3.5.2 Ecological assets

3.5.2.1 Ecological assets in the zone of potential hydrological change

The assessment of impacts on water dependent ecological assets was based on those contained in the current water-dependent asset register (Bioregional Assessment Programme, 2017; Bioregional Assessment Programme, Dataset 1). The current asset register does not necessarily match the asset register referred to in the earlier product (companion product 1.3 for the Namoi subregion (O’Grady et al., 2015); Bioregional Assessment Programme, Dataset 2). The water-dependent assets register for the Namoi subregion contains 1690 ecological assets (Bioregional Assessment Programme, 2017; Bioregional Assessment Programme, Dataset 1). Of these, 624 assets intersect with the zone of potential hydrological change, including 20 in the ‘Groundwater feature (subsurface)’ subgroup, 473 in the ‘Surface water feature’ subgroup and 131 in the ‘Vegetation’ subgroup (Table 33).

Table 33 Ecological assets in the assessment extent and zone of potential hydrological change

Data: Bioregional Assessment Programme (Dataset 1)

Six hundred and twenty-four ecological assets intersect with the zone of potential hydrological change (Table 33) and therefore have the potential to be impacted due to additional coal resource development. It is important to note that single assets may occur across a range of landscape classes.

Of the 131 assets in the ‘Vegetation’ subgroup, 102 are sourced from the National atlas of groundwater dependent ecosystems (GDE Atlas) (Bureau of Meteorology, 2012). The remaining 29 assets comprise 7 assets listed in the Collaborative Australian Protected Area Database (CAPAD), 1 Important Bird Area, 15 species listed under the EPBC Act and 6 threatened ecological communities, also listed under the EPBC Act (Table 34).

Table 34 Ecological assets associated with the ‘Habitat (potential species distribution) asset class in the ‘Vegetation’ subgroup within the zone of potential hydrological change

^aPunctuation and typography appear as used in the asset database.

Data: Bioregional Assessment Programme (Dataset 1)

All six nationally listed threatened ecological communities within the subregion intersect to some extent with the zone of potential hydrological change.

Figure 43 Number of ecological assets within different asset risk categories

Asset counts within a particular bounding box are unique but may occur across multiple landscape classes.

'some risk' = 'at some risk of hydrological changes'

'minimal risk' = 'at minimal risk of hydrological changes'

'more at risk' = 'more at risk of hydrological changes'

A total of 614 of the 624 assets in the zone of potential hydrological change are associated with ‘potentially impacted landscape classes’ where receptor impact modelling was carried out (Figure 43). These are discussed further in Section 3.5.2.3.

3.5.2.2 Ecological assets outside the zone of potential hydrological change

Of the total 1690 ecological assets within the assessment extent, 1066 do not intersect with the zone of potential hydrological change, thus it is very unlikely that these assets will be impacted due to additional coal resource development (Table 33 and Figure 43). These include 669 assets in the ‘Surface water feature’ subgroup, 13 assets in the ‘Groundwater feature (subsurface)’ subgroup and 384 assets in the ‘Vegetation’ subgroup.

Two assets, ‘Segment of Barwon River with KEA values’ (AID 5067) and ‘Segment of Currabubula Creek with KEA values’ (AID 5068) are listed in the Key Environmental Assets of the Murray–Darling Basin database and one asset, ‘Barwon River and fringing wetlands’ (AID 3339) is listed in the Environmental Assets Database. The remaining surface water assets that are very unlikely to be impacted were community nominated assets listed in the Water Asset Information Tool (WAIT) database (WAIT_Namoi (538 assets) and WAIT_Border Rivers-Gwydir (128 assets)).

In the ‘Groundwater feature (subsurface)’ subgroup, 13 assets from the WAIT_Border Rivers-Gwydir and the WAIT_Namoi databases are very unlikely to be impacted due to additional groundwater development. These all fall within the ‘Aquifer, geological feature, alluvium or stratum’ asset class.

