Sewage spill forecasting methods not up to the job

Climate change has shifted the intensity and variability of rainfall patterns so the UK’s bathing water forecasts are not protecting beach goers from swimming in sewage according to findings from a recently published academic review.

The researchers from the universities of Reading and Oxford and the Environment Agency have proposed multiple daily bathing water forecasts using recent advances in digital and forecasting technologies. They have warned that current bathing water forecast models “are not keeping the public safe at most of the UK’s 600-plus designated bathing water locations.”

The review found that current statistical models that produce early warnings use limited data that “often fails to capture extreme bacteria levels from sewage and agricultural discharges,” leaving authorities unable to  predict threats from pollution caused by sudden downpours that cause sewage overflows due to agricultural and roadway run-off.

Lead author of the findings published in the journal, WIREs Water, Karolina Krupska, of the University of Reading, said: “With existing pollution warning systems, beach users don't have good enough information to decide whether it is safe to go in the water. The science underpinning the next generation of bathing forecasting already exists, but these solutions have not been implemented.”

She went on to warn that authorities often lack the information needed to issue warnings: “Heavier summer downpours due to climate change are making the problem worse at the time of year when people are most likely to be at the beach.”

The authors’ proposed measures to strengthen protection for the UK’s bathers included:  

• more bacteria sampling during extreme weather events to achieve better statistical models;

• using of existing state-of-the-art high-resolution rainfall predictions to enable localised warnings, similar to those used for flood warnings; and

• using new machine learning forecast methods to provide more regular and accurate warnings for specific locations.