Aquifer Delineation Using the Tempest AEM System

Abstract

The Western Australia Department of Water and Environmental Regulation (DWER) utilized the Tempest system in a survey over the North Gnangara Mound, Perth Basin in 2013, to image hydrogeology relevant to groundwater resources important to Perth’s public water supply. In 2017, DWER extended the survey to target the Leederville-Parmelia aquifer, by flying an adjacent area covering the Dandaragan Plateau approximately from Gingin to Eneabba to the north, using an updated Tempest system. In total over 10 000 line kilometres have been flown covering a combined area of over 6000 km2. Borehole resistivity, lithological logs and groundwater chemistry from over 300 bores was used to help interpret and constrain the inversion of the acquired AEM data. Recharge zones, regional throughflow directions, faults that act as flow barriers, groundwater discharge zones, and the extent of regionally important aquitards have been able to be inferred and mapped. Estimates of the minimum thicknesses of fresh groundwater (< 500mg/L and < 1000 mg/L TDS) have been made for the Superficial and Leederville-Parmelia aquifers. The surveys have helped clarify hypotheses about faults that act as flow barriers and regional flow directions that are important for groundwater allocation planning. In this paper we present the results of both surveys, and key hydrogeological outcomes. We also compare the data from the two AEM surveys highlighting system developments, how these have led to improved data quality, and improved interpreted geological and hydrogeological outcomes.