Global warming has long been associated with warmer, wetter winters and hotter, drier summers in the UK.
Predictions made in the 1970s and 1980s are now becoming increasingly visible, but the term “global warming” itself can be misleading.
Rather than a gradual and predictable rise in temperatures, the UK is now experiencing increasingly erratic and extreme weather patterns, underpinned by a higher baseline in both ambient and sea temperatures.
Climate change becoming more apparent
Climate change is now widely recognised as a significant and visible challenge across the UK.
Spring and Summer 2025 were identified among the warmest on record, while Autumn temperatures also remained above average.
In fact, the last three years all fall within the five hottest years recorded in the UK.
At the same time, rainfall patterns have become increasingly uneven. Winters throughout the 21st century have generally become wetter, with Autumn 2023 to Spring 2024 recorded as the wettest period on record.
November 2025 also saw rainfall levels approximately 31% above average across England and Wales.
These increasingly unpredictable conditions are placing additional pressure on the UK’s already stretched water infrastructure.
Reservoir pressures and long-term supply concerns
Winter traditionally provides an important period for replenishing rivers, reservoirs and groundwater supplies.
However, while some parts of the UK may continue to manage the imbalance between wet winters and dry summers, other regions are likely to face growing difficulties, particularly as droughts and extreme weather events become more frequent and prolonged.
As part of the government’s “Plan for Change”, and in response to forecasts suggesting a potential shortfall of four to five billion litres of drinking water per day due to population growth, housebuilding and climate change, UK water companies have committed to developing nine new reservoirs by 2050.
Planned locations include Suffolk, Kent, East Sussex, Lincolnshire, the West Midlands, Oxfordshire and Cambridgeshire.
However, the first of these reservoirs is not expected to become operational until 2036, more than 40 years after the last comparable reservoir project was completed in the UK.
The long lead times involved in expanding water infrastructure may also have indirect implications for Legionella risk management in buildings and healthcare environments.
A changing environment for Legionella management
Legionella control in the UK is governed through a well-established framework led by the HSE and supported by detailed industry guidance.
This framework provides those responsible for managing buildings with practical strategies to minimise risks and protect occupants through appropriate vigilance and water hygiene management.
However, changing environmental conditions may increase the prevalence of Legionella bacteria reproduction in domestic and commercial water systems.
Fluctuating temperatures, reduced water availability and altered usage patterns all have the potential to create conditions more favourable for bacterial growth.
This raises important questions around whether less plentiful water supplies and increased conservation measures could contribute to greater Legionella risks in the years ahead.
The hidden risks of reduced water use
The average person in the UK currently uses approximately 141 litres of water per day, with national targets aiming to reduce this to around 110 litres per day by 2050.
While reducing consumption is essential for long-term sustainability, lower water usage could unintentionally create additional water hygiene challenges within building systems.
Reduced water demand may lead to:
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Increased stagnation and static water conditions;
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Higher incoming mains cold water temperatures for extended periods;
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Reduced flow rates caused by water conservation measures;
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More areas of domestic water systems operating between 20°C and 45°C — the temperature range associated with Legionella growth;
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Greater challenges managing infrequently used outlets;
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Increased risks in systems already affected by poor or outdated design.
At the same time, extreme weather events and flooding may increase disruption to water systems, creating further opportunities for contamination and erratic usage patterns that support bacterial growth.
Keeping water systems safe
Given the decades-long timescales associated with expanding reservoir capacity, there is growing recognition that water systems themselves may need to become more resilient to periods of reduced use and supply pressure.
While future solutions may involve new technologies and alternative water management strategies, many of the most effective approaches are likely to remain rooted in robust water hygiene fundamentals and improved system design.
Key preventative measures will continue to include:
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Maintaining strict control of hot and cold water temperatures;
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Regular cleaning and disinfection of water systems;
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Removing sludge, sediment and organic build-up;
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Reducing unnecessary aerosol creation where possible;
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Improving flushing regimes based on actual system demand and usage;
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Developing a clearer understanding of distribution networks and outlet usage patterns;
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Ensuring systems are appropriately sized and, where possible, independent;
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Expanding the scope of Legionella risk assessments to include climate-related contingencies;
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Ensuring staff remain trained, informed and competent as risks evolve;
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Feeding operational concerns back into future system design strategies.
Future-proofing healthcare water systems
Many of these measures already form part of current guidance, but climate change and increasing water scarcity may require them to be applied with greater scrutiny and consistency.
Historically, high water throughput has been central to minimising bacterial growth within domestic water systems. In the future, however, consistently high usage levels may no longer be guaranteed.
As healthcare estates continue progressing towards Net Zero targets and greater sustainability, balancing water conservation with effective Legionella control is likely to become an increasingly important consideration.
There is also likely to be growing reliance on UK guidance and regulation remaining proactive, ensuring future updates reflect the evolving risks associated with climate change, changing building usage and long-term water shortages.
For healthcare estates teams, designers and water safety professionals, the need to future-proof water systems against both environmental and operational change may already have begun.