Investigations in the Hindmarsh Tiers Basin have shown that there is no direct evidence for depletion of groundwater, although summer pumping casues 5 to 10 metre drawdowns near the centre of the area. The main aquifer, a Tertiary bryozoal limestone, is confined, and overpumping would cause a significant and rapid decline in potentiometric levels. An observation bore network has been established to monitor water levels to allow long term monitoring. The water budget is not refined enough to be used for managment of the resource, but does serve to guide future investigations. In particular the amount of water being extracted needs to be measure, the role of storage in both the Permian sand aquifer and the clay confining beds need better definition, and stream gauging of the Hindmarsh Tiers catchment itself would be useful. With large well yields in such a restricted area there is a danger of over-exploitation developing in a short period, as a small number of new irrigation bores could represent a major increase in withdrawals. Continued monitoring of both water levels and prior knowledge of new drilling in the area through the Water Resources Act, 1976 are the main tools available, unless further investigations are undertaken. An increase in the amount of water consumed is unlikely in the near future, unless there is a change in land use, such as market garden development. There is obvious runoff from irrigated areas, and a study of water requirements of pasture suggested that excess water was being applied. Further work by agricultural officers is desirable to help farmers minimise the amount of water used.