The Northern Territory Government takes a holistic, evidence-based approach to sustainably managing water in the Territory.
The Cambrian Limestone Aquifer (CLA) is vast and plentiful and contributes to water resources across a large area of the Territory.
Nerida Beard, A/Executive Director, Water Resources, said a recent study stokes uncertainty and suggests that the opposite is true.
"A recent flawed study by researchers from Griffith University makes selective and unsubstantiated claims that the CLA is significantly drying, raising undue concern about groundwater extraction and regulation in this vast area of the Northern Territory," Ms Beard said.
"The Griffith University study used data from NASA's GRACE (Gravity Recovery and Climate Experiment) satellite missions and focused on the 2011 to 2022 period to estimate changes in CLA water storage levels.
"2011 follows an exceptionally wet phase where groundwater levels were at the highest ever recorded while 2022 follows a period of consecutive poor wet seasons so lower storage levels are naturally expected.
"However, the study stops in 2022 and doesn't show that in fact the aquifer then experienced a significant rebound, returning water storage back to levels matching those before the dry spell."
GRACE satellite data maps month to month changes in Earth's gravity field that can then be used to estimate changes in terrestrial water storage at a continental or basin-wide scale.
While these estimations can provide useful insights, the process to separate changes in groundwater storage from water stored in soil, lakes, rivers and aquifers introduces uncertainty. GRACE data is also unable to provide information about the cause of change.
"The GRACE satellite data used in Griffith's study measures all terrestrial water storage over a huge area," Ms Beard said.
"Yet the authors of the study draw a very long bow in suggesting these changes are driven by increasing use of groundwater simply because the period of decline in storage occurred after water licences were issued.
"The study estimates losses of 6-8 cubic kilometres a year in terrestrial water storage and nearly 4 cubic kilometres in groundwater storage over the period.
"While these numbers may sound significant, when distributed across the full extent of the aquifer, the largest number equates to losses about the depth of your thumbnail - 1 centimetre to 1.5 centimetres per year."
The study's estimate of decline in groundwater storage per year is about 130 times greater than actual water extraction in the CLA.
This fact reinforces the NT Government's knowledge of the science, which shows changes in groundwater storage are driven by climate variation and that water extraction makes a minimal contribution.
The NT Government draws on nearly 70 years of hydrogeological science to inform water policy, planning and extraction decisions.
This includes foundational data from more than 550 monitoring bores and 150 surface water monitoring stations that provide detailed local information about the Territory's water resources.
"We take a conservative approach to water management and are informed by combining multiple lines of scientific evidence," Ms Beard said.
"This includes local and regional monitoring data, detailed resource assessments informed by drilling and research programs and integrated groundwater and surface water models, including GRACE data, to build a complete and accurate picture of how our water systems are performing.
"This information is sourced from NTG scientists with many years of scientific knowledge as well as scientists from CSIRO, Bureau of Meteorology, Geoscience Australia, universities and peer reviewed literature.
"It's normal to see natural fluctuations in aquifer volumes over time, especially over short 10-year periods.
"That's why government draws on decades of data to understand long-term patterns and ensure our management decisions reflect the full record, not just selective timeframes."
The NT Government's data shows that the Cambrian Limestone Aquifer remains stable and healthy, with recharge and extraction levels within sustainable limits.
Long-term monitoring indicates that water levels in key observation bores have remained consistent or recovered following dry periods, demonstrating the resilience of the system and its capacity to respond to natural climatic variation.
The Northern Territory Government will continue to apply rigorous, science-based monitoring and planning to ensure the sustainable management of the Territory's precious water resources.
