South West Water Project Enters Second Phase to Map Groundwater Infiltration Risk

An innovative project led by South West Water to map and predict areas most at risk of groundwater infiltration has moved into its second phase following a successful pilot.

The Groundwater Infiltration Risk Mapping Project is being delivered in partnership with the University of Exeter through the Centre for Resilience in Environment, Water and Waste, known as CREWW. The work forms part of ongoing efforts to improve the resilience of water and wastewater systems as infrastructure ages and climate pressures increase.

Why groundwater infiltration matters

Across England and Wales, hundreds of thousands of kilometres of sewers are more than a century old. As these networks age, they become increasingly vulnerable to leaks, bursts and groundwater infiltration, where water seeps into sewers through cracks, joints or damaged connections.

This extra water places additional pressure on sewer networks and treatment works. It increases the volume of water that must be treated, raises carbon emissions and costs, and heightens the risk of flooding and pollution.

South West Water’s project aims to tackle this by using geospatial technology, data-driven mapping and groundwater modelling to identify where infiltration poses the greatest risk. This allows action to be taken earlier and more precisely, before problems occur.

What the pilot phase achieved

Phase one of the project was completed in October 2024. During this pilot stage, the team developed a new approach to mapping and predicting high-risk areas within South West Water’s sewer network.

Using data from the Lower Otter catchment, the team produced a detailed risk map. This highlighted areas needing urgent attention, locations requiring close monitoring, and parts of the network where the risk of groundwater infiltration was low.

The mapping enabled operational teams to target maintenance work more effectively and intervene before issues developed.

Phase two now underway

The success of the pilot has led directly to phase two, which is now in progress and will run until October 2026.

This phase will expand the approach into two larger catchment areas in Dawlish and Camborne. The aim is to build a more comprehensive set of models and maps that can be used more widely across the region.

The new data is expected to inform future sewer network maintenance, as well as support decisions around drinking water resources, groundwater pollution prevention and long-term infrastructure planning.

What the partners say

Mark Jacob, Senior Asset Manager at South West Water, said: “Groundwater infiltration can be hard to see, but it can have a real impact on how our sewer networks perform. By combining local knowledge with new data and modelling techniques, we can make better decisions about where and when to intervene. This helps reduce the risk of pollution, lowers carbon emissions, and keeps costs down for customers.”

Nejat Zeydalinejad, Postdoctoral Research Fellow at the University of Exeter, added:
“The Groundwater Infiltration Risk Mapping Project is delivering cutting-edge geospatial and physics-based models to produce high-resolution hotspot maps for sewer networks across the South West.

“These outputs offer substantial benefits for South West Water and the wider community, supporting more targeted, efficient and climate-resilient decision-making. The global significance of this work is already clear, with four Q1 journal publications to date, including two in Water Research.

“We are excited to see Phase 2 progress and hope the project advances to Phase 3, where this multidisciplinary expertise can be applied to triage the entire sewer system of the South West, helping move towards a more resilient and sustainable wastewater infrastructure in a changing climate.”

Once the project is complete, South West Water will look at how the data can be used in future planning and operations as part of its wider commitment, through CREWW, to science-led and data-driven approaches that improve environmental outcomes and resilience.