This article misses the point that it is the geological destiny of the lower lakes to become saline particularly as sea level rises. The barrages are an unnatural attempt to arrest that process. Captain Charles Sturt found Lake Alexandrina to be brackish back in 1824 or whenever. Nearly two centuries later a pipeline has been built from well upstream (Tailem Bend) to the Murray mouth region because it seems to be a losing battle against salt incursion.

I think it's a bit rich for South Australia to demand that upstream water users give up their livelihoods just so the last few kilometres of the river system remain in an idealised state. Meanwhile planned new housing subdivisions near Adelaide will draw on upstream water. As 'Two Men in a Tinny' remarked it's frightening that a million people depend on that pipe. Make it two million in future. It should be a case of Subdivisions vs Coorong mullet but SA says they are entitled to both.

I think a weir should be built across the river at Pomanda Pt near Wellington and the sea barrages permanently opened. The channel to Lake Albert should be bulldozed over once again. A navigation channel should be dredged to Goolwa. Everybody adversely affected should be given the cash to buy a townhouse on the Gold Coast. Australia as a whole will be better off.

The Parramatta River empties into Port Jackson that includes Sydney Harbour. Melbourne's Yarra River empties into Port Phillip Bay.

We don't expect the Yarra River to keep Port Phillip Bay full of freshwater. But we do expect the Murray River to keep Lakes Alexandria and Albert full of freshwater, even during drought.

This is a crazy expectation that has been created by misinformation including from South Australians who think like Peter Smith.

Interesting the Yarra River has 57 per cent of its flow available to the environment. The Murray has a similar level of water extraction with 58 per cent remaining for the environment.

In June 2011, the Yarra was short-listed for a prestigious international environmental award, while the Murray River was being described by activist group, GetUp!, as on the brink of ecological collapse because of inadequate environmental flow.

The national discussion is so one-eyed and ignorant when it comes to the Murray-Darling.

The Murray Darling is a large catchment and the upper Murray and Murrumbidgee snow fed, so most years it can fill Lakes Alexandrina and Albert with freshwater. On average over the 42 years from 1968 to 2010, 5,920 gigalitres a year of freshwater has flowed over Lock 1. That's about 11 Sydney Harbour's full of freshwater each year into the Lower Lakes.

Of course the Southern Ocean could guarantee water for Lake Alexandrina during drought; except the gates have been kept shut to the Southern Ocean since February 1940. That is the 593 gates in the 7.6 kilometres of barrages (think sea dykes) built across the bottom of the Murray River's estuary.

The gates are opened to let floodwaters out, but never to let seawater in. The estuary has been destroyed.

Perhaps it's time to bite the bullet & decide that South Australia is just not a suitable place for large scale human habitation.

If it wants to exist, & even grow, it really is about time it started to pay it's own way. If it can't do that, or just doesn't want to, a moratorium should be placed on any further development of any kind, until it does. The rest of us are already contributing enough to the place.

My little council has spent more on gathering our local rain, for town water supply than has most of SA combined. Time to stop bludging folks. If you want a fresh water dam to play on, go gather your own water. Don't expect productive farmers upstream to go without, just so you can go water skying, in fresh water.

Most Ozzies are very willing to share with their neighbour, but when one neighbour becomes too demanding, & demands others go without so they can have it all, watch out for a savage reaction. I see it developing in many places in relation to the demand for fresh water boating, & cheep water distribution by SA today.

This estimate of "up to" 1000 gigalitres of fresh water that is supposed to be saved from evaporation in the lakes has ZERO basis in reality. Average depth of Lake Alex (at AHD+50cm) is 3 metres. So even in serious (1 in 50 yr) drought when the level drops to AHD it has only lost 1/6th of its volume. And that means open Barrages would only introduce the same amount.

