A United States intelligence assessment says fresh water supplies are unlikely to keep up with global demand over coming decades, increasing political instability, hobbling economic growth and endangering world food markets.
The report, by the office of the Director of National Intelligence, says areas including South Asia, the Middle East and North Africa will face major challenges coping with water problems that could hinder the ability to produce food and generate energy.
The report says what it calls water war is unlikely in the next 10 years, but the risk of conflict will grow, with global water demand likely to outstrip current sustainable supplies by 40% by 2030.
It says water in shared basins will increasingly be used by states to pressure their neighbours.
