From data to delivery - future-proofing stormwater investment
With £12 billion pledged to halve storm overflow spills by 2030, unprecedented monitoring, data analysis and collaboration will all be brought to bear - but the timeline must evolve into a long-term investment strategy.
The commitment of water companies in England and Wales to reduce stormwater overflows into rivers and seas in their 2025-30 asset management plans (AMP8) is commendable - and a significant step in responding to public pressure. However, it is only the beginning of what must become an enduring collaborative effort to build a more resilient future for stormwater management.
Achieving the ambitious 2030 goal will require an enormous effort - not only in capital projects, but in how the entire wastewater network is understood and managed. Given the scale of works and innovative approaches required, across a vast and ageing infrastructure, a more realistic target might be the end of AMP9.
Monitoring and data
One of the biggest game-changers is the enhanced monitoring required under Section 82 of the Environment Act 2021, requiring continuous collection of data upstream and downstream, from both combined sewage overflows (CSOs) and discharges from wastewater treatment works. This data will provide concrete evidence on where and why failures are occurring - and crucially, whether CSOs are to blame.
In a dynamic catchment many factors are at play and industrial effluent, along with agricultural and highway runoff, are major contributors to pollution that also need to be quantified and addressed. In turn, monitoring for specific contaminants in CSO discharges will capture true concentrations, which can be expected to be significantly lower than in raw sewage due to dilution.
This evidence base will enable utilities to make better, faster decisions on interventions - whether that is wastewater treatment upgrades, operational changes to sewer network management, or catchment initiatives and customer interventions. It will enable prioritisation of investment at those sites where the biggest impact can be made.
Smarter networks
Another promising area is the optimisation of existing sewerage infrastructure for storage during storm events. Managing flow through real-time control can prevent treatment plants from being overwhelmed.
Even simple interventions like storing rainwater from roofs in water-butts and using green infrastructure to absorb stormwater and redirect it into ponds and swales can smooth out surges and reduce pressure on the system.
Logistical realities
There are still logistical challenges ahead. Many CSOs are located on private land, making access to install and maintain monitors a challenge. Engagement with landowners adds time and complexity to technology rollouts. At the same time, maintaining thousands of sensors in difficult environments requires dedicated resources and ongoing attention.
The payoff is significant though. With accurate, granular data, water companies can refine their strategies and avoid misdirected investment and regulatory penalties. Reducing the millions spent annually on fines and mitigating reputational risk should be a compelling internal driver for change.
Resilience planning
Along with better management of wastewater discharges and less river pollution, improved stormwater and sewerage infrastructure builds resilience. As highlighted in the recent report Rethinking Resilience, published by GWI (Global Water Intelligence) and Xylem, the UK’s structured regulatory approach allows for more coherent and long-term resilience planning when compared to countries where funding is allocated annually.
Large-scale projects like the Thames Tideway Tunnel and the planned new reservoirs illustrate the need for parallel financing models alongside the AMP cycle to accommodate longer-term investments, but the direction of travel is clear - resilience must be embedded at every level.
No single solution will fix the problem of CSOs. Progress will rely on integrated thinking across utilities, regulators, consultancies and technology providers – supported by collaborative stakeholder engagement across catchments.
It is reasonable to expect cleaner rivers and coastlines within 10 years resulting from the investment being made. The £12 billion commitment is a strong start. Our ability to stay course will determine how quickly we can achieve all that we want to achieve.
Written for and first published in Water Magazine July 2025