Fractured rock aquifers

The Main Range Volcanics host the fractured rock aquifers of the subregion (Figure 8). These systems are primarily located along the eastern margin of the Condamine river basin. The basalts of these aquifers are covered, in part, with alluvium from this river basin. Average aquifer thicknesses are in the order of 28 m (Skelt et al., 2004). These volcanic rocks do not consist of a single homogeneous basalt flow or one single aquifer. Rather, the basalt sequence consists of many overlapping basalt flows with a maximum thickness of approximately 10 m each (Brodie and Green, 2002), which are stacked together and commonly separated by lower permeability layers including the clay-rich weathering profiles that developed between periods of volcanic activity.

These different zones of varying permeability affect the capacity of different basalt flows to store and transmit groundwater. At the top and the base of the basalt flows, zones consisting of broken vesicles commonly occur, and these provide considerable primary pore space that can contain and transmit groundwater. At the edge of the basalt flows, at the interface of the higher permeability basalts and the lower permeability overlying alluvial aquifers, groundwater discharges to the surface as springs, and these may feed streams (Brodie and Green, 2002).

Last updated:
16 October 2018
Thumbnail of the Maranoa-Baloone-Condamine subregion

Product Finalisation date