An international team of researchers headed by ANSTO has discovered clean fresh underground water ‘lenses’ near Cooper Creek in outback Queensland that could provide insights into how ecosystems along our dry-land rivers are sustained.
Surface water around inland Australia is unreliable and scarce, that is why shallow fresh groundwater is critical to supporting vegetation and maintaining a delicate ecological balance.
The study of these freshwater lenses will, therefore, help scientists better understand waterhole sustainability around Australia’s arid rivers and could have significant implications for land management.
Researchers from ANSTO as well as the University of Wollongong, University of Southern Queensland and University of Barcelona have joined forces in this project. By analysing water samples at a molecular level, scientists identified shallow groundwater of low salinity that formed these lenses which span up to 1 kilometre wide.
ANSTO hydro-geologist, Dr Dioni Cendón said that the relatively fresh water that can be found under the ground near the creek provides a cap on the much older, saltier water
“Our study shows that freshwater from the water holes does not immediately mix with regional saline groundwater. Interestingly, we also found that there is little or no contribution to underground fresh water reserves through nearby sand dunes,” Dr Cendón said.
The results of the study also indicate that natural flooding events may be crucial to maintaining freshwater lenses. Dr Cendón said this finding has implications in understanding other inland river systems like the Darling River which has been impacted greatly by human intervention.
“The information we have gathered helps us better understand the degree of exchange between waterholes and underlying groundwater. This is greatest during floods but is minimised at other times when there is no flowing water, and clay settles from receding floodwaters,” Dr Cendón said.
ANSTO researchers are analysing seasonal fluctuations in groundwater levels at Cooper Creek. Scientists will use this information to determine the time scales involved in the formation of these freshwater lenses.
Published: 06/06/2011