Groundwater monitoring commenced in 1975 to provide the basis for assessment of water level and salinity trends, thereby providing the necessary information for the development of appropriate management strategies to ensure the sustainability of the groundwater resources throughout the Tatiara Prescribed Wells Area. The depth to groundwater varies from 1 metre in the western portion of the area to 65 metres near the State border, with seasonal fluctuations from 0.2 to 2 metres. Salinities range from approximately 8500 mg/L, decreasing in an easterly direction, to 1000 mg/L. In some areas, it is evident that large groundwater withdrawals for irrigation are contributing to a long term decline in groundwater levels of up to 14 centimetres per year. Increases in salinity ranging from less than 5 to 200 mg/L per year are attributed to continuous leaching of salts from the unsaturated zone into the water table, caused either by recycling of irrigation water or else by increased vertical recharge fluxes. The clearance of native vegetation and the loss of high water use pastures (during the 1970s) is causing groundwater levels to rise up to 10 centimetres per year in some areas.