2.6.2.6 Parameterisation

Summary

This section reports on the process that was adopted to identify the initial hydraulic parameters of the numerical groundwater model: the hydraulic conductivity and storage parameters.

Two different approaches were adopted to identify the hydraulic conductivities of the shallow and deeper layers of the groundwater model. The horizontal hydraulic conductivities of the top layer were derived from 130 existing pumping test records, while those belonging to deeper layers were derived from drill stem tests (DST) and pumping test data. Two mathematical relationships were derived to describe the variation of hydraulic conductivity with depth, which were mostly based on data from geologically similar formations in the Surat Basin.

The upper and lower bounds of the storage parameters, the specific yield and specific storage, were derived from a previous modelling study conducted in the Surat Basin. The initial storage parameters were assumed to vary linearly with depth within those bounds.

Note that the parameterisation process described in this section merely provides initial estimates for the model parameters, which are significantly varied during the uncertainty analyses. Hence, the goal was to start the models with realistic parameter estimates that ensure numerically stable simulations.