A large proportion of water flowing through a local Cambridge beauty spot may be raw sewage, recent research by the Liberal Democrats suggests.

The investigation indicates that 40% of river flow at Sheep’s Green is sewage effluent, in concerning news for participants in traditional May Week river swimming.

Anglian Water has previously been ranked as the worst water company for monitoring how much sewage it discharges, with 49% of all sewage discharges going unmeasured. Data reveals that Anglian Water discharged sewage for at least 1689 hours in 2021, which amounts to more than 4.5 hours each day.

Environmental journalist Terry Macalister has suggested that he could smell sewage on one occasion when swimming in the river. 

Macalister also drew a comparison between pollution in the Cam to vandalising King’s College Chapel. “We’d never let that be damaged in any way. You could argue that the river in its biodiversity terms is the equivalent of King’s College Chapel and yet we’re abusing it and that needs to stop”. 

A spokesperson from Anglian Water told ITV News: “we’re investing £200m over a five-year period to basically stop storm spills or at least significantly reduce them.

“There are lots of things in the natural environment that can also cause poor water quality for rivers - from ducks and other animals swimming in rivers, to agricultural run-off, urban run-off. There’s lots of things people need to be mindful of when swimming”. 

This research follows concern about Weil’s disease in the Cam during May Week that caused some colleges to advise students not to swim in the river. Recently, concern has also grown nationally over untreated pollution being pumped into rivers and the sea, leading tourists to be warned to stay away from some beaches.

The government’s water minister, Steve Double, said: “We are the first government to take action to tackle sewage outflows. Work on tackling sewage overflows continues at pace.”