The city imports as much as 40% of its water from distant sources but has no large-scale operation for recycling wastewater. Water losses because of problems in the pipe network are also estimated at 40%.

9. London

Of all the cities in the world, London is not the first that springs to mind when one thinks of water shortages.

The reality is very different. With an average annual rainfall of about 600mm (less than the Paris average and only about half that of New York), London draws 80% of its water from rivers (the Thames and Lea).

According to the Greater London Authority, the city is pushing close to capacity and is likely to have supply problems by 2025 and "serious shortages" by 2040.

It looks likely that hosepipe bans could become more common in the future.

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10. Tokyo

The Japanese capital enjoys precipitation levels similar to that of Seattle on the US west coast, which has a reputation for rain. Rainfall, however, is concentrated during just four months of the year.