The Climate Change Committee has published a separate briefing summarising how the water sector has been assessed in the CCC’s third UK Climate Change Risk Assessment (CCRA), and what types of action to adapt to climate change risks and opportunities would be beneficial in the next five years.

The CCC has assessed the following risks for the sector:

• Risks to infrastructure networks (water, energy, transport, ICT) from cascading failures
• Risks to infrastructure services from river, surface water and groundwater flooding
• Risks to infrastructure services from coastal flooding and erosion
• Risks to subterranean and surface infrastructure from subsidence
• Risks to public water supplies from reduced water availability
• Risks to health from poor water quality and household supply interruptions
• Risks to aquifers and agricultural land from sea level rise, saltwater intrusion

The briefing says that water infrastructure, including 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 also 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.”

Recent research conducted to support the CCRA has indicated that “the vulnerability of interconnected systems may be significantly underestimated” the briefing says. Vulnerabilities on one infrastructure network can cause problems on others – and water infrastructure represents a significant part of this system.

The briefing cites extreme winter rainfall which leads to more flooding, leading to flooding of sewerage infrastructure, reduced water quality and potential health impacts as an example of a cascading failure in relation to water. The CCC warns:

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

According to the CCC, the risk of network failures is already high, potentially affecting hundreds of thousands or millions of people every year.

The briefing suggests that buried infrastructure, such as water pipelines, potentially faces increased risks as a result of more frequent damage in future due to flooding and subsidence. In addition, more frequent flooding could also impact on water treatment facilities leading to potential reductions in water quality with knock-on effects on health.

Future projections of more frequent and intense dry periods could also lead to concerns around the availability of public water supplies in future, especially in England and parts of Wales.

Beneficial actions in the next five years suggested by the CCC include:

• Improving resilience to a single infrastructure sector (such as protecting electricity substations from flooding) – the benefits 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.

The briefing describes river and surface water flooding as “already a large risk to UK infrastructure, with each season adding new evidence to underpin the significant magnitude of the threat.”

The CCC cites data which show that 487 water sites and 747 sewage treatment works are currently at significant risk from surface water flooding, with 147 water sites and 601 sewage treatment works at risk from river flooding across the UK.

Beneficial actions the CCC is proposing should be taken 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 and building on improvement in local hazard information.
• 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.