Extremely low rainfall in regional Victoria means the switch could finally be flicked on the state's controversial $6.1 billion Wonthaggi desalination plant.

The plant has produced no water since it opened in 2012, but dam levels have fallen by 130 billion litres over summer, which is 2.5 times the average summer loss for the past five years, Melbourne Water says. Melbourne’s dams are at 64 per cent capacity compared to 71.5 per…