The Murray & Securing our water supply

[rhino]

The lower lakes were not really seawater as such before the barrages were built. Lake Alexandrina, between Point Sturt and Point Mcleay, is actually quite shallow, and before the level of the lakes was artificially raised by the barrages, this rise in the lake bed acted as a sort of natural barrage. Sea water did get through, but it was mixed with the (majority) fresh water and was not straight seawater. Although there have been fossils of sharkes, etc, found in the cliffs near Blanchetown, these are from millions of years ago, not 100s of years ago.

Before the lower lakes can be flooded with seawater, the weir at Wellington would have to be built, which is another huge controversy. The people who live around the lakes don't seem to want the weir to be built, and they don't want seawater pumped into the lakes, but they don't want the lakes acidifying and drying out either. Go figure. The weir will not actually be at Wellington either, from what I understand, because of the great depth of the river there. It will be built at a much wider, shallower place in the vicinity of Pomanda Island.

If seawater is pumped into the lakes, it will, in fact, change the whole nature of the area. Pumping water out of the lakes to create dairy pasture will cease (it's declining now due to the drought, but when the drought breakes, how long will it take to flush the salt out of the lakes?).

[Wayno]

i believe the main issue with the wellington weir is that people who have boats moored immediately upstream won't have ready access out to the lakes (but i could be wrong). Quite frankly, if that's the main objection to the weir itself then it should be built if for no other reason than to hold additional fresh water in the river itself.

I understand the dairy pastures won't be able to pump direct from the lakes, but i believe the govt is already underway with building a freshwater pipeline around the lakes for the local communities, which presumably will be usable by farms as well.

Working on what basic information is available, it seems that flooding the lakes with sea water is not such a bad result. Even if/when the drought breaks should we then revert to purely fresh water in the lakes - what would be the benefit?

so many layers of lobbying and politics - what a mess!

[rhino]

Working on what basic information is available, it seems that flooding the lakes with sea water is not such a bad result. Even if/when the drought breaks should we then revert to purely fresh water in the lakes - what would be the benefit?

Storage. Without the use of the lower lakes for storage, a huge amount of fresh water will flow over the Wellington Weir (if the lakes are kept as seawater, the temporary weir will have to be permanent) and then over the barrages into the sea. The pipeline from upstream of the Wellington Weir will be taking water out of the river system, and the lakes will not be available for storage and drawing off fresh water. What will actually happen is that the salt water, being more bouyant, will sit above the fresh water coming over the weir, and it will be the first water flushed out over the barrages. How long it would take for the lakes to revert to fresh water by this process, I don't know.

[Wayno]

there's also discussion of a weir/barrage near clayton - what's the purpose of this?

[Wayno]

i found this neat pikkie of the current barrages and proposed weirs. It shows all 4 natural inflows to the lakes - the murray river, currency creek, finnis creek, and of course the ocean...

lakes_map.jpg (85.41 KiB) Viewed 2781 times

[rhino]

there's also discussion of a weir/barrage near clayton - what's the purpose of this?

I would hazzard a guess that the purpose of the Clayton Weir is to provide freshwater storage for water flowing down the Finniss River and, to a lesser extent, Currency Creek. These watercourses are fed from the Adelaide Hills and southern Mount Lofty Ranges - the wettest part of South Australia - and as such there is more likelyhood of them flowing (particularly the Finniss) than any other rivers flowing into the lakes. A weir at Clayton would create a freshwater storage pond between it and the Goolwa Barrage, as can be seen from the map in your subsequent post.

[Wayno]

interestingly, i've heard little talk in the media about The Coorong, or perhaps it is implicitly included when the govt/media say "Lower Lakes"?

The Coorong is on the sea-side of the barrages, and is presumably fed by salt water from the ocean? or is it freshwater (fed by ocassionally opening the barrages)?

[rhino]

The Coorong is on the sea-side of the barrages, and is presumably fed by salt water from the ocean? or is it freshwater (fed by ocassionally opening the barrages)?

The Coorong is brackish water - salt water from the sea mixed with fresh water from the river. Since the river stopped flowing to the sea a few years ago, the fresh water stopped flowing into the Coorong, and then the river mouth closed up completely, so the salt water couldn't get in either, and the Coorong started to dry up. For several years now, there have been dredges at the Murray Mouth, fighting to keep it open, but they can't seem to keep it wide enought or deep enough for a satisfactory ammount of water to enter the Coorong. What salt water makes it into the Coorong Channel (the bit between the Murray Mouth and the Coorong proper) cannot make it all the way into the Coorong before the tide turns, and it all flushes out again. With the river flowing out through the mouth, the water level remained that little bit higher, and enabled water to flow through the Coorong Channel more easily.

