2.6.2.3.3 Design and implementation

Unlike classical cellular groundwater models, analytic element models are grid-independent (Bakker, 2013). Their resolution is determined by the discretisation of the internal boundary elements, the points, lines and polygons representing groundwater level or flux boundaries. One of the key advantages of this approach is the flexibility regarding time stepping and spatial locations for outputting the calculated metrics. In the temporal domain it is necessary to define stress periods (i.e. periods in which the stresses and boundary conditions are constant), but it is not necessary to temporally discretise into time steps. This means the solution to groundwater flow equations can be evaluated at arbitrary points and times.

Yearly stress-periods are chosen as this corresponds to the temporal resolution of the available mine pumping rates. As the analytic element model is only simulating the change due to coal resource development, the simulation period starts in 2018, the earliest date mine pumping rates are available, and ends in 2102, as specified in companion submethodology M07 (as listed in Table 1) for groundwater modelling (Crosbie et al., 2016). The submethodology also illustrates that the stochastic approach guarantees that the drawdown is not under estimated (Crosbie et al., 2016, p. 30).