'The best bet for Asia lies in revitalising its vast irrigation systems, which account for 70 percent of the world's total irrigated land,' he added.

The study was released in connection with World Water Week, an international gathering of policy makers and experts underway in Stockholm.

The scenarios in the report did not factor in climate change, where rainfall is projected to become more erratic.

South Asia was mentioned as a region where there was strong potential for improvement, and the researchers also suggested engaging 'the private sector more actively in publicly managed irrigation systems', citing experiences from China.