The dataset was derived by the Bioregional Assessment Programme from multiple source datasets. The source datasets are identified in the Lineage field in this metadata statement. The processes undertaken to produce this derived dataset are described in the History field in this metadata statement.
Development of the MBC groundwater PAE considered predicted water level impacts reported in the Underground Water Impact Report (UWIR) for the Surat Cumulative Management Area (QWC, 2012). The predicted water level impacts have been calculated using a regional groundwater flow model designed to predict the impacts of groundwater extraction by the petroleum and gas extraction industries within the Qld portion of the Surat and Bowen Basins.
The Long-term Affected Area 95thpercentile maximum drawdown grids for the Walloon Coal Measures, Hutton Sandstone, Precipice Sandstone and Clematis Sandstone were assessed to determine the lateral extent of the 1m drawdown boundary (Figure 2-1). The 1 m drawdown boundaries, in some areas, extend beyond the MBC subregion boundary to the north. North of Roma, the modelled impact to water levels in both the Precipice and Clematis sandstones is predominantly as a result of CSG extraction from the Bandana Formation of the Bowen Basin in the Fairview and Spring Gully gas fields, which are located outside to MBC subregion. Therefore the 1 m drawdown extents for Precipice and Clematis sandstones north of Roma were not considered in the development of the PAE.
In contrast, the northern extent of the 1m drawdown boundary in the Hutton Sandstone, which extends beyond the subregion boundary toward the Hutton Sandstone recharge areas, has been considered. In this case the drawdown is a result of extraction within the subregion.
As a conservative approach, a 100 km buffer was applied to each drawdown grid and the most laterally extensive boundaries for each formation were incorporated into the PAE boundary. An exception is the easternmost extent of the PAE boundary, where it extends into the Clarence-Moreton Basin. In this case the PAE boundary is a combination of a 50 km buffer and the outer boundary of the Marburg Sandstone, which is a lateral equivalent of the Hutton Sandstone. It is considered that the use of a 100km buffer in this area is overly conservative.
The 100 km buffer extends to the north beyond the subregion boundary and either beyond or close to the outer boundary of the Hutton Sandstone. In this area, the outer edge of the Hutton sandstone has been used for the PAE boundary, as it is unlikely that the deeper formation will be impacted by extraction from within the MBC subregion. Elsewhere, where the 100 km buffer extends beyond the subregion boundary, the buffer has been clipped to match the boundary of the subregion where it coincides with the edge of the Surat geological basin. The PAE allows full assessment of impacts to the Hutton Sandstone and shallower aquifers as well as those areas of the Clematis and Precipice sandstones from extraction of groundwater within the MBC subregion. Furthermore, in the east the PAE encompasses current operating coal mines.
A further 50km buffer was appended to the initial 50km buffer (to create a total buffer of 100km) used to create the MBC GW PAE v01 dataset. This 100km buffer was used for western boundary of the PAE until it intersects with the subregion boundary, or existing PAE boundary. From there, the subregion boundary is followed, again, until it intersects the existing PAE boundary in the East. The Eastern and Northern boundaries remain the same as the version 01 PAE.
Bioregional Assessment Programme (2014) Groundwater Preliminary Assessment Extent (PAE) for the Maranoa Balonne Condamine (MBC) subregion - v02. Bioregional Assessment Derived Dataset. Viewed 25 October 2017, http://data.bioregionalassessments.gov.au/dataset/f98564f4-f857-49d4-89af-fd3d0547b892.
Derived From Bioregional Assessment areas v02
Derived From Natural Resource Management (NRM) Regions 2010
Derived From Bioregional Assessment areas v03
Derived From Bioregional Assessment areas v01
Derived From GEODATA TOPO 250K Series 3
Derived From Geological Provinces - Full Extent