Northern Stuart Corridor
The Northern Stuart Corridor Project includes two project areas: the Daly River Basin and Howard East area.
Daly River Basin
Groundwater in the Daly River Basin is predominantly extracted from the Oolloo Aquifer. In addition to supporting water consumption for agriculture and farming, the Oolloo Aquifer is also important for groundwater-dependent ecosystems, tourism and indigenous culture.
Previous investigations in the Daly River Basin indicated the potential for the Basin to be either structurally compartmentalised, or for tectonic pinching of the hydrostratigraphy, resulting in a potential restriction in groundwater flow across the basin. This project will focus on determining the degree of aquifer compartmentalisation to inform groundwater modelling and water allocation planning. Investigations will also provide baseline geoscientific data to underpin assessment of managed aquifer recharge (MAR) options in the Daly River Basin.
The main objectives of the project are to:
- Refine the basin structural and hydrostratigraphic architecture, with a focus on areas of the basin where there are major faults mapped in the underlying basement, and in pre-existing magnetics and airborne electromagnetic (AEM) datasets;
- Examine the potential for basin inversion, neotectonism and fault compartmentalisation, incorporating results from morphotectonics mapping and analysis;
- Develop a model for basin evolution, taking into consideration new evidence for basin inversion and neotectonics;
- Update hydrogeological conceptual models incorporating groundwater flow regimes, surface water-groundwater connectivity and inter-aquifer leakage; and
- Assess the potential for MAR schemes at key locations in the Basin.
There are ten aquifers identified in the Darwin Rural Water Control District. The main producing aquifer, the Howard Groundwater System, is used to support a strong horticultural industry, market gardens, and a public utility providing 20 percent of Darwin's municipal supply. The increase in population within the region is likely to increase pressure on the water resource. The Howard Groundwater System also discharges to several groundwater-dependent ecosystems throughout much of the dry season, sustaining several important environmental and cultural sites.
Previous investigations in the Howard East area indicated a potential seawater intrusion (SWI) hazard to the existing groundwater resource. Seawater intrusion can have major impacts on water quality in aquifers, rivers and estuaries, and can impact significantly on floodplain and wetland ecosystems. This project will focus on 3D mapping and characterisation of the potential SWI and fault structures in the Howard East area. The data and new knowledge will be used to underpin groundwater management and targeted monitoring strategies.
The main objectives of the project are to:
- Map major fault zones and their internal fault zone geometries and heterogeneity using airborne magnetics and AEM datasets;
- Develop a structural model for the mapped fault zones including the role of basement heterogeneity on fault localisation, and the role of faults in the development of karst aquifers;
- Investigate the nature of fault zone hydrogeology for the major fault zones, including conduit-barrier behaviour, and fault hydraulic parameters within the Koolpinyah Dolomite Aquifer;
- Delineate the SWI interface east of Darwin and within the mapped fault zones;
- Characterise temporal and spatial changes (if any) in SWI since the completion of the Northern Territory Coastal Plains project (2010); and
- Characterise the response of high-value vegetation to changes in groundwater quantity and quality.
The Project will deliver new data and products including:
- Airborne electromagnetic and magnetic data;
- Borehole datasets (e.g. geophysics, hydrogeology, hydrochemistry) compiled from existing and new bores;
- Surface nuclear magnetic resonance (NMR) dataset;
- Geomorphic, geologic, hydrogeologic, hydrostratigraphic and hazard maps; and
- A technical report describing revised geology, geomorphology, hydrogeological and hydrodynamic conceptual models; fault-zone hydrogeological characterisation; assessment of the groundwater resource potential and managed aquifer recharge suitability, and potential implications of new data and improved hydrogeological understanding for existing groundwater models, water allocation planning, monitoring strategies and groundwater management.
New data acquisition
In 2017 the project collected:
- 5,423 line-kilometre airborne electromagnetic and magnetic survey
- 59 boreholes logged for induction and gamma.
The project will carry out a number of data collection activities in 2018 including:
- Soil/regolith sampling;
- Additional surface and borehole geophysics;
- Groundwater and surface sampling; and
- Landscape mapping.
The Northern Stuart Corridor project is being undertaken collaboratively with the Northern Territory Department of Environment and Natural Resources.
Other key stakeholders include NT Power and Water Corporation, Northern Land Council (NLC), Tindal RAAF Base, NT Cattleman's Association, local indigenous groups and landholders.