The little town of Guyra in eastern Australia lies next to a freshwater lagoon just half a day's drive from Sydney, but its drinking water is due to run dry in 400 days' time.

The local authorities have been trucking in fresh water, built a pipeline to a local dam and will soon start drilling in the hope of finding new supplies. For Mayor Simon Murray, the biggest worry is that Guyra is not alone.

"A lot of towns are forecast to run out at the same time — and then where do you get the water from?" he said, referring to an area that is home to some 180,000 people.