In the Surat Cumulative Management Area (CMA) the Office of Groundwater Impact Assessment (OGIA) is responsible for preparing an assessment of the cumulative impacts from coal seam gas (CSG) development on groundwater.
CDM Smith's Dr Jon Fawcett, Dr Dougal Currie and Stuart Richardson provided technical support to OGIA for an 18 month-long project that investigated spring wetlands within the Surat Basin. This project assessed spring wetlands in detail to advance the understanding of how the wetlands interact with groundwater and how the wetland area, vegetation and macroinvertebrates respond to changes in the water regime.
A critical component of the project was identifying the influence soil and regolith have on groundwater flow to the wetlands, soil water processes (infiltration and recharge) and surface water flow. This information was essential in understanding the sensitivity the wetland and surrounding landscape is to changes in the water regime.
OGIA is an independent entity housed within the Department of Natural Resources and Mines, responsible for assessing potential future cumulative impacts of CSG on groundwater.
The following approaches were used to evaluate the soil and regolit:
- Interpretation of existing soil and landscape data around the soil permeability and soil water stores associated with wetlands;
- Interpretation of survey geophysics methods (GPR, EM surveys) to identify changes in subsoil conductivity and relate to soil hydrology and groundwater inflow zones; and
- Filed soil surveys, specifically targeting of changes in soil colour, sodicity and salinity associated with the wetlands, providing indications of waterlogging, evaporation of shallow water tables and surface water.