The objective of the Bioregional Assessment Programme is to understand and predict regional-scale cumulative impacts on water resources and water-dependent assets caused by coal resource developments in Australia’s major coal-bearing basins. Areas identified in a bioregional assessment (BA) as not being at risk of significant hydrological changes allow further local-scale investigation to be more focussed.
The Hunter subregion covers an area of 17,045 km2, which includes a significant part of the Hunter river basin and all of the Macquarie-Tuggerah lakes basin in NSW. Along the coast, the dominant land use is urban, with grazing, production forestry and nature conservation areas prevalent in the hinterland areas of Gosford and Wyong. In the Hunter River valley, there is a greater mix of intensive land uses including urban, coal mining, energy production and irrigated agriculture.
The subregion is of great ecological significance because a natural topographic break links coastal and inland NSW, and there is overlap between tropical and temperate climate zones. The asset register for the Hunter subregion (companion product 1.3 (Macfarlane et al., 2016; Bioregional Assessment Programme, 2017; Bioregional Assessment Programme, Dataset 1)) identifies 1652 water-dependent ecological assets, including World Heritage Areas, Ramsar-listed wetlands, and other nationally important wetlands and bird areas.
The area has a long history of coal production. Potential impacts on and risks to water resources and water-dependent assets due to additional coal resource development were assessed by comparing results for two futures: baseline coal resource development (baseline) and the coal resource development pathway (CRDP). In the Hunter subregion, the baseline includes 42 coal mines across the Western, Hunter and Newcastle coalfields. The CRDP includes all baseline coal resource developments plus 22 additional coal resource developments, including 6 proposals for new mines and 16 expansions to existing operations. Not all additional coal resource developments were able to be represented in the modelling. The potential impacts of the non-modelled developments are considered in Section 3.6.
A number of design choices have steered the direction of the BAs. These relate to the choice of modelled futures; the focus on changes in water quantity, with water quality considerations largely limited to the effect on stream salinity; the focus on cumulative changes at a regional-scale, rather than duplicating the local-scale modelling undertaken by mining proponents as part of the development approvals process; the adoption of a probabilistic approach to account for predictive uncertainty; the assessment of impacts by landscape classes to manage the inherent spatial variability; and the ‘rule-out’ approach by which the impact and risk analysis is directed to those landscape classes and assets where the changes in hydrology indicate a possibility of potentially adverse impacts.
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- 3.1 Overview
- 3.2 Methods
- 3.3 Potential hydrological changes
- 3.4 Impacts on and risks to landscape classes
- 3.5 Impacts on and risks to water-dependent assets
- 3.6 Commentary for coal resource developments that are not modelled
- 3.7 Conclusion
- Contributors to the Technical Programme
- About this technical product