The South Australian Government’s claim, as reported by ABC Online, that it cannot save the Lower Lakes and Coorong on its own and is reliant on support from the other Murray-Darling states is simply untrue.
As I wrote in The Land on May 15, the main problem in the lower Murray is developing acidity from the drying of the lower lakes, and the simple solution is to open the barrages at the bottom of Lake Alexandrina and let the area reflood with seawater.
Potential acid sulphate soils (ASS) are common along much of the Australian coastline. These soils formed after the last major sea level rise, which began about 10,000 years ago. The soils are harmless as long as they remain waterlogged. But, if the water table is lowered the sulphide in the soils will react with oxygen forming sulphuric acid.
In the case of the lower lakes near the mouth of the Murray River in South Australia, the barrages built 80 years ago are stopping inundation from seawater; in the same way the dykes in Holland are used to reclaim land. Indeed the Dutch have been managing associated acid sulphate soil problems for more than four centuries.
The drought continues in the Murray Darling Basin and so the barrages should be opened to flood the lower lakes. If a temporary weir was constructed at Wellington, the salt water would not go any futher upstream.
Despite the drought, South Australians have so far been receiving fully 76 percent of their annual entitlement when many NSW and Victorian irrigators have had no water allocation.
It is time the South Australians stopped blaming upstream irrigators for a drought beyond everyone’s control.
Acid Sulfate Soils have been associated with fish kills in coastal Queensland and New South Wales when land was inappropriately drained. For example, about 700 hectares of land near Cairns was drained in 1976, and since then it has been estimated that 72,000 tonnes of acid has flowed into Trinity Inlet.
Approximately 50 percent of the NSW cane land is underlain with potential ASS and inappropriate drainage of these soils caused a major fish kill in the Tweed River in 1987.
NSW farmers have since solved the problem through the implementation of less intrusive drainage and liming.
The can-do NSW farmers got on and fixed their problem, but the South Australians have instead provided money to CSIRO Land and Water to undertake a study, including to, establish the severity and spatial extent of the problem.
In the interim there will be lots of media releases and whinging, including about how they should be receiving more stored irrigation water from the Hume Dam in the Upper Murray or else their lake turns to acid.
There is in fact a simple solution to the problem in the lower Murray, open the barrages and let seawater re-flood the area.
Jennifer Marohasy BSc PhD has worked in industry and government. She is currently researching a novel technique for long-range weather forecasting funded by the B. Macfie Family Foundation.