M E D I A  R E L E A S E

National Centre for Groundwater Research & Training

Million year-old water: Australia's vintage  drop

November 13, 2012 - for immediate release

The most ancient water so far found in Australia is 1,100,000 years old and

comes from a region of the Great Artesian Basin in northern South Australia.

According to the deputy director of the National Centre for Groundwater Research

and Training (NCGRT) Professor Peter Cook, the age of Australia’s water not only

teaches us more about our ancient continent - but also how we can better

conserve and manage its largest and most precious resource: water.

“The fact that we have water of such an incredible antiquity also tells us how long

it will take to recharge if we use it up quickly and unwisely. Our vintage water

contains a warning from deep time,” he says.

“On the other hand, much of our groundwater is quite young - only a few years or

decades - and this means it is being recharged constantly, and is therefore at risk

of being polluted by activities and industries on the surface.”

Typically, water in the southern part of the Great Artesian Basic is aged from

100,000 to over a million years, indicating it is not likely to be recharged any time

soon - and must therefore be extracted and used with great care and forethought,

he says.

“As a rule, the younger waters lie closer to the surface, the more ancient ones are

deeper down.”

A case in point is the city of Perth, which depends for part of its water supply on

groundwater. While some of this is quite young and is replenished regularly by

rainfall, the deeper aquifers contain water up to 35,000 years old - laid down

around the time modern humans first appeared. “Clearly, you’d want to be careful

not to over-extract these deeper aquifers,” Prof. Cook points out.

In contrast, groundwater beneath the Darwin’s outer rural suburbs is mostly less

than 50 years old - and detailed measurements of its age have enabled scientists

to predict its rate of recharge with precision, which in turn has helped the city to

set sustainable extraction limits for householders and users.

“Dating groundwater is becoming a vital took in managing the nation’s water

supply,” Professor Cook explains. For example, since groundwater is connected

to surface water, knowing its age can help us to better plan and manage the

waters of the Murray-Darling Basin, and allocate them sustainably among the

different uses like agriculture, urban areas and the environment.

“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.

“For example there is a lot of fresh water in the Pilbara, where industrial and town

development is going ahead rapidly - but we still know little about the extent or

age of these resources. ”

Water is dated by analysing trace chemicals in it, Prof. Cook explains. For

instance atom bomb tests in the Earth’s atmosphere between 1945-1980 have left

a distinct trace of tritium in all the world’s waters, making it easy to date waters of

this age by measuring this chemical signal.

For more recent groundwater, scientists measure traces of chlorofluorocarbons -

the man-made chemicals used as spray can propellants and refrigerants between

about 1940 and their banning under the 1990 Montreal Protocol.

Dissolved carbonates are used by researchers to date water between 2000 and

40,000 years old using Carbon 14 dating methods.

Chlorine 36, with a half-life of 300,000 years, can be used to date waters from

50,000 to two million years old by dating the dissolved salt.

“But, as you can see, there is currently no easy way to date water aged between

2000 years and 70 years old, which is a gap we are currently working to fill,” he

adds.

Professor Cook says knowledge about the age of Australia’s groundwater is fast

becoming an essential ingredient in national sustainable management of all water.

“As a good rule, we need to understand the water, including its age, before we go

ahead and develop it for various uses,” he says.

“Since groundwater is connected to surface water, if we fail to do this and over-extract groundwater, it can drain rivers, lakes and wetlands at the surface, reduce

supplies to our towns and industries when we most need them - and kill large

areas of native Australian landscape which depend on underground moisture for

survival, especially during droughts.”

“Knowing how old our water is a part of sensible risk management for Australia -

now and into the future,” Prof. Cook says

The National Centre for Groundwater Research and Training is an Australian

Government initiative, supported by the Australian Research Council and the

National Water Commission.

FURTHER INFORMATION:

Professor Peter Cook, Deputy Director NCGRT, Phone +61 (0)8 8201 5632 + 041

985 4796

Professor Craig Simmons - Director NCGRT, Phone: +61 (0)405 184 645

Wayne Barbour - Media Contact NCGRT, Phone: +61 (0)407 379 587; Email:

wayne.barbour@flinders.edu.au

Web: www.groundwater.com.au

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