Model code and solver

The OGIA model is a finite difference numerical model based on the MODFLOW–2005 code (Harbaugh, 2005). Details of the OGIA model development are documented in GHD (2012) and summarised in QWC (2012). Section, Section and Section describe aspects of model development relevant to BA. One benefit of using the MODFLOW code is the large number of different modules available for simulating different groundwater flow processes and solving the finite difference flow equations. The PCG-N solver (preconditioned conjugate gradient solver with improved nonlinear control) is used to solve the finite difference equations because it is typically able to achieve convergence in models that are characterised by highly anisotropic hydraulic conductivity values, that is, hydraulic conductivity values that differ based on the direction of measurement. This solver is particularly useful for large sedimentary basins like the Surat and Bowen geological basins where significant contrasts between horizontal and vertical conductivity occur.

Model calibration and uncertainty analysis was performed using the parameter estimation (PEST) suite of software that allows model-independent parameter estimation and parameter/predictive-uncertainty analysis (Doherty, 2010). Details of the uncertainty analysis are documented in WaterMark Numerical Computing (2012) and summarised in Section .

Last updated:
17 October 2018
Thumbnail of the Maranoa-Baloone-Condamine subregion

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