But sea water would not even replace 1/6th of the 1000 GL claim. Being colder and more dense than the fresh water, this sea water would slide UNDER the fresh water and ensure that it is surface fresh water that continues to be evaporated. Marohassy's fantasies have been thoroughly tested at http://justgroundsonline.com/ and found seriously wanting.

1. Regarding the sea pushing in. Seawater will come in under the freshwater. Before the barrages this happened most autumns. The old fishermen say that before irrigation, before the weirs, locks, levees and sea dykes, the Murray River would flog down from September until maybe Christmas, filling the lagoon, then out the mouth. By Christmas flow had usually slowed and water levels dropped right down. Then when the South Westerly wind picked up the sea would pour in through the mouth and work its way across the lake.

So Lake Alexandrina was fresh in spring and summer, but salty by autumn.

What the old fishermen describe is an estuary: a transition zone. In these type of systems salt water comes in under freshwater, and moves across this type of coastal lagoon as what is known as saltwater ‘wedge'.

2. Regarding evaporation: Published studies which take into account meteorological variable and Lower Lake characteristics are in reasonable agreement and give an annual volume evaporated of between 878 and 1083 gigalitres per annum. For information on how this is calculated visit http://www.mythandthemurray.org/calculating-evaporation-from-the-lower-lakes/#more-62

So you accept that sea water will enter as a wedge, Jennifer, but persist with this clearly false and misleading suggestion that up to 1000GL of fresh water evaporation will be replaced by sea water evaporation. This is complete bollocks and Max Reese has demonstrated his incapacity to properly assess what you tell him.

You cannot contest the fact that most evaporation takes place in spring/summer when fresh water flows are greatest. And you cannot contest the fact that the times when modest sea water intrusions took place were in Autumn/winter when evaporation is lowest.

So even if there was no sea water wedge, and all water was well mixed, then sea water could not account for even a third of the total net evaporation. Include the wedge, and factor in the frequency of below average flow events and the REALISTIC potential for replacing fresh water evaporation with sea water evaporation is substantially less than 10% (100GL) and more likely lower than 5% (50GL).

Your claim is 95% BS.

Lance,

If there were no barrages (no sea dykes), during periods of prolonged drought the Lower Lakes would be mostly full of seawater. So during drought the evaporation would be more-or-less 100% of seawater.

During the recent Millennium drought, 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 Lake Albert supplied with adequate fresh water notwithstanding the Snowy diversions and strictly limited allocations for irrigation during the drought.

The South Australian government could have opened the 593 gates within the five sea dykes to let the Southern Ocean in, but instead kept the gates shut tight. This was not reported in the national media, instead, during the drought, television cameras focused on either the receding lake waters or the sand dredge working to keep the Murray's mouth open, conveniently avoiding images of the massive sea dykes in between.

As soon as the floodwaters arrived in the spring of 2010, the government opened the gates to let excess freshwater out.

And Jennifer, only parts of the lake were saltier, not sea salty (50,000EC), during minimal flow periods. Your continued implication that these piddly little two foot tides, when they are there at all, could change the composition of the entire lake do you no credit at all.

Nor does you continued debasing of terminology to the point where you claim a concrete wall with no contact with wave action is a "sea dyke". Any water barrier is defined by the task it performs and for 99% of the time this wall holds fresh water at a level 50cm above AHD. It only holds back sea water during the peaks of storm surges and the very rare times when river flows have ceased long enough for over 500mm of evaporation to take place.

In the Australian context, the only "sea dykes" we have is when the good ladies of Glebe spend the afternoon at Bronte Beach.

Lance

The word 'barrage', according, to the Macquarie dictionary (Macquarie Australian encyclopedic dictionary 2006), is a military term.

The dykes are known locally, and within Murray Darling Basin Authority publications, as the barrages, however, the correct term for an embankment restraining the waters of a river or the sea is a dyke.

The dykes hold back the Southern Ocean and created a freshwater reservoir with a storage capacity of 1,974 GL. The dykes are variously built of earthen embankment, concrete sluices, concrete piers and stop-logs. The Goolwa and Tauwitchere dykes include a lock.

