Big budget desal plant mothballed for another year

With many regions still to recovering from flooding, the Victorian government will not order any drinking water from the Wonthaggi desalination plant again this year.

Building was completed on the expensive plant in 2012 at a cost of about $3.5 billion, but again this year the government says the plant is not needed.

The State opposition says the plant costs $700 million annually in running costs and repayments even when not operational.

The plant was ordered during a devastating drought in 2007

Despite being mothballed for another year, water authorities say the desalination plant is "critical infrastructure" to prepare Victoria for a future with less water.

The plant has processed 455 gigalitres of water since being turned on in 2016-17.

The government this week said after four consecutive years of above-average rainfall, Melbourne's water supply for the year ahead remains secure - with water storage levels currently at 91 per cent.

Following independent technical advice from Melbourne Water - based on storage levels, projected weather patterns, and demand, Water Minister Harriet Shing on Monday announced there was no requirement for a desalinated water order for this year.

"While individual seasons or years may see high rainfall, the longer-term trend of warmer and drier conditions is expected to continue," the government said.

Ms Shing said: "Our water storage levels are currently healthy following three wetter than average years, and so an order of desalinated water is not required this year.

"However, the Desalination Plant remains a critical part of meeting our long-term water supply needs - particularly as the population increases."

Melbourne has 10 water storages but the key reservoir is the Thomson and Upper Yarra.

The Thomson makes up more than half of the city's storage capacity and is at 97.8 per cent capacity.

NSW, Queensland, South Australia and Western Australia also have desal plants.