2.7.2.1 Potentially impacted landscape classes

Prior to the qualitative modelling workshop, the zone of potential hydrological change was used to (i) identify ecological landscape classes that intersect it and are potentially impacted by the modelled hydrological changes due to additional coal resource development, and (ii) rule out landscape classes that do not intersect the zone and are therefore considered very unlikely (less than 5% chance) to be impacted by changes in hydrology. Qualitative and/or receptor impact models are only needed for those ecological landscape classes that are potentially impacted.

Qualitative models and receptor impact models were not built for ‘Economic land use’ and ‘Non-GDE vegetation’ landscape groups, which are not considered water dependent in the definition adopted for the bioregional assessments (BAs). Potential impacts on water-dependent economic assets are covered in companion product 3-4 (impact and risk analysis) for the Hunter subregion (Herron et al., 2018).

The zone of potential hydrological change, defined in Section 3.3.1 of companion product 3-4 for the Hunter subregion (Herron et al., 2018), encompasses the area where the predicted changes in groundwater drawdown and/or surface water hydrological response variables due to additional coal resource development could potentially impact water-dependent landscape classes and assets. The total area of the zone of potential hydrological change is 3213 km² and comprises four distinct groundwater drawdown areas linked by a potentially impacted surface water corridor in the Hunter river basin, and a fifth groundwater area and associated surface water corridor in the Macquarie-Tuggerah lakes basin (see Figure 17 in companion product 3-4 for the Hunter subregion (Herron et al., 2018)).

Table 5 lists the 19 ecological landscape classes in the Hunter subregion (see companion product 2.3 for the Hunter subregion (Dawes et al., 2018)) and identifies those that do and do not intersect the zone of potential hydrological change. All riverine landscape classes and eight of the nine groundwater-dependent ecosystem (GDE) landscape classes are present within the zone of potential hydrological change, although some GDE landscape classes are only represented by very small areas, such as the ‘Grassy woodland’, ‘Heathland’ and ‘Semi-arid woodland’ landscape classes. The ‘Spring’ landscape class is one of two landscape classes that do not intersect the zone and is ruled out of further consideration. Of the ‘Coastal lakes and estuaries’ landscape group, all landscape classes except ‘Drowned valleys’ are present within the zone, although several are only represented by very small areas, such as the ‘Creeks’ and ‘Barrier river’ landscape classes. Maps showing the landscape classes within each landscape group that are in the zone of potential hydrological change are provided in Section 3.4 of companion product 3-4 for the Hunter subregion (Herron et al., 2018).

Table 5 Length or area of each landscape class within the zone of potential hydrological change (zone)

Landscape class names as shown in companion product 2.3 for the Hunter subregion (Dawes et al., 2018). Also indicated is whether the landscape class is represented in a qualitative model (shown by model name) and/or a receptor impact model (RIM).

^aThe ‘Lowly to moderately intermittent’ and ‘Moderately to highly intermittent’ landscape classes from companion product 2.3 for the Hunter subregion (Dawes et al., 2018) are treated as one landscape class, listed here as ‘Lowly to highly intermittent’.

GDE = groundwater-dependent ecosystem, na = not applicable

Data: Bioregional Assessment Programme (Dataset 1)

Table 5 also identifies for those landscape classes within the zone of potential hydrological change, whether a qualitative model was built (indicated by the model name) or not and whether a receptor impact model was built. Six receptor impact models were built, representing five landscape classes; seven landscape classes have qualitative models, but not receptor impact models; five landscape classes that intersect the zone of potential hydrological change do not have qualitative models. Details of the qualitative models and receptor impact models are provided in Sections 2.7.3, 2.7.4 and 2.7.5 of this product, while the results from modelling the effects of baseline and additional coal resource development on landscape classes using these models are presented in Section 3.4 of companion product 3-4 for the Hunter subregion (Herron et al., 2018). The reasons for not building qualitative and/or receptor impact models for some landscape classes are outlined in Section 2.7.2.2, Section 2.7.2.3 and Section 2.7.2.4.