There are five dykes stretching a distance of 7.6 kilometres and they have dammed and damned the Murray River's estuary.

That Peter Smith should say “the natural environment CANNOT be restored…” not only says he acknowledges that the original environment of the Lower Lakes was estuarine, but assumes he has the right to tell the rest of us that we are stuck.

Locks and weirs along a river are one thing, but weirs across a tidal estuary are quite another. Even in 1903 engineers knew that the barrages would cause ‘harm’ to the Lakes, especially during drought. In 1903, “A Report by Experts”, about the feasibility of the barrages warned,

“Supposing the barrage to have been erected, if the supply of fresh water is not sufficient to provide for evaporation, the surface level of the lake will fall below that which is now maintained by the influx of the sea, large areas of the foreshore may be left dry, and the remaining submerged areas become little better than salt swamps. If the supply of water from the upper reaches of the river is not sufficient to keep the lakes reasonably full, the effect of the erection of the barrage as described above would be serious injury to the condition of the lakes instead of being an improvement.”

That ‘serious injury’ included acid suphate soils being exposed in 2009 when the Lower Lakes were allowed to dry down to one metre below sea level because the barrages were kept closed. Sea water at sea level would have kept those soils covered and also would have left enough water in the Lower Lakes for recreational uses to continue through the milenium drought.

It is not too late to restore the estuary should the nation decide the environmental merits are worthy.

http://nla.gov.au/nla.news-article4987833

Taswegian,
I am sorry but your lack of understanding the Lower River Murray is abvious from your post.

Lance,
Thank you for your posts bur as I have found disagreeing with Jennifer is a no – no!

Just to be a pedant Jennifer, in engineering a barrage is not military term. It refers to a specific type of dam.
http://en.wikipedia.org/wiki/Barrage_(dam)

And a Dyke is a levee, which is also as specific type of earthworks.
http://en.wikipedia.org/wiki/Levee

Just so you know the 'correct' terms.
I believe the dams referred to would classify as 'barrages', not dykes.

Peter,
I thought you were the spokesperson for Lock Zero, not one mention about it. I was of the belief that you wanted to construct Lock Zero below Tailem Bend and create a new pool upstream of the new lock and below D/S Lock 1 at Blanchetown, which would protect the pump stations at Tailem Bend,Jervois,Murray Bridge,Mannum and Swan Reach which supply potable water to Adelaide and other areas in S.A.. Remember we must learn to crawl first, that is establish this new pool first then look at the next stage i.e.automating the barrage gates.

Now you are descending to high farce, Jennifer. A barrier that holds fresh water a full 50 to 70cm above AHD is clearly NOT holding back the ocean as you claim. And during this most recent (1 in 100 year) drought the period of zero flow only lasted long enough for the lake level to drop to just below AHD. And that can only mean that 5/6ths of the original fresh water remained in place. If the barrages had not been there then the missing 1/6th could only flow in when the upper half of a tide was greater than AHD +0.5 metres.

That condition only applies for just one hour on the 3 or 4 days each month when tidal range is on that scale. For the rest of the days in each lunar cycle the upper half of the tidal range is much less than AHD +0.5 metres. So for all but 4 hours in each 672 hour monthly tide cycle there can only be minimal intrusion of sea water.

To suggest that these piddly little tides could completely exchange the remaining 5/6ths of the lake's fresh water with sea water in such a limited window is pathetic. Even storm surges will simply push the fresh water to the north before it reverts to its normal state.

The way you have been [Deleted for abuse] less informed members of the rural community with your snake oil is a disgrace. What next, Jubilation T Cornpone?

Spus42,
Peter is 56flood and I am the spokesperson for Lock Zero and I have not mentioned it for a reason as first we must make people realise that the opening or removing the Barrages would be a disaster in the Lower River Murray. A total investigation/study into Lock Zero is vital and we are still seeking that investigation and also the total up-g4rtading of the Barrages.

