Lower Lakes & Coorong
The Big Picture
The Murray-Darling Basin is experiencing the worst drought since records began in 1891. Record low inflows to the River Murray through drought and over-allocation are having a significant social, cultural, economic and environmental impact on the Lower Lakes and Coorong region. The unprecedented situation now facing South Australia is that the quality of the State’s water supply could be at risk because of increasing water salinity levels and acidification from exposed acid sulfate soils on the drying lakebeds and wetlands.
Current predictions indicate that South Australia’s climate will be more variable. As a result, we must plan for a future of reduced water availability as well as reducing our reliance on the River Murray, particularly for domestic water supply. The State Government is working with local communities and scientists, technical experts and engineers to:
- Address immediate drought response issues
- Plan for worst-case scenarios
- Develop long-term sustainable solutions.
The risks
Based on water levels at the end of March 2009, CSIRO has estimated over 15,000 hectares of acid sulfate soils in Lake Alexandrina and Lake Albert are acidifying as they progressively become exposed to the air because of falling water levels. A series of chemical reactions occur that generate large quantities of sulfuric acid and metal salts. In extreme cases, this acidification can cause ecological collapse, killing plants and animals and rendering the water unsuitable for any purpose.
In November 2008, the Murray-Darling Basin Ministerial Council approved a management strategy which provides acidification triggers for alkalinity and water levels which will determine if action needs to occur. The triggers are the detection of alkalinity levels at 25 milligrams per litre or if water levels fall to 1.5 metres below sea level in Lake Alexandrina or 0.5 metres below sea level in Lake Albert. Current scientific modelling indicates that these triggers could be reached by early 2010 if the drought continues.
Salinity levels are also increasing throughout the Lower Lakes and Coorong region, and in some areas the salinity levels are now too high for the water to be used for drinking, livestock of even irrigation.
Salt carried along the River Murray from upstream is naturally washed out to sea through the Murray Mouth. However, only a very small amount of water has flowed through to the sea since November 2005. This has resulted in a build up of salt in the Lower Lakes. High evaporation caused by high temperatures has also increased salinity in the region.
Drinking water should have a salinity level of below 1000 EC units, and some recent salinity readings in the Lower Lakes have been in excess of 5000 EC units.
Actions underway
The State Government has implemented a range of actions in response to the current situation and continues to prepare for worst-case scenarios if triggers are reached.
