Oral Presentation Australasian Groundwater Conference 2017

A qualitative assessment of the potential impacts of coal seam gas development on water-dependent assets in the Richmond river basin (#115)

David Rassam 1 , Matthias Raiber 1 , Justine Murray 1 , Tao Cui 1 , Mat Gilfedder 1
  1. CSIRO, Dutton PArk, QLD, Australia

This work describes a qualitative assessment of the potential impacts of CSG development on water-dependent assets in the Richmond river basin. The integrated understanding of the geology, hydrogeology and surface-groundwater interactions underpinned the development of a groundwater model that provided a quantitative assessment of the hydrological changes resulting from CSG development in the Richmond river basin (part of the Clarence-Moreton bioregion). Conceptual models were developed to describe the causal pathways, the logical chain of events that link coal resource developments to water-dependent assets. A landscape classification system was developed to characterise the nature of water dependency among assets identified in the area. The assessment identified hazards associated with CSG that could potentially result in hydrological changes. Four major causal pathway groups were identified: (1) Subsurface depressurisation and dewatering, (2) Subsurface physical flow paths, (3) Surface water drainage, and (4) Operational water management.

Ecosystems in the Clarence-Moreton bioregion were classified into 35 landscape classes to enable a systematic analysis of potential impacts on, and risks to, the water-dependent assets. Landscape classes were aggregated into landscape groups based on whether they respond similarly to changes in groundwater and/or surface water.

 The numerical groundwater model predicted drawdown, which was used to define a zone to ‘rule-in’ or ‘rule-out’ potential hydrological change. The zone is the area with at least a 5% chance of greater than 0.2 m drawdown due to additional coal resource development. This threshold is consistent with the most conservative minimal impact thresholds in NSW and Queensland State regulations within which potential impacts may need to be considered in an impact and risk analysis.

 Based on this integrated conceptual understanding, an informed decision to classify various assets as either, being potentially ‘impacted’ or ‘not impacted’, is made.

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