Either we fix the lake, or let it die

By Joe Gropler

As chairman of the Lake Bonney Management Committee (LBMC) I have been trying to keep Lake Bonney out of the papers and it has been going along fine until recently.

I think it is important that the true position is explained to enable sensible debate on the future of the lake.
For a couple of years now the LBMC (a committee of Berri Barmera Council) has been meeting on a regular basis to thrash out once and for all the best long term management plan for our beautiful lake.
We quickly found that every second person in Barmera had a plan on how to fix it.
As a committee, we then narrowed down the investigation to a mere 18 different scenarios.
We sought funding of $100,000 so that we could engage consultants.
We achieved this through a tender process and selected Tonkin Consulting (specialists in this field) to help us to find a solution to make Lake Bonney sustainable for the long term.

WE all agreed that as a committee the solution would be based on science and not personal opinion and that at the end of the day we would then move forward to progress the best plan.
It is unfortunate, but a handful of do-gooders are undermining the whole process and are in fact as a result, threatening the long term future of Lake Bonney.
You see, the 'do nothing' option is not really an option, and I will explain why.
Firstly there are 55 tonnes of salt entering the floor of Lake Bonney every day.
Secondly, the lake evaporates nearly its own volume each year (the evaporation rate for the Riverland is approximately 2.25m per year), or much more than 20GL from the lake.
The water that is evaporated leaves thousands of tonnes of salt behind and therefore the lake gets saltier and saltier each year until you would be able to drive on it.
The lake used to keep itself fresher years ago, as fluctuations in river height would remove a bit of salt now and again.
This has been stopped in recent years, as Lock 3 has been micromanaged to ensure that the salinity in Lake Bonney is prevented from coming out through Chambers Creek.
It is since this started happening that the lake salinity levels have escalated.
WHY has this happened? Well, it has been done to protect Loch Luna, Chambers Creek and downstream water users.
Murray Darling rules state that saline discharges into the River Murray are not allowed unless authorised and there are sufficient dilution flows occurring in the river to minimize the impact of the salt slug.
The Lake Bonney Management Committee has been successful in getting Water Minister Paul Caica to refill Lake Bonney on an annual basis. Mr Caica has also committed to look at the long term plans when released (he has a copy). This looks after Lake Bonney in the short term, but it is the long term that is of concern.
Our committee members (bar one) have decided to seek further funding of approximately $30,000.
This would be to look more closely at weir manipulation (to operate the lake between 9m ADH and 10.3m ADH, a rise of 500cm and a fall of 800cm) in combination with an extension to McIntosh Canal (either by extending the existing structure to Loch Luna or by the use of pipes extending over the wall at Lock 3).
This would replace the use of pumps as the water could be siphoned over without cost and be regulated as it does so.
Why do we need to use McIntosh Canal?
Because when there is a high flow of fresh water coming down the river it is important that we can move a large volume of saline water out of the lake and then return the boards in Lock 3 and push the fresh water back into the lake.
We only get a small window of opportunity to achieve this. Chambers Creek has in the past proven that it is too silted up to be able to cope with the volume and also it could be damaged by the discharge of very saline lake water.
FRIENDS and neighbours, unless this committee is given the support of the community the vocal minority will control what happens to Lake Bonney.
We all want our beautiful lake and we want it to be useable. I can’t see another grant coming along in the future, so I say to you all, choose carefully.
It is amazing to think that we could have saved all the scientists a lot of work and just asked our very own resident self-appointed experts.
It would have saved a lot of meetings for the rest of the committee as well. (Not very pleasant meetings, I might add).
If you would like to discuss Lake Bonney with me, feel free to contact me.

m Joe Gropler is chairman
of the Lake Bonney
Management Committee