Locating groundwater resources for Aboriginal communities in remote and arid parts of South Australia.

Abstract

Aboriginal communities in remote areas of South Australia require access to bore water for their non-potable supplies due to the aridity of the region. This water is often found in deep, fractured rock aquifers. Due to the anisotropic and heterogeneous nature of fractured rock aquifers, there is a significant risk of drilling costly dry bore holes in the attempt to find water. This project is a pilot study to gauge the effectiveness of magnetotellurics - a geophysical method that images the distribution of electrical conductivity in the subsurface - in mapping and characterising fractured rock aquifers in order to reduce the risk of drilling dry bore holes. This survey was carried out in the Nipapanha Community, in the Northern Flinders Ranges, South Australia. There is a need for an increase in bore water supply from the local fractured rock aquifer. Geophysical, hydrogeological and structural research has been carried out in the area, which will act as a guide for this survey, so that knowledge and techniques learned may be applied in poorly constrained areas.

Magnetotelluric data were recorded at 3000Hz and 500Hz over 40 sites around the target area in order to create a series of 5 2D profiles as well as a map of phase tensors at various frequencies. Controlled source magnetotelluric data from a previous survey carried out by Zonge Engineering were obtained and reprocessed and inverted to create a series of 6 inversions in order to increase coverage of the survey. Interpretation of the inversions and phase tensors in conjunction with hydrogeological information was able to identify areas of anomalous apparent conductivity, possibly corresponding to increased water content. Predominant directions of conductivity, corresponding to fracture orientation throughout the area were also identified.