Climate change is the biggest challenge faced by the Water Corporation.

Rainfall has dramatically decreased in many areas of our state. Since the 1970s May to July rainfall in the south west of WA has reduced by around 20 per cent State of the Climate 2018, Bureau of Meteorology.

Given this, the sources of water for our largest scheme - the Integrated Water Supply Scheme* - have changed dramatically. The amount of streamflow to our dams generated from each millimetre of rainfall continues to decline.

Before 1975, Perth’s dams would receive an average of 420 billion litres of streamflow each year, enough to supply the scheme even now. In comparison, during 2019 Perth’s dams received just 44 billion litres of streamflow.

In 2015, Perth’s dams received the lowest level of streamflow since records began in 1911 – with just 15.9 billion litres of water. To put that into perspective, that’s only enough water to supply Perth for around 15 hot summer days.

Water Corporation has been responding and adapting to climate change to secure water supplies for generations to come, by continually working towards our long-term targets outlined in Water Forever, first published 10 years ago. This plan adopts a three pronged approach, which includes:

  • Working with the community to reduce water use to help defer the need for investment in further new climate independent sources;
  • Developing new water sources; and
  • Increasing the amount of water recycled.

Water for the Integrated Water Supply Scheme is now comprised of a combination of sources, including desalinated seawater, groundwater, groundwater replenishment and streamflow into dams.

What we’ve achieved so far

Nearly half of the water used by our customers connected to the Integrated Water Supply Scheme can now be manufactured – independent of rainfall.


Perth has two desalination plants - the Perth Seawater Desalination Plant in Kwinana and the Southern Seawater Desalination Plant in Binningup – which can produce up to a combined 145 billion litres of water each year if required.

The Perth Seawater Desalination Plant began producing drinking water in late-2006 and was the first large-scale plant in Australia. It was the largest desalination plant in the southern and eastern hemispheres when constructed, and can produce up to 45 billion litres of drinking water a year.

In January 2013, Southern Seawater Desalination Plant began producing drinking water. This plant has the capacity to produce 100 billion litres of drinking water each year – direct from the Indian Ocean.  

Australia’s first Groundwater Replenishment Scheme

Did you know Perth is home to Australia’s first Groundwater Replenishment Scheme? Later this year, work will be completed on the second stage of our Groundwater Replenishment Scheme, which means the scheme will be able to produce up to 28 billion litres of water each year if required. 

Groundwater replenishment ticks two of the boxes outlined in Water Forever it provides a new, sustainable and climate independent water source, and an increase in water recycling.

Groundwater replenishment is an innovative process where highly treated wastewater undergoes advanced treatment to produce recycled water equivalent of drinking water quality. This water is then recharged to an underground aquifer, where it is ‘banked’ for later use as a drinking water source. Once the water is drawn out of the aquifer, it is further treated in the same process as groundwater is usually treated, and added to the drinking water supply scheme.

Construction of the first stage of the Groundwater Replenishment Scheme in Craigie (north of Perth) was completed in late-2017 and has the capacity to recharge up to 14 billion litres of recycled water to aquifers each year.

Our scheme in Perth was modelled on a similar scheme operating in Orange County, California, since the 1970s. If you have ever visited Disneyland in California, chances are you tasted this recycled water!


Traditionally, Perth relied heavily on streamflow into our dams as a water source, but declining streamflow has meant dams now play a bigger role as storage reservoirs.

We now ‘bank’ water produced through desalination and groundwater in its dams during the cooler months when demand is lower.

What can the community do?

Our Water Forever plans include working with the community and businesses to reduce water use. Reducing water use offers a cost effective and environmentally responsible option to reduce demand on scheme water supplies and potentially defer major capital expenditure.

Water saving efforts in Perth since 2001 helped save around 122.2 billion litres of water in 2017-18 – to put that into perspective, that’s more water than WA’s largest desalination plant produces each year!

By using water wisely, the community can help to defer the need for new water sources. Find out how you can save water.

*The Integrated Water Supply Scheme delivers drinking water to more than two million people in Perth, the Goldfields and Agricultural region and some parts of the South West each year.