HIGH levels of pollutants have been found in the River Frome, which passes through Oldbury Court and Eastville Park on its way to Bristol docks.
Measurements of phosphate and nitrate nutrients were carried out by a team of 193 volunteer ‘citizen scientists’ for the Bristol Avon Rivers Trust as part of its RiverBlitz event.
They took sampling kits and monitored rivers across the Bristol Avon catchment, including the Frome and its tributaries, in July.
The river conservation charity analysed the 293 samples, and its results show all of those collected in the Fishponds and Eastville area showed either high or medium levels of phosphates and nitrates, pollutants which can have harmful effects on wildlife.
Levels of both pollutants were high at Frenchay Bridge, the weir in Vassalls Park and two out of three samples taken at Snuff Mills.
Nitrate levels were high in one of two samples taken from the river in Eastville Park, with medium readings for the other phosphate and nitrate samples.
Invasive plant Himalayan balsam was also seen at Snuff Mills and Frenchay, and unusually large amounts of algae found in Eastville Park, where the river passes close to the lake.
BART says pollutants can enter streams and rivers from a variety of sources, including pesticides and fertilisers washing off fields, livestock waste, sewage overflows and treated sewage discharges.
Survey is a ‘snapshot’ of pollution on one day
BART chief executive Simon Hunter said: “As this presents just a single snapshot of phosphate and nitrate data, it is challenging to single out the cause and source of the particular issue.
“However, what our citizen science data does show is that there is a problem regarding the levels of nutrients entering our watercourse at that given time – in the case of the 2023 Blitz, following a significant rainfall event following a very dry period in summer.
“The causes of high nutrient levels are likely to be as a result of water industry discharges as well as misconceptions from homes and possibly businesses, and impacts from agricultural land-use too.”
A map produced by the Rivers Trust nationally records 75 overflows into the Frome from Wessex Water storm drains in Muller Road, Glenfrome Road, Eastville Park, Forest Road (via the Fishponds Brook), Grove Road, Filwood Road, Frenchay Park Road and Sheppard Road last year.
The source of the Frome is near Chipping Sodbury in South Gloucestershire and its upper reaches flow through a combination of farmland, villages and towns including Yate.
Higher levels of nitrates in upstream areas are likely to be linked to farming; phosphate levels – linked to sewage and urban run-off as well as agriculture – were higher downstream.
BART says 89% of sample locations across the region recorded high levels of nutrients, with only one out of 293 showing a low concentration: 83% of samples were high in nitrates and 42% high in phosphates, with levels of both higher than average over previous surveys.
Water company ‘committed’ to reducing sewer overflows
Wessex Water, which is responsible for the region’s waste water, recently featured in a BBC investigation into sewage releases into watercourses during dry weather last year.
A Wessex Water spokesperson said none of the sites were in the Frome Valley.
The spokesperson said: “Phosphates are the main pollutant in the Bristol Avon catchments. Wessex Water has already removed 100 tonnes of phosphate per year from water recycling centres and we’re spending a further £57 million to remove another 70 tonnes by 2025.
“The remaining phosphates largely come from agriculture and urban run-off, so we’re working with farmers and other landowners to reduce this through use of nature-based solutions.”
The company has 121 sewage treatment works, 714 pumping stations and 670 storm overflows within the River Avon catchment, which includes the Frome.
The spokesperson said it has spent £15 million on the Frome Valley relief sewer scheme, completed in 2018, which “provides additional sewerage capacity for new and future development in the area and safeguards river quality”.
He added: “Although overflows are licensed by the Environment Agency to protect properties from flooding and discharge mostly rainwater, we’re committed to reducing how often they operate and are investing more than £3 million every month on schemes to improve them.”
A map showing where samples were taken can be found at bristolavonriverstrust.org/riverblitz.