Lance
Peter R. Smith OAM is 56flood.
From one of my sources Ian Mott who I believe puts it perfectly in perspective: -
I think the impact of tidal intrusion has been overstated because the local tidal regime makes serious intrusions the exception rather than the rule. Given that half of each monthly lunar cycle involves very minimal tidal variation, and 16 hours of each remaining daily cycle also involves either minimal variation or outflow, then high tides can only occur for 1/6th of the year (ie 1/3rd of 50%).
The historical references to continuous fresh water then become a function of pure probability. The lake, due to its shallow nature, was no place for small boats during storm events as the chop would be very dangerous. And when these events coincided with high tides they were also effectively “off the radar”. And that means that any local anecdotal observations of the composition of lake water took place during the more than 5/6th (84%) of the time when no tidal intrusion was present. If peak tidal flows were also likely to produce dangerous flow rates near the populated centres then the interval in which saline intrusions would not be detected would increase to well over 90% of the time.
The strongest conclusion is that historical references to fresh water conditions in the lake are likely to be roughly representative of actual conditions but the sequence of anecdotal observations was unlikely to have picked up the character and scale of anomalous conditions. These anomalous sea water intrusions were unlikely to have lasted longer than 8 hours at a time. And given the distances involved in each transit, could not have extended far enough, under all but 9th decile circumstances (drought and storm surges), to impact on northern lakeshore ecosystems or agriculture.
And that means that the fears of total barrage removal are overstated but the impacts on river mouth closure of a larger tidal prism are such that the barrages need to remain in place until a better solution is shown to be working

Yes, 56Flood, the last sentence of that quote is the critical point. The barrages have played a major role in slowing down the closure of the Murray mouth. Mouth closure is not caused by sediment from upstream because that material would build up in the north of the lake and on the upstream side of the barrages. Mouth closure is caused by sand being swept in from the beach, mostly when storm surges coincide with the inflow phase of king tides.

SA has only one tide each day and they are asymetrical. That is, they have a rapid inflow over 8 hours and a slow outflow over 16 hours. And as the capacity of water to transport sediment is determined by the square of the velocity, the inflowing water moving twice as fast as the outflow, transports four times more sand in than the outflow removes. So the mouth under natural conditions will close up whenever river flows are insufficient to balance the equation.

The larger the tidal prism (the area inside the mouth x tide height)the larger the potential for sand deposition. So the barrages have played a vital role in keeping the mouth open. Removing them without an adequate alternative mechanism in place (see http://www.mdba.gov.au/files/submissions/Ian%20Mott%20-%20Landholders%20Institute.pdf ) will prompt demands for even more buy-backs to keep the mouth open. And that is not in the interests of farmers in SA or anywhere else.

Quite simple in practise, but just about totally impossible for Governments. Step one:- Construct Lock Zero. Step two:- Automate the Barrage gates. Step Three:- At very low flows and drought conditions open the Barrage Gates,allow sea water in ( USING THE ACTUAL YEAR OF 1915 AS A MODEL )which killed the Weeping Willows ( page 49 A Fresh History of the Lakes ) and turn Mannum's fresh river into a salt river and no mention of collapsing the river banks. The Murray Darling Basin rivers flow again as is happening now by using the automated gates and gradually flushing out the system below Lock Zero. Try to correct Lake Albert (The Pirie Street Idea) at Narung and if that fails have a look at Dr. Geddes has suggested by building a canal with a automated gate between the lake and the Coorong. Remember over 90% of the River flows out through the Mouth, very little actually reaches the Coorong.

Spud, has Dr Geddes written up his proposal? If so, do you have a link? I have little confidence in any action that maintains Lake Albert as a closed end system because "sloshing" of fresh water from outside has never worked anywhere unless it is associated with a much greater tidal range than the two foot tides (and less) down that way.

