* * * * *These pelicans are fishing at Blanchetown lock, Number One (of 26), closest to the mouth, after the barrages. Their catch will eventually be affected by the disastrous fish deaths round Menindee.
* * * * *
There are three stories here, all complex. All have the makings of a tragedy, the tragedy that the news right now is circling around — catastrophe today, forgotten tomorrow. But the story in the end will be told by the mouth of the Murray.
The Murray-Darling Basin covers a vast amount of territory in four states and the ACT, far more than most people imagine. In a blog in part about the floods in Toowoomba in Queensland I mentioned that the rain that fell in town during those floods could prospectively have ended up in Lake Alexandrina 2795km away: it’s downhill all the way.
But it wouldn’t today.
It wouldn’t today because in many places the Darling is dry. Between 1945 and 2008 (years at the end of two almighty droughts) there were never any ‘no flow events’. It was always a flowing river continuous from above Bourke to Wentworth where it meets the Murray.
At present where it’s not dry it is often de-oxygenated because of lack of flow, or covered in blue-green or the more dangerous red algae. Those factors will all kill fish (in their millions as it turns out) and the many other creatures which depend on that water, including the people who pipe it into their homes at Walgett (not the dry Namoi any more but bore water), Brewarrina (average annual water bill $1972, the highest in the NSW) and Wilcannia, all significant Aboriginal communities, all already significantly disadvantaged.
Bourke was once an important inland port. The evidence is still there. The paddle steamers with their cargoes of wool going south and supplies going north would tie up to the top rail of its wharf (at left). They could and did (if not for long) ply the length of the Darling and the Murray and from time to time steam out through the mouth to reach Adelaide.
But at Bourke now, and I remember the shock I got when flying in for the first time, they grow cotton, hundreds of thousands of acres of cotton, one of the thirstiest agricultural crops in one of the hottest and driest parts of this country. Representatives of the industry assure us that this is done in a highly efficient manner and that the product is of surpassing quality.
Why is the Darling dry? Because of the very bad drought that has affected western NSW for some time. No argument. The Darling runs almost exclusively through arid country where evaporation eats up 94% of the rain that does fall.
But a second reason is that cotton farmers — operating at all the black dots north of Pooncarie in the map above — have re-engineered the landscape to harvest every available flow. Two cotton-producing companies, Webster Ltd and Peter Harris Inc, have rights to 70% of the water in the headquarters of the Barwon-Darling. More than 80% of water taken from this region is unmetered. There have never been any prosecutions for water theft here. The Queensland government believes in very light touch regulation, whereas, in this arena, the NSW Govt aided and abetted by Barnaby Joyce when he was Federal Minister for Agriculture and Water Resources just seems straight out baldly corrupt.Damming floodwater at Cubbie Station.
Cubbie Station (see map above, near Dirranbandi, Qld) was formed by buying up 51 properties with their accompanying water rights to be the largest irrigated farm in the world today. It’s storage on the Culgoa runs for 28 kms. It has rights to 460,000 megalitres of water — more than the aggregate of every other water user downstream in NSW! — enough to grow 200 square kilometres of cotton.
That could be the case — but as well as the fuss the publicity of these facts has caused, there hasn’t been enough rain to make harvests of anything like this sort, to the extent that the property was put up for sale and sold in 2013 to a Chinese corporation. It seems true that there is no water at all in Cubbie’s storages at present. But there is a great deal, harvested according to a generous interpretation of the law, in the dams and storages of other cotton growers in northern NSW.
And then there was Barnaby Joyce’s brokerage of the Federal Government’s buy back of water rights from Tandou Station (near Menindee, also owned by Webster’s, chief executive Chris Corrigan) in two tranches totalling $112m. The government paid twice the going rate per litre for what is described locally as ’empty buckets’, water rights which are nominal only and never likely to be accessible except during major floods when most people have plenty of water. So $112m was spent on something which will have no possible benefit for downstream users or the general health of the river. Good money if you can get it, and top work thank you Barnaby.
