As stated in Section, the objective of the numerical modelling undertaken as part of a bioregional assessment (BA) is to probabilistically assess hydrological changes arising from coal resource development at water-related assets and receptors. The main objectives of the regional analytic element groundwater model (GW AEM) therefore are (i) to provide the drawdown due to additional coal resource development at the receptors located in the surface weathered and fractured rock layer (Section, Figure 3 and Table 4) and (ii) provide the change in groundwater levels underneath the Avon and Karuah alluvium for the baseline coal resource development (baseline) and coal resource development pathway (CRDP). These changes are used as the lower boundary condition for the Avon and Karuah alluvial MODFLOW models.

The MODFLOW models will simulate changes in groundwater level at receptor locations associated with the Avon and Karuah alluvium. The MODFLOW models will also estimate the change in surface watergroundwater flux to propagate to the surface water models (companion product 2.6.1 for the Gloucester subregion (Zhang et al., 2018)).

In addition to the drawdown due to additional coal resource development at the receptor locations, probabilistic maps of the drawdown under the baseline, the CRDP and the difference between the two (due to the additional coal resource development) will be provided.

There is no receptor for which changes in water balance are considered to be the hydrological response variable. While changes in water balance therefore are not an objective of the modelling, probabilistic estimates of coal seam gas (CSG) water production rates will be provided by the analytic element model while changes in the exchange flux between the surface weathered and fractured rock layer and the alluvium are discussed in relation to the MODFLOW models. A more comprehensive discussion on the water balance of the Gloucester subregion is presented in companion product 2.5 (Herron et al., 2018).

Last updated:
5 November 2018
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