1.1.4 Hydrogeology and groundwater quality


Within the rocks of the Cooper Basin, coarser sandstone units of the Patchawarra and Toolachee formations represent the highest porosity units. Water quality in the Cooper Basin aquifers is generally brackish to saline.

The main aquifers in the subregion are the Cadna-owie Formation and Algebuckina Sandstone, as well as the Namur and Hutton sandstones. The aquifer system is both artesian and non-artesian. Groundwater in the aquifers of the Eromanga Basin and the Lake Eyre Basin in the Cooper subregion is generally suitable for stock and domestic use. Water quality in the aquifers of the Eromanga Basin deteriorates down flow paths. This is interpreted as the result of mixing of dilute recharge water with more saline groundwater from the deeper parts of the basin. The Lower Cretaceous-Jurassic aquifers are characterised by sodium-bicarbonate-chloride waters, whereas the Cretaceous aquifers are dominated by sodium-chloride waters.

Groundwater from the Lower Cretaceous-Jurassic sequence is of good quality and suitable for domestic, town water supply and stock use, though it is generally unsuitable for irrigation because it is characterised by high alkalinity and sodium contents. Groundwater from the upper, Late Cretaceous, Winton and Mackunda formation aquifers has a higher salinity, but may be acceptable for stock water.

The Eyre Formation aquifer can be a useful aquifer for stock purposes, where water salinity is brackish to saline. Good quality groundwater can be found at shallow depths in alluvial sediments adjacent to the major watercourses.

On a regional scale, groundwater flows from recharge areas along the Great Dividing Range west toward the discharge zones of the Western Eromanga Basin. The watertable throughout the Cooper subregion lies in the Early to Late Cretaceous Winton Formation, and in the underlying Early Cretaceous Mackunda Formation and Cenozoic sediments overlying the Eromanga Basin sequence. The water levels in Quaternary floodplain sediments generally form a continuum with the pressure surface of the underlying rock aquifer.

The south-westerly flow direction is mirrored in deeper hydrostratigraphic units, such as for the Cadna-owie – Algebuckina and Cooper Basin hydrostratigraphic units.

Inter-aquifer connectivity and vertical leakage are important mechanisms in the Cooper subregion. This occurs from the lower, higher pressure aquifers through the overlying leaky aquitards and aquifers into the Cretaceous aquifers of the Mackunda Formation and Winton Formation, or the regional watertable.

Groundwater management within the subregion is undertaken in accordance with water management legislation for SA and Queensland.

Last updated:
5 January 2018
Thumbnail of the Cooper subregion

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