A new conversation on wastewater spills in the UK

The way we measure wastewater spills in the UK is being re-examined. Current metrics — frequency and duration — provide a narrow view and don’t always reflect the real consequences of spills on rivers, communities or investment priorities. Since the 2025 Northumbrian Water Innovation Festival, industry leaders are turning their attention to volume and impact as more meaningful measures. From the innovation that occurred in the Spill Intelligence Sprint of that event, this article outlines why the change matters, what the sector is saying and how fresh approaches are starting to take shape, with implications for the resilience of water infrastructure and community confidence in long-term flood management.

Why the current system doesn’t add up  

Counting how many times a spill occurs or how long it lasts tells only part of the story, and at present, this is how the regulation measures water company performance. A short event may look problematic on paper, but a single high-volume discharge can cause far more harm to rivers and communities. Without information on the scale of releases, pollutant concentrations or downstream effects, decision-makers struggle to know where to intervene first.  

The limits of this approach are widely acknowledged. Utilities face difficulty directing resources where they are most needed, regulators find it harder to assess outcomes, and communities lose confidence when data feels abstract or incomplete. The conversation is moving on: the sector wants metrics that better reflect reality.  

Volume and impact: The new lens on spills 

Industry voices are converging on two priorities:

• Volume, to capture the scale of discharge and pollutant load 

• Impact, to assess ecological damage, customer effects, reputational consequences and regulatory risk

Survey findings from our Spill Intelligence session highlighted strong support for this shift. Participants stressed that frequency and duration alone are too simplistic. Stakeholders called for greater visibility, better use of data and a stronger focus on customer perspectives.  

While measurement frameworks are still evolving, the sector is beginning to rethink traditional engineering responses to spills. Data and insights are being used to reframe problems and guide targeted interventions that deliver measurable improvements in wastewater outcomes. These include technologies such as flow meters, GIS mapping and predictive analytics, which enhance visibility and inform decision-making. Nature-based measures such as sustainable drainage solutions (SuDS) are being used to strengthen stormwater management, easing pressure on ageing water infrastructure and reducing the strain on networks during heavy rainfall.  

Examples such as Yorkshire Water’s Storm Spill Reduction Programme — which combines hydraulic modelling, data-driven planning and community collaboration — and projects like Havant Thicket Reservoir, which balance supply resilience with environmental protection, illustrate how the sector can adopt a more integrated approach. Together, these interventions demonstrate how insight-led thinking can inspire new approaches to tackling wastewater and flood management challenges without depending solely on conventional large-scale storage solutions.  

Building frameworks for smarter choices  

Technology alone will not solve the challenge. The sector needs a structured way to translate data into action. GHD is developing a spill management checklist to support this. Rather than prescribing specific interventions, the checklist brings together factors such as spill scale, location and readiness to respond, guiding investment towards areas where benefits are greatest.  

This framework is designed to support consistent decision-making across networks and catchments. It recognises that spills vary in character and consequence and that priorities must reflect compliance and the outcomes that matter to customers, regulators and the environment. Embedding this into wider sustainable water management practice will help link short-term responses with long-term resilience goals.  

What needs to happen next? 

• To more effectively manage wastewater overflows, the measures of water company performance can evolve beyond frequency and duration to include volume and impact. 

• Transparency and trust are essential. Customers, communities and regulators want data that reflects real-world outcomes. 

• Tools and approaches are available, from smart monitoring to nature-based solutions, but they must be applied at scale and with a clear purpose. 

• Frameworks for decision-making are needed to translate information into action, linking data to investment, water infrastructure upgrades and the long-term resilience of flood management systems. 

Our upcoming report on spill intelligence will explore these themes in greater depth. It will share industry perspectives, outline practical pathways for regenerating public trust and demonstrate how focusing on impact can help water companies identify and address the right spills. Our report will also highlight opportunities for aligning investment with the outcomes that matter most to customers, communities, and the environment. Stay connected to be among the first to access it.

About GHD

GHD is a leading professional services company operating in the global markets of water, energy and resources, environment, property and buildings, and transportation. Committed to a vision to make water, energy, and communities sustainable for generations to come, GHD delivers advisory, digital, engineering, architecture, environmental and construction solutions to public and private sector clients. Established in 1928 and privately owned by its people, GHD’s network of 12,000+ professionals is connected across 165 offices located on five continents.