Given the ferociously political nature of these issues, to be even-handed, if you want to read how Michael Murray, the general manager of Cotton Australia, responded to a particular set of criticisms by Sarah Hanson-Young, click here. In terms of lessons in media management it is worth noting how he dodges all the fundamental questions by focusing on specifics. He doesn’t for example have much to say about the appropriateness of cotton-growing for Australia. That is taken as given. He has recently said, “As an industry, we are growing very tired of being ‘the whipping boy’ for all the problems that are being brought on by this crippling drought”.
The ABC research unit offers the following. ‘In 2008-9 … whilst urban water users faced severe restrictions … and the vast majority of the [Murray-Darling] Basin was enduring the peak of the worst drought in living memory, the cultivation of cotton and rice consumed 981 gigalitres of water. This figure equates to the combined water consumption of Sydney, Melbourne and Adelaide (990 gigalitres) over the same period, to produce a crop with a combined value of less than $650 million, in a year when the gross value of national agricultural production was in excess of $46 billion’.
So, number one, the drought. Sure. But two, crazy use of the water driven by politically protected upstream commercial interests. And then there is three: the NSW government’s policy regarding the lower Darling, ‘de-commissioning’ the Menindee Lakes, a casual eco-catastrophe.
‘De-commission’. What a word. The five Menindee Lakes provide a buffer for the Darling, holding prospectively large amounts of flood water which can be released when river flows decline maintaining the health of the lower Darling as well as providing their own natural ecologies, an intriguing destination for Outback travellers and the lifeblood of Menindee, a small local community.
The lakes have also been the main source of Broken Hill’s water supply. (A modest proportion comes from captured rainfall and local natural aquifers.) Water has run through a 140km pipeline providing one important reason for maintaining good supplies of water in the lakes. That pipeline is ageing and needed about $110m spent on it to keep it in good working order. But that was not the decision of the NSW govt. It decided to build a new 270km pipeline from the Murray at Wentworth at a cost of $467m (also costing more than $25m annually, at least in the first four years, to run). 37.4 megalitres a day will be pumped from the Murray. A megalitre is one million litres. That would be 1.7 million litres an hour.
This is a pic of the last pipe going in. It’s done. Thus there is no need for the Menindee Lakes anymore (‘de-commissioned’), cotton growers can up their demands in the Darling headquarters, and the lower Darling doesn’t need to flow at all. All the flow can be used further north. That can happen. Mr Joyce has noted that this would be most beneficial, and that he thinks it should happen. The argument goes that the Lakes are sources of unsustainable levels of evaporation. At present it is intended to leave four of them with a puddlesworth each.
And the Murray?
‘Taking the city’s full allocation from the Murray will not have any effect on the river, according to Broken Hill water policy expert Stan Dineen. “That will have no impact,” Mr Dineen said. “It is only a small amount. [That’s up to 10 gigalitres or 10 thousand million litres a year]. They could lose that somewhere and wouldn’t even notice.”‘ (SMH, 17/4/18)
And that’s the second story: the Murray. What sort of shape is it in?
* * * * *
The Murray also runs in part through an arid landscape. This pic was taken at Truro, 30 kms from the lush vines of the Barossa (misspelt in an early edict from ‘Barrosa’, a battle the British lost in southern Spain in 1811). Just incidentally, for some unexplained reason people had started stringing up soft toys on fences near here.
But it’s almost gibber, stony desert. Truro hill is the last before the endless plains of the north, and somewhere down there in the haze the Murray is ambling, sedentary, often doubling back on itself as though uncertain of its destination, unable to make up its mind.
Not my photo of course, but a very good indication of the nature of much of the river’s course.
Unlike the Darling it doesn’t live off flood waters. It rises in the Australian Alps, nominally at Cowambat Flat not far from Mt. Kosciuszko, living off snow melt and the water that alpine swamps and peat and moss beds hold. The volume of its average annual flow is 10,900 gigalitres, but this is one of these cases where the idea of ‘average’ is plainly unhelpful. Recorded flows 1892-2008:The caption notes that for 2000-08 the average is 3,980GL, one-third of the long term average.
