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 PAE considered predicted water level impacts reported for 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 95th percentile maximum drawdown grids for the Walloon Coal Measure, Hutton Sandstone, Precipice Sandstone and Clematis Sandstone were assessed to determine the lateral extent of the 1m drawdown boundary. The 1m drawdown boundaries extend in some areas, beyond the MBC subregion boundary to the north. North of Roma, the modelled impact to water levels in both the Precipice and Clematis Sandstone is predominantly as a result of CSG extraction from Bandana Formation of the Bowen Basin in the Fairview and Spring Gully gas fields, which are located outside to MBC subregion. Therefore the 1m 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 50km buffer was applied to each drawdown grid and the most laterally extensive boundaries for each formation were incorporated into the PAE boundary. The 50km buffer extends to the north beyond the subregion boundary and either beyond or close to outer boundary of the Hutton Sandstone. In this area the outer edge of the Hutton sandstone has been used for the PAE as it is unlikely that the deeper formation will be impacted by extraction from within the MBC subregion. Elsewhere the where the 50km 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. An exception is the easternmost extent of the PAE. In this case the PAE is a combination of the 50km buffer and the outer boundary of the Marburg Sandstone which is a lateral equivalent of the Hutton Sandstone.
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. Further, in the east the PAE encompasses current operating coal mines.
Extract 1m drawdown grids:
For each of the 4 aquifer 95th percentile QWC drawdown grids (up95laal10, up95laal12, up95laal14, up95laal16) all values 1m and above were extracted. - ArcMap Reclassify Raster tool - Toolboxes\System Toolboxes\Spatial Analyst Tools.tbx\Reclass\Reclassify
Convert 1m drawdowns to polygon
ArcMap Raster to Polygon Tool - Toolboxes\System Toolboxes\Conversion Tools.tbx\From Raster\Raster to Polygon.
Convert all 1m drawdown grids to polygons.
Merge 1m drawdown polygons
ArcMap - Editor, select all polygons, copy into the one feature class, Editor-Merge.
Apply 50km Buffer:
Using ArcMap Buffer tool, apply 50km buffer to merged 1m drawdown polygon.
Toolboxes\System Toolboxes\Analysis Tools.tbx\Proximity\Buffer
Create the PAE:
In the North West, from the intersection of the MBC subregion and Hutton intake beds, follow the Hutton Intake beds boundary until the Eastern MBC subregion boundary, where the drawdown buffer extends past the subregion boundary. From there, use the Marburg Surface Geology boundary as the extent until it intersects back with the drawdown buffer polygon. Follow the drawdown buffer polygon south until it intersects with the MBC boundary in the South West, then follow the MBC subregion boundary again East along the Southern boundary until it intersects again with the drawdown buffer polygon boundary. Follow the drawdown buffer polygon boundary from the South to the Western edge and up to the North Western starting point to finish off the MBC groundwater PAE.
Bioregional Assessment Programme (2014) Groundwater Preliminary Assessment Extent (PAE) for the Maranoa Balonne Condamine (MBC) subregion - v01. Bioregional Assessment Derived Dataset. Viewed 25 October 2017, http://data.bioregionalassessments.gov.au/dataset/dd329995-fed3-425f-bb5d-fb0f33ed1360.
Derived From Natural Resource Management (NRM) Regions 2010
Derived From Bioregional Assessment areas v03
Derived From Bioregional Assessment areas v01
Derived From Bioregional Assessment areas v02
Derived From GEODATA TOPO 250K Series 3
Derived From Geological Provinces - Full Extent