Lake Albert is roughly 20% of the surface area above the barrages so it needs a significant through flow to prevent evaporation derived salinity increases. It wouldn't need to be as high as 20% of total river flows, just enough to completely exchange the entire volume about every 3 years. I don't know what the average depth of Lake Albert is but if it is the same 3m as Alexandrina then the volume is 18,000ha x 30ML = 540,000ML.

A third of this volume (180GL or 493ML/day), discharged much further down the Coorong's North Lagoon, would completely flush the 86,000ML lagoon twice a year and maintain it at similar salinity levels to the lakes (600 to 900EC) which would probably be too fresh for the local species mix. Sea water injected into the South lagoon via a pipe under the dunes could correct this imbalance as it flowed north.

We need to manage the Murray from the mountains down to the sea. There are old irrigation channels that seep and evaporate three times as much water as the remaining irrigators use. In places the system needs to be deepened; to reduce quite massive evaporation, which takes as much as 50% of current water flows.
Many irrigators would sooner have recycled water and its nutrient load; given, it would be vastly more reliable than any river system. We need to build many more small dams in upland areas to force vast quantities of water into the landscape, from where it doesn't evaporate and weeps back into the system during the dry times; thereby vastly extending vital environmental flows!
Particularly, given a climate changed future, where the feast or famine nature of our river system flows, will likely be even more accentuated and exacerbated than now.
We need to shift much of our current food production to Tassie and a seemingly vast untapped wealth of water and suitable land currently just grazed. We need other production strategies for those currently dependant on the Murray, like Algae based bio fuel production, which only borrows water and then returns most of it to the system cleaned up and divested of often problematic nutrient loads.
This would allow many farms and farmers to prosper as never before; and all those towns and villages who depend on them; and, for just a tiny fraction of the water current irrigation demands!
Rhrosty.

Lance there isn't a link it's notes from a meeting nine months after
a colleague and I in August,2009 had presented to the DEH in S.A.. The plan which involved changing Lake Albert from a blind end lake to a transit lake for water being discharged into the North Coorong. The water will be fresh during wetter times,estuarine during dry times. Some of this will flow into the Southern Coorong with "The Narrows" reversing the hyper saline conditions that are affecting the RAMSAR site. As usual we heard no more from DEH as it was a sea water/fresh water proposal for the drought period, Government policy was fresh water only.
He showed Lake Albert on a map "Increase Connestivity" with a channel and regulator and on a second map "Channel Lake Albert to Coorong to allow "FLUSHING".

Peter is more interested in protecting a political position, than recognising that a sensible solution must be found.
In fact he is so vindictively pleased that Lance does not agree with Jennifer that he has completely missed the vital point of the Ian Mott reference.
That is: we need to find a better solution.
This area of SA is affected by its coastal proximity. How much or how little it is affected is not really the issue.
SA is claiming they’re 'victims' of upstream.
They are claiming they should be allowed to be the same as the rest of the MDB when the rest of the MDB is clearly not affected by a coastal proximity.
With good planning and some foresight, SA’s position could be a huge advantage for SA as spud 24, Lance, Jennifer and the AEF are all trying to explain.
The current system with its barrages or dykes (or whatever), has proven to be unsustainable. They need to be either radically upgraded or their use needs to be sensibly rationalised.
It is time to move on and work for a good solution Peter.
We don't actually need more studies; we all already know that it has not been an environmental or human success story.
It’s time to recognise there have been some mistakes made and then we can perhaps work on fixing them.

Spud42,
You need to look at the geography again you need to re look at the desired possition of Lock Zero, near Wellington as it is the River Murray up stream of Wellington that must be protected from sea water invasion.
All major pumping stations that remove water for most of SA are up stream of Wellinton to Mannum.