How was it looking a week or two ago? Pretty good, even if there were a few too many jet skis for my taste.
But then hell hath no fury like debates about the Murray River.
Its water maintains huge irrigated industries, from dairy to wine (annual output of primary production round $4.5billion, Basin total round $8b). Then there are the countless millions (one estimate: $345m annually) spent by tourists.
But as well its ‘valley’ contains several thousand ‘key environmental assets’, like the Barmah forest, a small flood plain area believed to be very special to the local Yorta Yorta people, 16 wetlands (of a total of 32,000 in the Basin as a whole) protected as highly important under the international Ramsar convention along with more than 110 species of birds and animals which are threatened with extinction.
And then there is the small matter that in dry years it provides most of Adelaide’s potable water as well as maintaining the towns and industries of South Australia’s lower lakes, Albert and Alexandrina.
There are stakeholders growing out of your stakeholders, all sure that Armageddon will follow if their slice is cut more thinly.
So in we wade.
I would like to take as one text Myth and the Murray: Measuring the real state of the river environment by Jennifer Marohasy published as a ‘backgrounder’ by the Institute of Public Affairs in 2003. According to the ABC’s Michael Duffy: ‘She is the best-known proponent of evidence-based science [apparently a special sort] in the country.’
Ms Marohasy has good scientific credentials and this is her conclusion:
‘We have all heard about the declining health of the Murray River, including poor water quality, dying red gums and threats to the continued survival of the Murray cod — this is the popular view in urban Australia. Along the river, communities believe that the end of commercial fishing, a substantial restocking effort, improvements in on-farm practices and the construction of salt-interception schemes have resulted in a healthier river. The available evidence supports the local view and suggests that, with the possible exception of native fish stocks, the river environment is healthy.’
On salinity she provides evidence that suggests that there is no long term trend in salinity levels in the river as measured at three important locations (significant ‘take off’ points). She ventures beyond the river to its floodplain in a discussion of the impact of irrigation on the groundwater salinity which had destroyed the life of vast tracts of land between Kerang and Robinvale.
135,000ha of land were salt-affected in 1995. Thanks to massive effort, both public and private, the anticipated growth of the salt pans to 175,000ha (with the implementation of the restitution plan; 325,000ha without) has seen them actually reduced to less than 10,000ha.
We need good news, and that’s important news. One thing it means, which she seems to gloss over, is that if you put your back into a problem with some keen thought and common concern you might be able to fix it.
Fish: she acknowledges the take has reduced mightily since the early 20th century when it was common for the annual catch of Murray Cod to be in the order of 1500 tonnes. In 1928, there were 1300 commercial fishermen operating on the Murray. This had started to become economically unviable by the 1930s due to declining fish numbers. In 1993 the number of commercial fishers was down to 28 and now there are none. But, she says, the number of Cod and Silver Perch going up and down the Torrumbarry fishway has been reasonably steady over the 10 years for which she had data (1992-2002).
Her data on turbidity and unhelpful added nutrients like phosphorus show no special trend over the time series she has, and she pooh poohs the claim by the Wentworth Group (of distinguished scientists) that ‘vast numbers of 300-year old red gums are dying along the Murray floodplain due to extreme drought following a severely depleted river flow’. She persuades herself this is not true because the method of assessment was visual and not sufficiently rigorous, but also because the annual remedial flows that now flood the Barmah Forest (above) are correcting the problem.
She has also found a research paper that suggests rather courageously and against the flow of conventional wisdom that: ‘It is well documented that the Aboriginal presence, far from having a benign impact on the landscape, resulted in the extinction of many animal species and maintained the Australian flora, particularly in semi-arid regions, in a fire-mediated sub-climax.’ Her conclusion is that the Barmah Forest only exists because of the control on Aboriginal seasonal burning which resulted from European occupation.
