The assessment identified potential () associated with coal resource development that could result in hydrological changes, such as due to . Hazards in scope were further assessed by first estimating relevant hydrological changes through and groundwater modelling and then identifying potential on, and to, water-dependent and (described in the following sections).
After the potential hazards were identified, the chain of events that commonly arise from coal resource development were analysed and categorised into four groups (Figure 6):
- ‘Subsurface depressurisation and dewatering’ istriggered by extraction of groundwater to enable CSG extraction and dewatering of open-cut mine pits. This potentially directly affects the groundwater system and indirectly affects the surface water - groundwater interactions. Potential effects are likely to be in the short term (less than 5 years) for groundwater pressure changes, to long term (10 to 100 years) for changes in groundwater movement or quality.
- ‘Subsurface physical flow paths’ are initiated by activities that cause physical changes to the rock mass or geological layers, resulting in new physical paths that water may potentially gain access to and flow along. Potential effects are in the medium (5 to 10 years) to long term and are likely to be restricted to aquifer or aquifer outcrop areas, but can also affect connected watercourses within and downstream of mines.
- ‘Surface water drainage’ starts with activities that physically disrupt the surface and near-surface materials (vegetation, topsoil, weathered rock). Medium- to long-term cumulative effects are possible for watercourses within and downstream of development. Activities may include construction of walls and drains, interception of , realignment of streams, and groundwater extraction for CSG production or underground coal mining leading to of land surface.
- ‘Operational water management’ is triggered by modification of surface water systems to allow storage, disposal, processing and use of extracted water. Potential effects are likely to be in the medium to long term and include impacts on watercourses within and downstream of operations.
Many activities related to coal resource development may cause local or on-site changes to surface water or groundwater. These are not considered explicitly in because they are assumed to be adequately managed by site-based risk management and mitigation procedures, and are unlikely to result in .
Based on the licence conditions as summarised in the relevant environmental impact assessments, it was assumed that no water used in coal resource development is released back into the stream network.
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This schematic diagram is not drawn to scale. CSG = coal seam gas
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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