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Lake Alexandrina
LowerLakes2004.jpg
Lake Alexandrina is the largest of the Lower Lakes
Location South Australia
Coordinates Script error: The function "coordinsert" does not exist.
Type Freshwater
Primary inflows Murray, Bremer, Angas, and Finniss Rivers
Primary outflows Murray Mouth
Catchment area 1,061,469 km2 (409,835 sq mi)
Basin countries Australia
Surface area 64,900 ha (251 sq mi)
Average depth 2.8 m (9.2 ft)
Max. depth 6 m (20 ft)
Water volume 1,610 GL (430×10^9 US gal; 350×10^9 imp gal)
Surface elevation 0.75 m (2.5 ft)
Settlements Clayton Bay, Milang, Raukkan

Lake Alexandrina is a freshwater ephemeral lake located in the Fleurieu and Kangaroo Island and Murray Mallee regions of South Australia, adjacent to the coast of the Southern Ocean, about 100 kilometres (62 mi) south-east of Adelaide. The lake adjoins the smaller Lake Albert; together they are known as the Lower Lakes.

Nomenclature

Aboriginal naming

Names reported as being used for the lake by aboriginal people having an association with the lake include Mungkuli, Parnka and Kayinga.

European naming

The lake was named after Princess Alexandrina, niece and successor of King William IV of Great Britain and Ireland. When the princess ascended the throne and took the name Queen Victoria there was some talk of changing the name of the lake to Lake Victoria, but the idea was dropped.

Description

Lake Alexandrina is located north of Encounter Bay and east of Fleurieu Peninsula within the two following South Australian government regions - the Fleurieu and Kangaroo Island region and the Murray Mallee region. The Murray River is the major river to flow into Lake Alexandrina. Others include the Bremer, Angas, and Finniss Rivers, all from the eastern side of the southern Mount Lofty Ranges. The lake is shallow and contains a number of islands near the southern end. Loveday Bay is an inlet located at the south-east of Lake Alexandrina, adjacent to Tauwitchere Channel.

The lake empties into the sea via a channel known as the Murray Mouth south-east of the town of Goolwa, however when the river flow is low the mouth is often blocked by a sand-bar. Originally subjected to tidal and storm inflows of seawater, the lake is now maintained as fresh water by a a series of barrages known as the Goolwa Barrages which cross five channels between the mainland and three islands near the Murray Mouth.

Though connected to the ocean historically the fresh and salt water flows mixed very little, with the lake area remaining fresh over 95% of the time with normal river inflow. Salt water inflows from the ocean would result in relatively little mixing of fresh and salt water, either vertically in the water column or laterally across the flow stream. Hindmarsh Island is reputed to be the largest island in the world with salt water on one side and fresh water on the other. Lake Alexandrina is connected by a narrow channel to the smaller Lake Albert to the south-east.

History

In the Australian Aboriginal 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 large quantities of acid sulphate soils threatened to form. The soils on the lake beds are naturally rich in iron sulfides. When exposed to the air, such as may occur in a time of severe drought, the sulfides oxidize, producing sulfuric acid. The barrages now prevent seawater inflows that have prevented this phenomenon in every drought since the last ice age. A weir was proposed near Pomanda Point where the river entered the lake 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.

Protected area status

Australian government

Lake Alexandrina is part of the wetland complex known as the Coorong and Lakes Alexandrina and Albert Wetland which is listed as a Ramsar site. The wetland is also appears in the non-statutory list known as A Directory of Important Wetlands in Australia.

South Australian government

Lake Alexandrina includes the following protected areas declared under the National Parks and Wildlife Act 1972 - Currency Creek Game Reserve, Mud Islands Game Reserve, Salt Lagoon Islands Conservation Park and Tolderol Game Reserve.

Non-statutory arrangements

Lake Alexandrina is included within the boundary of the Lakes Alexandrina and Albert Important Bird Area which is an area considered by BirdLife International to be a place of ‘international significance for the conservation of birds and other biodiversity.’

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