Programme, which aims to improve human living conditions, takes a similar line. Corporations don't want to work in shanty towns and squatter colonies "because the places may be bulldozed at any time", says spokesman Sharad Shankardass.

The call for large dams comes after a period in which they seemed to have gone out of fashion. The World Bank, once the largest funder of dams in the world, has not given any loans for large new dams since the mid-1990s because of their poor value for money and massive environmental impact. It pulled out of the Narmada River project in India, and refused to fund the controversial Three Gorges dam in China. But last month the bank adopted a new water strategy that included a return to funding dams. "The developing world needs water storage," says Bill Cosgrove, vice-president of the WWC. "We cannot keep on not building dams just because in the past some of them turned out badly."

But some water scientists argue that funding large dams will take money from more useful water supply schemes, such as rainwater harvesting. The direct collection of rainwater on roofs and spare land is increasingly being seen as an effective way to give people access to water.

Next month, the UN Environment Programme will launch a drive to get Asian governments to invest in rainwater harvesting. "We could help up to 2 billion people in Asia alone," says Steve Halls, director of UNEP's International Environmental Technology Centre in Osaka, Japan.

Millions of villagers in China already collect water from their roofs. "The combined capacity is similar to the Three Gorges dam," Halls says.

Cities could get a third of their water by harvesting rain, but governments and private companies are reluctant to take an interest in such schemes, says Hall. "They prefer big prestige projects like dams."

Fred Pearce
Kyoto