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What are the potential impacts of additional coal resource development on water-dependent assets?

The impact and risk analysis investigated 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 108 water-dependent assets listed in the asset register (Dataset 19; Bioregional Assessment Programme, 2017; McVicar et al., 2015) were analysed for the subregion. They include:

  • 67 ecological assets, including the Karuah River and Port Stephens estuaries; 23 river or stream reaches, tributaries, anabranches or bends; three groundwater features (Karuah Alluvium, Manning Alluvium and New England Fold Belt); and 39 habitats of species
  • 22 economic assets, including water source areas, monitoring bores, water access licences and basic water rights, represented by groundwater production bores and surface water extraction points
  • 19 sociocultural assets.

Key finding 7

Of the 108 water-dependent assets nominated for the subregion, 30 are very unlikely to be impacted, because they lie outside the zone of potential hydrological change.


Ecological assets

Which ecological assets are very unlikely to be impacted?

Fifteen ecological assets fall outside the zone of potential hydrological change and so are very unlikely to be impacted. These include the Karuah River and Port Stephens estuaries; seven river or stream reaches, tributary anabranch or bends; and seven habitats of species.

The potential for impacts on ecological assets associated with riverine ecosystems is assessed as very unlikely (Section 3.5 in Post et al. (2018)).

It is very unlikely that more than 6 ha of a threatened ecological community (Lowland Subtropical Rainforest) are impacted (Table 28 in Post et al. (2018)).

Which ecological assets are potentially impacted?

Key finding 8

No detectable impacts are likely for ecological assets in the southern part of the subregion, given the limited additional coal resource development in this area. In the northern part of the subregion, potential impacts on ecological assets are expected to be minor and localised due to the small magnitude of modelled hydrological changes.

Out of the 67 ecological water-dependent assets in the subregion’s assessment extent, 52 assets are subject to potential hydrological change due to additional coal resource development because they are both water-dependent and within the zone of potential hydrological change. However, only 1.1 km2 associated with groundwater-dependent ecosystems is predicted to have potential for impacts on ecological assets (Table 24 in Post et al. (2018)).

Qualitative modelling predicted that groundwater drawdown negatively impacts on the potential habitat for koalas. An area of 0.6 km2 is the median estimate of potential koala habitat that overlaps with groundwater-dependent ecosystems experiencing drawdown greater than 0.2 m. Note that the chance of impact to potential habitats is often highly uncertain based on qualitative modelling.

Plant species and the threatened ecological community (Lowland Subtropical Rainforest) have very small areas (from 0 to 6 ha) of associated landscape classes within the zone of potential hydrological change (Figure 50 in Post et al. (2018)). Habitats where animal species are known to live range from 15 ha for the stuttering frog to 400 ha for the grey-headed flying fox and spot-tailed quoll.

Information about known habitats associated with species in groundwater-dependent ecosystems, and predictions about the occurrence of species within the assessment extent, are sourced from the BioNet database (NSW Office of Environment and Heritage, 2017).

The presence of potential habitats within the zone of potential hydrological change does not mean species are associated with particular landscape classes. For example, Guthrie’s grevillea is known to be associated with the ‘Wet sclerophyll forests’ landscape class but not with any of the other groundwater-dependent ecosystem (GDE) landscape classes. The Australasian bittern is only known to be associated with landscape classes that lie outside the zone, which are freshwater wetlands and saline wetlands. Also, not all habitat with potential to house certain species are known to occur within the Gloucester assessment extent. For example, the Australasian bittern, eastern bristlebird, red goshawk and Hastings River mouse are not known to occur within the Karuah-Manning Interim Biogeographic Regionalisation for Australia (IBRA) subregion which encompasses the Gloucester subregion.

Economic assets

Which economic assets are very unlikely to be impacted?

The Lower Manning River water source is outside the zone of potential hydrological change and thus very unlikely to be impacted. Thirty-six groundwater bores and 58 surface water extraction points in the Gloucester water-dependent asset register (Dataset 19; Bioregional Assessment Programme, 2017) are outside the zone of potential hydrological change and are thus very unlikely to be impacted.

A further 93 bores in the zone are unlikely to be impacted because they are monitoring bores or in fractured rock aquifers outside the area where there is at least a 5% chance that drawdown will be greater than 0.2 m.

Which economic assets are potentially impacted?

Five unregulated and alluvial water sources and two groundwater sources are potentially impacted by hydrological changes due to additional coal resource development.

