Lake Colac is part of the Corangamite basin that was formed in the early Pleistocene and Tertiary during the volcanic movement. Due to the volcanic commotion it had blocked the natural outflow of Lake Colac’s two tributaries, Dean’s Creek and Barongarook Creek causing the rivers to flow into the basin leaving muddy deposits (Williams 1992). Wind has also caused crescent shaped dunes to form creating many shallow lakes and wetlands. The surface area of Lake Colac is about 3,000 hectares and has the circumference of about 33km, which is relatively shallow with an average depth of no more than 2.5 metres (Colac Otway Shire Council, 2002a). It has very different areas of vegetation including the Otway hinterland forests, volcanic plains, farmland and a number of urban settlements (Management of Environmental Quality 2005). It has also been used by the Aboriginal people that goes back to at least 7000 calBP where they could cross the lake in times of drought and the use of eel traps and remains of twenty two skeleton remains from the area are held in the Museum of Victoria (McNiven 1998).
The location of Lake Colac is popular for fishing and water activities, also is an important habitat area providing feeding, resting and breeding coverage for over 20 species of waterbirds, including a huge number of migratory species that are listed under the agreement of Japan, Australia and China protection of migratory birds and habitats that are in danger of extinction (Department of the
