2.6.2.9 Limitations and conclusions

Summary

The simulations indicate that it is unlikely for the drawdown due to additional coal resource development to exceed 1 m in the surface weathered and fractured rock layer. At receptors in the alluvium, it is unlikely for the drawdown due to additional coal resource development to exceed 0.2 m.

The effect of coal seam gas depressurisation and the effect of faults as conduits to propagate depressurisation to the surface weathered and fractured rock layer is not distinguishable from the effects of coal mining.

The model choices and assumptions, such as the hybrid modelling approach and the representation of surface water – groundwater interaction, are shown to be conservative. Despite this conservative modelling approach, the predicted hydrological changes are in line with those predicted in earlier local modelling efforts.

The modelling framework is tailored to the specific coal resource development pathway and receptors and therefore should not be used for any other purpose without a rigorous reassessment of the validity of the model assumptions.

The modelling did highlight that improved characterisation of hydraulic properties of the surface weathered and fractured rock layer and more detailed information of local geology around development have the most potential to reduce predictive uncertainty.