Of the 339 bores and surface water extraction points in the zone, 304 are potentially impacted due to additional coal resource development. As the 58 monitoring bores in the zone are not used to pump water for beneficial use, impacts on these of changes in hydrology were not considered further for these bores. There is therefore a potential for impacts due to additional coal resource development at 246 bores and surface water extraction points in the zone of potential hydrological change (Figure 54, Table 32 and Table 33 in Post et al. (2018)).

The Gloucester Basin and New England Fold Belt groundwater sources are potentially impacted by groundwater drawdown due to additional coal resource development. The Avon River, Bowman River, Karuah River, Lower Barrington/Gloucester River and Upper Gloucester River unregulated and alluvial water sources are potentially impacted surface water economic assets (Figure 14).

Surface water economic assets

Key finding 9

The reliability of surface water supply in the Gloucester assessment extent is very unlikely to be affected by additional coal resource development. No change in cease-to-pump days is seen in the Upper Gloucester River and Karuah River (upper management zone) water sources. It is very likely that there will be fewer than 3 additional low-flow days per year in the Avon River, with an even smaller or no impact on cease-to-pump days.

Cease-to-pump rules apply to most water sources in NSW to ensure sufficient water is retained in unregulated rivers to meet environmental requirements. In the Avon River water source, pumping must cease when there is no visible flow into or out of the pumping pool; in the upriver management zone of the Karuah River, pumping must cease when flows are equal to or less than 3.5 ML per day at the Booral stream gauge; and in the Upper Gloucester River, when flows are equal to or less than 1 ML per day at the Gloucester River gauge.

Under the baseline for the 2013 to 2102 period, surface water modelling indicates a 5% chance that cease-to-pump days in the Karuah River (upriver management zone) and the Upper Gloucester water sources could exceed 50 days per year and 35 days per year, respectively. For the Avon River water source, there is a 5% chance of 80 or more days of flows per year below 1 ML per day, which is not the cease-to-pump threshold, but an indicator of the low-flow regime for the 90-year climate sequence modelled. This number of cease-to-pump days is very unlikely to increase by more than 3 days per year in the Avon River and 1 day per year in the Karuah and Upper Gloucester rivers.

It is very unlikely that reduction in water availability due to additional coal resource development, as assessed by a change in mean annual flows, will exceed 1.6 GL per year in either the Upper Gloucester River or Avon River water sources. This is well within the interannual variability due to climate, and corresponds to 1% and 2% changes relative to the assessment baseline (Table 34 in Post et al. (2018)).

Groundwater economic assets

Key finding 10

Five bores have a 5% chance of drawdown exceeding 2 m. Four are monitoring bores and therefore unlikely to lead to an economic impact; the one production bore is owned by AGL.

For more information see Table 37 in Post et al. (2018).

The NSW Aquifer Interference Policy (NSW Office of Water, 2012) requires that any proposal to extract water from an aquifer must address minimal impact considerations. Generally, if drawdown at a water supply work exceeds 2 m, then ‘make good’ provisions should apply.

Sociocultural assets

Which sociocultural assets are very unlikely to be impacted?

As of February 2016, 19 sociocultural assets in the subregion were identified as water dependent. Eighteen of them are located outside the zone of potential hydrological change, and are therefore very unlikely to be impacted.

Fifteen Indigenous assets were included in the sociocultural assets registered, including 11 assets for which locations were not provided. Based on the association of these assets with marine and estuarine environments, they are almost certainly located outside the zone of potential hydrological change and therefore not likely to be impacted. Information on Indigenous water assets is also available in Constable and Love (2015).

Which sociocultural assets are potentially impacted?

Key finding 11

The Washpool in the Karuah River, north of the town of Washpool, is the only sociocultural asset in the zone of potential hydrological change. However, due to the very small hydrological changes at this location, it is unlikely to be impacted by additional coal resource development.

The Washpool (Figure 49 in Section 3.5 of Post et al. (2018)) is a locally significant heritage site along the Karuah River north of the town site of Washpool at the Stroud Hill Road bridge. Although it is located within the zone of potential hydrological change, the small alterations to flow predicted at this location are unlikely to result in any change in water level at the Washpool, and are not expected to affect the social amenity provided by the site.

Figure 14

Figure 14 Economic assets in the zone of potential hydrological change

Pastel colours in background represent different water source areas.

Data: Bioregional Assessment Programme (Dataset 19, Dataset 20, Dataset 21)

Last updated:
8 November 2018