3.7.1.1 Potential hydrological changes

Numerical groundwater modelling predicted that it is very unlikely that drawdown due to additional coal resource development exceeds 0.2 m in the regional watertable, except within 15 km of New Acland Coal Mine Stage 3 and within 25 km of The Range coal mine. Drawdown in the regional watertable due to additional coal resource development exceeds 0.2 m in an area of 1544 km2 (1.2% of the total assessment extent of 129,956 km2), including 1095 km of streams (1.8% of the 60,958 km of streams in the total assessment extent). In comparison, drawdown in the regional watertable under the baseline has at least a 5% chance of exceeding 0.2 m in an area of 17,132 km2, which is 11 times larger than the equivalent area due to additional coal resource development.

The range of model predictions in the vicinity of New Acland Coal Mine Stage 3 indicates that additional drawdown in the regional watertable:

  • in excess of 0.2 m is very likely (greater than 95% chance) to cover more than 7 km2, which contains 4 km of streams, and very unlikely to cover more than 134 km2, which includes 55 km of streams
  • in excess of 5 m is very likely to cover more than 2 km2, which contains 4 km of streams, and very unlikely to cover more than 20 km2, which includes 9 km of streams. Median drawdown is up to 3 m under the baseline and up to 65 m due to additional coal resource development in the vicinity of New Acland Coal Mine in the regional watertable, which is up to 42 m thick in this area.

The greatest impact on water levels is in the Walloon Coal Measures, which is up to 200 m thick in this area. Near the mine, median drawdown in the Walloon Coal Measures is up to 3.6 m under the baseline and up to 24.9 m due to additional coal resource development.

The range of model predictions in the vicinity of The Range coal mine indicates that additional drawdown in the regional watertable:

  • in excess of 0.2 m is very likely over an area of 377 km2 (containing 231 km of streams) and very unlikely to extend beyond an area of 1409 km2 (containing 1040 km of streams)
  • in excess of 5 m is not very likely in any of the assessment units and very unlikely to extend beyond 90 km2 (which includes 31 km of streams).

Median baseline drawdown is up to 8.3 m in the regional watertable and up to 82 m in the Walloon Coal Measures, the target of CSG production, which is up to 170 m thick in this area. Median additional drawdown is less than 10.2 m in the Walloon Coal Measures, which hosts the regional watertable in the vicinity of The Range coal mine.

Last updated:
5 January 2018
Thumbnail of the Maranoa-Baloone-Condamine subregion

Product Finalisation date

2017
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