‘Poisoned by chemicals’: citizen scientists prove River Avon is polluted

<span>Salisbury Cathedral across the River Avon in Wiltshire.</span><span>Photograph: Penny Hicks/Alamy</span>
Salisbury Cathedral across the River Avon in Wiltshire.Photograph: Penny Hicks/Alamy

A citizen science programme has revealed the decline of one of the country’s most significant chalk streams after claims by Environment Agency officials that it had not deteriorated. The SmartRivers programme run by the charity WildFish, which surveys freshwater invertebrates, reported “strong declines in relation to chemical pressure” on the River Avon in Wiltshire. It said its data indicated a decline in the condition of the river over the last five years.

The charity compiled a report on its findings after the conservation groups say they were told at a meeting by the Environment Agency in August that “the Avon has not deteriorated in water quality in the last five years”. David Holroyd, head of water quality for Wiltshire Fishery Association, said the numbers of invertebrates collected in spring and autumn samples from 2019 and 2023 at 11 sites on the upper Avon had shown a decline.

He said the invertebrates were “the canary in the coalmine” and data suggested they were being “poisoned by chemicals in the river”.

WildFish says the findings highlight the crucial role played by citizen scientists in monitoring river health after a fall in the number of tests conducted by regulators in the last decade. The SmartRivers programme in England, Wales and Scotland now covers 95 rivers, according to a new report by the WildFish charity.

Freshwater invertebrates underpin the aquatic food ecosystem, ranging from riverflies and beetles to molluscs, worms and crustaceans. In the most recent results for all monitored rivers in 2022, volunteers found 268 different invertebrate species and counted 343,077 specimens. Invertebrate species have different tolerances to pollution. An analysis of the species present, along with their numbers, helps identify pressures on water quality from farming, sewage discharges and run-off from roads and residential areas.

Janina Gray, head of science and environmental policy at WildFish, said the ecological condition of a river was assessed under the water framework directive, a European Union directive transposed into legislation for England and Wales after Brexit. She said the current assessments “did not set the bar high enough”.

The Environment Agency had maintained the Avon had not deteriorated under the water framework directive classification in the meeting in August, said Gray, adding: “It is frustrating that the river is declining year on year and the legislation is not protecting it. This is one of the most protected rivers we have in this country. It is very diverse in terms of its fish population. If we can’t protect the Avon, there’s probably not much hope for many other rivers. We need a comprehensive monitoring network to be able to determine where the problems are happening which is why the SmartRivers is so important.”

Gray said WildFish was now working with the Environment Agency and other partners to identify the pressures on the river. An Environment Agency spokesman said: “On the River Avon, we are working with partners in the area to explore how we can best utilise citizen science evidence alongside our own monitoring data to further increase understanding of water quality.”

A recent analysis by WildFish reported that every river sample in the Windermere catchment for the SmartRivers programme was affected by United Utilities wastewater treatment works. It found that pollution-sensitive riverfly species showed declines of up to 76% compared with appropriate upstream habitat.

United Utilities said the plants operated in line with environmental permits.