The water, found in a region of the Great Artesian Basin in northern South Australia, was dated at 1,100,000 years, according to deputy director of the National Centre for Groundwater Research and Training (NCGRT) Professor Peter Cook.

He said the age of the water offered insight into how long it would take for groundwater reserves to be replenished if they were ever depleted.

Typically, water in the southern part of the Great Artesian Basic was aged from 100,000 to more than a million years, indicating it was not likely to be recharged any time soon – and must therefore be extracted and used with care, he said.

“Dating groundwater is becoming a vital took in managing the nation’s water supply,” Professor Cook explains.

“Some water in the lower Murray Basin has been dated to around 200,000 years.

"Many of our best wine-growing regions are using groundwater, yet we have only a sketchy understanding of its age and sustainability – which are important for the future of the wine industry.”

Since groundwater comprises around 90 per cent of the nation’s reserves of fresh water this knowledge is becoming increasingly vital, he adds – especially in cases where there is competition for its use, as is the case between coal-seam gas developers and farmers in some states.

“Unfortunately, there are still a lot of blank spots on the map of Australia’s water ages.

"Very often we tap a supply of groundwater without knowing how old it is or how long it takes to recharge.

"From now on it is important to know this before we develop new resources – and to manage existing ones better."