I’d like to believe her conclusion, just as she would like me to. Stay calm. We can put aside grounds for concern: everything is okay. The $13b assigned to correcting the problems of the Murray-Darling Basin is yet another example of irrational and futile government waste. And as far as she goes, she’s convincing and she does have some good points to make.
However, in typical IPA fashion, she begins her paper with a swipe at the CSIRO, the Wentworth Group and other collections of scientists (who swarm around this topic) and bureaucrats, accusing them of not listening to the locals who know and love their river, of relying on trivial evidence and then making it lean in an ideological direction thereby producing deceptive results unnecessarily catastrophising the facts. But if making a case for a pre-existing point of view is a sin, she’s standing in a bucket of guilt which goes well up past her withers.
In two moves that are typical, Ms Marohasy says: one, there is a category mistake. The bad guys treat the Murray as though it was a wild river. It is not, and hasn’t been for more than century when they started up the big pumps near Mildura.
While the Australian Bureau of Statistics report gives the impression that the ‘degradation’ to the Murray River by way of ‘salinity, loss of fish species and algal blooms’ is caused by water diversions leaving too little water in the river, a total water balance is not provided to enable a comparison of the amount of water extraction with the amount of water stored by the dams. In reality, as a consequence of the increase in government storage capacity (i.e., dams) over the last 50 years, the water level in the main stem of the river is unnaturally high for much of the length of river, most of the time.
She also offers a fairly well-rehearsed photo of the Murray to show what it can be like, ‘naturally’: the bed of the Murray at Koondrook downstream from Swan Hill in 1914.
There are five or six of these photos. They were all taken in the drought years 1901, 1915 and 1923, and are all immediately downstream of major irrigation outtakes which were hard at work.
But she’s quite right to argue that beginning with the idea that all engineering works should be removed from the river (there are more than 3000 dams on the rivers in the Basin) is nonsense, but it’s hard to find examples of this notion expressed, especially in government publications. It’s the proverbial straw man.
The second move is to say, there are no hard data. All these scientists at work, but they don’t know what they are doing. They are making conclusions from models and projections the terms of which are usually wrong. A typical complaint: No data are provided to establish an actual link between diversions and river health, and no other measured statistics are provided to give an indication of actual river health.
Well, the clear fact is that those scientists are hard at work. Marohasy’s paper was published some time ago (2003) and maybe there has been massive outcropping of research publication since that time, but a contrary document published in 2012 from one of her bêtes noires, the Cooperative Research Centre for Freshwater Ecology, has a source list of more than 3000 references to support its contentions, starting at ABS/ABARE/BRS (2009) Socio-economic context for the Murray-Darling Basin descriptive report and finishing at Zukowski S, and Walker KF (2009) Freshwater snails in competition: alien Physa acuta (Physidae) and native Glyptophysa gibbosa (Planorbidae) in the River Murray, South Australia. Those references are all related to her topic.
The CRCFE paper is not concerned with agriculture or tourism. It is A Review of River Ecosystem Condition in the Murray-Darling Basin. Its conclusion: Significant degradation of all systems examined.
The authors also point out that: Water dependent ecosystems are complex, dynamic networks with multiple feedback mechanisms that will respond to changes in either the physical or biological environment or the movement of material between components of the system in ways that can be difficult to predict. This places ecosystems in a similar category to the stock market or the human brain. This complexity affects our capacity to clearly ascribe causality to system changes, especially in situations where there have been various applications of multiple interacting pressures applied to the system.
The CRCFE paper makes specific conclusions about particular areas and one is the Coorong and Murray Mouth.
The Coorong and Murray Mouth is the only estuary within the Basin and therefore a critical window on cumulative change evident across the Basin, particularly in the lower sections. …The primary cause of decline across the Coorong, Lower Lakes and Murray Mouth has been identified as reduced inflows, changed magnitude and frequency of flooding exacerbated by drought.
