Section summarises the predicted changes in eight hydrological response variables caused by the additional coal resource development in the Galilee subregion. The impacts on each model node were generated from 10,000 replicates of the model runs using randomly selected parameter sets.

The prediction results show that the additional coal resource development in the Galilee subregion can have substantial impact on the hydrological response variables. The comparison among the 61 model nodes shows that for the hydrological response variables that characterise high-streamflow conditions, the relative hydrological changes are largest for the model nodes where the maximum additional coal resource development percentage is largest. In general, the biggest impacts (flow reductions of up to 20%) occur immediately downstream of additional coal resource development and are particularly evident in model nodes where the footprint forms a large proportion of the node’s catchment. For every high-streamflow hydrological response variable, the biggest impacts are predicted to occur at node 3 on Sandy Creek. This model node is located downstream of the South Galilee Coal Project.

The impacts due to the additional coal resource development on the low-streamflow hydrological response variables are more substantial than those on the high-streamflow hydrological response variables. However, they also appear to be associated with greater uncertainty in both the predicted change and the year of maximum change. For the low-streamflow variables the biggest impacts occur in the middle reaches of the Belyando River and reflect an accumulation of impacts from multiple developments.

These results also suggest that changes to low-streamflow characteristics are caused by a combination of the instantaneous impact of interception from the mine footprints and the cumulative impact on baseflow over time caused by drawdown of the watertable. The changes to high-streamflow characteristics are dominated by direct interception of runoff.

Last updated:
6 December 2018