IT’S long been theorised that groundwater deposits in Australia were likely to have fallen as rain thousands, if not hundreds of thousands of years ago, and now scientists are out to prove it.
Researchers from CSIRO can now test ancient groundwater up to a million years old with far greater accuracy thanks to a new analytics facility.
Designed and built by CSIRO, the Noble Gas facility built at the organisation’s Waite campus in Adelaide will provide new insights into the continent’s groundwater systems and contribute to the sophisticated science being applied to understand the effects to groundwater of further development in regional and rural Australia.
The testing facility is the first in the southern hemisphere. It uses the so-called ‘noble’ gases – helium, neon, argon, krypton and xenon – to better pinpoint and understand the age of groundwater, how long it takes to move through aquifer systems and how those systems are replenished.
Unlike other environmental tracers, noble gases don’t react chemically, have a unique signature and can be used to track extremely slow-moving water.
As Australia is a very old and flat continent, ‘fossil’ groundwater can take millions of years to travel through very large aquifer systems.
CSIRO physicist Dr Axel Suckow, who led the team that took three years to build the facility, has worked on similar testing facilities in the northern hemisphere.
The new Adelaide installation is one of fewer than a dozen comparable facilities worldwide, each of which is uniquely built to suit local groundwater conditions.
“It gives us a completely new tool to investigate groundwater in Australia, providing insight on groundwater resources from recent times to as far back as the last ice age,” Dr Suckow said.
“Noble gases are particularly useful in telling us about groundwater because they can be traced to show us how quickly, or slowly, water moves through underground aquifers, providing a better understanding of the connection between surface water and groundwater flow. It also shows the rate of replenishment of aquifers and whether if water can move between shallow aquifers and deep underground aquifers through geological layers,” Dr Suckow said.
“We need a better understanding of our groundwater systems and how they are replenished to ensure that, as we continue to use this valuable resource and with a changing climate, we also protect it from overuse or contamination.”
The noble gas helium, for instance, increases due to radioactive decay of uranium naturally present in the rocks through which groundwater flows.
“That means the higher the helium content in the groundwater, the older the groundwater is,” Dr Suckow said.
Noble gases can also determine temperatures and conditions at the time the water entered the underground system.
“If you give me a water sample that is 10,000 years old, then from the concentration of argon, krypton and xenon, I can tell you the ground surface temperature 10,000 years ago, which is very valuable information for paleoclimate studies inland,” Dr Suckow said.
The Adelaide facility is being used to assess groundwater resources and connection of aquifers in the Peel region south of Perth, groundwater resource development opportunities in the Fitzroy River basin in Western Australia as part of the Northern Australia Water Resources Assessment, and the impacts of unconventional gas development on groundwater systems through the Gas Industry Social & Environmental Research Alliance.