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.