Abstract

The Great Artesian Basin (GAB) is a regional groundwater system consisting of aquifers and confining beds within the sedimentary Eromanga, Surat and Carpentaria Basins. They underlie arid to semi-arid regions across 1.7 million km2, or one-fifth of the Australian continent. Artesian springs of the GAB are naturally occurring outlets of groundwater from the confined aquifers. Springs predominantly occur near the eastern recharge margins and the south-western and western discharge margins of the GAB. These zones of natural groundwater discharge represent areas of permanent water, with widely recognised cultural, spiritual and subsistence importance to Indigenous people for tens of thousands of years. The unique hydrogeological environments – discharge, hydrochemistry and substrate – support a range of endemic flora and fauna protected under the EPBC Act (1999). Springs have formed in many areas across the GAB; however, the largest concentrations occur near the south-western margins of the basin. Supporting these flowing artesian springs is a multi-layered aquifer system, comprising Jurassicto Cretaceous-age sandstones and siltstone, and confining beds of mudstones. Hydrogeological, hydrochemical and isotope hydrology studies show that most artesian springs and flowing water bores in the GAB derive their water from the main Jurassic–Lower Cretaceous Cadna-owie Formation – Hooray Sandstone aquifer and its equivalents. Focusing on springs in South Australia, this paper provides a summary of the hydrogeology of the GAB, including zones of recharge and regional groundwater flow directions, with a major focus on summarising understanding of the occurrence and formation of springs.