Lower Lakes Crisis
18 August 2009
Dear Minister Wetherill,
I would like to protest most strongly against the idea that the 50GL of “environmental” water to be released to the Lower Lakes will help avert the crisis of acid sulphate soils. I have attached a graph of Lake Alexandrina lake levels from 2004 to 2009. You will see that the 50GL will only raise the level by about 8cm after the water to be pumped from the Lake into the Goolwa channel is accounted for. This is in contrast to the 1.6m which the levels have fallen from the full state. As you know, the evaporation from Lake Alexandrina is expected to be in the order of 475GL this coming year, so most of the remaining portion of the 50GL will be lost to evaporation within a few weeks.
(click on image to enlarge)
It is disappointing to hear your statement that you are committed to a fresh water solution for the Lower Lakes. Minister Penny Wong has stated that there is not enough water in the whole Murray Darling system to save the Lower Lakes, which would need about 1,000GL immediately, and then an ongoing commitment of further water to maintain the level. This also flies in the face of predictions that we are likely to experience continued dry conditions with low flows to South Australia.
The spectre of acidification of the total water body in Lake Alexandrina is a very real one, and is predicted to occur when the level reaches -1.5m AHD. If this occurs, there will be very little that could survive in these waters. As well, the problem of exposed acidic soils will continue to threaten vegetation, fauna, agriculture, viticulture and societies living in the path of the prevailing wind, which will be laden with toxic dust. The so-called “bioremediation” efforts are unproven and so far have only be tried in a very small area around Goolwa, with the rest of the Lakes being totally ignored. To treat the whole system with this method would be an immense task, which would take time which we do not have at the moment, and is likely not to work in the long term.
This is truly a crisis of immense proportions, similar to that which occurred with the Aral Sea.
I beg that you reconsider your “Fresh Water Only” solution and seriously plan to return the Lower Lakes to the estuarine condition which they have been in the past. A tidal estuary would become a new vibrant wetland supporting biological diversity and thereby satisfy our Ramsar obligations, albeit with a different ecological character. Circulation of the seawater to prevent hypersalinity could be achieved with judicial opening and closing of the barrage gates.
This option would also have the huge benefit of saving the loss through evaporation of 475GL this coming year to 900GL when the Lake is full, water which could be used to restore the River Murray. This is our South Australian water which we do not have to go on our bended knees to the states upstream to allow water to flow down to us. It is irresponsible to allow this precious resource to be lost.
The proposed weir at Pomanda should be a permanent lock, which would need to be high enough to prevent the seiching of seawater over the top. In times of high flow which hopefully will return in time, fresh water will course into Lake Alexandrina as of old.
Looking forward to your response,
Elizabeth Gordon-Mills PhD