Chameleon,
Nothing could be further from the truth!
I have sought support from all political parties, support for Lock Zero as I believe the sensible solution is to totally upgrade the Barrages and construct Lock Zero.
Upgraded Barrages would allow for proper management of flows out of the Murray River’s mouth as SA are not
‘victims’ of upstream but ‘victims’ of bad management decisions.
As explained by Lance Boyle the tides are not able to keep the mouth open so other methods must be investigated and yes mistakes have been made and are continuing to be made but in regard to studies one must be done into the feasibility of Lock Zero as I believe then we can move on as Lock Zero is the only method to protect SA’s potable water supply.

56flood,
I thought my geography was fairly good on the area. Refer back to page 3 isn't that the section you are referring to.

Flood 56 or Peter (?)
Which part is not the truth?
a) That the continual political cry from SA is that it has been denied fresh water from upstream (and hence a victim)?
b) That the LRM and the LL and the Coorong are affected by their proximity to the coast and therefore can't be the same as the remainder of the MDB?
c) That some serious mistakes have been made in SA by SA and they need to be fixed?
d) You're enjoying the fact that Lance and Jennifer do not agree on the actual amount of sea water that most definitely did naturally enter the system? (neither of them deny that those Lakes did in fact have sea water incursions) or
e) That almost everyone here agrees that a better solution must be found?
Trying to maintain the status quo down there has proven to be unsustainable Peter.
It would be far better to just move on and accept that your part of the system can use it's proximity to the ocean as an advantage rather than treat it as a way to cry 'victim'.
Work with your natural environment, not against it.
Restore what you can and make sure you protect the potable supply for established communities.
It seems there are people like spud42 who know how to do that.
That is what other coastal communities do.
SA needs to do the same.
Most people who live near the ocean actually like it. Why don't you?

chameleon,
a) My political position is, as I said, I seek support from all political affiliations for a study into Lock Zero!
b) The tides near the Coorong/Murray mouth: -
Please believe me the Southern Ocean tides don’t work in the River Mouth’s future.
I will post that information in my next post.
c) Serious mistakes were made by not only SA and if you are talking about the Barrages at first there were 26 Locks proposed for the River Murray but this plan was altered in favour of instead of the farthest downstream Lock being at Wellington to construct the Barrages which were partly as a trade-off for Lake Mulwala.
d) Regarding Jennifer and Lance, sorry but Ms. Marohasy is incorrect and Lance is correct!
e) A solution MUST be arrived at but it must be in the BASIN’s best interests!
Re, “Trying to maintain the status quo down there” look seriously at the Barrage total upgrade and Lock Zero or any other feasible solution of which removing the Barrages is NOT on the Table.
I regret we CAN NO LONGER work with the natural environment because we have irreversibly altered alter the River Murray.
I love the ocean especially the fishing.

chameleon
b) The tides near the Coorong/Murray mouth: -
From Ian Mott,
I think the impact of tidal intrusion has been overstated because the local tidal regime makes serious intrusions the exception rather than the rule. Given that half of each monthly lunar cycle involves very minimal tidal variation, and 16 hours of each remaining daily cycle also involves either minimal variation or outflow, then high tides can only occur for 1/6th of the year (ie 1/3rd of 50%).
The historical references to continuous fresh water then become a function of pure probability. The lake, due to its shallow nature, was no place for small boats during storm events as the chop would be very dangerous. And when these events coincided with high tides they were also effectively “off the radar”. And that means that any local anecdotal observations of the composition of lake water took place during the more than 5/6th (84%) of the time when no tidal intrusion was present. If peak tidal flows were also likely to produce dangerous flow rates near the populated centres then the interval in which saline intrusions would not be detected would increase to well over 90% of the time.
The strongest conclusion is that historical references to fresh water conditions in the lake are likely to be roughly representative of actual conditions but the sequence of anecdotal observations was unlikely to have picked up the character and scale of anomalous conditions. These anomalous sea water intrusions were unlikely to have lasted longer than 8 hours at a time. And given the distances involved in each transit, could not have extended far enough, under all but 9th decile circumstances (drought and storm surges), to impact on northern lakeshore ecosystems or agriculture.
And that means that the fears of total barrage removal are overstated but the impacts on river mouth closure of a larger tidal prism are such that the barrages need to remain in place until a better solution is shown to be working

