- Bioregional Assessment Program
- Namoi subregion
- 2.7 Receptor impact modelling for the Namoi subregion
- 2.7.2 Prioritising landscape classes for receptor impact modelling
- 220.127.116.11 Potentially impacted landscape classes
The landscape classification for theof the identified 29 that were aggregated into 6 broad (see Section 2.3.3 of companion product 2.3 for the Namoi subregion ( )). Once the was developed for the Namoi subregion (as outlined in companion product 3‑4 for the Namoi subregion ( )) it was used to: (i) identify ecological landscape classes that intersect it and are potentially impacted by the modelled hydrological changes due to , and (ii) rule out landscape classes that do not intersect the zone and are therefore considered (less than 5% chance) to be impacted by changes in hydrology. Qualitative and/or are only needed for those ecological landscape classes that are potentially impacted.
There are two landscape groups that are automatically ruled out of this component ofregardless of their extent within the zone of potential hydrological change. Firstly, the ‘Dryland remnant vegetation’ landscape group is ruled out from potential impacts because it comprises vegetation communities that are deemed to be reliant on incident rainfall and local and do not include features in the landscape that have potential hydrological to or features (for further information, see Section 2.3.3 of companion product 2.3 for the Namoi subregion ( )). Secondly, the ‘Human-modified’ landscape group (comprising six landscape classes) is excluded from this analysis because it primarily comprises agricultural and urban landscapes that are highly modified by human activity, and contains a set of ecohydrological attributes distinct from the other landscape groups (for further information, see Section 2.3.3 of companion product 2.3 for the Namoi subregion ( )). Attributes of the water-dependency of some aspects of these landscapes are considered elsewhere (see Section 3.5 of companion product 3‑4 for the Namoi subregion ( )), that is, the potential impact of coal resource development on economic such as groundwater .
None of the 15of the ‘Non-GAB springs’ landscape class found in the assessment extent are located within the zone of potential hydrological change. Therefore, this landscape class can be ruled out as it is very unlikely to be impacted due to additional coal resource development.
The remaining 21 landscape classes, comprising 4 landscape groups that intersect the 7014 km2 zone of potential hydrological change, are considered dependent on groundwater or surface water regimes. These landscape groups, therefore, are potentially impacted due to additional coal resource development and are considered further in this product and through the remainder of theand analysis of the BA for the Namoi subregion (i.e. as presented in companion product 3‑4 ( )). The landscape groups are ‘Floodplain or lowland riverine’, ‘Non‑floodplain or upland riverine’, ‘Springs’ and ‘Rainforest’.
When developing ecological models for the Namoi subregion it was deemed necessary to develop a separate model for defining potential ecological impacts for the Pilliga and Pilliga Outwash IBRA subregions (2.7.5), the potential hydrological changes and impacts are presented for both a separate Pilliga region of the zone of potential hydrological change and the remaining ‘non-Pilliga’ areas or reporting regions for the relevant landscape classes (see Section 18.104.22.168 of companion product 3‑4 for the Namoi subregion ( ) for details on reporting regions).). The Pilliga and Pilliga Outwash IBRA subregions, or simply termed the ‘Pilliga region’ here, represent a unique set of landscapes within the Namoi subregion. By comparison to the other landscapes across the Namoi subregion, the Pilliga region has many unique attributes in terms of its ecology, geomorphology, underlying , soils and ecohydrology. Consistent with the structuring of the ecological models, outlined further in this product (see Section
The Table 5). Among these four riverine classes, the largest contribution is from the ‘Temporary lowland stream’ (2062.2 km) and ‘Permanent lowland stream’ (979.6 km) landscape classes (Table 5). All six of the non-riverine classes occur within the zone of potential hydrological change (Table 5). The largest non-riverine class by area is the ‘Floodplain grassy woodland GDE’ (421.7 km2) and ‘Floodplain grassy woodland’ (121.3 km2) (Table 5). Almost half of all the ‘Floodplain riparian forest GDE’ in the assessment extent (148.7 km2) is included in the zone of potential hydrological change (Table 5). Most of the areas classified as ‘Floodplain wetland’ and ‘Floodplain wetland GDE’ in the assessment extent (30.1 km2and 151.8 km2 respectively) form part of the zone of potential hydrological change (Table 5).contains all four riverine within the ‘Floodplain or lowland riverine’ and includes 61% of the entire extent of this group within the (