In the ‘Vegetation’ subgroup, 384 assets fall outside the zone of potential hydrological change; thus, it is very unlikely that these will be impacted due to additional coal resource development. These include 340 assets classed as ‘Groundwater-dependent ecosystem’ sourced from the GDE Atlas and 44 assets classed as ‘Habitat (potential species distributions)’. Of the latter, 36 assets are listed by CAPAD, 1 Important Bird Area (Bubdarra-Barraba IBA, AID 4687) and 7 species listed under the EPBC Act. These EPBC Act-listed species are very unlikely to be impacted due to additional coal resource development in the subregion, including four species that are listed as either endangered or critically endangered:

3.5.2.3 Assets associated with potentially impacted landscape classes

As discussed in Section 3.5.1, this product focuses the discussion of potentially impacted ecological assets by analysing the overlap between potentially impacted landscape classes (those classes where there is receptor impact modelling) and changes in their associated hydrological response variables. Where hydrological modelling is available for locations across the spatial extent of the landscape class, assets can be classified to be ‘at some risk of ecological and hydrological changes’ or ‘more at risk of hydrological changes’ due to additional coal resource development. While this approach uses hydrological information to infer impacts on assets, these locations also reflect potential changes in the corresponding receptor impact variable, which is consistent with assessing potential risks using multiple lines of evidence.

The threshold for identifying ‘more at risk of hydrological changes’ assets is defined as:

Thresholds chosen to identify ‘more at risk of hydrological changes’ assets within impacted landscape class are:

All assets associated with ‘potentially impacted landscape classes’ (614) show some change in their associated hydrological response variables and are deemed to be at ‘some risk of hydrological change’ (Figure 43). Ecological assets that solely intersect areas within a landscape class where surface water modelling was unavailable (see companion product 2.6.1 for the Namoi subregion (Aryal et al., 2018)) for the two potentially impacted landscape groups (‘Floodplain or lowland riverine’ and ‘Non-floodplain or upland riverine’) are also identified. The proportion of areas with surface water modelling varies between different landscape classes but can be as high as 94% (see Section 3.4 for further details). For these assets, it is not possible to quantify their risk level and are therefore termed ‘unquantified risk of hydrological change’. There are ten unique assets associated with the ‘unquantified risk of hydrological change’ category (Figure 43) in either the ‘Floodplain or lowland riverine’ landscape group or the ‘Non-floodplain or upland riverine’ group landscape.

In total, 135 unique assets are identified as ‘more at risk of hydrological changes’ (Figure 43). Of the 471 assets within the ‘Surface water feature’ subgroup that intersect with the zone of potential hydrological change, a total of 76 of these assets are deemed to be ‘more at risk of hydrological changes’. There are 69 surface water assets associated with the ‘Floodplain or lowland riverine’ and 46 surface water assets associated with the ‘Non-floodplain or upland riverine’ landscape groups that were deemed to be ‘more at risk of hydrological changes’ based on the thresholds described above. The breakdown of these assets is shown in Table 35. None of the assets identified as ‘more at risk of hydrological changes’ are listed in A directory of important wetlands in Australia (DIWA).

Table 35 Assets within the ‘Surface water feature’ subgroup and within the zone of potential hydrological change that are deemed as ‘more at risk of hydrological changes’ due to additional coal resource development, and their association with potentially hydrologically impacted landscape groups

^aThe spatial extent of assets often intersects multiple landscape groups.

Data: Bioregional Assessment Programme (Dataset 1)

For the ‘Floodplain or lowland riverine’ landscape group, 11 ‘Groundwater feature (subsurface)’ assets are potentially ‘more at risk of hydrological changes’ due to additional coal resource development (Table 36). There are 12 ‘Groundwater feature (subsurface)’ assets associated with the ‘Non-floodplain or upland riverine’ landscape group that are potentially ‘more at risk of hydrological changes’ due to additional coal resource development (Table 36). These assets are:

Table 36 Ecological assets within the ‘Groundwater feature (subsurface)’ group and within the zone of potential hydrological change that are deemed as ‘more at risk of hydrological changes’ due to additional coal resource development, and their association with potentially hydrologically impacted landscape groups

^aThe spatial extent of assets often intersects multiple landscape groups.

Data: Bioregional Assessment Programme (Dataset 1)

Within the ‘Vegetation’ subgroup a total of 47 assets are considered ‘more at risk of hydrological changes’ due to additional coal resource development. 29 and 20 assets intersecting ‘Floodplain or lowland riverine’ the ‘Non-floodplain or upland riverine’ landscape groups, respectively, in the asset class ‘Groundwater dependent ecosystem’ are considered ‘more at risk of hydrological changes’ (Table 37). Assets in the ‘Habitat (potential species distribution)’ asset class deemed to be ‘more at risk of hydrological changes’ due to additional coal resource development included 17 within ‘Floodplain or lowland riverine’ and 13 within the ‘Non-floodplain or upland riverine’ landscape groups (Table 37).

Table 37 Ecological assets within the ‘Vegetation’ subgroup and within the zone of potential hydrological change that are deemed as ‘more at risk of hydrological changes’ due to additional coal resource development, and their association with potentially hydrologically impacted landscape groups

^aThe spatial extent of assets often intersects multiple landscape groups.

Data: Bioregional Assessment Programme (Dataset 1)

One Important Bird Area, Pilliga IBA, was deemed to be potentially ‘more at risk of hydrological changes’ due to additional coal resource development.

This asset intersected with both the ‘Floodplain or lowland riverine’ and ‘Non-floodplain or upland riverine’ landscape groups and was deemed to be ‘more at risk of hydrological changes’ based on the increased probability of changes to surface water regimes (Figure 44).

While these assets have been identified as being ‘more at risk of hydrological changes’, the nature of water requirements of the flora and fauna of these reserves remains poorly understood. The Pilliga IBA is contiguous with the Pilliga Nature Reserve forming the largest intact native forests west of the Great Dividing Range and contains areas of low-to-moderate groundwater dependence, particularly along Bohena Creek.

Figure 44 Distribution of Pilliga Important Bird Area (IBA) ('Vegetation' subgroup) deemed to be ‘more at risk of hydrological changes’

CAPAD = Collaborative Australian Protected Area Database

Data: Bioregional Assessment Programme (Dataset 1)

Five assets listed as threatened ecological communities under the EPBC Act intersect with the zone of potential hydrological change and are considered to be ‘more at risk of hydrological changes’ due to additional coal resource development:

All five of these communities occur within landscape classes associated with the ‘Floodplain or lowland riverine’ landscape group. Three intersect with the ‘Non-floodplain or upland riverine’ landscape group: ‘Coolibah - Black Box Woodlands of the Darling Riverine Plains’, ‘Natural grasslands on basalt and fine-textured alluvial plains of northern New South Wales and southern Queensland’ and ‘White Box-Yellow Box-Blakely's Red Gum Grassy Woodland and Derived Native Grassland’. The latter two threatened ecological communities listed here intersect with areas deemed ‘more at risk of hydrological changes’ for both surface water and groundwater hydrological response variables, while the remaining three are associated with increased chances of changes in surface water regimes (Figure 45).

Figure 45 Distribution of assets in the 'Vegetation' subgroup classified as threatened ecological communities (TEC) and their intersection with assets classified as groundwater-dependent ecosystems

Data: Bioregional Assessment Programme (Dataset 1)

The water requirements for these communities are generally poorly understood. In NSW, Brigalow communities occur primarily on flat or gently undulating land characterised by heavy gilgaied clays that collect localised runoff (NPWS, 2002). There are no known studies of the groundwater dependence of Acacia harpophylla. Patterns of water use in A. harpophylla are tightly coupled to rainfall and the species can tolerate very low leaf water potentials (or very large soil water deficits, (Tunstall and Connor, 1981). Together these observations suggest that groundwater dependence of the dominants in these communities would be limited. There is scant knowledge on the water requirements of three of the threatened ecological communities: ‘Grey Box (Eucalyptus microcarpa) Grassy Woodlands and Derived Native Grasslands of South-eastern Australia’, ‘Natural grasslands on basalt and fine-textured alluvial plains of northern New South Wales and southern Queensland’ and ‘White Box-Yellow Box-Blakely's Red Gum Grassy Woodland and Derived Native Grassland’.

There is greater understanding of the water regimes of the Coolibah – Black Box communities, although detailed studies of their water requirements are rare. These communities are associated with floodplains, and the distinction between forest and woodland is related to the degree of flooding, with forests occurring on more frequently flooded sites and woodlands in areas where flooding is less frequent (Roberts and Marston, 2011). Blackbox (Eucalyptus largiflorens) trees are well adapted to hot and dry conditions, and are able to access saline groundwater to maintain transpiration during these periods (Holland, 2002), but require flooding every 3 to 7 years to maintain health. These floods may play an important role in flushing salts from the soil profile and ensuring seedling survival following seedling establishment (Roberts and Marston, 2011). Coolibah trees, on the other hand, are less reliant on flooding. Flood regimes for these trees on the lower Gwydir floodplain are described as ranging from 1 in 10 through to 1 in 20, and these events appear to be beneficial through the flushing of salts from the soil profile. Coolibah are believed to be dependent on large-scale floods for large-scale regeneration. Coolibah trees have low transpiration rates and the capacity to access and use highly saline groundwater, which help them survive long dry periods (Roberts and Marston, 2011).

