Investigation of Coastal Perth Basin North for Jurien Bay Town Water Supply with AEM

Jurien Bay is a small coastal town located 220km North of Perth, Western Australia, and relies on groundwater for town water supply (TWS). The bore filed is situation in the shallow Tamala limestones North Perth Basin. In late summer and autumn in 2020 the towns production bores recorded significant unprecedented increases in salinities. Airborne electromagnetic (AEM) survey was planned and undertaken to improve the understanding of the likely causes of rising salinity within the borefield and assist in water source planning. The secondary aims were to map the extent of the saline water interface and to improve understanding of the hydrogeology of the area. The 2021 AEM survey successfully mapped the extent of the saline water interface (SWI) and delineated other major hydrogeological features. The saline water interface was mapped as approximately 200 to 300 meters west of the production borefield. It was interpreted that the increased salinity in the production bores was more likely due to the thin freshwater aquifer being impacted by up-coning of underlining brackish groundwater, and not the inland movement of the coastal SWI. The AEM survey also confirmed the presence of major faults and fresh groundwater in the deeper aquifers such as the Lesueur Sandstone. This information has been crucial in planning for future water sources.