Great Artesian Basin

The Great Artesian Basin (GAB) is one of the largest artesian groundwater basins in the world and underlies approximately one-fifth of Australia extending beneath regions of Queensland, New South Wales, South Australia and the Northern Territory.

The Basin covers a total area of over 1, 711,000 square km and it has an estimated total water storage of 64,900 million megalitres (a megalitre is one million litres and is equivalent to about half the water in an Olympic swimming pool).

The Great Artesian Basin was formed between 100 and 250 million years ago and consists of alternating layers of water bearing (permeable) sandstone aquifers and non-water bearing (impermeable) siltstones and mudstones.

Natural discharge occurs mainly from mound springs in the south-western area.  Mound springs are natural outlets of the artesian aquifers from which groundwater flows to the surface.

Dating of the artesian waters has given ages of almost 2 million years for the oldest waters, which occur in the south-western area of the Basin.

History

The inland of Australia is traversed by streams but these rarely flow and have few permanent waterholes. Unpredictable rainfall and high evaporation meant that early dams and earth tanks built to service the growing population and pastoral industry were unreliable.

Prior to European settlement, Aborigines used the mound springs of the Great Artesian Basin. Some of these mound springs feature in Aboriginal myths and hold significant spiritual and cultural beliefs of indigenous communities. Mound springs were and still are a valuable resource for the support of wildlife.

Europeans first discovered the artesian groundwater in 1878 when a shallow bore sunk near Bourke in New South Wales produced flowing water.  ln 1885 the Queensland Government Geologist decided to drill a deep bore at Blackall, however, before completion of this bore, the first artesian flow in Queensland was obtained near Cunnamulla in 1887. Later that year Barcaldine became the first town with artesian water.

The number of bores drilled in Queensland increased from 34 to 524 in the ten year period from 1889 to 1899. By 1915 over 1,500 flowing artesian bores had been drilled throughout the Basin.

Thousands of kilometres of bore drains were excavated to distribute water around properties, thus allowing sheep and cattle to be raised on the vast Mitchell grass, mulga and Spinifex plains. Bore drains are small, open channels that can extend 100km or more.

The water from the Great Artesian Basin continues to be of vital importance to outback regions of Queensland, New South Wales and South Australia. This water is often the only available supply for towns and properties for their domestic and stock watering requirements.

The GAB also supplies water for minor irrigation works, key mining and extractive industries, the petroleum industry, an emerging tourism industry and limited industrial purposes.