nagement told a development conference in Canberra.

Globally, water usage had increased by six times in the past 100 years and would double again by 2050, driven mainly by irrigation and demands by agriculture, said Frank Rijsberman, the institute's director-general.

Billions of people in Asia and Africa already faced water shortages because of poor water management, he said.

"We will not run out of bottled water any time soon but some countries have already run out of water to produce their own food," he said.

"Without improvements in water productivity ... the consequences of this will be even more widespread water scarcity and rapidly increasing water prices."

The Sri Lanka-based institute, funded by international agricultural research organisations, is due to formally release its findings at a conference in Sweden later this month.

Rijsberman said water scarcity in Asia and Australia affected about 1.5 billion people and was caused by over-allocating water from rivers, while scarcity in Africa was caused by a lack of infrastructure to get the water to the people who need it.

"The water is there, the rainfall is there, but the infrastructure isn't there," Rijsberman told reporters.

He said more needed to be done to promote rain-fed agriculture and to increase water storage in Africa, where many people live with water scarcity.

THE PRICE IS NOT RIGHT

"Irrigation needs to be reinvented," said Rijsberman, adding irrigation in many countries was inefficient.

But scarcity problems could also be overcome by more efficient water use, recycling and better pricing of water, which in its bottled form was already rivaling the cost of oil.

Rising living standards in India and China would lead to increased demand for better food, which would take more water to produce, he said.

Rijsberman said the price of water would have to increase to meet an expected 50 percent increase in the amount of food the world will need in the next 20 years.

He said in Australia, five years into a drought, irrigation water costs less than five U.S. cents a cubic meter, compared to $1 to $2 per cubic meter for drinking tap water and $100 to $200 per cubic meter for bottled drinking water.

Australian Foreign Minister Alexander Downer, whose constituency covers the mouth of Australia's longest river system, the Murray-Darling, said solving water problems was a pressing problem for the world.

"Improving the efficiency of agricultural production and water use is fundamentally important to improving economic growth, sustainability and reducing poverty," Downer said.

The Murray-Darling runs through Australia's main crop and food-growing region but water flows have dropped dramatically because of drought and large amounts of river water pumped out to irrigate cotton.

Downer said Australian researchers were working with counterparts in China to develop new irrigation methods for rice, while Australian aid programmes were working to improve water in the Mekong River through Laos, Cambodia, Thailand and Vietnam.

A report on global water by environment group WWF released on Wednesday warned that rich nations, like Australia, were not immune to the coming water crisis.

It said Sydney was using more water than could be replenished and Australia had among the highest water usage in the world.

Each day, urban Australians use an average of 300 litres of water each, compared with Europeans who consume about 200 litres, while people in sub-Saharan Africa existed on 10-20 litres a day, said the report.