Projects
Turning seawater into a reliable water supply for Western Australia’s drying climate
Securing climate-resilient drinking water for Perth through sustainable, future-ready seawater desalination
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Video credit: Water Corporation.
As lead designer, Jacobs is supporting the delivery of the Alkimos Seawater Desalination Plant (ASDP) to ease the mounting pressure on Perth, Australia’s water system. The $1.2 billion (AU$2.8 billion) investment will deliver 39.6 million gallons (150 million liters) of drinking water each day with capacity designed to double as demand grows.
Perth’s water supply has fundamentally changed in recent decades. With average rainfall declining and streamflows into dams now a fraction of historical levels, traditional sources like surface water no longer provide a reliable supply. As a result, cities in Western Australia now rely on a diversified mix of climate-independent water sources, including groundwater, desalination and recycled water to ensure water security for communities.
In response, Jacobs is working with Acciona and Water Corporation as part of the Alkimos Seawater Alliance to deliver the ASDP — a major new source of climate-resilient drinking water for Western Australia.
Jacobs is delivering a scalable desalination solution that strengthens Perth’s long-term water security while balancing resilience, sustainability and constructability. The first stage of the plant will deliver 39.6 million gallons (150 million liters) of drinking water each day – with the scope to double this capacity in future.
A view of the plant under construction.
Addressing Perth’s evolving water supply pressures
Perth’s drying climate has had major impacts. Rainfall has dropped over the past 50 years, and flows into dams — once the city’s main water source — have fallen sharply. As a result, water planning can’t rely on rainfall alone. It now depends on resilient, climate‑independent solutions.
Looking ahead, the scale of the challenge is clear. Water Corporation modelling shows that by 2035, even with efficiency measures and water recycling, Perth will need an additional 75 to 125 billion litres (about 20 to 33 billion gallons) of climate‑resilient water to meet demand.
Delivering such a water supply will require responding to complex technical and environmental conditions. Coastal seawater quality can change rapidly, from sediment-heavy storm surges to algal blooms, requiring treatment systems that can adapt without compromising drinking water standards, particularly when blending desalinated water with groundwater sources.
The project site, located alongside existing critical water infrastructure, will require a design that enables future expansion without interrupting operations. The plant will also need to minimize impacts on sensitive marine and coastal ecosystems while meeting stringent regulatory and community expectations around environmental protection, visual amenity, noise and operational safety.
Together, these challenges required a solution that was adaptable and environmentally responsible.
Did you know?
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39.6 M
gallons per day (150 Million liters per day) Drinking water produced in Stage 1
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1.29 B
gallons per year (4.9 billion liters per year) additional supply via the integrated Eglinton Groundwater Treatment Plant
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2.5 miles
(4.1 kilometers) – the length of marine outfall tunnel
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1.6 miles
(2.6 kilometers) – the length of the marine intake tunnel
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132 kV
high voltage supply integrating solar photovoltaic and battery storage
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45 :1
Target (calculated) outflow dilution levels using innovative brine diffuser outfall structure
“The ASDP represents years of planning and detailed engineering coming together through a highly collaborative alliance. With design now nearing completion and construction activities ramping up, we remain on track to deliver first water in 2028. It’s an exciting milestone for Perth’s long term water security.”
A sustainable and scalable response
To tackle these challenges, Jacobs is building on the original concept design to create a coordinated and future‑ready solution with the alliance members. The plant will use a specialized pretreatment system that can handle cloudy seawater and algal blooms, ensuring it keeps operating reliably even when ocean conditions change.
Clean water will then be produced using reverse osmosis (a water purification process), supported by energy‑saving technology and UV disinfection to deliver safe drinking water with lower power use. The system will also blend desalinated water with treated groundwater from the nearby Eglinton plant, reducing chemical demand by adding minerals present in the groundwater.
The seawater intake and outflow marine tunnels — that run miles into the Indian Ocean — are designed and built in a way that will protect the reef, seabed and marine life and make construction safer and more efficient. Advanced digital tools, including real‑time monitoring and a “digital twin” of the plant, will help operators run the facility smoothly and maintain it more easily.
Sustainability is built into every part of the design, including low‑carbon materials, solar power and structures that reduce the plant’s overall environmental footprint. Part of the Alkimos Water Precinct, the plant sits adjacent to the existing Alkimos wastewater treatment plant and integrates into the surrounding environment with a western berm that helps reduce noise and visual impacts.
Image credit: Water Corporation. The pipelines will be tunneled beneath the seabed to avoid impacting the reef and marine life.
Future-ready
The ASDP is a cornerstone of Perth’s long term water security strategy. Jacobs’ global technical capabilities in desalination and local delivery strengths are enabling a highly resilient, low impact and future ready asset that integrates renewable energy, digital capability and sustainable engineering.
Desalination is already a key part of Perth’s water resilience. The seawater desalination plants at Kwinana and Binning up now supply about 30 to 40 percent of the city’s drinking water each year. As the climate continues to change, expanding this climate‑independent source will be critical to keeping Perth’s water supply reliable.
Once complete, the project will deliver a resilient and sustainable drinking water supply for decades to come.
