3.4 Impacts on and risks to landscape classes


The heterogeneous natural and human-modified ecosystems in the Gloucester subregion were classified into 20 landscape classes, which were aggregated into five landscape groups based on their likely response to hydrological changes: ‘Riverine’, ‘Groundwater-dependent ecosystem (GDE)’, ‘Estuarine’, ‘Non-GDE’ and ‘Economic land use’.

The ‘Native vegetation’ landscape class was ruled out from potential impacts, because it is classified as a ‘Non-GDE’ landscape and not considered water dependent for the purposes of bioregional assessments (BAs).

The following are very unlikely to be impacted because they are located outside the zone of potential hydrological change:

  • the ‘Estuarine’ landscape group
  • the ‘Freshwater wetland’ landscape class within the ‘GDE’ landscape group.

Intermittent and perennial gravel/cobble streams are the most extensive riverine landscape classes in the zone of potential hydrological change, and qualitative models and receptor impact models were constructed for these landscape classes. The receptor impact models determined the potential impact of hydrological changes using these variables:

  • annual mean percent canopy cover of woody riparian vegetation (perennial streams)
  • mean number of larvae of the Hydropsychidae family (net-spinning caddisflies) in a 1 m2 sample of riffle habitat (perennial streams)
  • mean number of the eel-tailed catfish (Tandanus tandanus) in a 600 m2 transect whose long axis lies along the mid-point of the stream (perennial streams)
  • mean richness of hyporheic invertebrate taxa (intermittent streams).

Overall, no changes are detectable in any of these receptor impact variables due to additional coal resource development. This is because the modelled hydrological changes in these streams are very minor.

Approximately 1.1 km2 of GDEs have a 5% chance of experiencing groundwater drawdown between 0.2 and 2 m. Most of the potential impact is in the ‘Forested wetlands’ landscape class. No GDE landscape classes are subject to greater than 2 m of potential drawdown. The water requirements of GDEs are poorly understood and there is large uncertainty as to the frequency, timing and duration of groundwater use in the Gloucester subregion. It is therefore unclear how much (if any) impact this additional drawdown is likely to have on GDEs.

Last updated:
8 November 2018
Thumbnail of the Gloucester subregion

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