Sedimentary basins are an important source of groundwater within Australia. Many such basins contain extensive multi-layered aquifer systems consisting of permeable sediments laid down at various times in the past. Some well known sedimentary basins include the Great Artesian Basin, the Murray Basin and the Officer Basin. Aquifer depths within these basins can range from a few hundred to thousands of meters.
Where aquifers outcrop they are recharged by direct infiltration of rainfall, flood events and, where intersected by rivers, river bed seepage.
Water quality varies from fresh to saline. As a general rule groundwater within large sedimentary basins is fresher in areas of active recharge, increasing in salinity as it travels through the aquifer, due to interaction with the aquifer material.
Sedimentary basins can contain vast amounts of groundwater. For example it has been estimated that the Great Artesian Basin contains around 8.7 million gigalitres of water (Australian Water Association 2007). This is equivalent to the volume of water contained within 129 800 Sydney harbours.