Chameleon,
Lake Alexandrina

Using the monitoring station about 1.5km upstream of the Ewe Island barrage as it seems that Boundary, Ewe and Tauwitcherie have a more direct influence on the lower part of Lake Alex. The last 12 month data show:
-starting from a baseline of about 500EC,
-salinities greater than 2000EC occurred on 125 days with the longest continuous period being 47 days during May to July,
-salinities greater than 6500EC occurred on 63 days with the longest period being 25 days in May to June.
-peak salinities of 26,000EC were reached or exceeded about 9 separate times.

Since June the barrage has been operated to reduce the incidence of intrusion so the data is conservative but it does give an idea of the percentage of time that seawater intrusions could have effected the Lakes in the past even in moderately high flow periods

Thanks for the data, Spud, but where, exactly were these readings taken and how far in did they reach? If they were taken just inside the barrage then they tell us nothing beyond the fact that the barrages need repair. What we actually need is a set of simultaneous samples along a couple of transects from Tauwitcherie Barrage to the northern lake shore, and for at least four points in the water column from bottom to surface.

And we need the same along the Goolwa Channel so we know exactly how far these intrusions are getting. The basic geophysics of narrow mouth to the sea, small tidal range, single tide (if any) each day and resulting slow flow speed tells us that normal (non-storm surge) intrusions cannot reach very far before the tide turns.

To draw any conclusions for the rest of the lakes on the basis of data collected at the source of the leakage is not only unwise, it is gonzo science.

Lance as it says 1.5 KM upstream of Ewe Island barrage. Unfortunately now for cost cutting reasons they have withdrawn the monitoring stations at Currency Creek,Finniss River,Clayton,Stony Point and Point Sturt 7 km SE Milang.

On May 22nd. 2011 when spring tides coincided with an intense low pressure system and storm winds to 40 knots. This event caused saline intrusion up past Point Sturt and to Milang and Mulgundawa in Lake Alexandrina. From May22 to July 31 there were 4 similar events but from June 1 the majority of the barrage gates were closed limiting the amount of sea water inflow.

Thanks. If the barrages had been open during those storm events the tidal prism would have been much larger and the rapid inflow would have transported a huge volume of sand from the beach into the mouth that the slower and longer duration outflow would have been unable to correct.

This would have restricted the inflow during both normal and subsequent storm events but the same gradual buildup of sand would have continued.

We need to be very careful about saline intrusion data taken just after a major flood because the mouth is much wider than the norm, the storm surge inflow volumes are greater, and the saline intrusions also extend further.

This is the fundamental inconsistency in Marohasy's position. She is using post flood saline intrusion data to justify an action that will only be even partially relevant in the next zero flow event in 20 or 30 years time. By then the mouth will only be open through a narrow dredged channel which will deliver minimal tidal inflows, as was the case in the last drought. It is only an 8th order issue at best.

Lance

Water levels upstream of barrages dropped to about 0.4m (at low tide) in the last couple of days as a result of the increased gate openings.
This has brought water levels here down closer to natural levels with tidal fluctuations.
No storm, no real winds, no king tides just a normal high tide but salinity at HI Bridge shot up to 41,051 EC and Ewe Island 31,660 at 6am this morning.
Just another example of what conditions would have like naturally in the past.

It was good to see Media Watch clear up any remaining misconceptions about Marohasy last Monday night.
How many times does she have to exposed for what she really is and does, before people stop paying attention to IPA big business shills?
Leave her in the same bin as Carter, Plimer and co.