Study reveals most polluted parts of Bristol rivers

Research by Bristol Avon Rivers Trust (BART) has found alarmingly high levels of nitrates and phosphates in the River Avon.

87 volunteer “citizen scientists” collected 143 samples from streams and rivers across the Bristol Avon catchment, which spans from the Cotswolds to the Mendips.

Volunteers tested the water for levels of phosphates and nitrates to give an annual snapshot of river pollution.

Nitrates and phosphates are amongst the most common pollutants of freshwater and have wide-ranging detrimental effects on wildlife.

They enter the river from a number of sources including pesticides and fertilisers washed into rivers, waste from livestock, sewage overflows used to provide relief from the sewer system and even treated sewage discharge.

70 per cent of samples collected across the Bristol catchment showed high levels of nitrate with only 6 per cent having low nitrate levels.

Phosphate levels were also elevated, with 70 per cent of samples showing high phosphate and just 13 per cent of samples having low phosphate.

Only 6 per cent of rivers had low nitrate levels in July 2022 – photo: BART

There was a significant increase in phosphate levels, with only 13 per cent of samples having low phosphate in July 2022 – photo: BART

Conham River Park, a popular wild swimming destination, had high concentrations of nitrates and phosphates in July, when wild swimming in the area is usually most busy.

According to BART, compared to previous years, these results were all higher-than-average pollution levels.

This is the seventh year of testing, which began in 2015, using relatively inexpensive water quality testing kits.

Simon Hunter, CEO of BART, warned that the water quality could “pose a health risk to people who enjoy using the river for recreation.”

“The public recognises our rivers as national treasures, but none of them are in good overall health,” he said.

“The RiverBlitz findings show that the Bristol Avon catchment is experiencing high nutrient concentrations, which are likely to have an impact on wildlife and in some cases pose a health risk to people who enjoy using the river for recreation.

Image of Bristol Avon RiverBlitz visualisation tool – photo: BART

The higher pollution levels recorded in 2022 could be a result of the low river levels, according to BART. Less water means that phosphates and nitrates are more concentrated and thus higher levels are detected by the water quality testing kits.

Simon Hunter  also blamed cuts to Environmental Agency funding for the lack of data around river water quality.

“The situation is complicated and should be monitored more closely to better understand and reduce the source of pollutions, but cuts in Environment Agency funding have resulted in less data being collected and fewer boots on the ground investigating issues.

“Needless to say, water quality improvements have stagnated.”

Citizen science can play a vital role in filling the gaps in monitoring across the Bristol Avon and provide evidence required to target improvements, Hunter said.

Data for each stream and river across all years is accessible to the public via the Bristol Avon RiverBlitz visualisation tool. The interactive map allows users to click on their local watercourse and see if it has high, medium or low levels of nitrate and phosphate.

Main photo: Conham River Bathing Water group

Read next:

• Critically endangered eel and Atlantic mackerel found in Bristol waterways
• Surge of support for campaign to tackle sewage pollution in River Avon
• Protestors strip off for wild swimming demonstration
• Safe swimming spot in Bristol’s harbour could be piloted as early as next year

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