Chapter 6 Characterisation of a Coastal Aquifer System in the Eyre Peninsula, South Australia, Using Nuclear Magnetic Resonance Methods Aaron Davis, Tim Munday, and Nara Somaratne Abstract The coastal aquifers of the Uley Basin, which are the most important source of potable groundwater for the Eyre Peninsula, consist of unconfined Quater- nary limestone overlying Tertiary clays and sandstones. Despite its importance, elements of the connectivity and total water resource basin remain relatively poorly understood. To address this, hydrogeophysical methods have been employed to better characterise the aquifer systems present. Interpretation of airborne electromagnetic data provided evidence for the delineation of the base of the Quaternary (limestone) aquifer and a basement low in the southwest corner of the South Uley Groundwater Lens, where there is a limited number of lithological bores or groundwater wells. The basement low, adjacent to the coast, suggests a preferential groundwater flow path and a possible connection between the Basin aquifers and the Southern Ocean. Geophysical methods are routinely employed for groundwater exploration, assessment, and aquifer characterisation, particularly where access to land is limited and where other investigation techniques such as drilling may be limited or prohibited. In areas of environmental significance, or where access is generally difficult, non-invasive hydrogeophysical methods offer an alternative to explor- atory drilling, by targeting areas of interest and better defining groundwater and aquifer characteristics in advance. We discuss the application of the hydrogeo- physical technique of surface nuclear magnetic resonance (sNMR) for groundwater assessment. Presently, sNMR is the only hydrogeophysical technique that allows for direct detection of groundwater in the subsurface. To better understand the possible inter-connectivity between the Uley Basin and the Southern Ocean; and as a precursor to considering whether new groundwater resources could be tapped, we investigate a series of (sNMR) soundings along a A. Davis (*) • T. Munday Earth Science and Resource Engineering, CSIRO, 26 Dick Perry Ave, Kensington, WA 6151, Australia e-mail: aaron.davis@csiro.au N. Somaratne SA Water, 250 Victoria Square/Tarndanyangga, Adelaide, SA 5000, Australia C. Wetzelhuetter (ed.), Groundwater in the Coastal Zones of Asia-Pacific, Coastal Research Library 7, DOI 10.1007/978-94-007-5648-9_6, # Springer Science+Business Media Dordrecht 2013 89