Completed 2021 Northern Stuart Corridor
The Northern Stuart Corridor project investigated areas around the northern half of the Northern Territory close to the Stuart Highway.
It included 2 project areas: the Daly River Basin and Howard East area selected due to their high-value groundwater resources.
Daly River Basin
Groundwater in the geological Daly Basin supplies 80% of water needs in the region including for town supply and industries such as agriculture, horticulture and forestry. Groundwater provides baseflow to the Daly River during the dry-season and is critical for sustaining ecosystems, tourism and for Indigenous culture. Groundwater is mainly extracted from the aquifers of the Cambrian Tindall Limestone and Oolloo Dolostone. However, the geometry of these aquifers is poorly constrained as borehole information is sparse.
A 3,500 km2 airborne electromagnetic (AEM) and magnetic survey was flown over the Daly River Basin in 2017 for reconnaissance-scale mapping of the groundwater system. The AEM data has been used to model the interfaces between the Jinduckin and Oolloo Aquifers and to improve understanding of basin-scale geological structures.
Benefits
These geophysical datasets improve knowledge on the size of aquifers and intervening aquitards, suggesting that the Oolloo-Jinduckin contact is deeper than previously thought in areas with sparse stratigraphic picks from boreholes. This new interface can be used to better constrain aquifer architecture in groundwater flow modelling and support groundwater management of this region.
Borehole geophysical and hydrochemical data were also collected in the Daly River Basin and are available via the Exploring for the Future Data Discovery Portal.
Northern Stuart Corridor project areas showing airborne geophysical (electromagnetic and magnetic) survey lines and location of borehole geophysics
Howard East
Up to 90% of Darwin’s water supply is sourced from Darwin River Dam. The remainder comes from groundwater supplied from Howard East Borefield (HEB) and McMinns Borefield in the Koolpinyah Dolostone Aquifer (KDA). Groundwater from the KDA is also essential for domestic use in nearby rural areas and for irrigated agriculture. Increasing demand coupled with a number of low-rainfall wet seasons has put pressure on this groundwater resource.
Previous work suggested that electrical conductivity anomalies in airborne electromagnetic (AEM) data within 5 km of HEB may be caused by saline groundwater within the KDA. This groundwater is separated from HEB by dykes and other geological features that effectively compartmentalise the aquifer (Fell-Smith & Sumner, 2011; Tan et al., 2012). Seawater intrusion can potentially affect water quality in aquifers, rivers and estuaries, and floodplain and wetland ecosystems.
Benefits
As part of the Exploring for the Future program, new groundwater and surface water chemistry, salinity monitoring, airborne electromagnetic (AEM) and borehole geophysical data have been collected. These contribute to building an enhanced conceptual understanding of the KDA near the HEB. Much of the area contains a fresh Mg-Ca-HCO3 type groundwater, as expected in dolomitic aquifers. However, highly saline Na-Cl type groundwater occurs in some locations near the coast, suggesting potential for seawater intrusion. Conductivity anomalies within the KDA are interpreted as pyritic shales, although drilling is required to confirm this interpretation and to investigate the salinity of groundwater in the KDA in this area.
Collaboration
Project collaborators included:
- The Northern Territory Department of Environment and Natural Resources (DENR), now Department of Environment, Parks and Water Security (DEPWS)
- Northern Territory Power and Water Corporation
- Northern Land Council (NLC)
- RAAF Base Tindal
- Northern Territory Cattleman's Association
- Local Indigenous groups and landholders
Outputs
New data acquisition
During the project, Geoscience Australia and partners collected:
- 5,423 line kilometres of airborne electromagnetic and magnetic survey data
- 53 boreholes logged for induction and gamma
- 33 groundwater and surface water hydrochemistry samples
- groundwater level and electrical conductivity data in 4 groundwater monitoring bores.
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