Water Sector Briefing

About this document

Findings from the third UK Climate Change Risk Assessment (CCRA3) Evidence Report 2021

This briefing summarises how the water sector has been assessed in the latest UK Climate Change Risk Assessment (CCRA) Technical Report, and what types of action to adapt to climate change risks and opportunities would be beneficial in the next five years.

This publication is available in PDF format at the end of the page >

Key messages

• Water infrastructure, such as reservoirs, dams, pipelines, water treatment plants and sewage treatment plants, are all at risk from the impacts of climate change, especially increases in the frequency and intensity of surface water and coastal flooding.
• Water infrastructure assets represent a key element of the UK infrastructure system and could affect, or be affected by, failures of other assets due to extreme weather, such as energy systems, transport and information and communications technology (ICT).
• There are also risks to buried infrastructure, such as water pipelines, with damage potentially becoming more frequent in future due to flooding and subsidence.
• More frequent flooding could also impact on water treatment facilities leading to potential reductions in water quality, in turn impacting upon health.
• Future projections of more frequent and intense dry periods lead to concerns around the availability of public water supplies in future, especially in England and parts of Wales. Private water supplies are also at risk.
• Aquifers near the coast could be at greater risk from saltwater intrusion due to sea level rise, though the risk is thought to be low in places where aquifers are important water sources.

Risks, opportunities, and benefits of further action

Average UK wide scores

• 

  I1. Risks to infrastructure networks (water, energy, transport, ICT) from cascading failures

  More action needed

  Read more

• 

  I2. Risks to infrastructure services from river, surface water and groundwater flooding

  More action needed

  Read more

• 

  I3. Risks to infrastructure services from coastal flooding and erosion

  Further investigation

  Read more

• 

  I7. Risks to subterranean and surface infrastructure from subsidence

  Further investigation

  Read more

• 

  I8. Risks to public water supplies from reduced water availability

  Sustain current action

  Read more

• 

  H10. Risks to health from poor water quality and household supply interruptions

  Further investigation

  Read more

• 

  N10. Risks to aquifers and agricultural land from sea level rise, saltwater intrusion

  Maintain a watching brief

  Read more

1. Risks to infrastructure networks (water, energy, transport, ICT) from cascading failures (I1)

Vulnerabilities on one infrastructure network can cause problems on others, and water infrastructure represents a significant part of this system.

Recent research conducted to support the CCRA has indicated that the vulnerability of interconnected systems may be significantly underestimated.

The risk of network failures is already high, potentially affecting hundreds of thousands or millions of people per year, particularly in urban areas.

An example of a cascading failure in relation to water occurs if extreme winter rainfall leads to more flooding, leading to flooding of sewerage infrastructure, reduced water quality and potential health impacts.

The magnitude of this risk is high both now and in the future across all four nations.

Beneficial actions in the next five years include:

• Improving resilience to a single infrastructure sector (such as protecting electricity substations from flooding), the benefits of which can become much larger when considering the cascading impacts that are then avoided.
• Using common formalised standards of resilience, such as the new ISO 14091 standard, across different infrastructure sectors including the water sector to help build systemic resilience across the whole infrastructure system.

Further details on this risk: Infrastructure Technical Chapter, risk I1

2. Risks to infrastructure services from river, surface water and groundwater flooding (I2)

River and surface water flooding is already a large risk to UK infrastructure, with each season adding new evidence to underpin the significant magnitude of the threat.

Data show that 487 water sites and 747 sewage treatment works are currently at significant risk from surface water flooding and 147 water sites and 601 sewage treatment works are at risk from river flooding across the UK.

The risk increases significantly from surface water flooding in the future, potentially doubling the risk in a 4°C warming scenario.

Conversely, the risks from river flooding to freshwater sites generally decrease in the future, and the risks from river flooding to sewage treatment works is expected to remain similar.

The magnitude of the risk to infrastructure as a whole is considered high now and in the future.

