Lake Alexandrina

Lake Alexandrina is a coastal freshwater lake located between the Fleurieu and Kangaroo Island and Murray and Mallee regions of South Australia, about 100 kilometres (62 mi) south-east of Adelaide.

Lake Alexandrina is a coastal freshwater lake located between the Fleurieu and Kangaroo Island and Murray and Mallee regions of South Australia, about 100 kilometres (62 mi) south-east of Adelaide.The lake adjoins the smaller Lake Albert (together known as the Lower Lakes) and a coastal lagoon called The Coorong to its southeast, before draining into the Great Australian Bight via a short, narrow opening known as Murray Mouth.

In Aboriginal mythology known as Dreamtime, the lake was inhabited by a monster known as the Muldjewangk.

Edward Wilson, visiting the lake in the 1850s described it as follows: "Lake Alexandrina is the finest sheet of fresh water I ever saw. Indeed so formidable did it look, with a stiff wind blowing up quite a sufficient swell to make one seasick, that I could scarcely believe it to be fresh. Such is the fact however. It is forty or fifty miles long by twelve or fifteen wide and the shores around it receded into the dim distance until they become invisible, in the way which we are accustomed only with ideas of salt water. Supplied almost entirely by the Murray, the whole lake retains the muddy tinge of which I have spoken, and this sadly detracts from the otherwise beautiful appearances of this magnificent sheet of water."

In 2008, water levels in Lake Alexandrina and Lake Albert became so low that there was a high risk of large quantities of acid sulphate soils forming. The soils on the lake beds are naturally rich in iron sulphides. When exposed to the air, such as may occur in a time of severe drought, the sulphides oxidise, producing sulphuric acid. The barrages now prevent the seawater inflows that had formerly prevented this phenomenon in every drought since the last ice age.A weir was proposed near Pomanda Point where the river entered the lake, in order to protect upriver and Adelaide's water supplies should it become necessary to open the barrages, but this plan was dropped by the South Australian government after a campaign by the River, Lakes and Coorong Action Group highlighted the many environmental problems such a weir would cause.