Transcript

River system research

Terry Hillman
t.hillman@latrobe.edu.au

Audio

You can also listen to the interview [MP3 11.3MB].

iTunes

Visit this channel at La Trobe on iTunesU.

Transcript

Matt Smith:

Welcome to the La Trobe University Podcast. I would be your host, Matt Smith. And I'm here today with Adjunct Professor Terry Hillman. Thank you for joining me, Terry.

Terry Hillman:

It's a pleasure. Thank you very much, Matt.

Matt Smith:

Now, you're here to tell me about the research you've been doing over a number of years that have centred over the Murray-Darling Basin and the Murray-Darling river system.

Terry Hillman:

Yes.

Matt Smith:

What sort of work have you been doing?

Terry Hillman:

Well, I've been retired from research, 10 years now. So, what little work I do is, really, is through students rather than me. But, I guess, freshwater sets that goes on in this campus and in the Murray-Darling freshwater sets here, which is also on the campus. It's primarily aimed at producing science that backs up how to manage these larges resistances, sustainable resources, really.

So, that's based in freshwater ecology in all its forms. And so, we're basically trying to understand how these systems work; particularly, how they respond to flow patterns and particularly, flow patterns that have managed and manipulated to produce our water supply.

Matt Smith:

Well, tell me about the basin. How big a catchment area we talking about?

Terry Hillman:

Kind of, about a seventh or a sixth of Australia. So, it's quite a space. In that seventh, that probably produces 40% to 50% of Australia's farming production; some of which is irrigated, much of which isn't. And to do that, it uses about 70% to 80% of the water out of the Murray system.

I guess, because that's such a big area, you kind of think of it as a big system. It is a big river in terms of space, in terms of length. But in terms of water—of course, Australia's a very dry continent—and the Murray-Darling Basin's not a seventh or 40 % of the surface area and it gets about five percent of the rainfall for the continent.

So, it's a very small system. In fact, obviously, the Amazon's the biggest river system in the world. And the annual flow of the Murray, if we didn't divert any, if it was just going out to the sea, that flows out of the Amazon about every 16 to 17 hours.

So, our total annual production, comes over the Amazon, one-half times a day. [Chuckles] So, it's a little volume of water but a long river.

Matt Smith:

And how much of Australia relies in that? What's its range use?

Terry Hillman:

Well, it produces about 70% of Australia's irrigated production, much of which is exported, of course. So, it's a critical human resource as well as a pretty good laboratory resource.

Matt Smith:

As far as our cities, Melbourne and Adelaide, relied on it for?

Terry Hillman:

Adelaide relies on it for about, 60% of their water. Melbourne is about to get some, but has never has in the past. But by and large, it's diverted for agriculture.

Matt Smith:

So, what challenges does it present to manage this sort of resource?

Terry Hillman:

Well, just taking that much water out of a river presents problems in itself, of course. And as a rule of thumb, people say that, once you take more than about a quarter of a flow out of the river system, you then start to run into ecological problems that you have to manage.

So, we're well above that mark. We're taking more than three-quarters, probably. And what that means is, of course, we change not only the volume of water that goes through it but, importantly, the seasonal pattern of water that goes through it. And the shape of an annual flood isn't the same as it used to be.

And also, of course, we miss out on things like over bank flows. Floods that would, in the past, have washed in a whole lot of material from the flood plain that feeds a lot of the insects and animals and so forth in the system.

As well as depriving it of water, we tend to deprive it of energy or food as well. And what that means is, even if creatures on top of the food chain, if you like, that are preying on other creatures like the big fish, for instance. Even if you gave them a favourable habitat, which they've always have, but even if they have that, they're still going to be much reduced in volume because of the lack in food going through the system.

It's estimated now, that the biomass of native fish—that the total quantity of native fish in they system is around a 10th of what it would have been, prior to European settlement.

Matt Smith:

But is it a healthy river system, then?

Terry Hillman:

It's healthy in spots. Some of the rivers in the system like the extreme northern ones, there's not much taken out of them. They're pretty much what they use to be and are indeed healthy. I'm involved in a program, which is attempting to use a number of different measures to assess the health of the whole basin and each of its rivers and various sections of each of its rivers at different scales.

It's showing that, by and large, certainly, all the southern parts—the ones that are more heavily populated—they're in very poor condition. And probably, at this stage, going downhill. A 'hole in the sky' idea, if you like. You know what I mean.

Nationally, as you're probably aware there's a whole lot of work going on, on the basin in an attempt to develop, what they're calling, sustainable diversion limits or sustainable yields of water which is the level at which you can avoid serious damage or it's unhealthiness and decline. And that will mean clawing back a lot the water that's currently used for irrigation which I would say, a lot, you know, a significant percentage of that.

The annual flow, and this is before climate change—who knows what it's going to be in the future—the annual flow over a hundred years is about 30,000 gigaliters per year. It is a significant amount. That then, needs to be used wisely, in a planned way, to support the various components of the ecosystem that would have been damaged at the moment.

Matt Smith:

Tell me about the Murray-Darling Freshwater Research Centre.