Beneficial actions in the next five years include:

• Develop consistent indicators of flood risk resilience for water infrastructure assets, supply and networks to create the right institutional conditions for adaptation, allow improvements across the board to be better measured over time, building on improvement in local hazard information, such as the Cabinet Office’s Resilience Direct platform which provides street-level surface water flood forecasts to local authorities and category 1 and 2 responders.
• Consistent indicators of resilience across sectors and for different sources of flooding to allow for improvements across the board to be better measured over time, to better understand the impact that adaptation is having.

Further details on this risk: Infrastructure Technical Chapter, risk I2

3. Risks to infrastructure services from coastal flooding and erosion (I3)

Sea levels are currently rising and the rate of rise is accelerating, including around the UK.

Coastal flood and erosion risk to infrastructure services, including those associated with water, will therefore grow.

The consequences of coastal flooding have been tempered over time due to improvements in flood defences, together with advances in flood forecasting, warning and emergency response and spatial planning. Despite this, notable coastal flooding incidents have still occurred that have significantly impacted infrastructure, and assets remain located in low lying coastal areas which will be threatened in the event of a defence failure.

In total, 22 clean water facilities and 91 sewage treatment works across the UK have been identified as at significant risk from coastal flooding. The risk will increase as sea level continues to rise.

Current projections show the likely change to be between 0.27 and 1.12 metres by the end of the century. The magnitude of the risk to infrastructure as a whole is considered medium now and in the future across the UK.

Beneficial actions in the next five years include:

• The use of adaptation pathways for the long-term planning of flood risk management, first used in developing the Thames Estuary 2100 flood risk management strategy, has been shown to be a promising technique that can be applied more widely in the UK.
• Given the uncertainties around sea level rise, ‘what if’ planning for high coastal risk scenarios can help with understanding what could be done in the event of very high rates of change.

Further details on this risk: Infrastructure Technical Chapter, risk I3

4. Risks to subterranean and surface infrastructure from subsidence (I7)

Damage to infrastructure due to subsidence often occurs as a direct result of shrinking and swelling of clay soils due to changes in soil water content. This form of subsidence is regarded as the most damaging geological hazard in Britain today.

The potential for increased levels of leakages and burst frequency in water pipes due to shrink-swell damage has been identified by water supply companies.

However, the current overall risk is deemed low rising to medium in future across the UK, and confidence in this assessment is low.

The magnitude of the risk to infrastructure as a whole is considered low currently, rising the medium across the UK by the 2050s.

Beneficial actions in the next five years include:

• Production of more accurate and consistent data for understanding the linkages between subterranean and other types of infrastructure, and understanding potential adaptation strategies, which is mainly limited to monitoring at present.
• More detailed information on sub-surface soil composition to predict future behaviour of buried water pipes, but this would be costly to achieve.
• Quantifying the uncertainty in soil properties.
• Increased ground and weather monitoring and the use of real-time decision support tools as a potential method to mitigate the risks of shrink-swell subsidence.

Further details on this risk: Infrastructure Technical Chapter, risk I7

5. Risks to public water supplies from reduced water availability (I8)

The UK faces an increased demand for water in a changing climate as well as reduced supply during dry spells.

It is projected that, without planned adaptation and under a central population scenario, a water deficit across the UK of between around 1,220 and 2,900 Ml per day could arise by the end of the century, equating to the daily water usage of between 8.3 to 19.7 million people.

Water is often stored in reservoirs, which are also vulnerable to high water flows and increased temperatures which can have implications on bank integrity.

Groundwater is another important water resource, particularly in southern areas of the UK, and could be particularly vulnerable to reductions in supply during drier conditions.

The magnitude of the risk is generally low for the present day (medium for England), but rises to medium and potentially high by the 2050s and beyond for most of the UK.

