For each bore, the OGIA model produces a time series of drawdown caused by the historical and baseline coal resource development (baseline) conditions and a time series of additional drawdown caused by the historical and coal resource development pathway (CRDP) conditions. The effect of implementing the CRDP, is the difference between these two time series. Two measures are used to summarise this time series: dmax and tmax. The maximum change in drawdown in the simulation period is dmax – that is, the maximum difference between the baseline and CRDP drawdown. Therefore, dmax can be either positive or negative. The time when this maximum drawdown occurs is tmax.
Figure 13 shows one of 200 possible realisations of the two possible coal resource development pathway futures from the calibrated predictive model. It plots groundwater drawdown through time from 1995 to 2102 for the baseline and CRDP. In this example, the maximum difference in drawdown between the baseline and CRDP is shown for bores in the Walloon Coal Measures, Hutton Sandstone and Main Range Volcanics model layers. In these examples, less than 0.35 m additional drawdown is predicted at RN30203 in the Walloon Coal Measures, less than 1.5 m additional drawdown is predicted at RN66782 in the Hutton Sandstone and over 5 m of additional drawdown is predicted at RN87532 in the Main Range Volcanics aquifer. The magnitude and timing of additional drawdown is a function of the distance of the bore from the modelled additional coal resource development (two open-cut coal mines) and modelled hydraulic properties.
In this figure, results are presented for only that part of the coal resource development pathway (CRDP) that can be modelled.
dmax = maximum change in drawdown
Data: Bioregional Assessment Programme (Dataset 1)
