More evidence to support Peter Andrews views on NSF and our understanding of this unique landscape.
From ABC Radio National on Saturday 7/10/00
http://www.abc.net.au/rn/science/earth/ ... 198245.htm
A exploration of Australia's ancient waterways with author Dr Mary White, author of "Running Down: Water in a Changing Land". She argues that we need to look to our landscape's ancient history to help us understand its limitations today.
Details or Transcript:
Alexandra de Blas: Well it was good news this week for the strangled Snowy River, with the announcement of a ten year, $300-million rescue plan to return 28% of its flow.
The demise of the Snowy is just one of the stories told by Dr Mary White in her latest book charting the evolution of our ancient rivers. In it she takes on big ideas and even bigger time scales, to shed light on the problems we face with many of our waterways today.
As she told Natasha Mitchell, the first Europeans came with very different ideas about what a river should do, and from lands that evolved quite differently from our own.
Mary White: The idea was that a river starts up on some high piece of land; it runs briskly and it runs into the sea, but what they didn’t realise is that very few of our rivers, we have very few rivers that are sort of normal rivers in that way, and in fact that in this land of ours, it’s so enormously flat, and the whole centre drains towards Lake Eyre, it’s inward draining, and most of the landscape in Western Australia which is an ancient shield, one of the ancient building blocks of the continent, that doesn’t drain anywhere at all, and so when they got to the other side of the Great Divide, which is our only sort of major elevated region along the east coast of the continent, they expected then that all the rivers, they came upon major rivers all running westwards, and they travelled ever further westwards and found no sea, obviously, and the accounts of the early travellers, it was all about looking for the inland sea.
Natasha Mitchell: And many of our waterways, our rivers, are ephemeral, they come and they go, according to the changes of the season. Now that must have been a bit mind-boggling for people seeing our landscape for the first time.
Mary White: I think very much so, and you have many accounts of the early travellers who said that ‘when we reached this point, the river that we had been following disappeared into a reed bed or it disappeared into a large swampy area’, and then they make the comment in their journals that ‘from this point on, we could not decide where the river went or which channel was in fact the river.’
Mary White: We need to understand that because of the very nature of this land with its unpredictable climate, and its flatness and all the rest of it, we need to have something approaching the original situation that had evolved with the landscape. You can’t change everything and get something that suits one’s European attitudes and European lifestyle and things, and not expect to have a fundamental affect on the basic landscapes.
I mean our plants and our animals and everything have evolved great lengths of time just as the landscape has evolved.
Natasha Mitchell: You’ve been reaching back much deeper into time; how far have you reached back to tell the story of the rivers in the Australian landscape?
Mary White: Well I’ve largely used Western Australia for that purpose, because the west is one of the ancient major building blocks of the continent, and so I mean you’re thinking about a huge time frame. You’ve got ancient landscapes, in Australia we have some of the most ancient land surfaces that are exposed anywhere on earth. And a lot of Western Australia’s modern rivers are occupying huge river valleys which were carved out into the landscape, anything up to 300-million years ago. And the interesting thing is that a lot of those river valleys, particularly the ones that sort flow fairly directly north-south, those were made by rivers that used to run from high mountains in Antarctica at the time when Australia was connected to Antarctica in Gondwana
. You’ve got modern rivers occupying a river valley which can be up to sort of 10 kilometres wide or something, that tells you of the size and the importance of the running rivers that used to be entering Australia from Antarctica, and of course when we separated in Gondwana and became an island continent, you literally cut in half, you cut those rivers in half, and then you had tilting of the edge of our continent at various stages and in various ways, and so very often the bottom, the part of our rivers that is now running in those valleys and entering the sea for instance in Bass Strait, those rivers are running backwards in beds in which rivers used to run the other direction before they were cut in half.
Natasha Mitchell: Now how on earth do you know all this? Where do you look to find evidence of an ancient river?
Mary White: Well I mean, where you’ve got a landscape that is an ancient landscape and it’s got all these valleys and things carved in it, like in Western Australia, you can see that so beautifully in satellite images. For instance even if you go in an aeroplane and it will fly from here to Adelaide, you can see the most amazing things below where you’ve got your river like a very thin line and you can see where it used to meander, because where you had the ancient billabongs, where you have got what amounts to a paleo-river underneath, you have much denser vegetation, so you can actually see sort of the scars of where the river used to be.
Otherwise a lot of the paleo rivers have been covered over by dune sands, and in Western Australia, for instance, in the Canning Basin, that whole area is a sand desert, and you’ve got deep sand on the surface, and you have no concept whatever of what there might be in the way of a river system underneath, but when they have a satellite, those satellites can sort of map changes in temperature of the ground below them, and because you’ve got water very often in the ancient river systems, that used to be underneath, it means that they are slightly cooler, and so by just mapping the temperature you find you get a sort of dendritic pattern appearing, which is the actual branching of a river system underneath the desert sands.
Natasha Mitchell: Some would say it’s a great theoretical exercise, looking at the ancient history of water and how it’s co-evolved in this Australian landscape, but the reality is that people are dealing with much shorter time frames in their day-to-day use of the land. So is it unrealistic for people to look back into the ancient history of this landscape, to inform their current day practices?
Mary White: Well I think it’s absolutely essential because when you are doing things unsustainably, the time comes when it’s forced upon you anyway, and you have people right high up in CSIRO saying that to go on as we are doing now in both our land and water management, is just not an option. All I feel is that unless you have a real concept of what the land is capable of, and for that you need to understand where we’ve come from in terms of other geological history of the land
, and unless you take all that into account there is no way that you’re going to be able to do things sustainably, you need this deep time sort of perspective.
It can be necessary to know these things, it’s not just done for fun, because if you’ve had a river flowing through an area, then you’ve got an area of deep drainage, even if it’s been covered over, you’ve probably got underground water draining along that river system, and it might be very important to know for instance, where to put a dam. I think in that latest book of mine I tell a story about someone in an area where there is some very large paleo rivers, and they got the best engineering advice, and they then built a dam, and they were very happy; it was a large and beautiful dam, and it was full of water, and one morning they came out and the dam was empty, and it had a large plughole in the middle and the water had simply gurgled down and got into one of the paleo rivers running underneath and they’d lost it.
Guests on this program:
Dr Mary E White
Author and paleobotanist
Her recent book is "Running Down: Water in a Changing Land"
Published by Kangaroo Press - An Imprint of Simon and Schuster Australia, 2000
ISBN: 0 7318 0904 1