Lake Illawarra

Lake Illawarra is a large coastal lagoon located in the Illawarra region of New South Wales, Australia.

It is situated south of Wollongong, north of Shellharbour, and northeast of Dapto. The lake covers an area of 35.8 square kilometres and has an average depth of 2.1 metres. It is filled by erosion from the Illawarra escarpment through Macquarie Rivulet and Mullet Creek. The maximum volume of water held in the lake is 74,275 megalitres.

On the western shore of Lake Illawarra is the Tallawarra Power Station, a natural gas-powered facility. The power station draws water from the lake for cooling purposes and returns it via an onsite water management system to maintain water quality. The lake environment was previously managed by the Lake Illawarra Authority until 2014 when it was replaced by the Lake Illawarra Estuary Management Committee. This committee includes representatives from Wollongong and Shellharbour City Councils, scientific advisors, community members, and local Aboriginal representatives. The lake receives significant amounts of nutrients and sediment from the catchment, impacting its flora species. In 2007, a permanent opening to the sea was created to address this issue.

Lake Illawarra holds cultural significance as the traditional custodians of the land were the Aboriginal Tharawal and Wadi Wadi peoples. The lake served as an important source of food and spirituality for these communities. It was named Tom Thumb's Lagoon by Matthew Flinders and George Bass in 1796.