How The Great Artesian Basin works

How The Great Artesian Basin works

Water in the desert. Imagine what that meant
to the early inhabitants of inland Australia in one of the harshest and most arid places
on the planet for them to know that they had permanent access to fresh water and wetlands.
No wonder Australia’s natural spring systems became so sacred for so many.
But when the lakes turn to salt pans and the rivers are sucked dry where does the water
come from? Okay, get your head around this. About two million years ago it rained on the
Great Dividing Range in Queensland. Today that same water bubbles up in South Australia.
Think about it. The last time this water saw the light of day giant hippopotamus-sized
diprotodonts were grazing on the coast, the Tasmanian Tiger was alive and hunting and
Australia was the home of a lion called the Thylacoleo that had the strongest bite of
any mammal in history, living or extinct. So, this water has been travelling at a painfully
slow pace through porous rocks deep underground. Sometimes it bubbles and soaks its way to
the surface through natural springs. At other times we’ve found ways to dig down and find
it. Either way, it is the key to life to about a quarter of the continent. We call it the
Great Artesian Basin. To explain how the Great Artesian Basin works
you need to know how it came to exist in the first place. So here it is, the past 250 million
years in a nutshell. Back in the Triassic Age Australia was joined
together with the other southern continents including Antarctica, South America, Africa
and New Zealand in a land mass called Gondwana. Now have a look at the top right quarter of
Australia. Can you see how it kind of forms a natural dip? That’s the area that will eventually
become the Great Artesian Basin. Over the next 140�million years huge events like
ice ages in Europe and tectonic plate movements cause the ocean level to rise and fall. When
the ocean levels rose water became trapped in that natural dip and formed a sea. But
when the ocean levels fell the whole area became land again.
When the seas drained away they left clay and silt deposits behind which hardened into
impermeable stone. Remember this. So now we’re back to dry land again but it’s
not desert yet and there are rivers crossing it. The rivers carried sand and gravel with
them which later joined together to form sandstone and that sandstone is the key to how the basin
works. Silt stones and mud stones are what scientists call impermeable. There’s no way
water can get through them. They’re like plugs. Check this out.
Okay. We’ve got our impermeable rock and we’ve got our sandstone. Okay.
It ain’t going through. Soaking it up. Now we wait.
Okay. Imagine our layers of impermeable and permeable stone deep underground. I’ll demonstrate.
This sponge is our sandstone, our permeable layer and if you see the water, it goes straight
through it. But if we put an impermeable layer – this frisbee � underneath, the water has
nowhere to go except forward or to the sides. When that happens the layer of sandstone is
called an aquifer. It’s a massive area. It stretches from Cape
York to Dubbo and Coober Pedy to the south-east corner of the Northern Territory. That’s almost
a quarter of Australia. When it rains on what we call the recharge bed areas of the basin
the water seeps down and collects in the aquifers. Scientists estimate that there’s around 65,000
million megalitres of water in the basin right now. A megalitre is a million litres. 65,000
million of them would be enough to cover all the land on the planet in almost half a metre
of water. So that whole basin area we saw earlier now
has aquifers running all the way through it and has become the Great Artesian Basin.

37 thoughts on “How The Great Artesian Basin works

  1. cool!
    maybe this time the water level rises, they will go through holes and penetrate through the upper level of ground and stuff, and somehow fill up the GAB to its max capacity.

  2. This whole system is being ruined by Coal Seam Gas Mining. If you have any appreciation of what this means, actively oppose this maniacal development.

  3. Qld govt are allowing toxic chemicals to be pumped into the precious irreplaceable resource without which whole eco-systems will die. How stupid can we get. Cant drink money. Cant eat gas.

  4. Say goodbye to our natural resource which is being injected with toxins as we speak. The CSG scheme is killing our land 🙁
    Give this land back to our First Nation Peoples to run, they are the true Conservationist.

  5. Im living in South Australia, and simply don't understand why the HELL I should be subjected to the pollution caused elsewhere if I choose to use ground water

  6. Some wells are drying up along with some springs and water pressure is dropping through many, if not most, bores throughtout the west. It seems naive at best to think that the Great Artesian Basin is being 'recharged' or 'replenished' by rainfall falling along the great divide. The water that is in the GAB took millions of years to accumulate, any water needed to 'top up' the GAB will similarly take millions of years, that's without using anymore water. The wastage from the GAB has been tremendous with bores running uncapped for more than a hundred years and it continues today. Take an example in the small town of Blackall in western Queensland where a bore has been running for more than a hundred years 24/7. It runs now as a tourist attraction to show them how bores work, water gushing out into drains that go nowhere only to evaporate in the 40 degree heat. Many tourists just shake heads amazed at the wastage of water. The GAB has a finite amount of water and it would serve us well to treat it as the precious asset that it most certainly is.

  7. hmmm, your maps shows the GAB slopes north to the sea (towards Darwin), and that is how the basin gets filled by the sea water. AND YET, the basin drains to the south towards Adelaide not to the north. The entire Darling-Murry system flow south not north!! So, what are you saying to that? i hope the rest of your hypotheses aren't as iffy as that

  8. In the not to distant future governments, the world over would have to turn to indigenous or first peoples like the Australian Aborigines for wisdom as to the wise use of the land. because these people had always worked with nature and not against her until their lives were interrupted by the Europeans. Some still hold sacred the land especially in the Americas and Australia. It was these people that thought modern scientist all about nature . They were ignored and abused by so call modern man but Climate Change is pounding on the Earths door and is promising devastating consequences.

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