Agricultural
16 May, 2023
How old is our groundwater?
An international study has seen new atom technology used to track the age and flow of groundwater in Oakey and surrounds.
Over the first half of May, landowners on the northern side of Oakey were contacted by researchers from the University of Adelaide.
Assisted by Dr Eric Donaldson, the group told the landowners about their mission to test the flow of groundwater in Oakey over a period of 11 days.
Together, the four men, Science leader, Dr Rohan Glover, CSIRO Lab Manager Dr Axel Suckow, Phd student Florian Meienburg from Heidelberg, and postdoctoral researcher Dr Tom Chambers had travelled from the University of Adelaide to Toowoomba to test their new atom-measuring technology, called ATTA (Atom Trap Trace Analysis).
The group came to Oakey at the suggestion of Professor Jochen Muller from the University of Queensland who is collaborating on this project suggested the researchers to use Oakey as a case study,
He had worked with Dr Donaldson previously, and knew there were several local wells at different depths in close proximity to each other.
The scientists were looking to apply a new isotope technology which would give them the ability to date the length of time groundwater had been travelling underground, and its input: the source of the groundwater (rainfall, river or flood).
Florian Meienburg said the group was lucky to find an AirBnb in Toowoomba "which was willing to let us store 6 pallets worth of equipment (over the 11 days)."
"In total, we sampled 21 wells from Kelvinhaulgh (south-west) to the Solar Farm."
The scientists were aiming to use two particular isotopes in the water - krypton-85 and argon-39.
They are a brand new tool to investigate groundwater movement, and only four laboratories world-wide are able to measure these.
Dr Axel Suckow says the use of argon-39 as a measuring tool is especially helpful given it fills the gap between krypton-85 (up to 40 years), and radiocarbon dating (2000+ years).
"Krypton-85 has a half-life of around 10 years, so we can use it to detect water that has infiltrated since
1980 and argon has a half-life of 269 years, so it's useful
for about 1500 years," he said.
"It's important for Australia because the European settlers clearing the land and chopping down trees, starting around 200 years ago which changed the groundwater."
The isolation of argon-39 is an incredibly difficult task as Dr Tom Chambers explains.
"It's like covering the surface of Australia with pavlovas topped with blueberries, and looking for a single pavlova that's topped with strawberries," he said.
"We are taking our water samples back to the lab."
"We're aiming to trap single atoms in a sophisticated laser system to measure them."
The ability to track groundwater has tremendous long-term implications for farmers, miners and the army base.
Postdoctoral researcher Tom Chambers said that after inquiring what their wells would be used for, the local Oakey landholders were happy to allow the scientists the use of their land.
"The community was really supportive," he said.
"They were always so happy to talk."
The ATTA technology was invented 20 years ago, and only five years ago was applied environmental situations.
"Getting that out of the lab and into the real-world was a difficult process," Tom said.
There are only four labs in the world with this type of technology, in China, the USA, at the University of Heidelberg (where Florian is from) and the University of Adelaide.
The process involved transporting six pallets of equipment to Oakey from Adelaide.
This including four pallets worth of bottles (48 gas bottles), with the ability to fit 20 litres of water in one gas bottle.
Florian's next aim is to assist Southern Cross University at the Hawkesbury River
He says the technology is a vast improvement on the previous methods used to date groundwater.
"We used to need tonnes of water to test, but we've got it down to 20 litres which is much more manageable.
The process of tracking the age and flow of our groundwater has many implications for miners, farmers, and the local Army Aviation Base.
Professor Andre Luiten, Director of the University's Institute for Photonics and Advanced Sensing which houses the ATTA facility said at the launch of the technology in 2019 that it was ever more necessary to track groundwater due to a changing climate.
"Australia relies on its groundwater for 30 per cent of its water supply for human consumption, stock watering, irrigation and mining," he said
"With climate change and periods of prolonged drought, surface water is becoming increasingly more unreliable and the use of groundwater is rising.
"We need to make sure it's sustainable.
"Because noble gases don't easily react chemically, they are the gold standard for environmental tracers to track groundwater movements.
"Before this new facility, researchers wanting to measure these ultra-low concentrations of noble gases had to rely on a very small number of overseas laboratories which can't meet demand for their services."
CSIRO Senior Principal Research Scientist Dr Dirk Mallants said at the launch that the technology was precise.
“Measuring ultra-low concentrations of these radioactive noble gases allows researchers to not only determine how old groundwater is, from decades and centuries up to one million years, but where it comes from and what the natural recharge rates are,” he said.
The results will likely take over a year to uncover, however the Oakey case study is part of a broader implementation of the technology across Australia.
Dr Axel Suckow said he was involved in ATTA analysis at the Eramanga section of the Great Artesian Basin at the Hutton Sandstone and Precipice Sandstone aquifers below the Walloon Coal Measures in western Queensland.
Here, the CSIRO discovered flow rates and recharge in the Precipice Sandstone were higher than in the Hutton Sandstone, concluding that the Hutton Sandstone aquifer was replenishing at a lower rate than initially thought.
This made the system more vulnerable to groundwater extraction, so further investigation was needed to determine how connected the Walloon Coal Measures was to the Hutton Sandstone aquifer.
The Oakey project is part of a two-year effort which will end in 2025.
