artesian basin

Great Artesian Basin

The Great Artesian Basin provides the only reliable source of water through much of inland Australia. The basin is the largest and deepest artesian basin in the world, covering a total of 1,711,000 square km. It underlies 23% of the continent, including most of Queensland, the south-east corner of the Northern Territory, the north-east part of South Australia, and northern New South Wales. The basin is 3000 metres (10,000 ft) deep in places and is estimated to contain 64,900 cubic kilometres of groundwater. The Great Artesian Basin Coordinating Committee (GABCC) coordinates activity between the various levels of government and community organisations.

Physiography

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 GAB 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 then covered by a layer of marine sedimentary rock shortly afterwards, which formed a confining layer - thus trapping 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 towards the south and west. (A much smaller amount enters along the western margin in arid central Australia, flowing to the south and east.) Because the sandstones are permeable, water gradually makes its way through the pores between the sand grains, flowing 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. It takes up to two million years for water to travel to the springs in the Lake Eyre area.

Water source

Prior to European occupation, waters of the GAB discharged through mound springs, many in arid South Australia. These springs supported a variety of endemic invertebrates (molluscs, for example). After European occupation, the Great Artesian Basin became an important water supply for cattle stations, irrigation, and livestock and domestic usage, and is a vital life line for rural Australia. To tap it, bores are drilled down to a suitable rock layer, where the pressure of the water forces it up, mostly without pumping.

The discovery and use of water held underground in the Great Artesian Basin opened up thousands of square miles of country in inland New South Wales, Queensland and South Australia, previously unavailable for pastoral activities. European discovery of the basin dates from 1878 when a shallow bore near Bourke, New South Wales produced flowing water. There were similar discoveries in 1886 at Back Creek east of Barcaldine, Queensland, and in 1887 near Cunnamulla, Queensland.

Water extraction from the GAB is essentially a mining operation, with recharge much less than current extraction rates. In 1983 there were close to 18 000 bores providing 1575 million litres of water. This included just under 2000 freely flowing bores and more than 9000 that required mechanical power to bring water to the surface. Many bores are unregulated or abandoned, resulting in considerable water wastage. The Australian Commonwealth Government announced additional funding in January 2007 in an attempt to bring these problems, which have existed for many decades, under control. Unfortunately, many of the mound springs referred to above have dried up due to a drop in water pressure, resulting in extinction of several invertebrate species.

Additionally, the basin has provided water via a 1.2 km deep bore for a geothermal power station at Birdsville. The heated water is 98 °C (208 °F) and provides 25% of the towns needs. Ergon Energy is expanding the 80 kW plant to completely meet Birdville's electricity requirements .

Whole of Basin Management

As the Great Artesian Basin underlies parts of Queensland, New South Wales, South Australia and the Northern Territory, which each operate under different legislative frameworks, policies and resource management approaches, a coordinated "whole-of-Basin" approach to the management of this important natural resource is required. The Great Artesian Basin Coordinating Committee (GABCC) provides advice from community organisations and agencies to State, Territory and Australian Government Ministers on efficient, effective and sustainable whole-of-Basin resource management and to coordinate activity between stakeholders.

Membership of the Committee comprises all State, Territory and Australian Government agencies with responsibilities for management of parts of the Great Artesian Basin, community representatives nominated by agencies; and sector representatives. The primary role of the Committee is to provide advice to State, Territory and Australian Government Ministers on efficient, effective and sustainable whole-of-Basin resource management and to coordinate activity between stakeholders.

The GABCC website provides up to date information and links regarding the Great Artesian Basin and can be accessed through their website www.gabcc.org.au

Current scientific thinking

A comprehensive background to the Great Artesian Basin, including an overview of the nature of the Basin, the extraction of water and the impacts of that extraction, can be found in the Great Artesian Basin Resource Study, developed by the GABCC to support the Great Artesian Basin Strategic Management Plan.

External links

  • L.A. Endersbee, "A New Understanding of the Groundwater Resources of the Great Artesian Basin", Australian Academy of Technological Sciences and Engineering
  • "The Great Artesian Basin", Queensland Department of Natural Resources and Water

References

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