Only one popular river spot for bathing and water sports in and around Oxford has bacteria within safe levels, a survey by a campaign group has found.
The other seven locations in rivers which are regularly used by swimmers, punters, rowers and kayakers, were found to have concentrations of harmful bacteria one and a half to three times above recommended safe levels, a study by the Oxford Rivers Project funded by Thames Water has found.
The study concluded that at most of these locations the pollution was from sewage, although some locations were also affected by livestock.
Claire Robertson, Thames21’s Oxford rivers project officer, said: “These results confirm what we expected to find: that levels of bacteria at our river recreation sites are higher than they should be. However, we don’t want people to be discouraged from swimming, punting, rowing and kayaking on Oxford’s rivers. They have a myriad of benefits, for personal health and wellbeing, and for the city as a whole.
“We are glad that Thames Water funded and supported this research. Now, it’s time for them and the various authorities to put together an action plan and find the funding to cut down sewage and agricultural pollution to safe levels, and soon.”
A section of the River Thames in the city, Wolvercote Mill Stream at Port Meadow, became only the second stretch of river in England to be given bathing water status last month.
The status means the waters will be measured for two types of potentially harmful bacteria between 15 May and 30 September each year.
But the Oxford Rivers Project has been working to highlight the quality of all the rivers in and around the city. Their study replicated tests which take place in bathing water designated areas such as Wolvercote Mill Stream.
Volunteer citizen scientists took water samples at least once a month from 18 sites across Oxfordshire and analysed them for levels of E.coli and intestinal enterococci, bacteria harmful to human health.
The bacteria levels were measured at a Thames Water laboratory, and the project was jointly funded by Oxford city council, the Rivers Trust and Thames Water.
One site on a small brook downstream of Church Hanborough sewage treatment works was consistently 50 times the level safe for bathing, even when the treatment works was not overflowing and apparently treating the sewage, the study found.
Ten sites on smaller upstream tributaries were also sampled. None met the level considered sufficient for bathing, ranging from close to the safe level within the Upper Thames and Windrush catchments, to seven times the safe level at Limb Brook and Evenlode catchments.
Richard Aylard, sustainability director at Thames Water, said: “Taking action to improve the health of rivers is a key focus for us. We are delighted that Wolvercote Mill Stream is now designated for swimming.
“Our own commitments to improve river health include reducing the annual duration of sewage discharges into rivers by 50% across the Thames Valley by 2030.” Aylard said the company had planned substantial investment in its water treatment sites to reduce spills of raw sewage, including a major expansion at Witney treatment works in Oxfordshire.
He said the company was on track to provide live alerts to discharges from all 468 permitted locations across the region, within an hour of discharges starting and stopping, by the end of 2022.
“We’re clear it’s completely unacceptable for any untreated sewage to enter rivers, whether it’s permitted or not,” he said. “Stopping discharges altogether will take time and sustained investment, however each step we take on this journey is a move in the right direction.”
