Melbourne’s water supply comes primarily from dams and reservoirs and water from the Victorian Desalination Plant which now provides an essential role in our city’s water supply.

Why we need a desalination plant

Victorian desalination plant
The Victorian Desalination Plant at Wonthaggi, in Victoria's south east.

The impacts of climate change bring more unpredictable weather and with more people wanting to call Melbourne home, by 2030 over 6 million Melburnians will need water every day. We are in the decade that matters when our demand for water could outstrip our supply, particularly in the drier years.

That’s why at Melbourne Water, we have been taking action and planning across 50-year time horizons to manage and protect this precious resource for our city.

The Desalination Plant was announced as a project during the Millennium Drought when water storage levels were critically low (16.5% in our largest reservoir). It can now deliver up to 150 billion litres of high-quality drinking water a year. That’s around one-third of Melbourne’s annual water needs – or around 60,000 Olympic swimming pools.

But because it can only meet part of our annual water demand, it needs to be used proactively to:

  • build a buffer in our storages, by regularly topping up our reservoirs
  • take pressure off our reservoirs during drier periods and droughts.

And we must keep looking to other resources to supply more, ensuring we have enough water today, tomorrow and for generations to come.

The Department of Energy, Environment and Climate Action manages the contract with the plant’s operator, AquaSure.

Take a look at the plant from above:

Annual desalinated water order

Each year the government decides how much water is needed from the desalination plant to support Victorians for the year ahead. On 1 April 2024, the Minister for Water announced no desalinated water order would be placed for 2024-25.

This decision was underpinned by carefully considering:

  • current water storage conditions
  • projected water demands
  • possible future climate conditions
  • the balance between managing security of supply and minimising customer impacts.

For more detail, read our technical analysis:

The desalination plant is critical infrastructure to prepare Victoria for a future with less water. Our desalination plant has supplied 457 GL of water from 2017 to January 2023.

Although it's currently not switched on, the Desalination Plant still plays an essential role in securing Melbourne’s water supply in the long term.

How desalination works

desalinated water outlet at Cardinia
Desalinated water entering Melbourne’s water supply network at Cardinia Reservoir.

The desalination plant removes dissolved salts from seawater, using a reverse osmosis process.

This produces high-quality drinking water that meets our strict quality requirements (like all our water), including standards set by the:

  • Australian Drinking Water Guidelines
  • Victorian Safe Drinking Water Act
  • World Health Organization.

Before entering Melbourne’s water supply system:

  1. Water quality is first tested at the desalination plant in Wonthaggi, and again at all delivery points.
  2. Desalinated water travels towards Melbourne through an 84-kilometre two-way pipeline – with pipeline offtakes enabling South Gippsland and Western Port to receive water from the plant, and from Melbourne, if needed.
  3. Desalinated water enters our supply network at Berwick and flows on to Cardinia Reservoir, where it mixes with water from our catchments.
  4. Water can then be transferred to Silvan Reservoir and on to most of Melbourne.

The plant’s power requirements are 100% offset by renewable energy.

Watch this video for more information:




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