Note: Where available, the PDF/Word icon below is provided to view the complete and fully formatted document
Impact of the Murray-Darling Basin Plan on regional Australia

CHAIR —Thank you for coming, Ian. Although the committee does not require you to give evidence under oath, I should advise you that this hearing is a legal proceeding of the parliament and therefore has the same standing as proceedings of the respective houses. Thank you for taking the time to be here. We have received your submission and we thank you for that. Would you like to make an opening statement and then be subjected to questions from the committee?

Mr Mott —Certainly. Can I just clarify: has everybody read it?

CHAIR —Yes. You do not have to go right through it.

Mr Mott —I do not have to wade through it all. Good. If you will excuse any hint of a messiah complex, I am here to basically save everybody the price of about nine full teaching hospitals or, on an annual basis, the price of educating 1,800 medical practitioners, which is about $900 million a year. Essentially, the Murray mouth has been one of those things that I really thought I should be looking at but have never had time to, so I have viewed it from a completely blank page and filled in the pages, and went from first principles. I think the key is that what is happening there is almost entirely related to the tidal dynamics where the simple hydrodynamics of the flows there closed the mouth and no amount of expensive fresh water will produce a lasting solution, because the wider the mouth becomes, the greater capacity of the tides and storm surges to close it back up again. It seems quite silly to be using expensive water for an ongoing function; to invest valuable water for what you would call a maintenance function when there is an abundance of cheap salt water that will do the same job. Are you looking at the revised submission or the original?

CHAIR —Submission 424.

Mr Mott —Okay, so you do have the latest one, because in the intervening time I have had a chance to go back over some of the numbers. There were a few assumptions in the first submission, but after proving up the actual tide variances and the impact of normal tidal flows and the storm surges, we are now able to point to a range of flow volumes for different sized pipes. The original mention was for a notional 3.6-metre diameter pipe going under the dunes which would be free of sand and below the wave zone, so the entrance would deliver clean sea water, not sandy sea water, into the Coorong. So there were assumptions made on the basis of a basic 3.6-metre pipe.

I then also compared a five-metre pipe, which is double the cross-section of a 3.6-metre, 5.09, and doubled that again to the 6.4-metre pipe, which runs between Tumut and Eucumbene. The Eucumbene tunnel basically was cut through 22 kilometres of solid rock and here we are talking about one kilometre of pipe sunk into sand. So in terms of measures that we have already taken to deal with water issues, this is comparatively modest.

When we get to a 6.4-metre pipe, I was able to break down the impact of a standard storm surge assumed to be only 20 centimetres. We know they go a great deal more than that. We know that a 40-centimetre storm surge is likely to deliver 40,000 cubic metres of sand into the mouth, but when we look at a 6.4-metre pipe, it will deliver over a million megalitres a year, only from the upper half of the tidal cycle. So whenever the tide outside is above the average height datum inside the Coorong, the pipe will flow and, with a fairly standard set of passive gates, that water can then flow the full length of the Coorong and out the mouth and, thereby, do exactly the same function as a million megalitres of fresh water flowing out the mouth.

I have looked at a couple of other options at the end, when we are looking at the alternatives. That is part 5. Really, when we look at those options 5.1, 5.2 and 5.3, which are basically the usual suspects, buy back three million megalitres of irrigation water to maintain a higher continuous flow, only half of this water is actually going to make it out the mouth at a time when it will serve a hydrological function. In the other half of the cycle there will be very little tidal movement; therefore, the flow is not in a condition where it will scour the mouth. So half of the three million megalitres buyback will not work, so it is a pure waste. All the other stuff about removing the barrages to restore the tidal prism does not work because, the moment the flow stops, the mouth closes and the tidal prism shrinks. The area inside the mouth and outside the barrages: if the mouth was effective or if all means of getting water into it were effective, there would be a much larger volume in that tidal prism but, because of the narrowness of it—as it closes it cannot function, so opening up the barrages further will simply add to the redundant part of the tidal prism, not the effective part.

So when we start looking at the details, I have looked at options like having a pipe at the far south and one halfway—in the Coorong—in each lagoon so it would push the water north, but this option does not really compare well to just sticking one big pipe down the far south and letting a million megalitres go through. It would completely restore the south lagoon—well, it is ecologically dead. So putting a larger pipe in there would basically double the habitat and, therefore, double the Coorong fishery, double its habitat value, and basically make it drought proof because the tides are not dependent on rain cycles or anything else. It will function all the time and it has the added advantage of delivering more water into the system when a storm surge is on, so it will adjust the equilibrium either side of the dune system in real time. When using fresh water, where do you manage it from? From within the barrages, or do you have to make a release from further upstream which takes three weeks to get there? So a pipe system will make real-time adjustments when they are needed so there is hydrological equilibrium as the storm surges occur.