Species listed under the EPBC Act deemed ‘more at risk of hydrological changes’ due to additional coal resource development are listed in Table 38. These include six bird species, two mammals and three plant species.

Three water bird species were deemed ‘more at risk of hydrological changes’ due to additional coal resource development: the Australian painted snipe (Rostratula australis), the cattle egret (Ardea ibis) and the great egret (Ardea alba). Of these, the predicted distributions of the cattle egret and the great egret were associated with landscape classes where the thresholds for both surface water and groundwater hydrological response variables were surpassed. In contrast, the predicted distribution for the Australian painted snipe was associated with landscape classes where only the groundwater threshold was surpassed. As a general rule, the groundwater and surface water requirements of all the listed species are poorly understood. Great egrets have preference for permanent waterbodies, and breeding appears to be linked to flood events. Although there is little available information on the frequency of flooding required to maintain populations, Rogers and Ralph (2011) suggest that large floods should occur every 3 years and smaller floods every 2 years to maintain habitats. The water requirements of the Australian painted snipe and the cattle egret are less clear. Both species inhabit wetland types ranging from temporary to permanent wetlands, but appear to favour shallower systems, and inhabit a wider range of habitats.

For the remaining species listed in Table 38, impacts are likely to be mediated through changes in habitat. Species were listed as being potentially water dependent on the basis of their association with water-dependent habitats. All species listed in these habitats (Table 38) are ‘more at risk of hydrological changes’ from groundwater drawdown or changes in surface water regimes, which may impact on habitat through reduced canopy cover and health, in the short term, or a reduction in stand density over longer periods. However, understanding of these processes is limited at present. For koala, the groundwater-dependent river red gum (Eucalyptus camaldulensis) is a preferred food tree in the region and a range of eucalypt species such as E. populnea, E. blakelyi, and E. largiflorens are regarded as secondary food sources (NSW OEH, 2016a).

Changes in surface water regimes may similarly impact the habitat of the white-bellied sea eagle (Haliaeetus leucogaster), the koala (Phascolarctos cinereus), the long-eared bat (Nyctophilus corbeni) and the slender darling pea (Swainsonia murrayana), where these habitats overlap with impacted riverine landscape classes.

Table 38 Species listed under the Commonwealth’s Environment Protection and Biodiversity Act 1999 in the ‘Habitat (potential species distribution)’ subgroup deemed ‘more at risk of hydrological changes’ due to additional coal resource development, and their association with surface water and/or groundwater hydrological response variables identified by their intersection with water-dependent landscape groups

^aPunctuation and typography appear as used in the asset database.

Data: Bioregional Assessment Programme (Dataset 1)

3.5.2.4 Assets associated with other water-dependent landscape classes

Within the ‘Floodplain or lowland riverine’ and the ‘Non-floodplain or upland riverine’ landscape groups, there were a number of landscape classes for which quantitative ecological models were not elicited. These include the ‘Floodplain grassy woodland’ and ‘Floodplain grassy woodland GDE’ landscape classes in the ‘Floodplain or lowland riverine’ landscape group and the ‘Grassy woodland GDE’, ‘Non-floodplain wetland GDE’ and ‘Non-floodplain wetland’ landscape classes in the ‘Non-floodplain or upland riverine’ landscape group that are potentially exposed to a 50% chance of groundwater drawdown of greater than 2 m. Similarly, no models were elicited for the ‘Rainforest’ or ‘Springs’ landscape groups. Table 39 summarises the number of assets that intersect with landscape classes that are potentially at risk from additional groundwater drawdown. In total, 64 unique assets deemed ‘more at risk of hydrological change’ were associated with these additional landscape classes. However, only 26 of these assets are additional to those already identified in Section 3.5.2.3 as being ‘more at risk’. These additional assets identified as ‘more at risk’ include the EPBC Act-listed species Malleefowl (Leipoa ocellata) and ‘Leard Cca Zone 3 State Conservation Area’.

Table 39 Number of assets associated with landscape classes for which quantitative models were not elicited but potentially exposed to a 50% chance of groundwater drawdown of greater than 2 m

^aThe spatial extent of assets often intersects multiple landscape groups.

GDE = groundwater-dependent ecosystem

Data: Bioregional Assessment Programme (Dataset 1)