This area is one of the distinct physiographic provinces of the larger
East Australian Basins division, and includes the smaller
Wilcannia Threshold physiographic section.
Geology The water of the Great Artesian Basin is held in a sandstone layer laid down by continental erosion of higher ground during the
Triassic,
Jurassic, and early
Cretaceous periods. During a time when much of what is now inland Australia was below
sea level, the sandstone was covered by a layer of marine sedimentary rock, which formed a confining layer that trapped water in the sandstone aquifer. The eastern edge of the basin was
uplifted when the
Great Dividing Range formed. The other side was created from the
landforms of the
Central Eastern Lowlands and the
Great Western Plateau to the west. Most recharge water enters the rock formations from relatively high ground near the eastern edge of the basin (in Queensland and New South Wales) and very gradually flows toward the south and west. A much smaller amount enters along the western margin in arid central Australia, flowing to the south and east through the
permeable sandstone, at a rate of one to five metres per year. Discharge water eventually exits through a number of
springs and
seeps, mostly in the southern part of the basin. The age of the groundwater, determined by carbon-14 and chlorine-36 measurements combined with hydraulic modelling, ranges from several thousand years for the recharge areas in the north to nearly 2 million years in the south-western discharge zones.
Water source Prior to the arrival of Europeans, waters of the Great Artesian Basin (GAB) discharged through mound springs, many in arid South Australia, such as
Witjira-Dalhousie Springs. These springs sustained a variety of endemic invertebrates, such as
molluscs, and supported extensive Aboriginal communities and trade routes. After the arrival of Europeans, the springs facilitated exploration, and allowed the provision of faster communications between south-eastern Australia and Europe, via the
Australian Overland Telegraph Line. In essence, water extraction from the GAB is a mining operation, with recharge much less than current extraction rates. In 1915, there were 1,500 bores providing of water per day, but today the total output has dropped to per day. This included just under 2,000 freely-flowing bores and more than 9,000 that required
mechanical power to bring water to the surface. Many bores are unregulated or abandoned, resulting in considerable water wastage. These problems have existed for many decades, and in January 2007 the Australian Commonwealth Government announced additional funding in an attempt to bring them under control. However, many of the mound springs referred to above have dried up due to a drop in water pressure, probably resulting in extinction of several invertebrate species. The
Olympic Dam mine in South Australia is permitted to extract up to of water daily from the Great Artesian Basin under the
Roxby Downs (Indenture Ratification) Act 1982. The underground copper and uranium mine commenced operations in 1988 and is expected to continue operating until approximately 2060. In addition, the Basin provides water, via a bore, for a
geothermal power station at
Birdsville. Water emerges from the bore at and provides 25% of the town's electricity needs. After being cooled, the water is also the source of the town's drinking water. ==Whole of Basin management==