2.6.2.4.5 Initial conditions

The transient simulation of the model is for a period between 1983 to 2102. This corresponds to a baseline simulation period between 1983 and 2012 and a simulation period of 90 years to evaluate the effects of additional coal resource development from 2012 to 2102. The initial conditions prior to 1983 are obtained using a steady-state simulation of the model. Long-term average river stages obtained from the AWRA-R simulation were used to define the river boundary for this simulation. The groundwater pumping as reported in Section 2.6.2.4.4 was not included in this steady-state simulation. This is because these relatively high rates are known to correspond to an unsteady state and would result in substantially lower water levels particularly in the alluvial aquifers if used in the steady-state simulation. However, it is acknowledged that this representation does not capture the agricultural extraction from the 1970s onwards and this can have an effect on the water levels in the alluvial aquifers. For this reason, the comparison of the model predictions to observations to constrain the simuations was performed only for the period starting from 1993.

The first stress-period of the model used this steady-state simulation to obtain the initial conditions that were used for the subsequent transient simulations. Thus distinct steady-steate initial conditions were obtained for every model simulation with a distinct set of model parameters.