Water: Artesian Basin

The Great Artesian Basin is the lifeline of the north as it supplies the pastoral and mining industries and communities with water in the driest zone of South Australia. Extending from Marla in the west, to Marree and Dubbo (NSW) in the south, the Great Dividing Range in the east and Cape York to the north, the Great Artesian Basin is one of the largest artesian basins in the world.

It covers an area of 1,711,000 square kilometres or 23% of the Australian continent. The South Australian portion covers an area of 376,000 square kilometres which is 38% of the State. The total volume of water stored in the basin has been estimated at 8 700 million megalitres.

Created between 100 and 250 million years ago the Great Artesian Basin consists of alternating layers of water bearing (permeable) sandstone aquifers and nonwater bearing (impermeable) siltstones and mudstones. The thickness of this sequence varies from less than 100 metres on the edges of the basin to over 3000 metres in the deeper parts of the basin. Some of the sandstone sequences contain oil and gas where conditions are suitable. The main aquifer in South Australia is the Algebuckina Sandstone and Cadna-owie Formations. The Cadna-owie Formation is covered by the Bulldog Shale which forms a partly effective confining layer. An upper aquifer, the Coorikianna Sandstone, is rarely used because of its high salinity.

Water exits the Basin through a number of naturally occurring springs or seepages, particularly around the southern perimeter of the Basin. The springs are called mound springs because of the build up of mineral salts at the vent or outflow point. Mound springs support a diverse variety of flora and fauna. Elsewhere bores are drilled and the pressure of the water itself forces it to the surface. In the past access to the bores and springs has not been controlled and environmental damage has been done.

from: Great Artesian Basin : South Australian Department for Water, Land and Biodiversity Conservation factsheet [2002]