Are the Lower Lakes of the River Murray historically freshwater lakes?Freshwater has been common in the Lower Lakes during most of the past 6,000 years but seawater intrusions occurred regularly during times of low flows. After 1900, with the advent of significant irrigation schemes in New South Wales, Victoria and South Australia, seawater intrusions became common. Since 1940, the barrages have maintained an artificial separation between freshwater and seawater. Refer to the full discussion paper (266KB) and the proposed flow regulators in the Goolwa Channel, Finniss River and Currency Creek. To date, only the Clayton Regulator has been constructed. None of the options address the fundamental problem of insufficient water in the Lakes. As a result, Milang (on Lake Alexandrina) or Meningie (on Lake Albert) are left high and dry. How much water do the Lakes lose to evaporation?The Lakes lose 750 to 950 GL annually (ref MDBC) which is approximately 4 times Adelaide's annual water consumption. See fast facts for more water stats.
 GL = Gigalitre = 1,000 Megalitres or 1,000,000 Kilolitres or 1 billion litres What are the water levels of the Lower Lakes?See water level charts for average water levels for Lake Alexandrina, Lake Albert and the Goolwa-Clayton Channel.What are the problems confronting the Lower Lakes and Coorong?The main problems are acidification, biodiversity loss, soil salinisation and desertification. Read more.What are the options currently being considered?What is the proposed Wellington Weir?The proposed Wellington Weir is a temporary weir near Pomanda Island that will separate the River Murray from Lake Alexandrina. Read the Draft Environmental Impact Statement. The Supplemental Environmental Impact Statement (EIS) is now available as of July 2009. (EIS is a large 5MB file)What is acid sulphate soil?Acid sulphate soil (ASS) is the common name given to soils and sediments containing iron sulphides, the most common being pyrite. When exposed to air after being disturbed, soils containing iron sulphides produce sulphuric acid and release toxic quantities of iron, aluminium and heavy metals. Read more on acid sulphate soils.What is the acidification water level trigger?This is the level at which acidity being formed in the lake sediments can no longer be neutralized by the alkalinity of the sediments and lake waters. Any water levels below these will expose large areas of acid sulphate soils and any subsequent refilling (including future freshwater inflows or the introduction ofseawater) will likely result in the acidification of the water body. The current modelled critical acidification threshold water levels are minus 1.5m AHD for Lake Alexandrina and minus 1.0m AHD for Lake Albert. What would water levels be if the barrages were opened?Seawater levels would vary with the tides and average 0.18m AHD (ref BoM Victor Harbor datum) Tidal variation for the Lower Lakes would be lower due to the Murray Mouth and channels restricting water flows.  What is the Murray-Darling Basin Authority (MDBA)?The Murray-Darling Basin Authority is a new authority which for the first time gives a single Australian government agency responsibility for managing the water resources of the Murray–Darling Basin. It came into effect on 15 December 2008 when it absorbed all the functions of the former Murray–Darling Basin Commission (MDBC), which ceased to exist.What is paleolimnology?Palaeolimnology is the study of past conditions in lake systems and the use of lake sediments to tell us about past environments. These techniques provide scientific evidence for the presence of seawater in Lake Alexandrina and Lake Albert.What is an estuarine ecosystem?Estuaries are coastal regions affected by both marine influences, such as tidal flows, and riverine influences, such as freshwater flows and sediments. Estuarine ecosystems typically support many biological niches resulting in high biological diversity.How is salinity measured?Salinity is measured according to the electrical conductivity (EC) of the water, in micro Siemens per cm at 25°C (μS/cm). 1 EC unit corresponds to 0.7mg/L of total dissolved salts; 1000 EC = 1000 μS/cm = 640 ppm. The salinity of seawater is approximately 50,000 EC. The salinity at Goolwa is currently approximately 30,000 EC, i.e., 60% the salinity of seawater. For information on salinity in the Lower Lakes, refer to the South Australia Department of Water, Land and Biodiversity salinity study.How much freshwater is available?As of 3 March 2010, the total active (useable) water in storage in the Murray Darling basin is 1,920 GL (Giga Litres), or 21% of capacity (ref MBDA). By comparison, approximately 1,200 GL is required to return the Lower Lakes to full supply level and a further 1000 GL of conveyance water is required to transport the water down the river.  Content on this site is licensed under a Creative Commons Attribution 3.0 License. |
