How to predict pollution risks from sewer overflows to coastal waters
New research published in Environmental Pollution improves our ability to predict short-term pollution events in bathing waters.
Led by Hao Wang, Anouk Blauw, Eline Boelee and colleagues in Deltares, the team have developed a new Source-to-Sea Model that tracks microbial pollution from urban wastewater systems all the way to coastal beaches. By identifying where pollution originates and how it moves through rivers and estuaries, the model could help support future forecasting systems and climate-resilient water management.
Read the paper
Highlights
- The Model tracks E. coli pollution from urban wastewater sources to coastal bathing waters.
- The predictions reproduced beach water quality patterns with 89% accuracy.
- Results found that the most extreme pollution events were mainly caused by nearby combined sewer overflows (CSOs).
Heavy rainfall can overwhelm sewer systems, causing combined sewer overflows to release untreated wastewater into rivers and coastal waters. With climate change expected to increase the frequency of intense rainfall events, understanding and predicting these pollution spikes is becoming increasingly important for protecting public health and water quality.
Hao Wang said: “Using data from a three-year study, we can show that the highest E. coli concentrations were largely driven by local sewer overflows. The model also captures peak pollution events at downstream beaches, helping to identify pollution hotspots and areas where mitigation measures could have the greatest impact.”
The new source-to-sea framework provides a transferable tool for tracking microbial pollution across connected river, estuary and coastal environments, supporting both future climate resilience planning and the development of real-time water quality forecasting services.
Full citation:
Hao Wang, Anouk Blauw, Jos van Gils, Eline Boelee, Émile Sylvestre, Gertjan Medema,
Modelling peak microbial pollution events caused by combined sewer overflows in a source-to-sea system, Environmental Pollution, Volume 409: https://doi.org/10.1016/j.envpol.2026.129053.
