Tasmania's groundwater resources are extracted by at least 8000 known bores and wells.
The estimated annual use of groundwater in Tasmania is about 50 000 ML, of which about 25 000 ML are extracted from boreholes for irrigation, town water, domestic use and stock watering. The remaining 25 000 ML is extracted during the de-watering of mines.
Except in a very small number of cases, yield from an extraction bore alone is not likely to be sufficient to supply centre pivot irrigation systems. It is only slightly more likely that a bore would provide sufficient yield to act as a sustainable supply to augment a dammed reservoir supply for a centre pivot system.
In central northern Tasmania water is pumped from Tertiary basalt aquifers into dams and used for travel irrigators. Typically the yields obtainable from Tasmanian bores makes them most suitable for dairy, stock, domestic or other rural uses.
The nature of Tasmanian aquifers means that there is always some uncertainty as to whether a water bore will actually yield useable quantities of groundwater. With intergranular aquifers, prediction of the success of a proposed borehole can be made with some degree of certainty. For fractured rock aquifers, the borehole must encounter sufficient water-bearing fractures to produce a useable quantity of water. The distribution of fractures depends upon a variety of influences, and cannot necessarily be predicted from the surface. Prospectivity of particular fractured aquifers may therefore vary greatly, depending upon location. Where aquifers have been tested the usual depth of successful bores (excluding spear bores into sand) is between twenty and seventy metres.
