With a surface area of about 234 square kilometres or 23,000 hectares and a circumference of about 150km, Lake Corangamite is Australia’s largest permanent lake, lying in a basalt depression formed when a lava flow blocked the drainage system. It is overlooked by rocky outcrops, such as Red Rock, formed during the period of volcanic activity which occurred between this area and Mount Gambier eastern South Australia.
The name Corangamite is said to be derived from the local aboriginal word for ‘bitter’ or 'salt water', and was first applied as the name of Joseph Pollock's station in 1838. It refers to the high salt level of the water, usually about three times that of sea water. Lake Corangamite has never been completely dry since European settlement began, although the flow of water in and out of the lake can be negligible in drier years, the evaporating water resulting higher salinity levels. The rising salt levels also results from the diversion of inflowing waters undertaken by the Rural Water Commission of Victoria in attempts to minimize flooding of farming lands adjacent to the lake.
Lake Corangamite from Red Rock.
Lake Corangamite is virtually a ‘closed’ lake. During the wet years of the
1950s the water level rose so much that it nearly overflowed. There is evidence
that before the end of the Little Ice Age the lake was an ‘open’ lake, owing
to the wetter climate at the time.
Beaches of tiny coxiella shells form the shoreline of the lake.
The lake provides a habitat for a large population of approximately
75 bird species which feed on its fish and shrimp, and it is one of the most
important water-bird habitats in Victoria. At the southern end of Lake Corangamite
is Vaughan Island, one of the few pelican breeding colonies in Victoria, and
the lake is also home to strawnecked and sacred ibis and black swans.
Other notable birds of the lake are Australian shelduck and chestnut teal which roost and moult in large numbers, as well as the freckled duck, double-banded plover and the banded stilt.
Because of its rising salinity exaggerated by continuing drought conditions, fish numbers in Lake Corangamite are decreasing, posing some threat to the bird life which feed on them. In better times the lake is home to populations of short-finned eels, common galaxias, flat-headed gudgeon and small-mouth hardyheads. Creeks flowing into the lake contain mosquito fish, smelt, common galaxias and perches, both Yarra pygmy and southern pygmy.