Desalination at the heart of Australia’s water future

Drawing on GHD’s experience across Australia’s desalination projects, we’ve observed a clear shift in how the water sector approaches resilience. Water authorities are looking beyond emergency responses to focus on long-term system security for growing communities. Through the evolution of desalination technology and thoughtful design approaches, current projects are laying the foundation for the next generation of secure, climate-ready water systems.

Australia’s big coastal cities once relied almost entirely on dams. The Millennium Drought — a prolonged dry period from the late 1990s to the late 2000s that brought some of the lowest rainfall on record — exposed a major risk: Our storages can fall faster and further than expected. Sydney and Melbourne watched dam levels drop at alarming rates, prompting governments to invest in seawater desalination as a reliable safety net.

Lessons from the Millennium Drought continue to inform Australia’s approach to climate-independent water, as discussed in More feasible, faster: Accelerating climate-independent water.

Unlike rain-fed sources, desalination can operate in any climate, which makes it a critical part of modern water strategy. This shift towards desalination is evident in planning documents across the country, including Victoria’s Water Grid Strategy and the Lower Hunter Water Security Plan, which support the development of the new Belmont Desalination Plant.

In Victoria, the recently released Water Security Plan for Greater Melbourne, Geelong and connected towns identifies the need to expand the state’s seawater desalination capability as part of a broader portfolio of supply options. The Plan recognises that growing demand and a drying climate will require additional, climate‑independent sources beyond the capacity of the existing Victorian Desalination Plant and flags further investigation into desalination expansion alongside recycled water and efficiency measures.

Desalination is also increasingly being considered beyond traditional municipal supply. The Northern Water Supply project in South Australia is a large‑scale seawater desalination plant designed primarily to supply industrial and economic development customers rather than urban drinking water systems. The project highlights the growing role of desalination in supporting industrial resilience, reducing pressure on inland water sources and enabling long‑term economic growth in water‑stressed regions.

As climate patterns become more uncertain, desalination offers communities confidence that safe drinking water will always be available.

While desalination has existed for decades, the last 30 years have transformed its efficiency and affordability. Specific energy consumption has fallen by about 75 percent since the 1980s, thanks to improved membranes and modern energy recovery devices. Most Australian desalination plants now use a reverse osmosis (RO) system — a pressure-driven process that pushes seawater through specialised membranes to remove salt, producing fresh drinking water and a by-product called brine.

For municipal plants, the RO system typically comprises two passes. In the first pass, most of the salt is removed and in the second pass, the water receives a finer level of treatment to “polish” it to drinking water standards. Some modern designs only send the lower-quality portion of the first pass through the second, reducing energy use without compromising final water quality. This approach gives consistently high-quality water while operating efficiently.

What is more important than the technology itself is what it enables: Desalination is now more sustainable, predictable and accessible, providing climate-resilient water to communities in need. A desalination plant is more than membranes and pumps; it is a system of interconnected decisions, from how seawater enters the plant to how treated water blends into the network and extends to how waste is treated, all of which determine how reliably water reaches homes, businesses and essential services.

Source water shapes everything.

Seasonal shifts in the ocean can influence water quality in ways that directly affect plant performance. Algal blooms, storm-driven turbidity, shipping movements and nearby estuaries all play a role. While these variations may seem subtle, they can affect the stability of treatment processes throughout the year. This is why year-round water quality sampling is essential to inform treatment design.

Projects in Adelaide, Sydney and the Gold Coast have shown that even small changes in algae or turbidity can lead to operational challenges over time. For engineers, this is a technical consideration. For communities, it is about reliability — knowing taps will run regardless of what the ocean is doing that week.

Understanding the source water is the foundation for a plant that performs consistently and supports the people who rely on it.

Intakes and outfalls are a plant’s physical connection to the ocean and often the part of desalination the community cares most about.

Offshore open intakes are common across large Australian plants because they draw water from areas less affected by storm sediment or coastal activity, supporting stable treatment and reducing the risk of interruptions. Equally important is how brine is returned to the ocean. Modern outfall systems disperse it quickly in deeper waters, which protects ecosystems and supports high expectations for environmental care. Opportunities to combine the desalination outfall with an existing wastewater outfall has further reduced environmental disturbance and accelerated project delivery, reflecting a broader industry shift toward smarter, more integrated infrastructure that leverages what already exists. Ultimately, good intake and outfall design is not just an engineering solution; it is a story about balancing coastal protection with cultural and community values and is a key consideration of the site selection process.

Desalination has traditionally required more energy than conventional water treatment, but the way we supply that energy is evolving rapidly. Many plants now operate alongside renewable power purchase agreements or are connected to cleaner grids as Australia’s energy mix continues to shift.

The Victorian Desalination Plant, for example, operates on 100 percent renewable energy through the purchase of renewable energy certificates (RECs) equivalent to the total electricity consumed by the plant and its transfer pipeline. This approach supports both regional and metropolitan communities without placing additional pressure on emissions targets.

New technologies and design innovations are making modern desalination plants far more energy efficient than they once were. As renewable energy becomes more accessible and treatment processes continue to evolve, the balance between energy use and community benefit grows stronger. The true value of desalination lies not only in the water it produces, but in the stability it provides during droughts, bushfires or when water-quality challenges place pressure on traditional supplies.

Across Australia, desalination is becoming one part of a broader, more resilient water portfolio. Combined with recycled water, stormwater harvesting, groundwater and traditional surface water sources, it helps create systems that can adapt to climate change while supporting communities fairly and reliably over time.

Future planning is now centred on designing plants that protect sensitive coastal environments, integrating desalination more closely with recycled and stormwater initiatives and transitioning to cleaner energy systems as renewables expand. Modular desalination designs are also gaining interest, allowing plants to scale with population growth and changing community needs. At the same time, water authorities are prioritising transparent public engagement and strengthening long-term asset resilience so these systems continue to perform well for decades.

The direction is clear: Desalination is no longer just a treatment technology; it is a pillar of Australia’s water security, supporting people, place and prosperity today and for the generations that will live with the decisions we make now.