The River Test now hosts a near‑continuous network of nearly 20 sondes that deliver half‑hourly readings of dissolved oxygen, ammonia and water temperature along the river's entire length. The partnership between Southern Water, local communities and campaign groups follows 2024 storm‑overflow incidents and protests at Fullerton. Data is currently available to riverkeepers and campaigners, with public access planned within a year. Southern Water says it is investing £84 million to improve water quality on the Test, including £28 million at Fullerton.
First‑of‑its‑Kind Real‑Time Sensor Network Launched To Protect River Test Chalk Stream
Recent pollution incidents led to the project to constantly monitor water quality along the length of the River Test [BBC]
A near‑continuous network of nearly 20 sensors has been deployed along the full length of the River Test to provide round‑the‑clock monitoring of water quality in what organisers say is the first scheme of its kind in the UK.
Each monitor contains probes which sample specific indicators of water quality and pollution with the data sent back day and night [BBC]
How the Network Works
The instruments, known as sondes, report every 30 minutes on dissolved oxygen, ammonia and water temperature. Readings are already accessible to riverkeepers and campaign groups, with public access expected within a year. The continuous data stream is designed to show not only when pollution events occur but also where and how contaminants enter the river corridor.
The River Test is the longest chalk stream in the UK rising at Ashe near Basingstoke and flowing 40 miles to Southampton Water [BBC]
Geoff Cooper, a member of the Pan Parish River Pollution Forum and a local Liberal Democrat councillor, said the system covers the river from source to mouth and major tributaries and described the rollout as "ground‑breaking and exciting."
Practical Benefits For River Management
Seth Crosswaite, a riverkeeper at Houghton Lodge, explained that real‑time upstream and downstream readings will help responders locate pollution sources and assess impacts on spawning grounds. "What you want to see in a chalk stream is clean gravel — that's what the fish need to spawn on," he said.
The River Test is world famous for fly fishing and an internationally important habitat [BBC]
Background And Response
Concerns about the River Test rose in 2024 after heavy rain triggered storm overflows and sewer outlets to discharge into the river during what Southern Water described as "exceptional circumstances." In March that year hundreds of residents and campaigners protested outside Southern Water's Fullerton Waste Water Treatment Works; campaigners say that protest prompted greater local engagement from the company.
"That made Southern Water realise just how angry people were," said Geoff Cooper, noting the company subsequently opened channels for collaborative work with community groups.
Investment And Wider Monitoring Aims
Southern Water says it is investing £84 million to improve water quality on the Test, including £28 million at Fullerton Waste Water Treatment Works. The company describes the voluntary monitoring programme as going beyond its own assets to consider other pressures on the river corridor — from agriculture to potential illegal connections.
Joff Edevane, Environment and Water Quality Lead at Southern Water, said the sondes will give riverkeepers a joined‑up daily picture of what is affecting water quality and will help prepare for forthcoming legislation.
For local residents, campaigners and riverkeepers the new sensor network is seen as a practical tool to help safeguard a highly prized chalk stream. Organisers hope the clearer, continuous data will guide targeted fixes and protect the River Test for future generations.
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