Novel AEM Data Acquisition Strategies for Groundwater Resource and Managed Aquifer Recharge Mapping in the Australian Landscape Context

Abstract

Experience over the past 15 years has demonstrated that the use of airborne electromagnetics (AEM) for near-surface hydrogeological investigations often requires high resolution data to map key functional elements of the hydrogeological system. In the Broken Hill Managed Aquifer Recharge (BHMAR) project, the AEM acquisition strategy was governed by the need to rapidly identify and assess a number of potential managed aquifer recharge (MAR) and groundwater resource targets over a large area (>7,500 km2) of the Lower Darling Valley, with a high degree of confidence, and in very short timeframes. A flight line spacing of 200-300m successfully mapped the key elements of the hydrostratigraphy, neotectonic features, and 14 potential MAR and groundwater targets. Subsequently, AEM data were re-inverted, enabling comparison of line spacing of 200 m, 600 m, 1 km, 2 km, 5 km and 10 km. Utilising the information gained from this exercise, a novel survey design was developed using a systems analysis approach incorporating a range of conceptual hydrogeological and geological models, morphotectonic and structural mapping, and temporal remote sensing and hydrogeological data. Trialling this approach, a few widely-spaced AEM transects identified potential new groundwater resources over a large area of the Middle- and Upper- Darling River Valley.