- Land-surface fluxes: two fixed parameters for defining evapotranspiration processes (see Section 18.104.22.168.2); there is also a multiplier used in the analysis to vary the recharge input.
- General-head boundary behaviour: one fixed parameter that is the conductance of all lateral boundaries (except the boundary to the Werrie Basin) and the ocean floor.
- – groundwater fluxes: four parameters that define the boundary conditions for the movement of water from groundwater to the river. River stage height varies with riverbed depth. The two leakage limiter parameters are fixed in the model (see Section 22.214.171.124.3).
- Hydraulic properties: nine parameters to define porosities and vertical and horizontal hydraulic conductivities with depth for the interburden (lithologies 1 to 6) and the alluvium (lithology 7) (Section 126.96.36.199.1).
- Unsaturated flow: two fixed parameters in the van Genuchten unsaturated flow equation (Section 188.8.131.52.2).
- Hydraulic enhancement: four parameters to characterise the magnitude of and depth over which hydraulic conductivity changes occur due to longwall mining (see Section 184.108.40.206.3).
Table 7 summarises the groundwater model parameters, including the reference values, ranges over which parameters are varied in the uncertainty analysis (see Section 220.127.116.11) and salient points. As identified above, a number of these parameters are dealt with in other sections of this product.
The range of conductivity and values explored in the uncertainty analysis and its comparison with measured data is shown in Figure 26 and Figure 31 of companion product 2.1-2.2 for the (). As mentioned above, an upscaling analysis may be performed to yield a for hydraulic conductivity, and the result of such an analysis is shown in Figure 21, which motivates the uncertainty bounds in Table 7. Figure 21 shows the probability distribution for the measured data in the depth interval 0 to 100 m. In this interval, conductivity measurements vary between 10–7 m/day and 30 m/day. The data have been binned into nine bins: the first lies between 10–7 m/day and 10–6 m/day, the second between 10–6 m/day and 10–5 m/day, and so on up to between 101 m/day and 102 m/day. Figure 21 shows that the data are roughly uniformly distributed into these bins, with slightly more of measurements occurring in the central bins than in the outer bins. Figure 21 also contains a probability distribution for the upscaled conductivity that is derived from the measured data, and its comparison with the uncertainty bounds for a 50 m depth from Table 7. Upscaling is discussed further in .
Conductivity enhancement above and below mines is discussed in Section 18.104.22.168.3, and the wide range of variation (5 orders of magnitude, and heights ranging between 100 m and 500 m above longwall workings) reflects the wide variation that may be experienced in different mining scenarios (; ).
Table 7 Groundwater model parameters: their reference values and the minimum and maximum values used in the uncertainty analysis
BP = bord-and-pillar; E = ephemeral; ET = evapotranspiration; GW = groundwater; PET = potential evapotranspiration; P = perennial; LW = longwall; na = not applicable; OC = open-cut; SW = surface water
Product Finalisation date
- 22.214.171.124 Methods
- 126.96.36.199 Review of existing models
- 188.8.131.52 Model development
- 184.108.40.206 Boundary and initial conditions
- 220.127.116.11 Implementation of the coal resource development pathway
- 18.104.22.168 Parameterisation
- 22.214.171.124 Observations and predictions
- 126.96.36.199 Uncertainty analysis
- 188.8.131.52 Limitations and conclusions
- Currency of scientific results
- Contributors to the Technical Programme
- About this technical product