LOCATING GROUNDWATER RESOURCES FOR ABORIGINAL COMMUNITIES IN REMOTE AND ARID PARTS OF SOUTH AUSTRALIA

Finding and utilizing reliable water supplies for desert communities is an important task which is often relatively difficult and expensive. This is especially the case in the remote north-west of South Australia (SA), where there are a number of small communities on Aboriginal land, with populations often of less than a hundred people. Rainfall is sparse and intermittent (less than 200 mm/yr), and residents rely on groundwater for nonpotable supplies. Drilling is generally restricted to targeting sandy beds in shallow (< 50 m) sediments. These beds are often thin and laterally discontinuous, leading to problems with long-term well production. Wells that target deeper fractured rock aquifers may be more successful, but such boreholes are more expensive and difficult to install.

The aim of our work is to develop an effective geophysical technique for using relatively cheap natural-source magnetotelluric (MT) imaging to identify the most prospective location for a borehole in such environments. The cost of working in these communities is high partly due to their remoteness (often more than 1000 km from the nearest population centres), making natural-source MT an attractive starting point, with no need for large teams or bulky transmitting equipment.

The first completed phase of our work tested the technique at Nepabunna, an Aboriginal community in the northern Flinders Ranges. The site was chosen for its accessibility and pre-existing hydrogeological and geophysical datasets. Unfortunately, resistive ground and cultural noise from local electric power lines led to distorted electromagnetic responses corresponding to the upper 200 metres, making it difficult to interpret the data in hydrogeological terms. Currently we are working with government authorities to select a more remote site with conditions more suited to the technique, such as conductive shallow sediments overlying fractured basement. Such conditions are common in northwest SA, and we hope to have a fieldwork project underway later this year.