1.1.2 Geography


The Northern Sydney Basin bioregion covers an area of about 17,390 km2, of which the Hunter subregion covers about 17,045 km2. It is located just north of Sydney, NSW. The Hunter subregion is primarily defined by the geological Sydney Basin and the river basins of the Hunter River and the Macquarie-Tuggerah Lakes, which are in part defined by ridge lines associated with the Hunter Range, Liverpool Range and Great Dividing Range. It is approximately 230 km north–south and 210 km east–west. Elevation in the subregion ranges from sea level to 1241 mAHD (metres above Australian Height Datum), and it is mostly undulating with relative low slopes in the northern part of the subregion (along the Hunter River and its tributaries), with relatively rugged terrain found in the southern part of the subregion primarily associated with the heavily dissected rock outcrops of the Triassic Hawkesbury Sandstone.

The Hunter Estuary wetland is a nationally and internationally significant wetland. Soils are mainly Tenosol (30.0%), Kurosol (27.3%) and Ferrosol (13.1%); another seven soil types are also present. Pre-European vegetation was dominated by eucalypt forest and approximately 40% of the subregion retains this vegetation cover. In the remaining parts of the subregion much of the vegetation has been cleared. A wide range of land uses occur in the subregion; grazing is the most widespread (covering 40% of the subregion). Vegetation height exceeds 40 m in the forests.

There are numerous rivers in the subregion dominated by the Hunter River and many others which drain the Barrington Tops, and the Goulburn River and Growee River that drain the remnant native forests in the south-western part of the subregion associated with the Hunter Range. From a groundwater perspective it is essentially a closed system, with the majority of groundwater resources associated with alluvial and aeolian aquifers. Fractured rock aquifers are of less importance due to marginal water quality.

About 838,000 people live in the subregion, including the important regional urban centres of Newcastle, Central Coast, Maitland and Cessnock. Water for these towns is extracted from local rivers and groundwater systems and there are several major dams in the subregion. Three of these dams produce hydro-power; however a much more significant proportion of NSW’s electricity requirement is generated by coal-fired power stations located in the Hunter subregion, which are fueled by coal mined within the subregion.

The climate is sub-tropical on the coast becoming more temperate inland, characterised by summer dominant precipitation. Mean precipitation over the last 30 years (1982 to 2012) for the subregion was 793 mm/year with a mean potential evapotranspiration (PET) of 1728 mm/year; considerable spatial variation across the subregion and temporal variation is ‘hidden’ in such subregion-averages. There were no distinctive precipitation trends over this period but there was a decreasing trend for PET due to declining rates of wind speed, net radiation and vapour pressure deficit offsetting PET increases associated with rising air temperatures. Future precipitation may decrease and accordingly there may be a decrease in runoff generation from the Hunter subregion.

Last updated:
18 January 2019
Thumbnail of the Hunter subregion

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