Bioregional assessments can be updated – for example, incorporating new coal resource developments in the groundwater or surface water modelling. Existing lists such as the (Macfarlane et al., 2016; Bioregional Assessment Programme, 2017; Dataset 10) will remain relevant for future assessments. If new coal resource developments emerge in the future or more data become available to represent some of the non-modelled mines in the , the data, information, analytical results and models from this assessment provide a comprehensive basis for re-assessment of potential impacts under an updated CRDP. It may also be applicable for other types of resource development. Guidance about how to apply the Programme’s methodology is documented in detailed scientific submethodologies, listed in the references.
Extending this bioregional assessment should focus on improving confidence in assessing impacts in the landscape through more mapping of groundwater depths, vegetation communities and their water requirements, and identification of groundwater-dependent ecosystems.
Surface water and groundwater monitoring
Monitoring is important to evaluate the risk predictions of this bioregional assessment. Monitoring efforts should reflect the risk predictions, with the greatest effort directed to areas where the changes are predicted to be the largest and local-scale information supports the regional-scale assessment of risk. Monitoring in locations with lower risk predictions can help to confirm the range of potential impacts and identify unexpected outcomes. In the Hunter subregion, monitoring of groundwater levels in the five discrete drawdown zones due to additional coal resource development is recommended. Suggested priorities, based on potentially impacted bores, are the Sydney Basin – North Coast, Jilliby Jilliby Creek, Tuggerah Lakes and South Lake Macquarie water sources. In addition, groundwater level monitoring the area west of the proposed West Muswellbrook Project, where the drawdown area is likely to extend beyond the drawdown area due to only baseline mines, is recommended, starting before its development.
Priorities for streamflow and groundwater monitoring, based on streams identified as potentially at risk from large changes in flow regime, are Wyong River and Dora Creek, but also possibly Loders Creek, Saddlers Creek and Wollar Creek. Streamflow and groundwater monitoring could be of value in Mannering, Morans, Stockton, Wallarah and Wyee creeks given potential changes in flow regime that may arise from the proposed Mandalong Southern Extension Project. Monitoring of the Goulburn and Hunter rivers should continue, given potential changes in baseflow. Additional streamflow monitoring in the Wybong Creek would help to assess potential impacts from the proposed West Muswellbrook Project. Measurements and monitoring of key water quality parameters at hydrological monitoring sites can contribute to better understanding of surface water – groundwater interactions.
Assessing impacts on ecosystems
It is recommended that monitoring of changes in select indicators of ecosystem condition in potentially at risk streams and groundwater-dependent ecosystems accompany any monitoring of hydrological changes. The expert elicitations conducted in the bioregional assessment have identified potential indicators and associated impact variables that could be used for this purpose. The large reflected in the receptor impact models from the expert elicitations can be reduced by collecting data on measurable ecosystem components that are sensitive to changes in hydrology. How frogs, hyporheic invertebrate populations, Hydropsychidae larvae and/or tree canopies respond to changes in water availability and flow regime in different environments – and the extent to which changes in these ecosystem components propagate through to other components of the ecosystems they occupy – require greater understanding. Any alternative methods of assessing the condition of water-dependent ecosystems adopted by relevant state agencies should also be targeted at these potentially at risk ecosystems.
Water dependencies of some of the different ecosystems are not well understood and may be site specific. The landscape classification approach represents a generalisation and a loss of site specificity. The impacts on coastal swamp forests within the ‘Forested wetland’ landscape class were not assessed and are a gap in this bioregional assessment. Similarly, the qualitative model developed for the ‘Rainforest’ landscape class was premised on rainforests that occupy low-order stream and gully habitats. Most rainforest communities are unlikely to be impacted, because if they are dependent on groundwater at all, it is local groundwater sources. rainforests on the Wyong River are potentially impacted by additional coal resource development, but impacts were not quantified. Experts were uncertain about aspects of freshwater wetland hydrology, including interactions with the regional watertable.
Both the mapping of vegetation and the nature of the water dependence of some identified groundwater-dependent ecosystems are a significant source of . Assessment of impacts on water-dependent assets would be improved by review of vegetation mapping and ongoing research to identify groundwater-dependent ecosystems and determine the degree of groundwater dependency in the subregion. This will improve understanding of the interactions between changes in groundwater availability and the condition of groundwater-dependent terrestrial vegetation.
Actual water requirements of different plant communities during different life stages is only approximately known. Future assessments would be assisted by more work to identify suitable bioindicators of ecosystem condition, or alternative methods of assessing the condition of water-dependent ecosystems.
A summary of the assumptions and limitations of the qualitative and receptor impact models that emerged during the expert elicitation workshops is provided in the receptor impact modelling for the Hunter subregion (see Section 2.7.6 in Hosack et al. (2018a)). Knowledge gaps and research opportunities are identified for some models. A more comprehensive listing of the gaps and opportunities that have emerged during the assessment is provided in Section 3.7 of Herron et al. (2018c).
Groundwater modelling data
Sparsely distributed and poorly documented data was an issue in the Hunter subregion, particularly for depth to , and contributions to baseflow from groundwater. Improved mapping of depth to groundwater, and its spatial and temporal variation, has potential to constrain hydrological change predictions and enhance the context for the interpretation of the ecological impacts due to hydrological change. Interactions between changes in groundwater availability and the condition and persistence of terrestrial groundwater-dependent vegetation remain uncertain due, in part, to sparse mapping of groundwater depths outside of alluvial layers.
The greatest potential to reduce predictive uncertainty in the groundwater modelling lies in improved characterisation of hydraulic properties of the sedimentary rocks, especially the and storage parameters. Historical groundwater levels are controlled by a dynamic interaction between recharge, the geomorphology of rivers and the hydraulic properties of aquifers. A calibration to groundwater levels will only constrain the hydraulic properties if the recharge and river geomorphology are well known at a regional scale.
Although the locations of major faults are known, the extent to which they act as conduits of water between geological layers over different depths is not well understood and is thus a knowledge gap.
Consultation with Indigenous communities to determine Indigenous assets was not undertaken for the subregion. However, a report is available that outlines an approach to engage with Indigenous communities and collect information on Indigenous water assets in the subregions and bioregions within NSW (NSW DPI, 2016).
There were nine Indigenous assets from the Register of the National Estate within the water-dependent asset register for the Hunter subregion (Macfarlane et al., 2016; Bioregional Assessment Programme, 2017; Dataset 10). Identifying water-dependent assets valued by local Indigenous communities would provide a more comprehensive account of sociocultural assets, even if many of those assets are already in the water-dependent asset register through other sources, such as a wetland that may have both ecological and Indigenous value.
Climate change and land use
In comparing results under two different futures in this assessment, factors such as climate change or land use are held constant. Future assessment iterations could look to include these and other to more fully predict cumulative impacts on a landscape scale.
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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
- Contributors to the Technical Programme