The Gift of the GAB

(This post originally appeared in Bobby Dazzler Newsletter #60, December 2013.)

Australia would be a very different place without the gift of the Great Artesian Basin, and several other smaller artesian basins. Many Outback towns, villages and properties depend for their water supply on bores and springs which bring the vital fluid to the surface. For example, the towns of Coober Pedy (SA) and Winton (Qld) depend on water from the GAB. Alice Springs water comes from the nearby Amadeus Basin (not shown on map).

The Great Artesian Basin (1,700,000 sq kms), which covers more than one fifth of the country, is the largest and deepest artesian basin in the world. It occupies substantial parts of Queensland, Northern Territory, South Australia and New South Wales. It is 3000 metres deep in places, and is estimated to contain 64,900 cubic kms (yes, kilometres!) of water, held inside porous sandstone. It was formed about 100 million years ago when much of inland Australia was below sea level, and the water-saturated sandstone was covered by a layer of sedimentary rock, thus trapping the water under pressure.

Artesian_BasinsIn due course, fault lines in the rock led to the formation of natural springs in many areas, such as Dalhousie Springs in the far north of South Australia, and the mound springs near the Oodnadatta Track. In the 1870s, the first bore was sunk into the GAB, and since then, many hundreds of bores have been drilled, some as deep as 2000 metres. The artesian water normally flows freely without the need for pumping, and at a temperature between 30 and 100°C. It often contains mineral salts and/or (smelly!) sulphur compounds, and needs to be treated before it can be used, even for irrigation. The big demineralisation towers can still be seen along the old Ghan railway line, where artesian water was treated before it could be used in the steam locomotives.

Replenishment of the GAB occurs mostly from rainfall on the relatively high ground on the western side of the Great Dividing Range, which runs down the East Coast. The water soaks into the ground until it reaches the sandstone stratum, and then percolates slowly westward at the rate of 1 to 5 metres per year. Carbon dating has shown that some water emerging from Outback springs has been under the ground for about two million years! Which of course makes the point that if we use up all the artesian water, we may have to wait two million years for the GAB to fill up again. That’s a long time between drinks!

flowing bore

 

 

 

 

 

 

 

Concerns have been expressed in many quarters about the rate at which artesian water is being used. Until recent times, many remote-area bores were left running continuously over many years, but there are now requirements for capping bores so that they can be used more efficiently. The Olympic Dam and mining complex in South Australia uses 35 million litres of water drawn from the GAB every day.

It’s obviously not an easy matter to measure the rate of depletion of water in the GAB, but some scientific studies have concluded that in certain areas, the amount of water remaining in the Basin has been measurably reduced.

Another concern is that “fracking” associated with coal seam gas extraction will contaminate subterranean water, including artesian basins, with toxic chemicals. One thing we can be certain about: loss of access to usable water from our artesian basins would have a massive impact on Australia.

Footnote: Back in 1896, Banjo Paterson wrote a poem about artesian water, and the first stanza goes like this:

Now the stock have started dying, for the Lord has sent a drought,
But we’re sick of prayers and Providence – we’re going to do without,
With the derricks up above us and the solid earth below,
We are waiting at the lever for the word to let her go.
Sinking down, deeper down,
Oh, we’ll sink it deeper down:
As the drill is plugging downward at a thousand feet of level,
If the Lord won’t send us water, oh, we’ll get it from the devil;
Yes, we’ll get it from the devil deeper down.

The full text of the poem, an account of the circumstances in which Paterson wrote the poem, and some interesting background on artesian water can be found at http://www.qhatlas.com.au/great-artesian-basin-water-deeper-down .

Please give us your thoughts on the use of artesian water, or on fracking, and maybe where you’ve seen bores running. Just click on “Add a comment” or “Comments” below. (You don’t have to give your name – just use a nom-de-plume.)

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About dazzlerplus

Writing about the things that interest me helps me to discover what I think. One of my loves is the Australian Outback, and I travel out there often, and when possible take friends with me.
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8 Responses to The Gift of the GAB

  1. Cynthia says:

    I always wondered about the sanity of having vineyards outside of Alice Springs. It takes stunning amounts of water to grow grapes in a desert. If there were nowhere else in Australia to grow grapes, I might understand, but that’s not the case. Is it really worth the risk? Just wondering. Because running out of water would definitely create problems.

    • dazzlerplus says:

      Hi Cynthia, you’ve raised an interesting point! Chateau Hornsby has been producing wine since 1977, and I’m told the quality has steadily improved to the point where their wines are now quite well respected. They are of course dry reds and whites (!)
      It would seem to make more sense to grow grapes somewhere else, but I suppose people take up all sorts of challenging/illogical projects. I’m not sure how big the vineyard is, but it’s not large by commercial standards.
      If the Alice Springs water supply were to fail, there would be a mass of problems. A town of some 25,000 people with most modern amenities simply couldn’t survive, and I imagine the demise of the vineyard would be one of the minor issues.

      • Cynthia says:

        There’s also Rocky Hill Vineyard, which produces a thousand tons of table grapes a year. I understand the desire to face a challenge — that almost defines Aussies. But it does make one think that perhaps a bit more study of the aquifer might be in order. I know that here in the U.S., the major aquifer in the center of the nation has been lowered dangerously over the last couple of drought years. So water reserves are definitely something to keep an eye on. I was encourage about your comments regarding capping outlets in many places. I can remember seeing the water gushing out of pipes in a number of places (always remarkably hot water, too). Glad to know people are at least considering potential consequences.

  2. Susan Emeleus says:

    Hi Rob, I remember being on an outback trip in 2010 and the leader told us the water we were soaking in had probably taken a million years to get to us. I hadn’t known about it taking such a huge time, and it does make me worry about fracking processes that won’t be able to undo any damage. Sue Emeleus

  3. Mandy says:

    The sweetest water I have ever tasted came from the Desert Basin in north west WA. It would be criminal to lose or exploit that resource.

    • dazzlerplus says:

      Yes, I agree it would be criminal. But it’s a bit like having a bank account you can draw money out of, but you have no idea what the balance is. So you don’t know whether you’re drawing out your last dollar, or whether there’s still $10,000 in the account (and there’s some wealthy benefactor who’s depositing $1000 every month).

      • Susan Emeleus says:

        That’s a great way to think about it. Only if they go ahead with the fracking stuff, we might find out what the balance is when it’s too late.

  4. Pingback: Aah Spa | Rocky Springs Rambles

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