About the Great Artesian Basin
The Great Artesian Basin is one of the largest underground fresh-water reservoirs in the world. It underlies approximately 22% of Australia – occupying an area of over 1.7 million square kilometres beneath the arid and semi-arid parts of Queensland, New South Wales, South Australia and the Northern Territory. The GAB is Australia’s most important water resource, and for more than a century it has sustained much of the pastoral and community needs of a fifth of Australia’s landmass.
European discovery of the Basin dates from 1878 when a shallow bore was sunk near Bourke, NSW, and produced flowing water. The discovery and use of underground water opened up thousands of square miles of country, previously unavailable for pastoral activities. The GAB became an important water supply for cattle stations, irrigation, livestock and domestic usage, and is still a vital life line for rural Australia. To tap it, wells are drilled down to a suitable rock layer, where the pressure of the water forces it up through casing, mostly without pumping.
From the beginning of the discovery of this artesian water, most bores were allowed to flow freely and uncontrolled onto the ground, running into open drains to water stock. However, even in well-maintained drains, up to 95 per cent of this water was wasted through evaporation and seepage.
It was recognised by the early 1900′s that control over GAB groundwater was inadequate as there was a steady reduction in water pressure and volume due to the increasing number of free-flowing bores drilled. Even a hundred years ago, it was realised that the extraction and use of waters from the Basin was unsustainable – but there followed more than a century of mismanagement.
It was not until 1954 that the Artesian Water Investigations Committee provided a published report, which was addressed separately in each State. This disjointed approach was an impossible way to manage a resource spanning three States and the Northern Territory. Read more on GAB Management.
More than 20 years ago, some landholders began capping and piping their bores, and the water was then piped through poly pipe to tanks and troughs, to water the stock. This eliminated the water running down open drains, and an estimated 95% of water was thus saved. But it was a very expensive exercise, and many could not afford it, so it was not until 1999, when govt. funding became available, that capping and piping of bores began in earnest. In 1999, a government initiative called GABSI was introduced, whereby bore-owners were offered government assistance (between 40% to 60% of the cost) as an incentive to cap their bores. This was a breakthrough, and is the single greatest thing that has ever happened to the GAB. But there is still too little funding to undertake capping & piping on a large enough scale, and the process (the paperwork, applications, approvals etc) is too slow. And there is only one drilling rig available.
GABSI 3 program has just been confirmed, but the funding won’t be available until July 2011, so it will be another two years before any further capping works are commenced. A further two years of wasted water Read more on GAB Management.
There is much evidence concerning the waters of the GAB that confirms that the waters are of plutonic origin. These include the combination of natural gas and water, helium concentrations, fluoride, and hydrogen sulphide, and the high temperature gradients. The temperature of the water ranges from 30 degrees C. to 100 degrees C. Also the fact that when a bore was drilled and water gushed out in geysers 30 metres in the air – this was not the result of slow seepage through sandstone, but the release of water stored in the earth’s crust, under pressure.
The accepted view of the Great Artesian Basin (in all govt. papers, and taught in schools and universities) is that it is an open system that is regularly topped up by rainfall on the highlands around its perimeter, particularly on the slopes of the Great Dividing Range to the East. The govt. geologists claim that the Basin’s tremendous sandstone strata reach the surface in these intake zones and surface water can readily percolate down into the porous rock from where it begins its long journey beneath the Western Plains.
However, this is deceptive and misleading. In the government’s most recent report from the Bureau of Rural Sciences (Habermehl et al 2009), it states “recharge rates range from 0.5mm to 10mm (millimeters) per year, with a maximum of approximately 40mm per year.” How could this water, travelling at that rate, possibly recharge the Basin (which is 3000 metres deep in places) in less than many millions of years? Another paper (Love et al 2000) claims that by using Cl dating methods, recharge in south-west of the GAB is between 0.08 and 0.24 mm (millimetres) per year, and flow velocity is 0.24 m per year. To quote the DWE’s Water Sharing Plan document: “Water flow through the sandstone is extremely slow, it is estimated that the time taken for water to travel from the recharge areas to the western parts of the GAB can be up to two million years”. And this is the best case scenario – the other scenario is worse.
The other point of view (which is widely accepted by many scientists, hydrogeologists and professors) is that there is strong scientific evidence to prove that the waters of the GAB are ancient, stored in the earth’s crust – and are finite. These experts state that the GAB will run out, it is a closed system, but whether it lasts us 20 years or 100 years, depends entirely on how we manage it. At the present time, we have already wasted 100 times the volume of Sydney Harbour (that is wastage, not usage) and we are at present wasting water equivalent to the volume of Sydney Harbour (0.5 million megalitres) each year.
So the best case scenario (according to the govt. documents) is that it will take several million years to replenish – the worst case scenario, is that it won’t replenish at all. In reality then, does it matter which theory is correct, as it is ludicrous to suggest the govt’s estimated rate of recharge (if it exists at all) could be of any benefit to the GAB? We claim (and independent hydrogeologists have agreed) that this rate is so miniscule, that it cannot ethically be called “recharge” – which implies that the water level is being topped-up, when in actual fact it is not being replenished at all.
And so we would insist that until the govt. admits that the GAB is not recharging and that the waters are finite, in fact while there is any debate whatsoever about the science of how or whether the GAB is recharging, that NO further water is sold off until the science on this can be debated. And that what water is remaining must be used sensibly, and all waste eliminated, so that it will last as long as possible for future generations.
Emeritus Professor Lance Endersbee AO, FTSE, Hon FIE Aust., Hon MEI Canada, F. ASCE was a civil engineer of long experience in water resources development. He was awarded an AO (Officer, Order of Australia) for his services to engineering and education. He was a world authority on rock behaviour and tunnelling, and former President of the Institution of Engineers Australia. He firmly believed that water extracted from the Artesian Basin does not come from the Basin Strata but from the bedrock beneath them.
“As soon as I saw the traditional explanation I knew it was wrong. It was wrong fundamentally”, Professor Endersbee said on ABC Radio. “The idea of water falling on the hills in Queensland and seeping through the sandstone strata all the way to Roxby Downs in South Australia for example – a distance of thousands of kilometers – was absolutely absurd.”
According to the Professor, the fact that bores go down four and five thousand feet, is a clear indication that the water does not come from the sediments of the basin itself but from the original rock below. This theory holds that the water coming up the bores is not rainwater that has trickled beneath the plains, but ancient water that has for eons laid quietly within the fractures and joints of the original crustal formations with which it came into being. The water supply is a closed system that can not be replenished. Once dry, said Professor Endersbee, the artesian bores will never flow again.
Critically, the Professor said that the long term decline in water pressure being experienced right across the Basin is telling us that the huge volume of water extracted over the past century and more means there is “not much” left. If the Professor was correct and water extraction from the Great Artesian Basin has been completely unsustainable, it is terrible news for the Australian economy and for the livelihood of thousands.