The world's drinking water supply is shrinking.

A global survey of 50,000 rain gauges shows that despite heavier rainfalls, less water is making it into catchments because of drier conditions linked to climate change.

Access to water has never been more highly prized, and the dollar value of arable land is rising as a result.

Unsurprisingly, big investors have started to notice, and in one case one of the world's biggest private investors, the Harvard University Endowment Fund, has been quietly buying up vineyards in California that sit above groundwater supplies.

So is it an isolated case, or a sign of the times?

Today on The Signal, we look into the looming water resource grab, and ask whether private companies could buy up access to water here in Australia.

We also test whether Australia is ready for a world where water is increasingly valuable.

Featured:

Professor Ashish Sharma, School of Civil and Environmental Engineering, University of New South Wales

Russell Gold, Senior Energy Reporter, The Wall Street Journal

Professor Quentin Grafton, Crawford School of Public Policy, Australian National University