Australia’s buried sea of water is being mined faster than it refills
The Great Artesian Basin is Earth’s largest and deepest artesian system, covering about 1.7 million square kilometres—22 percent of Australia. Water runs 30 to 100 °C, yet extraction far outpaces recharge, so every bore is partly a mine.
It underlies most of Queensland plus parts of the Northern Territory, South Australia, and New South Wales, reaching 3,000 metres deep in places and holding an estimated 64,900 cubic kilometres of water. The water sits in sandstones worn from higher ground during the Triassic, Jurassic, and early Cretaceous, later capped by shales laid down when an inland sea covered the region. Most recharge enters high ground on the eastern rim and creeps south and west, with a little seeping in along the arid western margin; carbon-14 and chlorine-36 dating puts its age at thousands to nearly two million years.
Before Europeans arrived, the basin surfaced through mound springs, notably at Witjira-Dalhousie and elsewhere in South Australia’s dry north, which sustained endemic snails and other invertebrates and supported Aboriginal travel. Tapping it opened thousands of square kilometres away from rivers to grazing. By 1915 some 1,500 bores yielded 2,000 megalitres a day; output later fell to about 1,500.
Today the Olympic Dam mine may draw up to 42 megalitres daily, and Birdsville’s 1.2 km geothermal bore delivers water at 98 °C that generates about a quarter of the town’s power and, once cooled, supplies drinking water. Four jurisdictions manage the basin under different laws, advised by a coordinating committee of agencies and community representatives.
New pressures keep arriving. In 2011 the ABC’s Four Corners aired concerns that coal seam gas extraction was depleting and contaminating the aquifers, and fracking fluids can involve more than thirty chemicals. Glencore proposed pumping as much as 110,000 tonnes of CO2 annually into one of the basin’s formations; hydrogeologist Ned Hamer warned that the acidified water could dissolve rock and release heavy metals.
Source: Great Artesian Basin
