The Victorian Desalination Plant was built to meet our growing water needs as we face ongoing challenges from population growth and climate change. Learn how it works and the role it plays in securing our water supply.

Victorian desalination plant

Why we need a desalination plant

The Victorian Desalination Plant plays a critical role in Melbourne’s water future.

It was announced as a project during the Millennium Drought when water storage levels were critically low (16.5% in our largest reservoir), and 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 early and often to:

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

The Department of Environment of Land, Water and Planning manages the contract with the plant’s operator, AquaSure.

Take a look at the plant from above:

Annual desalinated water order

Acting Water Minister, Richard Wynne, ordered another 125 gigalitres for 2021-22 – the same amount as the 2020-21 order. The order commenced on 1 July 2021.

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.

Without the desalinated water ordered since 2017, our water storages would be around 15% lower (as at 1 January 2021).

For more detail, read our technical analysis:

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

How desalination works

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 and 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.

Did you know? The plant’s power requirements are 100% offset by renewable energy.

Watch this video for more information:

Last updated:
7 September 2021