[Wayno]

this is probably a stupid idea, but surely the cost of the wellington weir ($110+m) could be used to build/operate a couple of small desal plants very quickly and pump "fresh" water into the lakes for the next 2+ years?

The trial desal plant at Pt Stanvac only took a couple of months to install. It produces approx 100,000 litres of 'high-grade domestic quality' water per day. Reduce the desal'ed water quality and i bet that volume could easily be quadrupled.

Also, i'm not sure how much water is actually required to cover the lakes area and avoid the acidification problem, but given the drop dead date for flooding with sea water is ~Feb 2010 we could start pumping in desalinated water from mid-2009 24hours a day 7 days a week....

[rhino]

That sounds like it would work, Wayno, well done. The local council at Marion Bay built a desal plant last year for $500K, so if you take that out of $110million, there's a lot of money left for power to run the thing, especially if green energy can be used. I wonder if a small power station in the sea, using wave energy, would work down there - the waves seem to be constant and quite powerful down on Goolwa Beach.

[rhino]

From today's Adelaide Now:

Garrett to make weir call
MARK KENNY, POLITICAL EDITOR
January 08, 2009 12:30am

ENVIRONMENT Minister Peter Garrett will reveal today whether the South Australian Government can flood the Lower Lakes with salt water and build a weir at Wellington without an environmental impact statement.
The Advertiser understands Mr Garrett is considering whether he has a responsibility to intervene under the terms of the Environment Protection and Biodiversity Conservation Act.
An affirmative answer would mean the SA Government would be required to submit an environmental impact statement to Mr Garrett before any works could commence.
With the Lower Lakes under severe stress from a lack of fresh water, some ecologists believe the only solution is to remove the barrages which keep salt water from entering it.
But critics argue that allowing salt water into the predominantly fresh-water environment would irreversibly change its ecology.
While the SA Government is yet to decide on the measures in any event, experts predict Mr Garrett will conclude an EIS is necessary given the global significance of the wetlands.

[Wayno]

yep Rhino, as suspected - no decision as Garrett wants an EIS to be done (which will take months). Why the heck one has not been done already is beyond me - a comical bunch of amateurs...

From ABC Online

Decision on sea water in lower lakes postponed

Salt water won't be flowing into the lower lakes in South Australia any time soon.

Environment Minister Peter Garrett has announced that there will be further environmental assessments before any final decision is made.

But Greens Senator Sarah Hanson-Young says that a decision needs to be made now.

"I'm glad to see that the Minister hasn't just given it a green light without an environmental impact assessment, but what I am disappointed about in is that there's no indication about what either the South Australian state or Federal Government will do in securing that fresh water that we all know is what is desperately needed," she says

[Wayno]

Can't believe the fed govt is going to throw $42b at the populus to 'maybe' postpone a recession, when they could easily solve a major part of Australia's water woes for a quarter of that amount.

Is it just me or does something smell funny here?

[stumpjumper]

In reply to myself, I can add...

Water Security Minister Karlene Maywald announced on Tuesday the purchase of 35 gigalitres of water for $75 million. I usually pay 88c per 1000 litres for filtered tap water, but Maywald's purchase of river water cost $2.14 per 1000 litres.

I contacted Maywald's office about this, and when I finally got to speak to someone who knew what was going on, she said that the water Maywald purchased should not be seen as equal to water through the tap. It is not actually wet water, but is 'virtual or prospective water', and its existence depends on rainfall.

So rather than buy water, Maywald has bought entitlements to water should that water come into existence.

The problem is that she is buying licences from willing sellers. If an irrigator holds three licences originally granted free by the government allowing a total of say 3 gigalitres, but is restricted to say 1 gigalitre for the foreseeable future, they are selling say a one gigalitre licence for $2 million dollars. There's actually no real water involved, nor is there likely to be.

This was not explained in the media release, which stated that Maywald had 'bought 35 gigalitres of water for environmental flows'.

I suppose that the government now owns the water licences (most of which were given to the licence holders free of charge) and the water they might represent.

I asked whether any of the money came from the $50 million the government has collected from the River Murray Levy. Only $1.4 million of this has been spent on buying water licences (and the virtual water they represent etc etc). $45 million has been spent on reports and consultants to look at ways of saving water.

It looks like the only thing that flows through Maywald's office is cash.

By the way, does anyone remember Howard saying that the proceeds of Telstra 2 would be applied to the Murray Basin problem?

Why are our politicians hydrophobic??

[Wayno]

stumpjumper, i can only add one word to your posts - *sigh*