Groundwater from the Quaternary Limestone aquifer in the Uley South Basin has been an important resource for the Eyre Peninsula since the 1970s, currently meeting approximately 70% of water demand through the South Australian Water Corporation’s (SA Water) supply network. However, this groundwater resource is sensitive to variation in rainfall (recharge) and extraction, and may be prone to risks from over-exploitation including increased salinity via inflow from the underlying Tertiary Sand aquifer and seawater intrusion. Therefore SA Water commissioned South Australia’s Department for Environment and Water to simulate groundwater flow and impacts of potential future groundwater extraction and climate change in the basin.
A multi-model approach was taken to simulating groundwater flow in the Uley South Basin, acknowledging conceptual uncertainty. Additional parameter uncertainty work was also conducted. The Seawater Intrusion package (SWI2) was used in MODFLOW to simulate the position and movement of the freshwater-seawater interface. Model scenarios were developed in consultation with SA Water, and simulate the impacts of various extraction regimes under a changing climate. Model results show that pumping to meet projected demand by 2040 may have adverse impacts on the resource, while reduced pumping in the short term is likely to lead to groundwater level recovery. The results have helped SA Water to plan future supply options for the Eyre Peninsula.