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- 5 Outcome synthesis for the Namoi subregion
- What are the potential impacts of additional coal resource development on water-dependent assets?
The impact and risk analysis (Box 6) used multiple lines of evidence to investigate how hydrological changes due to additional coal resource development may affect water-dependent assets, such as bores, heritage sites or habitats of species.
A total of 1889 water-dependent assets listed in the asset register (Table 2; Bioregional Assessment Programme, 2017; Dataset 12; O’Grady et al., 2015) were analysed for the subregion, including:
- 1690 ecological assets, including
- 15 species and 6 ecological communities listed under the Commonwealth’s Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act)
- Lake Goran (listed as a nationally important wetland)
- Important Bird Areas
- a number of important alluvial aquifers, groundwater management zones and groundwater-fed springs
- 168 economic assets, comprising 10,418 elements that are grouped into 88 surface water and 80 groundwater management units
- 31 sociocultural assets, comprising 22 heritage sites and 9 Indigenous sites.
Potential impacts on assets were assessed by overlaying their extent on the zone of potential hydrological change (Box 4, Box 6). The assessment took a precautionary approach: it identified potential impacts if an asset or any part of it is within the zone of potential hydrological change.
Assets with areas that exceed thresholds of hydrological changes are identified as ‘more at risk of hydrological changes’ relative to other assets (defined in Box 10).
Ecological changes were not predicted for assets, because receptor impact models (Box 8) were developed for landscape classes, not individual assets. Section 3.5.5 of the impact and risk analysis (Herr et al., 2018a) provides an example of assessing potential impacts on assets.
Parts of some assets were deemed ‘more at risk of hydrological changes’ relative to other parts of that asset. Categorisation assists the rule-out process and in identifying where further local-scale assessment is warranted. Assessment units that overlap with an asset are categorised as ‘more at risk’ based on the degree that modelled hydrological changes exceed thresholds of risk. These subregion-specific thresholds are based on expert opinion and defined using hydrological response variables (see Section 3.5 of Herr et al. (2018a) for more details on the thresholds). Box 10 Categorising risk for assets
Ecological assets
Which ecological assets are very unlikely to be impacted?
Of the 1690 ecological water-dependent assets in the Namoi assessment extent, 1066 (or 63%) are outside the zone of potential hydrological change and are very unlikely to be impacted, including:Key finding 8
These seven EPBC Act-listed species include:
- the critically endangered leek orchid (Prasphyllum sp., Wybong)
- the endangered Australasian bittern (Botaurus poiciloptilus)
- the endangered Booroolong frog (Litoria booroolongensis)
- the endangered Tarengo leek orchid (Prasophyllum petilum)
- the vulnerable red goshawk (Erythrotriorchis radiatus)
- the vulnerable Belson’s panic (Homophilis belsoni)
- the migratory black-faced monarch (Monarcha melanopsis).
See Section 3.5.2 of the impact and risk analysis (Herr et al., 2018a) for more details.
Which ecological assets are potentially impacted?
Of the 1690 ecological assets in the assessment extent, 624 are in the zone of potential hydrological change. Of these assets in the zone, 161 are found in areas that are ‘more at risk of hydrological changes’ relative to other areas. For 10 assets in the zone, risk could not be quantified because surface water modelling was not available. Key finding 9
Of the 624 ecological assets in the zone, 20 are in the ‘Groundwater feature’ subgroup, 473 are in the ‘Surface water feature’ subgroup and 131 are in the ‘Vegetation’ subgroup. Those assets of interest in the ‘Vegetation’ subgroup include:
- 102 assets from the National atlas of groundwater dependent ecosystems (GDE Atlas)
- 7 assets listed in the Collaborative Australian Protected Area Database (CAPAD)
- 1 Important Bird Area
- 15 species listed under the EPBC Act
- 6 threatened ecological communities, also listed under the EPBC Act (Table 34 in Herr et al. (2018a)).
Table 2 Water-dependent assets in the assessment extent and the zone of potential hydrological change
Economic asset numbers are not individual bores but water access entitlements that could include one or multiple bores or water rights.
Data: Bioregional Assessment Programme (2017, Dataset 12)
Ecological assets were considered to be ‘more at risk of hydrological changes’ if any of their spatial extent intersected with areas exposed to larger changes in groundwater and/or surface water regimes as defined by thresholds of change in their hydrological response variables.
