UNCOVERING THE GROUNDWATER RESOURCE POTENTIAL OF A REMOTE PART OF NORTHERN SOUTH AUSTRALIA THROUGH THE APPLICATION OF REGIONAL AEM AND MAGNETICS COUPLED WITH TARGETED FINER-SCALE INVESTIGATIONS.

摘要

The source of adequate groundwater resources to support community and industry (pastoral and mining) in the arid APY Lands of northern South Australia has been the subject of considerable concern since the establishment of cattle stations and community centres in the early 1900s. Although small, locally confined fractured rock aquifer systems have been defined, finding large sustainable sedimentary alluvial aquifers has been problematic despite numerous drilling campaigns over 60+ years. Challenges to their identification include a complex, apparently compartmentalised sedimentary (regolith) cover sequence, highly varying alluvial aquifer thicknesses, and the paucity of spatial information. The low sporadic rainfall/recharge and high average annual evaporation results in a highly variable groundwater quality adding to the complexity of resource determination. The role of geophysical data in addressing these shortcomings has been the subject of more recent investigation. Local scale exploration airborne EM data sets have highlighted the spatial complexity of the alluvial aquifers in the region. Airborne magnetic data, also acquired to promote mineral exploration through the area, confirmed a complex faulted basement present beneath these cover sequences. Several large-scale structures/faults have been identified as possible sustainable groundwater sources. These structures are also coincident with, and control the orientation of, a deeply incised and complex palaeo-drainage system which is now buried. The complexity of the larger and more extensive palaeovalley aquifers that may represent a larger sustainable source of water for both community and industry, have been revealed in a regional AEM survey undertaken in late 2016. This survey, involving both fixed-wing and time domain helicopter EM systems, has finally revealed the resource potential of a remote part of the State and affords the opportunity to secure water resources and support development for the area in the longer term. This paper documents the regional nature of these sedimentary aquifers and their varying character.