This discussion of the hydrology of the Adelaide region is confined, in general terms, to the occurrence, availability and salinity of surface and ground waters, with particular regard to shallow groundwaters. Other phases of the hydrologic cycle including precipitation are important aspects but are not considered here. The surface drainage system which has developed on the Eden Fault Block and its escarpment has determined the form and structure of the coastal plains, (Fig, I) which in their upper sediments provide storage in shallow aquifers for considerable bodies of ground water. The three streams traversing the plains add a material annual quota of intake to the aquifers but in addition intake from the short consequent streams in the vicinity the Eden and Burnside faults is probably large, although there is little quantitative data available. The drainage pattern and the distribution of groundwaters according to salinities is shown in report.