A total of 161 ecological assets were deemed to be ‘more at risk of hydrological changes’ (Box 10), including:
- 76 surface water features
- Cadna-owie Hooray Equivalent Great Artesian Basin recharge area
- Great Artesian Basin Groundwater Management Zone
- Gunnedah Basin Groundwater Management Zone
- Lower Namoi Alluvium Groundwater Management Zone
- Narrabri watertable aquifer
- Upper Namoi Alluvium Groundwater Management Zone
- Westbourne Formation
- the Pilliga Imortant Bird Area
- the potential habitats of 5 threatened ecological communities and 11 threatened species listed under the EPBC Act.
The 11 threatened species listed under the EPBC Act include the koala, an iconic animal for the Namoi subregion. It is ‘more at risk of hydrological changes’ because habitat with the preferred food tree, the river red gum, accesses groundwater and changes to surface water regimes may increase the reliance on groundwater.
The largest proportion (by area) of assets is associated with two ecosystems: ‘floodplain or lowland riverine’ and ‘non-floodplain or upland riverine’. The percentage of areas with surface water modelling varies between different landscape classes but can be as high as 94% (see Section 3.4 in Herr et al. (2018a) for further detail). A total of 10 ecological assets intersect parts of the stream network where surface water modelling was not available and thus it is not possible to quantify their risk level.
Economic assets
Economic water-dependent assets comprise surface water and groundwater sources, their associated water access licences and basic water rights, and water supply infrastructure.
Which economic assets are very unlikely to be impacted?
Outside the zone of potential hydrological change are 48 assets from the ‘Surface water management zone or area’ asset subgroup and 8 assets from the ‘Groundwater management zone or area’ asset subgroup.
Impacts on surface water economic assets were assessed in terms of water availability, reliability of supply, environmental water releases and potential for greater than 5% chance of more than 2 m additional drawdown. Water availability for Bohena Creek, Coxs Creek, Bundock Creek and Baradine Creek unregulated water sources is not impacted due to additional coal resource development.
The deeper groundwater layers could be used as economic assets by extraction bores or ecological assets as the source water for springs. The zone of potential hydrological change in the deeper Pilliga Sandstone extends no farther than 2 km beyond the zone of potential hydrological change defined by the overlying regional watertable, and there are no extraction bores or springs in this 2 km fringe, so identifying potentially impacted bores using the zone defined by the regional watertable is appropriate.
Of the 31 groundwater sources in the Namoi assessment extent, 17 are very unlikely to experience impact due to additional coal resource development. Of the 2555 bores identified as being within the zone of potential hydrological change, 504 are within the groundwater zone of potential hydrological change (Box 4) and are therefore potentially impacted (Table 42 in Section 3.5.3 of Herr et al. (2018a)). It is very unlikely that the 2051 bores solely within the surface water zone of potential hydrological change will be impacted due to additional coal resource development.
Which economic assets are potentially impacted?
Surface water economic assets
Maximum reductions in annual flow in the Namoi Regulated River due to additional coal resource development are less than 1% and unlikely to lead to reductions in water availability. Additional reductions in annual flows in all unregulated water sources are less than 1% of the annual flow under the baseline. Additional increases in cease-to-pump days are less than 12 days per year at all locations. Key finding 10
Potential reductions in water availability were identified in the following unregulated water sources: Mooki River, Maules Creek, Driggle Draggle Creek, Bollol Creek, Merrygowan Creek, Tulla Mullen Creek and Lake Goran unnamed creek, but these are all less than 1% of the total water availability in each unregulated water source under the baseline (Table 44 in Herr et al. (2018a)).
Reductions in water availability are also possible in the Namoi Regulated River water source. These are all much less than 1% of the total water availability under the baseline, although total reductions can be as high as 4.2 GL per year (Table 45 in Herr et al. (2018a)).
Cease-to-pump rules apply for most water sources in NSW to ensure sufficient water is retained in unregulated rivers to meet environmental requirements. For example, in the Lower Coxs Creek Management Zone, users must cease to pump when flow is equal to or below 15 ML per day at Tourable Gauge and 11 ML per day at Boggabri Gauge (Table 46 in Herr et al. (2018a)).
