Climate-independent water: Global lessons for the UK's water future

Part one of our special coverage: The water transition argued that the future belongs to societies that create water abundance rather than simply manage scarcity. In part two, this column, Greg Finlayson looks at what the United Kingdom (UK) can learn from the countries that moved first. Read or listen to part one.

The UK can accelerate desalination and potable reuse by learning from countries that have already planned, delivered and operated these systems at scale. Australia tested rainfall-independent systems during the Millennium Drought. California spent decades making potable reuse a mainstream water source. Singapore made recycled water part of national identity. Perth, in Western Australia, rebuilt its supply portfolio around climate-independent water as rainfall patterns changed.

The UK is now at an important strategic point. The Environment Agency’s 2025 National Framework identifies the scale of additional water that may be needed by 2055 in England, including around 5 billion extra litres per day for public water supply and a further 1 billion litres per day for other sectors of the economy. Those figures create a clear planning task: decide which sources are needed, where they should connect to the system, how they should be regulated and how communities should be engaged.

Desalination, potable reuse and demand management work best as complementary tools. Demand management remains the fastest and usually cheapest source of water. Leakage reduction, smart metering, household efficiency and better industrial practice all matter. Climate-independent supply adds another layer of resilience.

The task is to combine efficiency, reuse, desalination and system integration into a timed portfolio, with each source assigned a defined role.

Australia’s Millennium Drought was a defining planning event. From the late 1990s to 2009, major cities saw storages fall and long-standing assumptions about rainfall, inflows and supply security were tested. Governments, utilities and communities responded with a mixture of demand management, interconnection, reuse and desalination.

For the UK, those choices provide evidence on timing, sequencing, public engagement, network integration and operating modes.

The main Australian lesson is portfolio sequencing. Water efficiency bought time. Restrictions slowed the decline in storages. Interconnections improved system flexibility. Desalination added a source that did not depend on rain. Reuse added another tool where source water, regulation and public acceptance made it practical.

The timing was harder than the engineering. Sydney moved from a readiness-to-construct position to construction as the drought deepened, then saw the drought break and storages recover. That sequence shows why real-options thinking matters. Climate-independent supply has value as insurance, flexibility and system resilience. Its benefit extends beyond production volumes in wet years.

After 2010, Australian systems behaved differently because their hydrology differed. Sydney and Melbourne used desalination as standby capacity, switching plants on when storages fell and off when systems recovered. Perth, facing a structurally drier climate and sharply reduced dam inflows, uses desalination as a near-continuous source.

The same technology served different system roles. That distinction matters for the UK. Desalination can be drought insurance, baseload supply or strategic reserve, depending on the catchment, storage position, network, energy market and risk appetite.

Potable reuse carries a different public challenge. The process engineering is mature: advanced treatment trains built around microfiltration or ultrafiltration, reverse osmosis, ultraviolet disinfection and advanced oxidation are well established. Public, regulatory and political support must be built early, so that each technical step is explained, demonstrated and understood before major commitments are made.

Orange County in California shows what sustained trust-building can achieve. Its Groundwater Replenishment System now produces 130 million gallons per day of purified water, enough for about 1 million people and recycles 100 percent of local reclaimable wastewater flows.

The project did not succeed through technology alone. It combined board commitment, engineering validation, public outreach, transparent operation and a clear account of why the project mattered: less imported water, less ocean discharge of waste and a more reliable local supply.

Singapore reached the same conclusion through a different route. NEWater was named, explained, tested and made visible. Demonstration, expert review, public tastings and a visitor centre turned recycled water into one of Singapore’s national taps. PUB, Singapore’s National Water Agency, reports that NEWater quality has consistently exceeded World Health Organisation and United States Environmental Protection Agency drinking-water requirements through extensive testing and monitoring.

The UK can also learn from inland American reuse. Colorado adopted the first state direct potable reuse rules in the United States in 2022. Texas moved from emergency direct reuse in drought to permanent schemes, with El Paso now developing a direct-to-distribution plant.

These examples show how staged regulation and demonstration projects can turn reuse into a normal part of the supply portfolio.

For the UK, reuse can help catchments manage environmental recovery, growth and supply resilience together.

Desalination and potable reuse are often discussed as separate options. In practice, they are manufactured renewable water. Both use advanced treatment. Both rely heavily on reverse osmosis. Both can be delivered through repeatable global designs. Both can reduce dependence on rainfall. Each has a different system role.

Potable reuse often has a lower energy requirement than seawater desalination because the source water is less saline. It can reduce treated effluent discharges and relieve pressure on rivers, aquifers and coastal waters. It also depends on wastewater availability, treatment integration, public acceptance and clear regulation.

