Water quality along the stretch of the River Thames which will host the iconic Oxford v Cambridge Boat Race has been classified as poor by clean water campaigners, as a result of E coli from sewage pollution.
Testing carried out along the four-mile route, which the university rowing teams will tackle on Sunday, has revealed E coli levels which are three times above the threshold for poor bathing water status.
When a site is classified as “poor”, the Environment Agency advises against bathing due to the risk to human health.
The Boat Race is a longstanding tradition going back to 1829. Last year’s event was also plagued by anxieties about sewage in the river, and, after Cambridge had won, the Oxford team revealed that some of their number had been ill in the lead-up.
Other river-based sporting events have also been affected; in May a Thames swimming race which has been held for more than 120 years was cancelled over sickness fears.
Sir Steve Redgrave, the Olympic gold medallist, said rowers needed to be protected from polluted water. “It’s a real worry that in 2025, unsafe water quality in the Thames is still a concern. Rowers, river users, and the public deserve better.”
The testing, carried out every weekday between 10 March and 7 April at the beginning, middle and end of the race route between Putney and Mortlake, revealed that 29.5% of samples exceeded safe limits for entering the water, and were almost three times the threshold for bathing waters rated “poor”.
It was also a particularly dry spell of weather. Raw sewage discharges from storm overflows are only supposed to take place during exceptional weather, like extreme rainfall or intense storms. Spills of raw sewage during dry weather could be illegal.
The route does not have bathing water status but campaigners for River Action, who carried out the testing, used the threshold as a benchmark to indicate the threat to public health.
River Action said the monitor on a sewage outflow at Kew – upstream of the race’s finishing post – went offline in January, and remained out of operation during the entire testing window.
As well as raw sewage, Thames Water treatment plants discharge treated sewage into the river on a daily basis.
River Action believes the pollution from sewage treatment plants – which have no legal limits imposed on them for E coli – are a major but overlooked factor in the unsafe water quality.
Erica Popplewell, River Action’s head of communities, said the victorious Boat Race crew should think twice about throwing their cox in the water after the race, as is the custom.
She said systematic reform of the water industry and its regulators was needed.
“The public demands Thames Water and regulators act now to improve sewage treatment infrastructure,” she said.
“Thames Water has profited from pollution for years whilst the government has failed to enforce the law. It’s time to refinance the company without burdening bill payers and end pollution-for-profit.”
She called for Thames Water to be put into government hands and operated for public benefit.
But attempts to take the struggling water company into a special administration regime – which would put it temporarily into government hands – failed last month after the court of appeal allowed Thames Water to go ahead with a £3bn bailout loan at an interest rate of 9.75%, which was described as “eye-watering” by a high court judge.
Average bills rose this month from £436 to £588 a year, but the company wants to increase them further.
Rachel Dulai, sustainability lead at British Rowing said: “Our ‘guidance for rowing when water quality is poor’ covers the precautions rowers can take to remain healthy when doing the sport they love - the Boat Race and the competing clubs have issued this guidance to their athletes.
“There are over 30 rowing clubs that row along the Boat Race’s championship course on the Thames every day and we’re constantly working with clean water partners to push for cleaner water, as well as carrying out regular testing to keep our community as informed as possible.”
Thames Water said tests carried out by River Action and the Fulham Reach Boat Club showed water quality was excellent.
“Rivers are very dynamic environments, and samples can vary hugely within a short period of time. The Boat Race route is not a bathing water area and so we are not funded to routinely disinfect or sterilise final effluent.
“In addition, the Thames Tideway tunnel has prevented 6,376,450 cubic metres of sewage from entering the tidal Thames since it was connected earlier this year and will reduce the volume of discharges entering the tidal Thames in a typical year by 95%.
“We have and continue to deliver a record amount of investment to address our ageing infrastructure and the health of rivers.”
• This article was amended on 11 April 2025. An earlier version stated that Thames Water had carried out tests at the Fulham Reach Boat Club; however, these tests were conducted by River Action and the club.
