Eighty-one parameters were used in the 220.127.116.11.3.1 some of the parameters were identified to have an insignificant influence on the model predictions. These parameters were then either fixed or tied to the independent parameters leaving a total of 37 parameters that varied in the and analyses. These parameters can be broadly grouped by model function into parameters relating to:model. After the stress test described in Section
- land-surface fluxes: three fixed parameters for defining evapotranspiration processes (see Section 18.104.22.168.2); one parameter each for the diffuse, irrigation and flood used as multipliers vary the recharge input to explore uncertainty in these components of recharge
- general-head boundary behaviour: two fixed parameters to explore variability in the head and conductance of all lateral boundaries
- 22.214.171.124.3) – groundwater fluxes: five parameters that define the boundary conditions for the movement of water between groundwater and the river. River-stage height varies with riverbed depth. Two parameters that limit the minimum and maximum hydraulic conductivity of the riverbed and two parameters that define the slope of the riverbed in any model cell are used to compute the conductance of the riverbed in all river cells (see Section
- hydraulic properties: parameters to define horizontal and vertical hydraulic conductivities and storage that varies with depth for each model layer (Section 126.96.36.199.1)
- hydraulic enhancement: two parameters to characterise the magnitude of and depth over which hydraulic conductivity changes occur due to longwall mining (see Section 188.8.131.52.3)
- drains: three parameters control the conductance of the open-cut mines, longwall mines and coal seam gas .
Table 10 summarises the groundwater model parameters, including the minimum and maximum values of the range over which parameters are varied in the uncertainty analysis (see Section 184.108.40.206) 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 storage values explored in the sensitivity analysis and its comparison with measured data is shown in Figure 19 (which is Figure 21 in companion product 2.1-2.2 for the Namoi subregion ( )). 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 19, which motivates the uncertainty bounds in Table 10.
Conductivity enhancement above and below mines is discussed in Section 220.127.116.11.3, and the wide range of variation (four 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 10 Groundwater model parameters: minimum and maximum values used in the uncertainty analysis
Package refers to the MODFLOW package that the parameter belongs to, these are: recharge (RCH), river (RIV), general-head boundary (GHB), evapotranspiration (EVT), layer properties flow (LPF), time varying materials (TVM) and drain (DRN). Note refers to the treatment of the parameter, linear is uniformly distributed between minimum and maximum, log is log transformed and then fitted uniformly between minimum and maximum, fixed means the parameter does not vary between model runs and tied means that the parameter is made equal to another parameter in the list.
PET = potential evapotranspiration; ET = evapotranspiration; GHB = general-head boundary; SW = surface water; GW = groundwater; CSG = coal seam gas
Product Finalisation date
- 18.104.22.168 Methods
- 22.214.171.124 Review of existing models
- 126.96.36.199 Model development
- 188.8.131.52 Boundary and initial conditions
- 184.108.40.206 Implementation of the coal resource development pathway
- 220.127.116.11 Parameterisation
- 18.104.22.168 Observations and predictions
- 22.214.171.124 Uncertainty analysis
- 126.96.36.199 Limitations
- Currency of scientific results
- Contributors to the Technical Programme
- About this technical product