Claims that the Cambrian Limestone Aquifer is significantly drying have been rejected by the Northern Territory Government, which says decades of local monitoring and hydrogeological science show the aquifer remains stable, resilient and well within sustainable limits.
The Cambrian Limestone Aquifer underpins water supplies across a vast area of the Territory and is managed under a framework the Government describes as conservative and evidence-based. That approach has come under scrutiny following a recent study by researchers from Griffith University, which used satellite data to suggest a substantial decline in groundwater storage.
Acting Executive Director of Water Resources, Nerida Beard, said the study raised unnecessary concern by drawing conclusions unsupported by the full body of available evidence.
“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,” Beard said.
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Why satellite data alone tells an incomplete story
The Griffith University research relied on data from NASA’s GRACE satellite missions and focused on the period between 2011 and 2022. GRACE measures changes in Earth’s gravity field to estimate total terrestrial water storage across very large areas.
Beard said the selected timeframe was critical to the interpretation of the results.
“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,” she said.
“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.”
While GRACE data can provide valuable insights at continental or basin-wide scales, the NT Government says the methodology cannot reliably isolate groundwater changes from soil moisture, surface water or other components of terrestrial storage, nor identify the drivers behind those changes.
“The GRACE satellite data used in Griffith’s study measures all terrestrial water storage over a huge area,” 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.”
Extraction volumes versus climate-driven variability
The NT Government also disputes the scale of groundwater loss suggested by the study, particularly when compared with actual licensed extraction.
“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,” Beard said.
“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.”
More importantly, the estimated annual decline in groundwater storage is about 130 times the volume of water actually extracted from the aquifer each year. According to the Government, this reinforces long-held scientific understanding that climate variability, not extraction, is the dominant driver of short-term storage changes.
A long-term, multi-layered evidence-base
The NT Government says its water management decisions are informed by nearly 70 years of hydrogeological investigation, drawing on one of the most extensive monitoring networks in Australia.
This includes data from more than 550 groundwater monitoring bores and 150 surface water monitoring stations, providing detailed local-scale information that satellite data alone cannot resolve.
“We take a conservative approach to water management and are informed by combining multiple lines of scientific evidence,” 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.”
That work is supported by expertise from NT Government scientists, CSIRO, the Bureau of Meteorology, Geoscience Australia, universities, and peer-reviewed research.
“It’s normal to see natural fluctuations in aquifer volumes over time, especially over short 10-year periods,” Beard said.
“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.”
Stable system, ongoing scrutiny
According to long-term monitoring results, water levels in key observation bores within the Cambrian Limestone Aquifer have remained consistent or recovered following dry periods, demonstrating the system’s capacity to respond to climatic variability.
The NT Government says recharge and extraction remain balanced within sustainable limits and that it will continue rigorous monitoring and planning to safeguard the Territory’s groundwater resources.
As scrutiny of groundwater systems increases nationally, the Government argues that policy debates must be grounded in comprehensive datasets and long-term trends, rather than short-term analyses that risk overstating decline and undermining confidence in well-managed aquifers.