The application of AEM to mapping sea-water intrusion at La Grange, WA

Abstract

We describe interpretation of an AEM survey around the La Grange allocation area, WA. This survey was designed to map aquifer bounds and the sea water intrusion, and then to assess groundwater in the region, and to facilitate planning water use. The simple, stratified nature of sediments of the western onshore Canning Basin allowed us to use blocky layered earth models and we found that five-layer models were the most parsimonious. After deriving surfaces representing the top of the Jarlemai siltstone and the top of the sea water ingress, we were able to effectively characterise the spatial characteristics of the sea water intrusion. We found that in places, sea water intruded 40 km inland, and could be found at a depth of over 250 m.