The Gloucester subregion (Figure 2) spans an area of 348 km2 and is defined by the underlying Gloucester Basin, a small sedimentary geological basin. It is north of Newcastle in NSW, and extends 55 km north-south at its longest, and 15 km east-west at its widest.
A small east-west ridge across the middle of the subregion forms a catchment divide between the Manning and Karuah river basins. Northern-flowing rivers contribute to the Manning River and discharge to the Tasman Sea beyond Taree, while the southern-flowing rivers contribute to the Karuah River and discharge into Port Stephens.
The subregion contains two main aquifers, an alluvial aquifer and weathered bedrock aquifer within 150 m of the ground surface. The subregion is a closed hydrogeological system, which means groundwater is confined within its boundary. Groundwater quality data indicate in-situ mineralisation, with salinity levels increasing with depth from nearly fresh to brackish. There are also elevated naturally occurring concentrations of strontium, iron, bromine and methane in both aquifers. Currently, commercial, industrial, irrigation, mining, stock, domestic and farming activities use up to about 0.52 GL per year of groundwater.
The main natural and human-modified ecosystems in the assessment extent were categorised through a landscape classification (Box 6), based on the subregion’s geology, geomorphology (physical features), hydrogeology (the way water moves through porous rocks), land use and ecology. See ‘What are the potential impacts of additional coal resource development on ecosystems?’ for more information.
The community nominated assets that they consider important due to their ecological, economic or sociocultural values (Bioregional Assessment Programme, 2017; McVicar et al., 2015). These include ecosystems such as stream vegetation that provides habitat for frogs, groundwater used for agriculture, and sites of cultural significance. See ‘What are the potential impacts of additional coal resource development on water-dependent assets?’ for more information.
Coal resource development
The coal resource development pathway (Box 1) defines the most likely future for the subregion as at October 2015. It includes two baseline mines (Duralie and Stratford) and four additional coal resource developments: a new open-cut coal mine at Rocky Hill, expansions of the two baseline mines, and the Gloucester Gas Project Stage 1 coal seam gas development. Note that the Gloucester Gas Project Stage 1 has been withdrawn and in December 2017 the NSW Planning Assessment Commission refused consent for the Rocky Hill Coal Project to proceed.Key finding 1:
Coal is extracted from two existing open-cut coal mines in the subregion, Duralie Coal Mine and Stratford Mining Complex, owned by Yancoal Australia Ltd. They are known in the assessment as baseline mines (Figure 2 and Figure 3).
Coal seams in the geological Gloucester Basin (Figure 4) are present within the:
- Alum Mountain Volcanics
- Dewrang Group, including two coal seams that are the coal resource of the Duralie Coal Mine
- Craven and Avon subgroups of the Gloucester Coal Measures, from which the Stratford open-cut mine extracts coal.
The coals are thicker and of better quality on the eastern margins of the Gloucester Basin. No conventional hydrocarbons are produced from the basin; however, it has been an area of significant interest for coal seam gas (CSG) exploration.
This assessment focused on the potential cumulative impact of four additional coal resource developments. These include mine expansions for the two baseline mines; a new open-cut mine at Rocky Hill, proposed by Gloucester Resources Limited; and the Gloucester Gas Project Stage 1 CSG development by AGL Energy Limited.
In December 2017 the NSW Planning Assessment Commission refused consent for the Rocky Hill Coal Project to proceed. In addition, AGL announced in February 2016 it would not proceed with Gloucester Gas Project Stage 1, and would relinquish its petroleum exploration licence for the Gloucester region to the NSW Government (AGL, 2016). Both the Rocky Hill Coal Project and the Gloucester Gas Project Stage 1 were included in the hydrological modelling for the coal resource development pathway (CRDP), which was finalised in October 2015. Therefore, this assessment was based on these developments proceeding.
The timeline of construction and production for each coal resource development is shown in Figure 5.
Figure 2 Coal resource development in the Gloucester subregion
The coal resource development pathway includes baseline coal resource developments (commercially producing as of December 2012) and additional coal resource developments (ACRD, the coal resource developments most likely to proceed in future, as assessed in October 2015). Close-ups of (a) and (b) are shown in Figure 3. See Figure 4 for cross-section of line A–A’.
Data: Bioregional Assessment Programme (Dataset 2, Dataset 3, Dataset 5); AGL (Dataset 4)
Figure 3 Close-up of coal resource development in the Gloucester subregion
The coal resource development pathway includes baseline coal resource developments (commercially producing as of December 2012) and additional coal resource developments (ACRD, the coal resource developments most likely to proceed in future, as assessed in October 2015).
Figure 2 shows the location of insets (a) and (b) within the broader subregion. See Figure 4 for cross-section of line A–A’.
Data: Bioregional Assessment Programme (Dataset 2, Dataset 3, Dataset 5); AGL (Dataset 4)
Figure 4 Simplified regional cross-section for the geological Gloucester Basin
Figure 3 shows the location of the line A–A’ within the Gloucester subregion.
Source: Roberts et al. (1991). Note that this figure is not covered by Creative Commons. It has been reproduced with the permission of NSW Trade and Investment.
These timelines were used in the hydrological modelling based on information available in 2015.
ACRD = additional coal resource development, CRDP = coal resource development pathway (Box 1)
Context statement, product 1.1 (McVicar et al., 2014) Coal and coal seam gas resource assessment, product 1.2 (Hodgkinson et al., 2014) Description of the water-dependent asset register, product 1.3 (McVicar et al., 2015) Conceptual modelling, product 2.3 (Dawes et al., 2018) Surface water numerical modelling, product 2.6.1 (Zhang et al., 2018) Groundwater numerical modelling, product 2.6.2 (Peeters et al., 2018) Compiling water-dependent assets, submethodology M02 (Mount et al., 2015) Developing a coal resource development pathway, submethodology M04 (Lewis, 2014)FIND MORE INFORMATION
Product Finalisation date
- Executive summary
- Explore this assessment
- About the subregion
- How could coal resource development result in hydrological changes?
- What are the potential hydrological changes?
- What are the potential impacts of additional coal resource development on ecosystems?
- What are the potential impacts of additional coal resource development on water-dependent assets?
- How to use this assessment
- Building on this assessment
- References and further reading
- Datasets
- Contributors to the Technical Programme
- Acknowledgements
- Citation