Maroondah Dam

Bushfires burn around Maroondah Dam on February 11. Photo: Craig Abraham

More than 10 billion litres of Melbourne's drinking supplies have been rushed out of fire-threatened dams since Victoria's bushfire nightmare began.

- Contamination feared
- Five dams affected
- Worst affected: Maroondah, O'Shannassy dams

Melbourne Water confirmed this morning it had shifted another 1.3 billion litres out of Upper Yarra Dam to the relative safety of Cardinia reservoir overnight, in a bid to protect the quality of drinking supplies.

That means just over 10 billion litres have been moved since the day that is now known as `Black Saturday'.

Ash and debris from fires can contaminate water, and Melbourne Water managing director Rob Skinner said several of Melbourne's dams may need to be temporarily decommissioned for up to three months if contamination is as bad as feared.

Maroondah Dam and O'Shannassy dam are the most likely to be decommissioned, after being the worst affected by the bushfires.

Mr Skinner said five of Melbourne's nine major dams had their forest catchments affected by the bushfires.

But luckily for Melbourne, the two biggest sources of water - Thomson and Upper Yarra dams - have been largely unaffected by bushfires.

Mr Skinner also warned that the ability of Maroondah and O'Shannassy to collect water could be reduced for up to 30 years because of forest regrowth.

Young trees are typically thirstier than the older ones lost in fires, meaning that dam yields, and Mr Skinner said dam yields at O'Shannasy could fall by 30 per cent by 2040.

O'Shannassy is the source of about 12 per cent of Melbourne's water.

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