Combined, the three open-cut coal mines in Victoria's Latrobe Valley are more than four times the size of Sydney Harbour.
The State Government is assessing whether they will all be turned into lakes when they close, which is due to occur by the middle of the century.
Late last year, the Government released a report that outlined plans to fill the mines with water drawn from the Latrobe River system, which runs through the region and connects to the Gippsland Lakes.
The three mines have a water allocation from the Latrobe system and the Government is planning on using that water to fill them when they close.
The Government's mine rehabilitation commissioner, Professor Rae Mackay, said filling the mines with water was the preferred outcome because it would stabilise them.
( Image by https://pixabay.com/users/nedu503-28610/ )