Beneficial actions in the next five years include:

• Adaptation efforts in the sector are well advanced, assisted by five yearly Water Resource Management Plans, which take a 25 year outlook, and price reviews, where water companies set the price, service and incentive package for a five year period.
• There are several options for further adaptation to reduce the risk of deficits further, including tightening building regulations, enhanced water metering and drought research.

Further details on this risk: Infrastructure Technical Chapter, risk I8

6. Risks to health from poor water quality and household supply interruptions (H10)

Reduced summer precipitation resulting from climate change will increase the likelihood of periods of water scarcity which, together with demand increases from economic and population growth, may lead to interruptions of household water supplies. This would have health, social and economic impacts, particularly for vulnerable households.

Parts of the UK, particularly within south-east England are already water stressed.

Climate change may also increase the risk of contamination of drinking water through increased runoff and flooding events that overwhelm current water treatment approaches.

Assessments of the impacts of climate change on future water supply have found that low flows and deficits are more likely by the middle of the century in England and parts of Wales.

Beneficial actions in the next five years include:

• Improve water quality by reducing the risk of surface water flooding, including through implementation of Sustainable Urban Drainage Systems (SuDS).
• Average personal water consumption in the UK is high by European standards, and water companies are actively putting in place measures to bring demand down, like water metering and offering water efficient devices like low flow taps and toilets. Further reductions in water use by households would make them less vulnerable to water shortages, and the economic benefits are higher when these measures are built into new homes and/or when householders need to upgrade an appliance like a toilet or washing machine.

Further details on this risk: Health, Communities and Built Environment Technical Chapter, risk H10

7. Risks to aquifers and agricultural land from saltwater intrusion (N10)

If sea levels rise relative to fresh groundwater levels saltwater can enter the aquifer and increase salinity in agricultural land.

Saltwater cannot be used to irrigate crops or be consumed by people.

The risk is currently low at present and most likely to remain low in future unless a much greater rate of sea level rise was to occur than most estimates expect (the likely range for the UK being between 0.27 and 1.12 metres by 2100).

Current risk management procedures should remain adequate to adapt to the risk subject to further review. However, it is noted that the risk in south-east England may be greater than the rest of the UK, partly because of the combination of saline intrusion and expected reduced summer rainfall affecting aquifers, where some provide public water supplies, for example in Dungeness in Kent.

Beneficial actions in the next five years include:

• Further research on changes in exposure and vulnerability, including in the context of the latest scientific data on sea level rise.
• This could occur alongside further investigation into the operational use of adaptation pathways related to changes in sea level rise, precipitation patterns and safe abstraction rates.
• Better storage and use of excess winter rainfall and other methods to maximise sustainable use of surface water resources (e.g. rainwater harvesting and on-farm reservoirs) to conserve groundwater resources at a sustainable level and mitigate against saline intrusion.
• Continue monitoring the impact on aquifers to assess whether risks are increasing.

Variations across the UK

Background

The UK Government is required by the UK Climate Change Act 2008 to assess the risks and opportunities from climate change to the UK every five years and respond to the risks via a National Adaptation Programme, covering England. The devolved administrations also publish their own adaptation programmes in response to the risk assessment.

For this third UK Climate Change Risk Assessment, the Government’s independent advisers on climate change, the Climate Change Committee (CCC), have been asked to prepare an independent risk assessment setting out the latest evidence on the risks and opportunities to the UK.

Over 450 people from more than 130 organisations have contributed to preparing the assessment. The risks have been assessed using the latest climate projections for the UK which were updated in 2018 by the Met Office. These briefings summarise some of the key topics that are assessed through the Technical Report, to enable readers to understand the key messages and where to find more detail.

Where to find more detail

Each risk or opportunity in this briefing has an identifier code linked to the full analysis, which is available in the CCRA3 Technical Report. Readers are encouraged to use these briefings to locate the parts of the Technical Report of most relevance to them.

Alternatively, if you would like a summary of the analysis by UK nation, please go to the national summary documents: