How science found liquid gold in the desert
Standing on the red dusty earth in the middle of the arid lands of northwest South Australia, it becomes glaringly obvious just how important water is for these remote communities.
The Aṉangu Pitjantjatjara Yankunytjatjara (or APY lands) is a large, sparsely populated area where summer temperatures soar high into the 40s and rainfall averages about 230mm per year.
There is no water in sight.
Held under title by Traditional Owners, the landscape is as beautiful as it is harsh but as CSIRO has discovered…it is also deceiving.
A collaboration between CSIRO, Flinders University and the South Australian Government, under the auspices of the Goyder Institute for Water Research, has unearthed water-bearing palaeovalleys systems below the surface, which are tens of millions of years old.
The project, which included three stages and took place over a decade, investigated the role large buried palaeovalley systems can play as a potential groundwater resource for community and enterprises such as mining and grazing. The local community and APY Executive Board were supportive of the project.
CSIRO’s Dr Tim Munday a Research Director with Deep Earth Imaging and Dr Mat Gilfedder a Senior Research Scientist with CSIRO Land and Water joined forces to lead the research investigations with Flinders University for the project known as the Goyder Institute’s G-FLOWS (Finding Long-term Outback Water Solutions) project.
“The G-FLOWS team has now created the most detailed and refined information on palaeovalleys across the whole APY region,” Gilfedder says.
“This work is a big step forward and was supported by an 11 well drilling program, which provided critical insight into the palaeovalleys as a potential water resource.”
“These valleys started to erode and form about 60 million years ago. For the last 5 million years they have been filled up with sediments and wind-blown sand and hidden from view,” Munday added.
“People have known about these valleys for a long time but knowing precisely where they are has been more difficult.”
Refining the discovery of an ancient water source
This third and final stage of the G-FLOWS research program allowed for more informed decision-making and prioritisation for more targeted drilling to secure water supplies.
The final report outlines the work:
• Mapped palaeovalley locations with significantly improved accuracy across the APY Lands;
• Used multiple lines of evidence to investigate palaeovalley evolution, aquifer character and palaeovalley architecture, groundwater chemistry, recharge and flow.
Making use of an ancient water source
CSIRO used groundwater modelling to better understand the rate of groundwater recharge and the movement of water through the landscape. They also used water chemistry and environmental tracer analyses to better understand the age and quality of the water.
“This research gives a sense of what they (the palaeovalleys) are made of and how the water quality varies. At the main investigation site, while holes were drilled to 115 metres, the main water-bearing zones were around 50-65 metres below the surface,” Gilfedder says.
A potential groundwater resource for these remote areas in South Australia, is a much lower cost option than bringing water into communities.
Director Water Science and Monitoring, SA Department for Environment and Water Neil Power said the G-FLOWS work has provided a better picture of not only where these channels are (potentially saving money on extra drilling) but also the potential capacity of the identified water sources.
“Until now, there hadn’t been concentrated work to identify how much water these valleys might hold. This goes a long way to supporting possible future economic development, local community water supplies and water for agricultural purposes,” Power says.
A timeline of discovery
The success of the entire 10-year project lies in that it used multiple science disciplines and expertise to paint an accurate and detailed picture of the valleys. This included utilising existing mapping, conducting extensive airborne electromagnetic (AEM) surveys, on-ground information via drilling, testing of water chemistry and environmental tracer analyses as well as groundwater modelling.
The airborne electromagnetic (AEM) surveys used aircraft to cover long transects across the landscape. A large loop attached to the aircraft is charged with pulses of electricity to generate a magnetic field. By measuring how this magnetic field decays over time, geophysicists can interpret the electrical conductivity of the ground beneath.
The technique is traditionally used for mineral exploration but the G-FLOWS project used it to provide precise maps of palaeovalley shape and distribution. They were then able to pinpoint locations for drilling.
Looking to the future
Through the G-FLOWS work, researchers have developed a probabilistic modelling approach as a framework for groundwater prospect mapping.
While this approach is broadly applicable to many parts of Australia, some aspects such as airborne EM surveys will likely be most useful in the search for palaeovalley groundwater systems.
The South Australia government is already looking at using the method in the Braemar region east of the Flinders Ranges, an area of considerable magnetite iron deposits. It is also an area where ancient palaeovalleys are also known to be present.
In the meantime, the research to discover the life force below the red dust in the remote arid areas of South Australia is likely to continue.
“We still have some questions about the timing and flow of water through these ancient palaeovalley systems, which will help to understand how to manage these potential water resources”, Gilfedder says.
“They contain water that is of value for communities, environment and industry. To get all the answers, we will need additional exploration.”