Lake Corangamite
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| Lake Corangamite | |
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| Coordinates | |
| Lake type | endorheic, hypersaline |
| Primary inflows | Pirron Yalloak Creek, Woady Yaloak River, Salt Creek, various springs (3 m³/s) |
| Primary outflows | evaporation |
| Catchment area | 4079 km²[1] |
| Basin countries | Australia |
| Max. length | 150 km |
| Surface area | 234 km² |
| Average depth | 5 m (average when full) |
| Max. depth | 7 m |
| Islands | Vaugn Island |
| Settlements | none |
| References | [1] |
Lake Corangamite is Victoria’s largest natural lake, located near Colac in south-west Victoria, Australia in the Lakes and Craters region of the Victorian Volcanic Plains. The lake is hypersaline, and salinity levels have increased dramatically as the lake level has dropped in recent decades. It is Australia's largest permanent saline lake, covering approximately 230 km2 with a circumference of about 150 km.[2] It is listed on the Ramsar list of wetlands of international importance and is very important to the local environment and local bird species.
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[edit] Physical features and hydrology
The waterbody is surrounded to the south and east by rocky outcrops (known locally as the stony rises) which were formed by lava flows from Mount Porndon to the south-west and Mount Warrion to the east. The spectacular 'Red Rocks' maar crater complex overlooks the south west shore. The Mount Warrion flows caused the lake to form by blocking drainage to the east.
As is typical of lakes in the area, the eastern flanks of the lake consist of lunettes formed by wind borne sediments blown from the lake during periods with dry climates.
Flow into the lake is extremely variable and negligible in the driest years. Currently it is endorheic (there is no outflow) but during the wet decade of the 1950s the lake flooded and became connected via a series of wetlands and lakes to Lake Murdeduke and the Barwon River. It has never been completely dry since European settlement,
The main inflows are from Pirron Yaloak Creek flowing from the Otway plains to the south, the Woady Yaloak River flowing from the flanks of the Victorian midlands to the north, and Salt Creek flowing from the plains to the north-west. The Pirron Yaloak has high nutrient loads due to dairy farming in its catchment.
In response to the floods of the 1950s, the Woady Yalloak was diverted away from Lake Corangamite and into the Barwon River. The diversion is managed on the basis of a trigger level for the lake, above which the diversion is enacted. This has not occurred in recent years. Levels have been dropping for decades and it is possible that it will dry completely. In 1980 the salinity was approximately that of seawater [3] and has since risen at least 4x that of seawater[4]. It is believed that for centuries prior to the 1840s rainfall and runoff were similar to those of the 1950s. [5].
[edit] Fauna
[edit] Fish
Aquatic fauna once included fish species such as Short-finned Eel, Common Galaxias, Flat-headed Gudgeon and Small-mouth Hardyhead. These may still survive in refuges such as Pirron Yaloak creek and various freshwater springs flowing from the stony rises on the south west side of the lake. Springs on the south east side have dried - possibly due to over exploitation of the Warrion Aquifer for irrigation. More recently the fauna included brine shrimp and a species of isopod.
[edit] Birds
In the past the lake has supported internationally-significant numbers of Banded Stilts.[2]
The lake was previously an important breeding site for waterbirds. Most recently Pelican colonies occurred at Wool Wool rocks and Vaughn Island. However as water levels have dropped, prey have disappeared and foxes have gained access to the colonies, which have now been abandoned. After receiving substantial grants from the government to undertake conservation works, the owner of Vaugn Island used earth moving equipment to remove habitat such as rocks and remnant vegetation.
[edit] Notes
- ^ a b An Audit of the Ecological Condition of Australian Rivers
- ^ a b Australian Nature Conservation Agency. (1996). Directory of Importanr Wetlands in Australia. (2nd edition, pp.728-9). ANCA: Canberra. ISBN 0-642-21378-X
- ^ W. D. Williams (1995) - Lake Corangamite, Australia, a permanent saline lake: Conservation and management issues. Lakes & Reservoirs: Research & Management 1 (1), 55–64.
- ^ Age Newspaper article - Saltwater haven turns to dust as big dry bites hard
- ^ Water Research Foundation of Australia; 1975 symposium: the 1973-4 floods in rural and urban communities; published 1975
