The Hidden Gem that keeps Australia Running
Australia boasts one of the driest continents in the world, home to both arid and semi-arid regions, the Australian climate features a tropical north, arid interior and temperate south. These culminating factors pose a serious challenge to water supply, Australia’s advantage, however, is that it is also home to the largest artesian basin in the world – The Great Artesian Basin.
Discovery of Artesian Water
Artesian water was discovered in Australia in 1878 during a time when scientists had been questioning the disappearance of water from the Murray-Darling Rivers system.
At the time, several investigations were underway. An appeal had been made enquiring into a claim that less than 1.5% of the rain falling in the upper Darling River catchment flowed past Bourke, whereas in a reflecting area in the Murray River, the discharge appeared to be closer to 25% of the catchment rainfall.
Further along in South Australia, scientists had been investigating mud springs in Lake Eyre and realised they were natural artesian wells, suggesting the area suited artesian conditions. This was confirmed when further exploration uncovered a flowing supply from a reconditioned deep well in Kallara Station, NSW, the first flowing bore in what would be the Great Artesian Basin.
It wasn’t long before small flows had been established in shallow bores near similar springs in Queensland, NSW and South Australia, with the encouraging results, soon large artesian flows were obtained from depths of over 300m.
How it Works
The Great Artesian Basin is made up of a series of interconnected sedimentary basins that existed from the late Triassic Period until the Late Cretaceous. The basin is the largest in the world, taking up 1/4 of Australia’s continent.
The water is held within porous sedimentary rock formations known as aquifers. These rocks provide enough space between grains of sediment to allow water to flow through the rock. Each aquifer is covered by impermeable rock units known as ‘cap rocks’, usually non-porous mudstone that is impermeable which seals the pressure of the water.
Important aquifers include the Jurassic-age Precipice Sandstone, the Jurassic Hooray Sandstone, the Cretaceous Cadna-owie Formation, the Jurassic-Cretaceous Gilber River formation in the Gulf Country and, to a lesser extent, the Cretaceous Winton Formation.
The aquifers surface mostly in the Eastern Highlands, here rain falls on the areas where porous rocks are exposed, and gravity ensures that some of the water is absorbed and flows underground and slowly makes its way west into the interior of the basin.
Boreholes drilled into the subsurface sedimentary rock of the basin intersect these porous aquifers.
A flowing bore occurs when the uptake area is above the surface height – known as an artesian bore. If the surface height is above the uptake, it will need pumping to the surface – known as a sub-artesian bore.
Artesian water within the bore flows mostly east-west in the Great Artesian Basin, or north-south in the central part of the Gulf of Carpentaria. This flow pattern has been carefully mapped by examining all the bores within the Great Australian Basin. The water takes many years to travel from the Eastern Highlands to the centre of the basin with some water dated at 2 million years old.
The mud springs or artesian springs are mostly found in the west, where water naturally finds its way to the surface. These springs have been in place for millions of years and, in the dry environment of western Queensland, they are an oasis for life. Over time, they have developed a unique suite of plants and animals.
The Basin as a Resource
After the discovery of the basin, the country was quick to uptake further boring, especially in the western areas of Queensland that had been suffering from major droughts. One particularly intense drought in western Queensland in 1881 saw the Government create a Water Supply Department to provide more adequate water supplies for inland towns. Unfortunately, initial attempts proved fruitless. These early bores only achieved shallow depths with the resulting water too saline for human consumption. It wasn’t until four years later following another drought that they decided to important plant and operators for deep drilling.
The first of the deep bores to be completed was on Thurralgoonia Holding, near Cunnamulla, a flow of 363 m3/d being obtained at 393 m. This discovery had a great impact in Queensland and there was rapid expansion of drilling. By 1889, 34 artesian bores had been completed, with 524 by 1899. In 1888, the drilling of 13 more bores for town water supply was approved, and their waters markedly improved the living conditions and health of the western communities. By 1900, artesian bores for 24 inland towns had been completed or commenced.
Now, the Great Artesian Basin is a vital resource supplying pastoral and agricultural industries as well as providing for many town water supplies. It is one of the only reliable resources of fresh water throughout much of inland Australia and is tightly monitored for its protection. If you are interested in any of the protection policies and plans in place, feel free to visit the Queensland page.