A single signed digraph model was created for the ‘Floodplain or lowland riverine’ landscape group that captured most of the key linkages within and between the riverine and floodplain habitats. From this model, key Table 5). There are two landscape classes in the ‘Floodplain or lowland riverine’ landscape group (non-Pilliga region) where was assigned as a hydrological response variable: ‘Floodplain riparian forest’ and ‘Floodplain riparian forest GDE’. The corresponding for forests was identified as change in projected foliage cover. The frequency of was identified as being an important driver of the riparian (‘Floodplain riparian forest’ and ‘Floodplain riparian forest GDE’ landscape classes) as well as the off-channel water bodies or floodplain wetlands (‘Floodplain wetland’ and ‘Floodplain wetland GDE’ landscape classes). The experts at the qualitative modelling workshop considered the presence of tadpoles from the Limnodynastes genus as the key receptor impact variable for floodplain wetlands. The cease-to-flow attributes of the regime were considered as critical hydrological response variables for the riverine landscape classes and were assigned: annual number of and annual maximum zero-flow spells. Assemblages of macroinvertebrates in the edge habitat were deemed to be appropriate receptor impact variables for gauging impacts on these cease-to-flow attributes of the flow regime.were selected for a subset of the landscape classes. Given the expertise and resources available at the qualitative modelling workshop for the , it was decided that be developed for a subset of landscape classes of this group (
Receptor impact models were not constructed for the ‘Floodplain grassy woodland’ and ‘Floodplain grassy woodland GDE’ landscape classes. While these classes occupy a large proportion of this landscape group within the zone of potential hydrological change, they are considered less sensitive to hydrological change given their reduced reliance on groundwater and surface water (see Section 2.7.3 for more details).
Table 5 Extent of all landscape classes in the assessment extent and zone of potential hydrological change for the Namoi subregion
Landscape class names as shown in companion product 2.3 for the Namoi subregion (). The relevant reporting region, qualitative model and receptor impact model is given for each landscape class.
aExtent of each landscape class is either an area of vegetation (km2), length of stream network (km) or number of springs (number).
bValues for the extent in assessment extent are the same regardless of reporting region.
GAB = Great Artesian Basin; GDE = groundwater-dependent ecosystem
Data: Bioregional Assessment Programme (Dataset 1)
For the areas outside the Pilliga region in the Table 5). The remainder of the stream network is classified as ‘Permanent upland stream’ (92.6 km), ‘Temporary upland stream GDE’ (34.7 km) and ‘Permanent upland stream GDE’ (14.2 km) (Table 5). Most non-riverine landscapes in the ‘Non-floodplain or upland riverine’ landscape group in the zone of potential hydrological change are in the ‘Grassy woodland GDE’ landscape class (72.8 km2). The ‘Upland riparian forest GDE’ landscape class makes up a very small area of the zone of potential hydrological change (2.9 km2) along with a small area of ‘Non-floodplain wetland’ (13.1 km2) and ‘Non-floodplain wetland GDE’ landscape classes (8.1 km2) (Table 5).(i.e. Upper Namoi, Mid Namoi and Lower Namoi reporting regions), the most common riverine within the ‘Non-floodplain or upland riverine’ in the zone of potential hydrological change is classified as ‘Temporary upland stream’ (745.1 km) reflecting the intermittent or ephemeral nature of many of the stream segments (
Three different components of this landscape group were considered for the qualitative modelling given the general lack of hydrological and spatial Table 5). Cease-to-flow attributes (zero-flow days and zero-flow spells) of the regime were assigned as for the upland riverine model. The corresponding included changes in macroinvertebrate assemblages and the probability of the presence of tadpoles from the Limnodynastes genus (Table 5). For upland riparian forest, and events were considered the key hydrological response variables. The potential impacts on this landscape class were quantified using projected foliage cover (Table 5).between the landscape classes across the zone of potential hydrological change. The level of fragmentation and lack of spatial overlap between the ‘Upland riparian forest GDE’, ‘Grassy woodland GDE’ and the ‘Non-floodplain wetland’/‘Non-floodplain wetland GDE’ landscape classes suggested limited potential for hydrological and ecological connectivity. The upland riverine qualitative model included all upland riverine landscape classes and the adjacent vegetation (‘Upland riparian forest GDE’) landscape class. Three were formulated based on this qualitative model: upland riverine (two separate models) and upland riparian forest (
In addition to the upland riverine system, a qualitative model was developed for the non-floodplain wetlands in this landscape group (Table 5). However, no elicitation or quantitative modelling was conducted because these wetland systems were considered a low priority given their unknown levels of groundwater dependence. A qualitative model was also developed for the ‘Grassy Woodland GDE’ landscape class and this is discussed below in Section 22.214.171.124.4.
