The State Government has announced it has placed an order for 50 gigalitres of desalinated water to be delivered next summer.
Melbourne's water storage is now at 63.8 per cent capacity, down from 72.1 per cent at the same time last year.
Water Minister Lisa Neville said the decision was made based on advice from Melbourne water retailers following a "significant decline" in storage levels in the past two years.
"Last year we lost 152 gigalitres of water so this is a really significant decline in our storages so this is a top-up I suppose, a buffer for our storages," she said.
The Government said inflows into the catchment were at 306 gigalitres in 2015, which was worse than average inflows at the height of Victoria's millennium drought, which were 376.
"It will see an impact of $12 a year on each household ... but this is about making sure that we can continue to provide certainly to business, continue to grow jobs, and also ensure that our kids can play on sporting ovals that aren't cracked."
