Australia is dry, hot, unimaginably infertile and the most inhospitable of all inhabited continents. Yet, underneath the parched land, lies one of the world’s largest source of groundwater—a vast underground aquifer, trapped within layers of impermeable rock and clay, containing an astounding 65,000 cubic kilometers of fresh water, enough to fill the Great Lakes of Northern America nearly three times over. Even the world largest freshwater lake, Lake Baikal, is 2.7 times smaller than the Great Artesian Basin.
The Great Artesian Basin lies beneath parts of Queensland, New South Wales, South Australia and the Northern Territory, stretching over 1.7 million square kilometers, or over one-fifth of the Australian continent. It extends 2,400 km from Cape York in the north to Dubbo in the south. At its widest it is 1,800 km from the Darling Downs to west of Coober Pedy.
A mound spring fed by an artesian well in South Australia. Photo: Mandy Creighton/Shutterstock.com
The Great Artesian Basin was created over a span of millions of years during the Triassic, Jurassic, and early Cretaceous periods, when much of what is now inland Australia was below sea level. During this period the deposition of sediments formed alternating layers of permeable sandstone and impermeable siltstones and mudstones. Some 300 million years ago, this basin was uplifted and the Great Dividing Range was formed creating a barrier that prevented rainwater and runoffs from reaching the ocean. Instead, the water sat and sank into the earth and became trapped in the sandstone layers hundreds of meters down. Over time the accumulated water became a vast underground reserve.
The Great Artesian Basin is a confined aquifer, which means that the water in the sandstone layers is under great pressure from the surrounding rocks and layers of impermeable clay. When a well or a bore is sunk into such an aquifer, the pressure in the aquifer causes water to flow naturally up to the surface without the need of pumping. The average depth of bores in the Great Artesian Basin is 500 meters, but some bores have been drilled to depths of 2,000 meters. The water from deeper bores are almost at boiling temperature because of the immense heat and pressure at such depths, allowing several spa and sanatoriums to sprung up. There was also a geothermal power station at Birdsville in Queensland, until its closure in 2018.
Basin water also emerges naturally through cracks in the rock, flowing into springs, shallow water tables, creeks and rivers. This occur mostly in the southern part of the basin where the water is close to the surface.
Water from the Great Artesian Basin is the lifeblood of much of Australia’s interior, and has been since humans set foot on this continent. This water has enabled the aboriginal and Torres Strait Islander people to occupy the arid and hostile environment for more than 40,000 years. Aboriginal peoples have strong cultural, social and spiritual connections with the springs and their associated ecological communities and landscapes, which are protected by lore and customs. Some of these springs feature in Aboriginal myths and hold significant spiritual and cultural beliefs of indigenous communities.
Beel's Bore, Hariman Park near Cunnamulla. Photo: Powerhouse Museum/Flickr
European settlers first discovered artesian water from the Great Artesian Basin in 1878 when a shallow bore sunk near Bourke in New South Wales produced flowing water. Many bores were soon drilled and by 1915 over 1,500 flowing artesian bores had been drilled throughout the Basin. The discovery and use of this water allowed the settlement of thousands of square kilometers of country far away from rivers that would otherwise have been unavailable for pastoral activities. Even towns and cities sprang up around artesian bores.
There are more than 18,000 boreholes at present, discharging 1.3 billion liters of water everyday, although much of this is lost through evaporation and seepage. Many bores are unregulated or abandoned, resulting in considerable water wastage. According to the Department of Agriculture, Water and the Environment of the Australian Government, wastage accounts for 95 percent of water even in well-maintained drains. Conserving and sustaining the Great Artesian Basin is thus a priority for the Australian Government. They are trying to achieve this by implementing bore capping and piping, educating the farmers on how to manage Basin water, and conducting research to develop new management arrangements.
Hot water bore hole into the Great Artesian Basin in Thargomindah. Photo: kdliss/Wikimedia Commons
In the past hundred years, water pressure in the Basin has fallen by a quarter because of extraction and low rates of recharge. Consequently, several free flowing springs have dried up, probably resulting in the extinction of several invertebrate species that relied on this springs for survival.
Another rising concern is that the extraction of coal seam gas can contaminate the Basin with toxic chemicals threatening the lives and livelihood of thousands of people in hundreds of communities. Dozens of chemicals are used in the process of hydraulic fracturing and their long-term impact on aquifers, agriculture and people is widely known, but the Australian media accuses interested parties of fudging data or withholding information from land owners. High levels of chemicals including lead, aluminium, arsenic, barium, boron, nickel and uranium have already been found in groundwater in north-western NSW.
“The single most vital important point when considering this [Santos Narrabri coal seam gas] project is that water is life,” said Anne Kennedy president of the Artesian Bore Water Users Association and the Northwest Alliance. “Matthew Currell [a researchers who found several conflicting information in the Narrabri gas project environmental impact statement] has pointed out how critical water is and the Great Artesian Basin is Australia’s greatest resource as we move towards a time when wars will be fought over water, not oil or gas.”
Artesian water baths in Lightning Ridge. Photo: kdliss/Wikimedia Commons
References:
# Great Artesian Basin, Department of Agriculture, Water and the Environment
# http://www.derm.qld.gov.au/factsheets/pdf/water/w68.pdf
# The Great Artesian Basin and coal seam gas, CSIRO
# Britannica
# Wikipedia
# Gabrielle Chan, Toxic waste could endanger drinking water if Santos CSG project goes ahead – report, The Guardian
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