A general-head boundary was implemented in areas where the simulated aquifers continue beyond the groundwater model domain (Figure 12). As indicated by the three-dimensional hydrogeological model described in companion product 2.3 for the Clarence-Moreton bioregion (Raiber et al., 2016b), some aquifers simulated in the groundwater model do not terminate at the model’s northern and southern borders. Hence, general-head boundaries were used along the southern and northern sides of the groundwater model domain. Although the eastern side of the groundwater model domain follows the extents of the Walloon Coal Measures, the Richmond River alluvium does extend beyond this boundary as far as the coastline, so a general-head boundary was applied to the cells that intersect the Richmond River alluvium along this part of the groundwater model domain. The hydraulic conductance for the general-head boundary was allowed to vary by using three multipliers (Table 4) during the sensitivity and uncertainty analysis. Note that they were not transient parameters, that is, they were varied across simulations but kept constant during individual simulations.
The western side of the groundwater model domain that follows the extents of the Walloon Coal Measures, the eastern side of the groundwater model domain that does not intersect the Richmond River alluvium, and the bottom boundary of the groundwater model domain were all assumed to be impermeable, and were hence assigned no-flow boundaries.
Figure 12 Grid shell and grid lines of the Clarence-Moreton groundwater model
Red and blue cells show locations where General-Head Boundary and River packages were applied, respectively.
Table 4 Adjustable parameters associated with initial and boundary conditions during sensitivity and uncertainty analysis, and their corresponding bounds
*A multiplier is a dimensionless scalar to scale up/down parameters. For example, RCH_1 is a multiplier for the recharge of recharge zone 1 with a range from 0.2 to 2. This means that the recharge of recharge zone 1 was varied in a range between 0.2 and 2 times of the initial recharge of recharge zone 1.
na = not applicable
Data: Bioregional Assessment Programme (Dataset 1)
