The Colac supply system provides water to customers in Colac's urban and rural districts, extending as far north as Cressy.
Colac's water is sourced from the Olangolah and West Gellibrand reservoirs, both in protected, forested catchments in the Otway Ranges.
Water is piped 25 kilometres to a service basin adjacent to Colac Water Treatment Plant in Elliminyt where it is filtered, disinfected and fluoridated before being distributed to customers.
Colac's water supply system is discrete — it is not connected to Geelong's supply system.
Despite being geographically closer to Colac, Birregurra is supplied from the West Barwon Reservoir, which also services Geelong.
Birregurra's water is diverted from the Wurdee Boluc inlet channel.
Water is filtered and disinfected at a small treatment plant in Birregurra.
Forrest is supplied with water directly from the nearby West Barwon Reservoir, which also supplies Geelong.
Forrest's water is filtered and disinfected at a small dedicated treatment plant.
Gellibrand's water is pumped from Lardner Creek to a storage tank and treatment plant.
Following filtration and disinfection, it is piped to a clear water storage and then gravity-fed to the township.