WA’s new major water source is coming

Declining rainfall and a growing population, means WA will soon need a new major water source to meet Perth's needs. 

To help reduce our dependence on rainfall and groundwater, we are preparing to deliver a new seawater desalination plant. This will help provide secure, sustainable drinking water.

Where is the preferred site? 

Alkimos is the preferred location for a future desalination plant. To meet the needs of our growing city, the plant will be able to supply 100 billion litres a year of drinking water. That's enough to fill Optus Stadium 100 times!

Read a transcript of this video

The Alkimos Seawater Desalination Plant (ASDP) is proposed to be on Water Corporation land, next to the existing Alkimos Wastewater Treatment Plant, within the future Alkimos Water Precinct.

The infrastructure will be hidden behind large, vegetated sand dunes to absorb noise and protect visual amenity.

Why do we need a new water source?

Our scientists and long term supply planners have spent the last 20 years diversifying our water sources to secure our water future. To ensure the liveability of our city, a new desalination plant is required and here’s why:

Declining rainfall 

Since the 1970s, rainfall in southern WA has reduced by around 20%. This has seen an average 80% reduction in streamflow (rainfall runoff) stored in our dams. Modelling shows the drying trend will continue. Winter rainfall is forecast to decrease by 15% in 2030.

Before 1975, Perth’s dams received an average of 420 billion litres of streamflow each year. That's enough to meet Perth’s drinking water needs, even with today’s population. Now, we average less than 70 billion litres. Learn more about how Perth’s water sources have changed over time.

Reduced groundwater allocation 

Perth's groundwater system remains vital to meeting our water needs. This makes up 40% of the largest scheme we manage, the Integrated Water Supply Scheme. 

By 2028, our annual groundwater allocation is reducing by 27%. We need another rainfall-independent water source to make up this shortfall. 

Groundwater comes from rain that trickles down into our aquifers. It gives us the lakes, wetlands, bushland and urban trees that make our city green. Groundwater is also used in local community parks and recreation areas, school grounds, local businesses and 1 in 4 household gardens through bores. 

Population growth

According to City of Perth, the population of our popular capital is forecast to grow to 2.9 million people by 2031 and 3.5 million people by 2050. This will make us the third largest city in Australia and see a significant increase in the water demands from the community. 

Renewable energy 

It’s no secret desalination is extremely energy intensive. That’s why we will source 400 megawatts of renewable energy from WA renewables projects. This will help meet the total annual energy needs of ASDP and WA’s existing desalination plants in Kwinana and Binningup by 2035.

The same amount of power needed to operate these plants will be fed back into the grid in the form of renewable energy. You can learn about the desalination process here.

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Keep up to date with the Alkimos Seawater Desalination Project, the plan and its development on our project page.

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