- Bioregional Assessment Program
- Gloucester subregion
- 1.1 Context statement for the Gloucester subregion
The context statement brings together what was known about the geography, geology, hydrology and ecology of the Gloucester subregion as at May 2014.
The Gloucester subregion spans an area of about 348 square kilometres between Stroud and Gloucester, north of the Hunter Valley, New South Wales. The population of the Gloucester subregion is around 5000, concentrated in the towns of Gloucester and Stroud.
The Gloucester subregion coincides with the geological Gloucester Basin. This coal-bearing basin extends from north to south for approximately 55 kilometres and is just 15 kilometres at its widest point.
The present geological architecture of the Gloucester Basin suggests that it has experienced a complex structural history. There is some uncertainty around the detail of the Gloucester Basin’s structure, subsurface features and fault locations due to sparse and low-resolution data as well as a high degree of variation in rock layers.
The geological formations within the Gloucester Basin include Permian coal measures (Dewrang Group and Gloucester Coal Measures) which overlie the Alum Mountain Volcanics.
The Dewrang Group includes two coal seams that are mined at the Duralie Coal Mine in the south of the basin. The Stratford and Bowen Road open-cut mines extract coal from upper and middle seams of the Gloucester Coal Measures. To date, the basin is an area of significant interest for coal seam gas exploration.
Surface water and groundwater
The long-term average annual rainfall (from 1900 to 2012) for the subregion is around 1700 millimetres.
The Gloucester subregion contains rivers that flow into the Manning and Karuah river basins. The northern part of the subregion sits within the catchment of the Gloucester River, a major tributary of the Manning River. The southern part sits within the catchment of the Karuah River.
The main surface water resources of the Gloucester subregion include the Avon, Gloucester, Barrington, Mammy Johnsons and Karuah rivers, most of which are unregulated.
The Gloucester Basin is a closed hydrological system containing two main aquifers: an alluvial aquifer and a bedrock-hosted aquifer up to 150 metres below the surface.
A topographical divide across the middle of the basin influences groundwater and surface water flow. From this divide, regional groundwater flow is predominantly towards the south and the north.
Current groundwater use of up to about 520 megalitres per year is for commercial or industrial, irrigation, mining, stock, domestic and farming activities.
Very little of the Gloucester subregion lies within conservation reserves and the subregion has been extensively cleared for agricultural, horticultural and urban use.
There are 12 endangered communities and four endangered species listed under various state and Commonwealth legislation that may be present within the Gloucester subregion. Much of the remnant vegetation in the subregion lies within areas classified as ‘Other minimal use’ or ‘Water’, and is mainly distributed along the margins of the Gloucester subregion, on or adjacent to hill slopes or along watercourses.
No groundwater dependent ecosystems have been identified within the Gloucester subregion.
- 1.1.1 Bioregion
- 1.1.2 Geography
- 1.1.3 Geology
- 1.1.4 Hydrogeology and groundwater quality
- 1.1.5 Surface water hydrology and water quality
- 1.1.6 Surface water – groundwater interactions
- 1.1.7 Ecology
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