Could desalination be the answer to the Southwest's water crisis? How can seawater help us combat drought? By Charlotte Cox and Robert Hall, Channel Islands Investigations
The demand for water is projected to surpass supply within 25 years, according to government forecasts. So, is turning seawater into drinking water a viable solution for the Southwest? While some countries rely on desalination, the British Isles' only fully operational plants are in Jersey and the Isles of Scilly.
Plans for similar sites across the country have faced strong opposition due to cost and environmental concerns, as toxic brine released during the process can cause harm (https://www.bbc.co.uk/news/articles/cpww53vevjzo).
The government confirms that nine sites in England are in the pipeline, including one in the Southwest, with the Environment Agency emphasizing desalination as part of a comprehensive strategy to ensure resilient water supplies for the future.
How does desalination work?
Desalination plants extract salt from sea or estuaries, purifying the water to make it suitable for drinking. Worldwide, over 22,000 plants are operational in 170 countries, according to research commissioned by the International Desalination and Reuse Association.
Many Middle Eastern countries and small nations like Malta, the Maldives, and the Bahamas rely heavily on desalination to meet their water needs.
Corrado Sommariva, former president of the International Desalination Association, highlights the critical role of desalination in regions like the United Arab Emirates, where arid climates, scarce rainfall, and limited freshwater resources make it a matter of life and death.
While the UK's rainfall and water management capabilities mean desalination is not an immediate necessity, Sommariva suggests it could be a valuable long-term strategy to enhance resilience against climate change.
Jersey Water in the Channel Islands has been treating seawater through desalination since 1968, addressing rising demand and limited storage capacity.
Jersey is self-sufficient in water supply, with reservoirs holding just 120 days' worth of water, significantly less than the UK average. This vulnerability to low rainfall periods makes desalination a reliable and scalable solution.
The system, set to undergo a £26 million upgrade, is expected to play a crucial role as climate change intensifies water supply challenges, according to chief water operations officer Mark Manton.
In 2025, the plant was operational for 200 days, and in the summer, it ran from July 15 to mid-September, costing approximately £180,000 in energy and manpower. Manton acknowledges that increasing desalination usage could lead to higher water bills.
The plant in the Isles of Scilly, where about 40% of drinking water comes from the sea, is another example of desalination in action.
Why isn't desalination more widespread in the UK?
Historically, the UK hasn't faced a pressing need for desalination due to natural rainfall, reservoirs, and efficient water distribution. However, climate change is altering this landscape, according to the Department for Environment, Food, and Rural Affairs (Defra).
Defra warns that water demand will exceed supply by 2050 if no further action is taken. To address this, £104 billion in private sector investment is proposed to build eight new reservoirs, eight desalination plants, large-water transfer schemes, and 8,000 kilometers of water mains pipes.
However, construction obstacles persist. A desalination plant in Cornwall has been delayed due to concerns over marine life and the potential harm caused by salt-laden brine pumped into the sea.
Campaigners, like Jenny Tagney from the Friends of Par Beach group, argue that the evidence for desalination's benefits is not yet strong enough to justify the environmental impact.
Tagney questions the wisdom of investing in desalination when it's only used once every two years.
Cornwall Wildlife Trust also plans to hold South West Water accountable for its desalination plans.
South West Water remains committed to improving water resilience in the Southwest, considering population growth, summer tourism, and the impacts of climate change, including droughts.
A desalination plant in the Southeast, the only one outside the Isles of Scilly and Jersey, is currently non-operational. Thames Water built the £270 million plant in Beckton in 2010 to provide drinking water during droughts, but it has faced financial challenges and customer bill increases.
The plant is temporarily unavailable due to reservoir safety works, but Thames Water intends to operate it in the future.
Elsewhere, a petition with over 1,800 signatures opposes a desalination plant near Southampton Water, citing concerns about brine's environmental impact.
What are the risks associated with brine?
Brine, a byproduct of desalination, poses significant threats to marine life due to its high salinity and potential contaminants. A 2019 study revealed higher-than-expected levels of brine in the sea and detailed the risk of hypoxia to marine species.
Technological advancements are being explored to extract metals and salts from brine more sustainably.
Mark Manton assures that the impact of brine at the La Rosière plant in Jersey is minimal due to the island's unique tidal range, which disperses the brine.
What does desalination mean for water bills?
Desalination is considered one of the most expensive methods of producing drinking water, as it requires high-pressure pumping through membranes with tiny filters, consuming significant energy. This cost is ultimately passed on to consumers.
The Jersey plant operates for about 200 days annually, and in 2025, it ran for 120 days, costing £180,000. Manton acknowledges that increased desalination usage could lead to higher water bills.
An upgrade in 2026 will boost the plant's capacity by 50%, from 10.8 million liters to 16.2 million liters per day, at a cost of £26 million. This upgrade is part of a £48 million five-year investment by JW, with customers contributing to the cost.
Water bills are expected to rise by an average of £60 from January 1, 2026, with further increases predicted for future years.
Manton emphasizes that desalination is more expensive than conventional treatments due to energy requirements, but it provides a safety net against water shortages.
South West Water's £3.2 billion investment includes desalination, with a third funded by customer bills. Annual water bills increased by 32% to £686 in April 2025, compared to the 26% average increase across England and Wales.
Sommariva also advises caution regarding costs, noting that desalination offers resilience but is not a panacea due to higher construction and energy costs in Europe compared to the Middle East.
Will desalination become cheaper and cleaner?
Defra reports that technology is being developed to make desalination more efficient and environmentally friendly.
The University of Manchester's National Graphene Institute is researching graphene, a thin and strong material, to create more durable and efficient membranes for water filtration.
Project leader Prof. Rahul Raveendran Nair believes this technology can reduce brine waste and improve energy efficiency.
Kiran Tota-Maharaj, professor of water resources management and infrastructure at the Royal Agricultural University, emphasizes the importance of desalination for water resilience and security in the UK.
He suggests that desalination technology will be used to convert seawater and clean existing water reserves, which are becoming polluted by chemical contaminants.
Tota-Maharaj calls for a reevaluation of desalination's environmental impact, citing the need for significant technological improvements to address concerns about ocean discharge.