Desalination has an abundant source, particularly for a coastal country and can provide high-reliability drought capacity. It also requires careful management of energy demand, brine, marine approvals and network integration.

The UK can approach the choice as a portfolio design task. In some regions, reuse may be the lower-cost, lower-carbon baseload option. In others, desalination may provide stronger drought resilience. In many cases, the sequence will be staged: pilot and demonstrate reuse, develop indirect potable reuse where environmental buffers are useful, prepare direct potable reuse rules and use desalination where the demand profile and coastal network support it.

Large desalination and potable reuse plants are delivered worldwide by a relatively small group of specialist firms. They bring repeat experience, current benchmarks, proven equipment choices and operating knowledge from multiple jurisdictions. That expertise is valuable.

It also means the client-side delivery model needs to capture and retain knowledge deliberately. A global contractor may deliver these plants repeatedly. A water company or regulator may see one such project in a generation.

The best delivery models bring global and local knowledge together from the start. Global firms know the latest designs, costs, operational issues and procurement patterns. Local teams know the catchment, network, abstraction pressures, ground conditions, regulator expectations and community history. Early collaboration lets each side add value before key choices are fixed.

Independent owner’s advice can shape the front end before major spending begins. The most influential decisions are made before most of the money is spent, i.e. site selection, source choice, treatment concept, network connection, discharge strategy, planning pathway, water-quality basis and procurement models. Early advice needs to be globally benchmarked, technically current and independent enough to test the client’s assumptions and the market’s claims.

Regulatory clarity turns global experience into local delivery rules. Desalinated water has been approved for drinking supply across Australia under existing drinking-water quality frameworks.

Potable reuse is more complex, with deep and mature precedents. California adopted direct potable reuse regulations in 2023, effective from 2024, after decades of indirect reuse experience and expert review. Colorado regulated direct potable reuse before demand peaked. Singapore built support through testing, expert scrutiny and visible public education.

The UK can define a clear, risk-based pathway that draws on these precedents while reflecting local institutions and environmental settings.

That means coordinated guidance across drinking-water quality, environmental regulation, marine impacts, planning and public health. It also means being precise about different forms of reuse: non-potable reuse, indirect potable reuse, direct potable reuse and direct-to-distribution supply each involve different technical, regulatory and community considerations.

Clear distinctions will help regulators, utilities and communities move through each stage with fewer unresolved questions.

The strongest public case for renewable water may combine river recovery and drought security. Every litre supplied through reuse or desalination is a litre that does not need to be abstracted from a stressed river, chalk stream or aquifer.

Reuse can also turn treated effluent from a disposal problem into a water resource, reducing discharge pressure where schemes are properly located and operated.

This matters in the UK because the water debate now joins supply, river health, abstraction reform, housing growth, food production and economic resilience. A scheme presented as part of restoring rivers, protecting rare chalk streams and supporting growth with less environmental pressure gives communities a clearer reason to support it.

The UK’s next steps can be specific.

1. Continue demand management because water saved is still water supplied.
2.  Identify where reuse, desalination and transfers each have a system role.
3. Begin public engagement before preferred options harden.
4. Establish regulatory pathways for potable reuse in stages, drawing directly on jurisdictions that have already done it.
5. Bring independent global benchmarking into the earliest project decisions, when influence is high and committed spend is still low.

The lesson from Australia, California and Singapore is straightforward: much of the hard learning has already been done. Drought planning shows the value of diversified supply. Potable reuse shows the value of trust built early. Desalination shows the importance of defining the system role clearly. Regulation shows how evidence can be converted into practical delivery confidence. Early decisions shape outcomes more than late capital spend.

The UK’s projected water need is large enough to justify a new supply mindset. It can draw on countries that have already tested the technology, regulation, engagement and delivery models. Climate-independent water is proven. The task now is to use those lessons early enough to define projects clearly, regulate them efficiently and build public support before delivery decisions are fixed.

This column is part of a Nexus special coverage series exploring the water transition and how renewable, regenerative and adaptive water systems can underpin long-term prosperity.

Catch up on:

• Read: The Water Transition: Why abundance, not scarcity, must define the next decade
• Listen: Introducing the Water Transition

Over the coming months, the series will explore:

• Water governance and economic competitiveness
• The water transition: What water can learn from energy
• Adaptive water planning: Why 100-year plans no longer work
• Desalination versus reuse is the wrong debate
• From sustainability to regeneration
• The data centre dilemma: who should pay for water security?
• Data centres are a wake-up for the water transition