A TEM survey that was carried out across the area between an extensive linear topographic depression in the western Nullarbor Plain and the Trans Australian Railway line corridor has identified the expected 50 metre thick resistive layer (Nullarbor Limestone) overlying more conductive layers below the water table. An observed increase in depth to the conductive layer over a 2 km wide zone is interpreted as a possible groundwater recharge site, with fresh water from rainfall runoff likely to be penetrating the Nullarbor Limestone through localised fractures to form a 20 to 40 metre-thick lens lying above otherwise saline groundwater. Assuming that there is 10-20% porosity in this karstic water table aquifer, the current interpretation would suggest the presence of an untapped groundwater resource of between 4 and 16 ML/km of low salinity water. The anomalous TEM feature has been detected over about 27 km of survey transect and is still open at both ends.