2.3.2 Summary of key system components, processes and interactions


The flow processes and interactions in the Gloucester subregion are controlled by the layering, faulting and fracturing of the coal measures and shallow weathered and fractured rock layer. At the scale of the geological Gloucester Basin, groundwater recharge occurs at the margins and areas of outcropping lower layers, and discharges in the central valley floor and associated alluvial deposits. Under most natural conditions the streams and rivers in the Gloucester subregion are gaining and connected to local groundwater.

Coal mine and coal seam gas (CSG) operations can induce changes in groundwater level at any worked or drilled depth in the geological column. The spatial and temporal influence of groundwater level changes is controlled by local hydraulic properties, and complicated by fracturing and faulting of layers. A reduced groundwater level may cause a groundwater level drop in a stock or domestic bore that makes it harder to extract water, or cause the bore to dry out periodically. Another potential effect of reduced groundwater level is to induce flow away from the alluvial aquifer that would otherwise discharge as baseflow to a stream.

Connectivity by direct linkages due to faulting and fracturing enhance the effects of groundwater level changes due to human activities. However, the role of faults and fractures as carriers or barriers of flow, their location in three dimensions particularly local versus regional extent, and their propensity to change their nature due to water pressure changes are all poorly known in the Gloucester subregion.

Last updated:
23 October 2018