As far as estimating costs on this, I am not an engineer, but the fairly standard process is to start with the basic raw materials of the pipe, which is concrete and reo bar, multiply that by three for what it might mean sitting in a plant, then add a zero for every margin and everything else that goes with it. When we look at that, even if you doubled it again we would be likely looking at $100 million dollars for a single 6.4-metre pipe that would deliver the same amount of water as $3 billion worth of buyback. So the implications are basically that there is an overwhelming duty to examine a viable option, or a potential viable option. It is not a matter of whether it might fit with the prevailing narrative. Once it is there, the process has a duty to investigate it properly, and that investigation should take place before any decisions about further buybacks take place, simply because it is a relevant matter which must be considered for a proper exercise of power. So, yes, that would probably best leave it open to questions now.

CHAIR —Thanks, Ian.

Mr McCORMACK —Thanks, Ian, for your very comprehensive report. I know we all have a real interest in getting the right outcomes for the Murray-Darling Basin and ensuring that water is well managed and used. What drives you to put such a comprehensive report together? What drives your passion for this subject, could I ask?

Mr Mott —A misspent youth. That would probably be a good start. I keep running across things that spark my curiosity and, once my curiosity is roused, I am in a situation where if I do not fix it, it will not get fixed. I am semiretired, so I have the time to reflect on things that other people do not. You probably know yourself that sometimes you are just a pace moron because you are working so fast and with so many variables that you just do not have the time.

Mr McCORMACK —He was looking at me, too, when he said that.

Mr Mott —I will look up there if it makes it any better, but we have all been there, right?

CHAIR —I ask the witness not to criticise Mr McCormack!

Mr Mott —It is almost like we are synergistic, where some of our intellect is essentially dumber than the individual parts unless we have the time to sit down and reflect on all this stuff. It is a luxury. Originally I was just investigating this stuff because it was something I thought I should know about. Then it took over and the tail wagged the dog.

CHAIR —Have you looked at the Lake Albert issues in terms of salinity in the Narrows?

Mr Mott —As far as the Narrows goes, at the moment there is a volume of water above average height in the lower Coorong that will flow out north through the Narrows. I suspect there might be a need for a dredge or something there to open it up to make it function properly. The Narrows is so far from the Murray mouth that serious tidal variation does not happen there unless it is long-term stuff; unless it is a very long-duration wave motion.

CHAIR —There have been suggestions from some people that a similar proposal to the one you are talking about here in the southern lagoon be done from Lake Albert out into the ocean.

Mr Mott —I suspect if there were three large pipes, one either side in the Goolwa and the Tauwitchere Channel plus one at the far end of the Coorong, you would have your three million megalitres and you would have it adjusting in real time. That basically takes all the ecological pressure out of the system. That would free up an awful lot of water, including part of the existing flow. When we look at the annual evaporation load from both Lake Alexandrina and Lake Albert, we are really only looking at about half a million meg.

If we solve the problem of the mouth by not wasting perfectly good water, there is then the capacity to underwrite a freshwater solution for the lakes in perpetuity, basically. I think the normal long-term average flow is five million megalitres out the mouth and if the need for that is reduced then the problem of half a million megalitres to keep Lake Alexandrina and Lake Albert in perfect condition with fresh water is solved. That is the whole point of it: we free up an existing use of fresh water by using sea water in the way that it originally worked so that the artificial landscape behind the barrages can be one of the beneficiaries of the surplus created.

Mr SECKER —It may be of interest to my colleagues that I proposed something like this 10 years ago as a simple farmer option, using gravity and sea water to freshen up the Coorong, which has been under stress for a long time because we have not had the flows down there. My simple farmer background said water would actually help to keep the mouth open and clear. This has been explained quite well, certainly much better than I could because I am not an engineer. Even though Ian says he is not an engineer, he certainly has a far better understanding of it than I would. I was interested in your 2.44, ‘Pipes under the dunes’. It looks like you are going to push water uphill. Why wouldn’t you have it above the AHD line and use gravity to bring the water in?

Mr Mott —It may be flowing through the pipe uphill but the way to the water above it at the ocean—

Mr SECKER —Yes, of course.

Mr Mott —So it does not matter whether it is uphill or down. In fact, any irrigation farmer would tell you that we do not actually need to have the pipe underneath. We could put it over the top, the way every farmer gets his poly pipes over the bund into the thing, and it would siphon. For ecological purposes it is better to have it buried so that nobody can see it, nobody can complain about it and there is no disruption. It is just maintaining equilibrium.

It is interesting: nobody has been able to quantify it, but there is already a flow. There must be a groundwater flow through the dunes already. It beggars belief that you would have up to half a metre variance in summer in the Coorong, between there and average height datum outside, for there not to be a groundwater flow of sea water already taking place under the dunes. So all we are doing is improving the conduit. We do not know how to quantify it and it would cost a bucket of money to find out but it is already happening in a small way.


Mr Mott —Can I ask you a question? Are you familiar with—

Mr SECKER —I represent the Coorong.

Mr Mott —Good, but are you familiar with West Lakes?

Mr SECKER —Yes. That is actually where I got the idea.

Mr Mott —Okay; so it has been around.


Mr Mott —I have been googling crazily to find things. I can work by assumption. I am assuming it is pumped, though, is it?

Mr SECKER —No; gravity. As I understand it, it is just gravity with a one-way pipe so that the water cannot go back.

Mr Mott —So it is exactly the same thing.