The evidence of the relationship between reduced inflows and declining ecological condition has been well documented and researched. The Coorong and Lower Lakes are listed as a Ramsar Wetland of International Importance, with an Ecological Character Description benchmarked for 1985 when the site was listed. In preparing the Ecological Character Description clearly stated that the character of the site at the time of listing was already ‘seriously degraded’.
The overriding driver of the condition of the Coorong and Lower Lakes is altered hydrology. Reduced flow volumes, reduced frequency and duration of medium-sized flood events in spring, and increased risk of the Murray Mouth closing are the main factors implicated in observed environmental changes at the site.
Half way along the Coorong last January (2019).
As the Murray approaches the coast, it forms the terminal lakes of Alexandrina and Albert (the ‘lower lakes’) before dividing into five channels that flow into the Murray Mouth area.
At the river’s end, the Murray water either flows into the sea or enters the Coorong, a system of tidal lagoons and coastal dunes that stretches approximately 100 kilometres southeasterly from the mouth.
The actual mouth of the river is a relatively narrow, and at time restricted, tidal inlet that flows between a much wider gap in the coastal dunes. This channel is the only open ocean link for the river, and also forms the only connection between the sea and the saltwater lagoons of the Coorong.
The Murray Mouth forms part of the Coorong National Park, and the entire Murray estuary is listed as a Ramsar Wetland of International Importance. Although the environment of the estuary has altered significantly due to European settlement, the lower lakes, Murray Mouth and the Coroong continue to be areas of outstanding national and international conservation value, especially as a habitat for birds. Stormboy for example.
These are the facts as presented by Bruce Thom, Chair at the time of the National State of Environment Committee.
One [Murray-Darling] Basin Plan objective is for the mouth to “remain open at frequencies, for durations, and with passing flows, sufficient to enable the conveyance of salt, excess nutrients and sediment from the Murray-Darling Basin to the ocean”. A target for the mouth was for it to be open without the need for dredging in at least 95% of years. But this target is far from being met; more realistically we estimate that the mouth will require dredging in at least 95% of years.
But how permanently was the Murray mouth open away, or over time was it periodical, and therefore something we don’t need to worry about? Was the mouth open or not, for example, when Sturt came on it in 1830? A vocal and vehement group surrounding Ms Marohasy say, no. He had trouble getting through the mud flats, and the opening was closed. But from Sturt’s journal: ‘The entrance appeared to me to be somewhat less than a quarter of a mile in breadth. Under the sand hill on the off side, the water is deep and the current strong. … The mouth of the channel is defended by a double line of breakers.’ The natural closure of the mouth may well be possible, but this is not the evidence I would choose for confirmation.
But, some say, that issue is only a symptom. We need to get on to the real problem. ‘The blocked Murray mouth has become a symbol of greed, and unsustainability. This has spurred water reform. But this is misguided and ignores history and the nature of barrier estuaries.’ This comes from the ‘Myth and the Murray Group’. Where they want to focus attention is on the estuarine nature of the lower lakes. Are they a changing transition zone between salt and fresh water influenced by tides, wave patterns, seasons, floods, droughts, or are they and have they always been fresh?
In 2006 water levels in Lake Alexandrina fell precipitously from 0.85 metres above sea level to -1.10 metres below. There was simply not enough water in upstream dams to keep both Lake Alexandrina and the adjacent smaller Lake Albert supplied with adequate water. And this is what the Goolwa Channel looked like.So why didn’t the sea rush in to accommodate this variation in levels?
Because of the Barrages. The five Goolwa Barrages, 7.6 km of them in total, were constructed in order to reduce salinity levels in the lower reaches of the River Murray, Lake Alexandrina and Lake Albert. From the 1900s, with the advent of increasingly large irrigation schemes, landowners along the lower reaches of the river strongly urged the construction of these barrages, primarily to keep the water fresh in the lower reaches of the River Murray, as well as Lake Albert and Lake Alexandrina.
