38 wells have been drilled testing 3 geological environments. Results indicate : (1) Crystalline Precambrian rocks yield small supplies with salinity 15 000 to 20 000 mg/L. (2) Adelaidean slates and quartzites are capable of moderate yields, but salinity after extended pumping has risen to 7 000 mg/L. (3) 2 Ordovician sandstone units (Mount Chandler Sandstone, Blue Hills Sandstone) were investigated. Salinity of Blue Hills sandstone is about 2000 mg/L. Indulkana is currently being supplied from 2 wells in the Mount Chandler Sandstone. Salinity in these wells may rise to about 5 000 mg/L. A complete potable water supply is not possible except at high cost. Dual water supply scheme using water of different qualities is proposed.