The Pilliga region within the Table 5). A small fraction of the ‘Permanent lowland stream’ landscape class (14.3 km) intersects with the Pilliga region in the zone of potential hydrological change (Table 5).contains both upland and lowland riverine reaches. ‘Temporary upland stream’ (530.4 km) and ‘Temporary lowland stream’ (624.6 km) make up the majority of the riverine networks, reflecting the highly ephemeral and/or intermittent nature of the drainage network (
Given the unique characteristics of the Pilliga’s stream network (i.e. low relief, intermittent flow patterns), a qualitative model, in consultation with the local experts, was developed for both upland and lowland riverine classes – Pilliga riverine (Table 5). This meant that both lowland and upland riverine landscape classes share a similar model that encompasses both the riverine and systems. From this model, key were identified: , change in annual and . The workshop used two different to indicate potential ecological impacts in this system: projected foliage cover of riparian trees and number of families of aquatic macroinvertebrates. A qualitative model for the ‘Grassy woodland GDE’ landscape class was also formulated, but no quantitative modelling was developed.
The ‘Grassy woodland GDE’ Table 5). This landscape class includes a collection of different vegetation communities and habitats, however, given the concentration of this landscape class in the Pilliga region of the zone of potential hydrological change, a qualitative model was developed by the workshop participants with a focus on the ecology of this region (Table 5). Given the limitations on resources at the workshop and the surrounding the nature of dependency of vegetation in the Pilliga region, a receptor impact model was not formulated for this landscape class.makes up most of the non-riverine landscapes in the Pilliga region (561.7 km2) and a small portion (72.8 km2) of the total 634.5 km2 of this landscape class across the entire is located outside of the Pilliga region (
The ‘Rainforest’ Table 5). A qualitative model was developed for this landscape group that emphasises the relationship of key ecological components and dynamics. Given the limited extent of this landscape class within the landscape group and the large degree of associated with its groundwater dependency it was decided not to formulate a quantitative for this group.occupies a limited area within the , with the ‘Rainforest’ intersecting 4.0 km2 of the zone and the ‘Rainforest GDE’ landscape class intersecting 0.3 km2 (
Two Table 5). However, it was decided by experts that given the nature of the flow paths associated with these springs, impacts from additional resource development would be difficult to quantify and it was not pursued further.are known to occur within the , which are classified as ‘GAB springs’ based on their association with underlying sandstone . These two springs are located on the eastern edge of the Pilliga Basin and are thought to be primarily recharge springs, given their location on the eastern fringes of the Great Artesian Basin (GAB) ( ). A qualitative model was formulated for a typical recharge GAB spring (
Product Finalisation date
- 2.7.1 Methods
- 2.7.2 Prioritising landscape classes for receptor impact modelling
- 2.7.3 'Floodplain or lowland riverine' landscape group
- 2.7.4 'Non-floodplain or upland riverine' landscape group
- 2.7.5 Pilliga riverine landscape classes
- 2.7.6 'Rainforest' landscape group
- 2.7.7 'Springs' landscape group
- 2.7.8 Limitations and gaps
- Contributors to the Technical Programme
- About this technical product