<P> A severe drought in 2005 - 2007 triggered major investments, including the Tugun desalination plant and the Western Corridor Recycled Water Project . When rainfall became abundant in 2008 - 2010 and reservoirs were full, the state government decided in 2010 to put the Tugun plant in stand - by mode, operating at less than 10% of capacity, and to close down a new advanced wastewater treatment plant on Gibson Island in order to save power and chemicals . </P> <P> Canberra draws its water supply from three separate catchment systems: The Cotter River catchment, within the ACT; the Googong system on the Queanbeyan River in New South Wales; and the Murrumbidgee River, at the Cotter Pump Station . All these rivers drain into the Murray River which is ultimately part of the Murray - Darling Basin . </P> <P> Some 90% of Melbourne's drinking water comes from uninhabited mountain ash forests high up in the Yarra Ranges east of Melbourne . More than 157,000 hectares has been reserved for the primary purpose of harvesting water . These water supply catchments have been closed to the public for more than 100 years . Melbourne's water supply system is based on the principle that it is better to start with the highest quality source water than having to treat it to reach required standards . According to Melbourne Water, Melbourne is one of only about five cities in the world that has such protected catchments . Water from the forests flows through streams in reservoirs, which provide security of supply for times of drought . One of these reservoirs is formed by the Thomson Dam on the Thomson River located about 130 km east of Melbourne in Gippsland, from where water flows through a 19 km long tunnel through the Great Dividing Range into the Upper Yarra Reservoir and then onto Silvan Reservoir for distribution as drinking water in Melbourne . In recent years, drought has resulted in depletion of much of the water in the reservoir of the Thomson Dam . </P> <P> In June 2007, the Victorian State Government announced a new plan to provide water security for Victoria's growing population and economy by diversifying and boosting water supplies, networking the State's water resources in a Victorian Water Grid and enabling a rapid and flexible response to changing future water needs . The plan includes A $4.9 billion of projects to secure Melbourne and Victoria's water supplies for the long term, including: </P>

Why does melbourne have such good drinking water
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