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.