Terry Hillman:

They're, primarily, attempting to provide the ecological knowledge that's needed; particularly then, to use that water in a way that will support the system. I mean, if you just stop diverting that much and just let it run, it would do some good but it wouldn't be sufficient.

So, in order to be sufficient, it has to be used in a planned way. And to do that, you have to understand how various aspect of river flow affect the animals that live in them. Flowing water is, obviously, a transport mechanism for food from the catchment to these organisms.

It provides signals. For instance, most of their lives, native fishes are stimulated to migration breed by particular aspects of the flow regime. So, that has to be accounted for. And at the same time, we then, have to supply the sorts of habitats that they need to complete that recruitment successfully. So, there's a whole lot of ecological knowledge needed to be able to use the bit of the water that we're trying to use to make the river healthy—to use that in an intelligent way. So, that's basically the sort of research that goes on. And that covers everything from detailed looks at some chemical aspects of the water, particularly, carbon, of course. Because, obviously, carbon drives the system; right through to ecology of various fish species, ecology of insects.

The MDFRC has the most complete collection of freshwater insects in Australia—to do with the Murray-Darling, at least. So, in fact, they have a specimen of everything that's known out of the Murray-Darling system. And that's new, if you're going to measure and see and know for who they are and what they do.

At the moment, we have a number of research people, particularly, research students, fresh graduate students, looking at various aspects of, what are called backwaters or slack waters in rivers. It appears, because they are relatively still or the water is not moving so, that, kind of, supports a whole lot of very small creatures which appear to be key to the feeding, particularly, of larval fish and therefore, to their successful recruitment of the population.

It looks as if we need to keep those little backwater systems functioning in a healthy way, if we're going to get fish through from the egg stage, if you like, through to big fish.

Matt Smith:

Ideally, for a river system to be healthy, should we be leaving it alone?

Terry Hillman:

I guess, if we walked away from the river completely—wouldn't ever go back to what it was, of course because as well as using the water, we introduced a whole lot of organisms that weren't there before. So, there are all kinds of species that are there; some native ones have disappeared and wont be back. So, we've changed it forever, what ever we do but not, desperately.

And sure, if we stopped fooling around. If we took out the dams and stopped fooling around with the water and stopped taking it and using it, it would return to something of it's former self.

We can't really do that, of course, naturally, we have to. Without the production from the water and it's a nice human resource, it supports a huge tourism industry apart from the productive agriculture. That's why we have to have the, sort of, ecological knowledge to be canny enough to manage the system—to look after its ecosystem but at the same time get to use some water and get so share it, if you like.

Matt Smith:

What do you see as the next logical step as to how we should be helping the river system?

Terry Hillman:

Well, we're facing some very serious issues with regard to managing it. Because, as you're probably aware, most of the models now predicting that the southeastern part of Australia will be particularly hit by climate change.

So, the estimates for the southeastern rivers or the Murray-Darling system—which supplies most of the water incidentally because there are no wetter areas—that flows and then will decline by somewhere between, the best estimates are, loose about 15%. The worst, loosing over half that flow. That changes the system completely.

If gives a number of challenges, it means that both agriculture and the ecosystem have to do without as much water as they've had; it also presents particular problems for people who are trying to conserve their systems, trying to manage them to be ecologically sustainable. Because we're really changing the base level of water in the system, if you like. Changing the nature of the river; to what? It's very hard to predict.

If we, sort of set our goals for consolation on what has been in the river in the past, we kind of, finish up with totally 'out of fish' view of life. Because the base flows in the system would no longer support it even though chronic change, obviously, induced by people by and large. It's still something that would affect the ecosystem whether they are there or not.

To give an example, most of the trusted models of climate change are saying that there'll be no more snow on the Australian Alps in about 30 years' time—20 to 30 years' time. Snow is just a sign of rainfall and stuff. In terms of the amount of water in the system, it might not change that much. But what it does change is the seasonal pattern that the river flows in.

In the past, the snows lay there until late spring and you have a melt and you get a spring flush of water through the system. That does several things. It tends to move water around the flood plain which is good for the flood plain and good for the river and the things it brings back. But more importantly, perhaps, a whole lot of organisms produce that annual peak as a signal to migrate or to start breeding all sorts of things.

If there's no snow, two things will happen. First of all, a lot of the small streams in the mountains are charged by the ground water which, actually, comes largely from snow melting slowly and moving into the ground. So, that can disappear. So, it'll become dry. But more importantly, that signal will be gone or rivers will run when the rainfalls on the mountain instead of being stored up in snow.

So, what that means to the system, who knows? We're just trying to find out at this stage. But it's a reasonable guess that it will create quite substantial changes far and beyond the volume of water that's involved, is the timing and shape of the flow, in time, will just foul up some of those signals.

Trying to restore some of these systems into the future is not a straightforward thing. And it's not entirely based on what we've learned from what we know from the past.

Matt Smith:

Terry Hillman, thank you for your time today.

Terry Hillman:

Thank you, it's been a pleasure. Thank you.