We are in a way on a collision course

Professor Frank Rijsberman, head of the International Water Management Institute

Agricultural experts say the world's farms will need to use much more water over the coming 25 years to feed the world's growing population.

Environmentalists say we should extract less from rivers, lakes and underground sources to prevent further damage to ecosystems.

There is, however, an increasing demand from cities for more and more water for industry and domestic use.

Experts say water resources will be put under extra strain as the world's population grows

Professor Frank Rijsberman, head of the International Water Management Institute, says this divide must be bridged.

"We are in a way on a collision course. These two different viewpoints, embedded in all these sectoral plans, don't add up. We're warning the we can't really continue on that path, that we have to get these two groups together."

Search for solutions

At this week's Stockholm Symposium, re-using water will be one solution to be examined; the trouble is that, after it has been used once, water may be contaminated with bacteria and viruses, organic chemicals or heavy metals.

A civil engineer from California, Takashi Asano, says that means recycled water may be best used not for drinkable household supplies, but for agriculture, industry and recharging groundwater systems, although it must still be cleaned first.

The meeting will also talk about ways of improving conditions in Lake Victoria in East Africa, where alien fish species and pollution have devastated the lake's ecology.

There will also be discussion in defence of dams as a method of providing water, including the controversial Narmada Dam in India, whose opponents say is being built at the expense of local people and the natural environment of the region.