Under the baseline for the short-term period from 2013 to 2042, surface water modelling indicated no changes in cease-to-pump days for Baradine Creek, Maules Creek or Coxs Creek at Boggabri. Increases in the number of cease-to-pump days for Bundock, Bohena, Coxs Creek at Tambar Springs, and the Mooki River at Breeza are possible, but these are limited to an additional 12 cease-to-pump days per year at most (Table 47 in Herr et al. (2018a)). Bohena Creek has a 5% chance that cease-to-pump days during the 2043 to 2072 long-term period may increase by 9 days. The Mooki River at Breeza (node 35) has a large number of cease-to-pump days under the baseline due to its larger threshold (≤50 ML/day). Two locations on Coxs Creek (hydrological model nodes 28 and 29) also have larger cease-to-pump days under the baseline, which do not change noticeably due to additional coal resource development.
Groundwater economic assets
Nine groundwater sources (Gunnedah-Oxley Basin MDB; Lower Namoi; Peel Alluvium; Southern Recharge; and Upper Namoi zones 3, 4, 5, 7 and 8) are potentially impacted due to additional coal resource development (Figure 46 in Herr et al. (2018a)). All groundwater sources (except for Lower Namoi and Upper Namoi Zone 5) have bores with a greater than 5% chance of more than 2 m additional drawdown (see Table 43 and Figure 49 in Section 3.5.5 in Herr et al. (2018a)).
Of the 8953 bores in the assessment extent, 8424 are very unlikely to be impacted due to additional coal resource development. Outside the mine pit exclusion zone, there are 118 bores with a greater than 5% chance of more than 2 m additional drawdown, 14 with greater than 50% chance and 1 bore with greater than 95% chance (Figure 15). Key finding 11
The coal resource development pathway includes baseline and additional coal resource developments (ACRD).
Data: Bioregional Assessment Programme (Dataset 5, Dataset 13)
Sociocultural assets
The water-dependent asset register for the Namoi subregion (Table 2; O’Grady et al., 2015; Bioregional Assessment Programme, 2017; Dataset 12) contains 31 sociocultural assets, including 22 heritage sites and 9 Indigenous assets (Table 48 in Section 3.5.4 in Herr et al. (2018a)).
Which sociocultural assets are very unlikely to be impacted?
Seventeen sociocultural water-dependent assets are outside the zone of potential hydrological change. It is very unlikely that hydrological changes due to additional coal resource development will affect these (Table 48 in Section 3.5.4 in Herr et al. (2018a)).
Which sociocultural assets are potentially impacted?
Fourteen of the 31 sociocultural water-dependent assets identified in the assessment extent are in the zone of potential hydrological change, and are therefore potentially impacted. Of these, 12 assets are heritage sites and 2 are Indigenous sites.
Assessment of the impact of potential hydrological changes on assets requires a quantitative understanding of the nature of their water dependency which is not within the scope of this bioregional assessment. Assets in the zone include:
- the Indigenous assets, Boggabri Lagoon and the Burburgate Carved Tree
- built infrastructure, such as the Wee Waa and Gunnedah courthouses
- heritage-listed buildings, cemeteries and graves.
Further details are available in Table 49 and Figure 50 in Section 3.5 in the impact and risk analysis (Herr et al., 2018a).
The Bioregional Assessment Programme does not have the expertise to comment on potential impacts of changes in hydrological regimes on the value of Indigenous assets and built infrastructure. Evaluating potential impacts on these sites would require further local-scale assessment.
Explore potential impacts on water-dependent assets in more detail on the BA Explorer, available at www.bioregionalassessments.gov.au/explorer/NAM/assets Description of the water-dependent asset register, product 1.3 (O’Grady et al., 2016) Water-dependent asset register, list for product 1.3 (Bioregional Assessment Programme, 2017) Impact and risk analysis, product 3-4 (Herr et al., 2018a) Compiling water-dependent assets, submethodology M02 (Mount et al., 2015) Impacts and risks, submethodology M10 (Henderson et al., 2018) Landscape classification (Dataset 9) Spatial overlay of hydrological changes in the regional watertable databases (Dataset 1)FIND MORE INFORMATION
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- Executive summary
- Explore this assessment
- About the subregion
- How could coal resource development result in hydrological changes?
- What are the potential hydrological changes?
- What are the potential impacts of additional coal resource development on ecosystems?
- What are the potential impacts of additional coal resource development on water-dependent assets?
- How to use this assessment
- Building on this assessment
- References and further reading
- Datasets
- Contributors to the Technical Programme
- Acknowledgements
- Citation