Letters to the editor: December 19, 2019

Hundreds march across the Murray Bridge road bridge, protesting a plan to build a weir at Wellington and abandon the Lower Lakes to salt water, in 2009. Photo: File.
Hundreds march across the Murray Bridge road bridge, protesting a plan to build a weir at Wellington and abandon the Lower Lakes to salt water, in 2009. Photo: File.

All this talk of the weir at Wellington and the removal of the barrages in the Lower Lakes is giving me a real sense of déjà vu.

What's more is that the information coming out about this is just as inaccurate as it was back in the years between 2006 and 2009.

The lakes were originally freshwater lakes.

The amount of water flowing down the river and discharging to the sea through the River Murray mouth stopped seawater from entering those lakes.

For thousands of years, this was the case.

It was not until Europeans started extracting water from the river and altering the amount of water entering the lakes that seawater began invading.

This occurred from the late 1800s.

The barrages were not built to create a freshwater environment but to preserve one.

Here are the facts as I see it.

Opening up the barrages or building the weir at Wellington won't return the lakes to their original state, as many people seem to think.

Rather, it would change what was originally a predominantly freshwater system into a lake with salt concentration levels higher than the ocean.

If this was to occur, there would be a great risk of salt water moving up the River Murray, compromising the environment - which is protected by the international Ramsar Convention - and risking the water supplies for many South Australians.

I understand that New South Wales is in a dire situation at the moment, but the only thing that will help them is for it to rain, not what the NSW Deputy Premier is proposing South Australia do.

Statements which call for the Wellington weir and removal of the barrages are as ridiculous as suggesting that all the other 3500 man-made structures should be removed from the system.

The men driving piles into the river bed at the proposed weir site a century ago discovered that the piles would simply disappear.

A decade ago the former state government encountered a similar situation when they spent tens of millions of dollars and found no suitable foundation for a weir.

A healthy river system needs flows all the way to the sea and so we must ensure that the Murray Darling Basin Plan stays in place.

Adrian Pederick, state Member for Hammond

Opening barrages would not save water

Many communities, particularly in northern New South Wales, are currently under significant pressure and are struggling due to severe drought.

South Australians sympathise with these communities - we understand because we were also in that position during the Millennium Drought.

While the concept of letting seawater into the Lower Lakes has been raised from time to time, it is important to note that there would be no water savings from opening the Lower Lakes to seawater.

The South Australian government exhaustively explored this option during the Millennium Drought, when falling lake levels and exposure of acid sulfate soils threatened the environment and water supplies.

Opening the barrages would require construction of a permanent weir at Wellington to protect communities that access fresh water upstream, with significant construction and ongoing maintenance costs.

Even if it was technically possible to construct the weir in the first place - there is some doubt that it is actually possible - South Australia would still need all of its entitlement to create the required volume to be passed over the weir to avoid major water quality issues in the newly created weir pool, hence no water savings would be achieved.

While the lack of water savings discounts the legitimacy of any proposal to open the barrages, it should also be acknowledged that opening the barrages to allow seawater into the Lower Lakes would destroy the ecological character of a wetland of international importance.

The action of opening the barrages would be a breach of Australian law.

Peter R Smith, Mannum