Mr Mott —It must prove I am not a raving nutter then.

Mr SECKER —Yes. I have raised this with the state government and—

CHAIR —It could mean that there are two of you in the room.

Mr Mott —I do not trust that guy either!

Mr SECKER —The state government has shown no interest in it and they say it is all too hard because it is under a Ramsar agreement. Have you done any work on how it might have an effect on the environment in the Coorong? It is hypersaline and this would make it pretty well matching with sea water but some people might say that it might have an adverse effect against hypersaline. I am not sure how you can have an adverse effect on hypersaline, but have you done any work on that?

Mr Mott —My understanding is that the condition in the lower Coorong is primarily from diversion from the Upper South East drainage system that has drained a lot of farmland and rather than putting it into Salt Creek they have shot it into the sea. I spoke to the radio people down there and they mentioned this. They favoured just returning that fresh water, but the cost of doing that would be far greater than letting the sea in, bearing in mind that the ecological benchmark, the best outcome, in the Coorong is a wide open mouth so that the tides can send lots of fresh salt water in there. You cannot then argue that sending more of it would degrade the system, when all you can get is a brine shrimp or something in the far end. I cannot see how anybody could possibly trigger the precautionary principle from that, because you would have to establish where there are threats of serious or irreversible ecological harm, when in fact if there is any adverse outcome—

Mr SECKER —You close the pipe.

Mr Mott —you block the pipe. So the precautionary principle is out the window there because it is not a serious threat and it is reversible.

Mr SECKER —There is a reflows program, as a matter of interest, taking water out of that South-East Drainage Scheme. That is just about completed. That will actually put some water into the Coorong, but nowhere near enough, in my opinion.

CHAIR —That is fresh water.

Mr SECKER —It is drainage water, so it can be E. coli of up to 7,000 or 8,000. So it is not totally fresh, but it is better than what is there.

Mr Mott —The other problem with that is that it will be less dense, it will be warmer and it will flow over the top, so it is not going to mix, whereas to get all this stuff circulating it would be better to have one big pipe and get it mixing properly and flowing. If local rainfall had been 1,500 millimetres sometime in the past, that is what the Coorong would have been, but it is not going to get it and not any time soon.

Mr ZAPPIA —Ian, thanks very much for your submission. Have you discussed this with the state government, or anyone else that perhaps does have an engineering background, to in a sense back your proposal? If you have discussed it with the state government, what sort of response have you had?

Mr Mott —No, I have not discussed it with the South Australian government. I was going to write an article for Jennifer Marohasy’s blog on the Coorong and I thought I had better get up to speed. Then when I was halfway through it, I said, ‘Heavens, this looks more like a submission,’ so I turned it into a submission. So that is where it is.

Mr ZAPPIA —You have not run it by anyone else with authority to perhaps peer review your submission?

Mr Mott —No. I am assuming that this will be as good a peer review as you can get. If I have trod on any toes, I am sure I will fluff them out and they will have a crack at me somewhere. That is the easiest way. But it is already working at West Lakes and there are no adverse impacts there—in fact, it certainly seems like a big improvement. Looking at the geography, that area would have been the far end of a closed tidal system as well, which means that it would have been degraded under a 500-millimetre rainfall. The catchment is not big enough. So the problem was already solved for one per cent of the volume of the area of the south lagoon. It works. Basically, from here, I do not know where it goes. All I can do is put it out there. I am not wedded to it, but this seems like as good a forum as anywhere to get it going.

Mr SECKER —I certainly hope that as a committee we can at least recommend that it be assessed and some costings made. I doubt whether it would cost $100 million, but I will not know that until it is assessed. If we can make that sort of recommendation, you would get a lot of support from me on it.

Mr ZAPPIA —Can I just say for Ian’s benefit that I also raised a similar concept, in discussions on the day of the visit to the Coorong, with one of the locals who had good knowledge, and he was not so convinced that it would work. But that is another matter.

Mr Mott —I have had the same, talking to some of the people down there. Others just say, ‘Why didn’t I think of that?’ It is looking remarkably like bleeding obvious, so I can hardly claim credit for it, but if it nudges along, well and good. I have never actually been there, so if somebody wants to tip a bucket on me for that, that is very good, it is a cheap point, but sometimes it just takes an outside eye to notice things that just go through to the keeper. And if I have helped you too, then well and good.

CHAIR —We are right on time. We do thank you for making that submission.

Mr Mott —Thank you. Is there any more we can do to push it along? So from here you do agree that it is worth investigating?

CHAIR —That is not our job today. But you have got a simple farmer and a simple weightlifter supporting you, so I do not think you can do much better than that.

Mr Mott —And a simple grumpy white male in front of you, yes. It may help in your promoting of it that it would take about four grand for a young, thrusting barrister to take out a prerogative writ to compel the basin authority to look at it, because in fact a judge would not be concerned with whether or not it would work; he would merely be concerned with whether it merits investigation. So it is a no-brainer. Thank you.

CHAIR —Thanks, Ian. There will be a transcript of today’s hearing that will be sent to you and if there are any corrections or additional material that you would like us to have, please let us have it. Thanks very much.

[1.16 pm]