Work commenced in 1935 and was completed in 1940. Their impact is to cause an increase in water level of approximately 50 cm as far upstream as Lock 1 at Blanchetown (274 km from the mouth).
So, from one perspective anyway, ‘instead of being a healthy estuarine ecosystem of 75,000 ha, characterized by mixing of brackish and fresh water with highly variable flows, the barrage construction has transformed the lakes into freshwater bodies with permanently raised water levels and distorted ecology’.
The first part of this view is confirmed by early maps. Like this one, the first: John Arrowsmith 1838.
But there’s another equally vehement point of view. Contrary to what many believe today, salt water intrusions into the lake environment were not common until after 1900 when significant water resource development had occurred in the River Murray system (Sim and Muller: A Fresh History of the Lakes to the Mouth 1800-1935). This study describes the sense of South Australian injustice at the consequences of the Victorian and NSW irrigators and essentially makes a historical case for the existence of the barrages. They were essential for a fair water deal for South Australians, and even so Victorians could take less out of the damned Murray.
And as Bruce Thom writes they provide major contribution to the closure of the mouth. The tidal basin pre-barrages was approximately 100 square km and post-barrages around 10. As a consequence the power of the tidal exchange was greatly reduced. Along with this reduction and the progressive extraction of river flows upstream, sand from the sea began to accumulate at the river mouth. The river started to choke such that in the early 1980s and again during the millennial drought it closed. Sand from alongshore and offshore was feeding into the entrance so that dredging was required. We now know that only major flood flows such as occurred in late 2010 can flush the sand from the entrance. Massive sand volumes within the entrance have further weakened tidal flows and the sand keeps coming once flood flows subside.
So, should we prop up an artificial freshwater environment which generates these negative consequences? The people building the housing development and marina at Goolwa think so. So do the people working the farms which surround the lakes. So do the citizens of Adelaide whether they realise it or not, because only this way can the fresh quality of the backup supply of their drinking water be guaranteed.
Or should we join the climate change deniers who have chosen to make the estuarine nature of the lower Murray an issue, and open the barrages, especially the Mundoo barrage which lines up with the mouth and which would help significantly with scouring to keep the entrance open? The silting of Lake Alexandrina would be significantly reduced. It might even help to save the Coorong.
What’s the official line? This is from a paper ‘All about the barrages’ published, but not endorsed by (!, so cautious), the Murray-Darling Basin Authority in 2011 and updated in 2017. The ‘Key Messages’:
- There are different opinions on whether the Lower Lakes were predominantly freshwater, estuarine or saline before European settlement. However, the weight of evidence shows that the Lakes were mainly fresh, with short periods where some flows from the sea entered the Lakes.
- The barrages are not the only cause of ecological change in the Lower Lakes; decreased flows from upstream usage has a big impact.
- Removing the barrages might have some limited environmental benefits, for example, preventing acid sulphate soils in the Lower Lakes area during severe droughts. At the same time though, this would allow sea water to flow in causing drastic changes to the ecology. It would not return the environment to a ‘natural state’ without significant reduction in upstream water usage. A natural estuarine environment – where substantial quantities of fresh and sea water mix – would only be returned if the natural end-of-system flows were returned.
- Removal of the barrages would not reduce the need for freshwater flows into the lakes, which are not simply ‘lost’ to evaporation, but rather flush salt from the entire system and also provide base flows for water delivery and environmental benefits along the entire river.
The authors point out that:
It is true that the construction of the barrages has significantly changed the ecology of the Coorong, Lower Lakes and Murray Mouth; particularly in times of drought. However, simply removing the barrages would not reinstate these original ecosystems. Firstly, we must factor in the effect of the development that has already taken place in the Basin. Water used for irrigation, agriculture and drinking has significantly reduced flows from what would have been the natural situation, and it is not practical or desirable to stop these activities.
And neither it is. But …
* * * * * * *
It wasn’t me, said the Minister.
