Assessing spatial and temporal recharge distributions using regularised parameter estimation of a groundwater flow model: A case study of Uley South Basin (South Australia)

Quantifying spatial and temporal recharge distributions is often a prerequisite for effective groundwater modelling. Unsaturated zone models and field-based techniques (e.g., chloride mass balance) have been used to estimate recharge increasingly over the last few decades. However, groundwater data (used for model calibration) are seldom used to inform these recharge estimates where they may be in error.

In the current project, we use a contemporary calibration technique (regularised parameter estimation) to provide insight into recharge (and other hydraulic parameter) distributions in Uley South Basin – a coastal aquifer located on the southern Eyre Peninsula (South Australia) that serves as the region’s primary freshwater supply. Recharge is particularly important in the management of this resource given that groundwater pumping is based on recharge estimates directly. More generally, we set out to address the question: “to what extent can we enhance our understanding of recharge through the calibration of a groundwater flow model?”

In order to achieve this, we adopt a sequential calibration strategy. Firstly, model calibration is used to estimate hydraulic parameters whilst fixing recharge estimates obtained independently. The model is then endowed with greater flexibility by possessing a set of recharge parameters. Upon re-calibration (and whilst maintaining equivalent constraints on parameters through regularisation), we evaluate the subsequent adjustments in the recharge and hydraulic parameter fields thus informing spatial and temporal patterns in recharge. Additionally, we use simplified versions of the recharge estimates to support our methodology (and findings).

External funding: Goyder Institute PhD scholarship (focus on climate change impacts on groundwater, which will form a subsequent sub-project).

Primary NCGRT researcher: Matthew Knowling

Major collaborators: Adrian Werner, Daan Herckenrath

Research Program

Hydrodynamics and Modelling of Complex Groundwater Systems