Middle East water crisis warning

The amount of water available per person in the arid region will halve by 2050, a report from the bank estimates.

It blames climate change and population growth for new pressures on supplies.

Governments in the region should tackle water waste, build more efficient networks and reduce water use, the World Bank says.

Farming challenge

The bank's report suggests agriculture is a key target area.

With 85% of water-use devoted to agriculture, the report suggests countries such as Morocco will have to cut back on irrigation and switch to crops that require less water but earn more money.

According to its figures, declining water quality has already knocked around 1% off gross domestic product in Morocco, Algeria and Egypt, and nearly 3% in Iran.

"We've simply got to reduce the amount of water used, especially in agriculture," said Julia Bucknall, natural resource management specialist at the World Bank, addressing reporters Rabat, Morocco.

She added that water firms needed to cut water lost by evaporation.

"If we plan for the future, it's a lot simpler than crisis management further down the line," said Ms Bucknall.

more from the BBC