As the Minister travelled past residents with placards in hands, the wash from the speed boat stirred up the dead fish causing the crowd to cover their noses.
After avoiding the 150 protesters gathered, Mr Blair met with a select few in a different spot 400 metres upstream amid a heavy police presence.
‘It stinks, it’s rotten, it’s putrid. And it’s not just in the river, it’s in our water systems through town,’ chairperson of the Menindee Barkandji Elders Group Patricia Doyle said. ‘When you shower you can smell this water. Drinking this water? It’s awful’.
Darryn Clifton from the Darling River Action Group said Mr Blair was being disrespectful. ‘A good mob of people turned out here today to listen to what he [Mr Blair] had to say and he came here and said nothing.’
A spokesperson for the Minister later denied there was ever an official event organised with locals. Minister Blair said he had not been responsible for the water flow levels.
It was me, said the Federal Drought Envoy!
“We have taken water, put it back into agriculture, so we could look after you and make sure we don’t have the greenies running the show basically sending you out the back door, and that was a hard ask,” he said in the recording.
“A couple of nights ago on Four Corners, you know what that’s all about? It’s about them trying to take more water off you, trying to create a calamity. A calamity for which the solution is to take more water off you, shut more of your towns down.”
* * * * * * *
And what about the Coorong? What will happen to it?
The Coorong gets gradually more salty as it runs more than 100 kilometres from the north lagoon down to the south, and as that happens the biodiversity changes too.
“As you come down that gradient the biodiversity changes from being lots of little fishes at the top end, and when you get to the south lagoon there’s just one fish left. In hyper saline water, three times as salty as the ocean, it’s really salt tolerant,” Mr Paton said. “Some people would know it as whitebait, but it’s hardyhead. There’s one prominent invertebrate, it’s a little chironomid, and there’s one key aquatic plant, a plant called Ruppia tuberosa. Only three living things. …
Your best post yet David. Bravo. I shared it on Twitter. All Australians need to read it.x
This is well written and researched as usual. It’s further evidence that the whole country is Edward Kangaroo; roo ted.
Part of what facinates me regarding the fish kill at menindee is that the menindee lake scheme acts as a large fish trap, there are vertical slot fishways on weirs in the lower darling at burtundy, pooncarie and weir 32 menindee. While many migh draw attention to the so called mismanagement of the menindee lakes and that they have been full twice in recent years and apparently drained, before the menindee lake scheme the lakes wouldn’t have filled that often, but they would have drained naturally that quick.
The problem is fish are unable to move further upstream, as they can not get past the menindee main weir, the natural flows that the fish required to migrate up the darling from the murray are now diverted into the lakes. This will have major impact on fish that have used such floods migrate to spawn, as simple search of silver perch (bidyanus bidyanus) warrego can reveal… if these fish are unable to get from the murray to the warrego to spawn? Critically endangered status!
For the menindee lakes to be a nursery habitat for native fish firstly they would have to be able to access the lakes, but currently that is not possible as neither the menindee main weir or the lake menindee outlet regulator allow fish passage. This only leaves fish upstream of the menindee main weir to be able to access the lakes? Oh they are unable to do so as yet again the man made structures of the menindee lake scheme don’t allow fish passage and unfortunately many of the manmade structures are undershot design weirs that have major adverse impacts on fish, eggs and larvae that unfortunately pass through them.
Anyone with any experience in breeding native fish will be aware of plankton ponds or artemia, it isn’t the amount of water that the menindee lakes have been modified to hold that makes them the nursery habitat of native fish, it is the production of phytoplankton and zooplankton when the lakes first fill is what makes them nursery habitat. And that is only a benefit for mere months, providing that suitable volumes of plankton rich flood waters are allowed to flow the lower darling to the murray at the right time year to provide conditions suitable to entice fish up the lower darling from the murray where they get trapped between weir 32 and the menindee main weir…
Thanks for that thoughtful comment Boots.
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