Friends of The Dart Water Quality Data review
Friends of the Dart Water Quality Data Review
Between March and September 2025, Friends of the Dart carried out extensive E. coli monitoring across 30 sites in the River Dart catchment. This work forms part of Phase 3 of our scientific initiative, designed to track pollution, identify hotspots, and support action on water quality. We also analysed Environment Agency (EA) and South West Water (SWW) data to build a fuller picture of bacterial loading in the River system.
What is E. Coli?
E. coli is a bacterium found in the intestines of humans and other warm-blooded animals, where it occurs naturally and helps indicate the presence of faecal matter. When detected in river water, it usually comes from sewage discharges, agricultural runoff, or leaking or misconnected drainage systems. Its presence signals recent contamination and the possible presence of other harmful pathogens that pose risks to human health, especially for swimmers and others who come into direct contact with the River. Elevated E. coli levels also affect the wider ecosystem, reducing overall water quality and signalling underlying pollution pressures within the catchment.
Key Findings
Several tributaries consistently contributed high E. coli levels to the main River. The Stoke Gabriel Stream, River Hems, Malt Mill Lake, and the Bidwell Brook stood out as the most polluted, with many samples exceeding the EA threshold for poor bathing water quality. Other tributaries, such as Old Mill Leat, Rattery Stream and the Harbourne, tended to show lower median levels but greater variability, particularly after rainfall.
Of the monitored sites on the main River, Dartington Beach, Dartington Pontoon, Steamer Quay, and the area around Staverton Sewage Treatment Works showed persistently elevated readings. Given the heavy use of these sites for swimming, kayaking, dog walking and paddleboarding, continued monitoring remains essential.
Tributary Insights
Stoke Gabriel Stream carried the highest bacterial load, with extremely elevated upstream concentrations of E. Coli.
River Hems and Malt Mill Lake also showed consistently high pollution levels, likely contributing to downstream water quality issues.
Bidwell Brook recorded high site-level results, although dilution in the main River appears to reduce its overall impact.
River Mardle and several smaller streams showed a mix of moderate levels and rainfall-driven spikes.
Pollution Sources
SWW data indicate that several sewage assets across the catchment experience frequent or long-duration spills. Harbertonford STW, Scorriton STW, Rattery STW, Kilbury STW, and Totnes Town Pumping Station were among the highest-impact assets. In some tributaries, however, spill data alone could not account for the levels observed, suggesting agricultural or other diffuse sources may also be contributing.
What Happens Next
Based on this season’s findings, winter monitoring will take a more targeted approach:
High-risk tributaries—including the Hems, Malt Mill Lake, and Stoke Gabriel Stream—will receive focused sampling and walkover surveys to pinpoint pollution sources.
Core community sites—Still Pool, Dartington Beach, Dartington Pontoon, and Steamer Quay—will continue to be monitored twice per month.
Lower-risk designated bathing sites—Holne Weir, Stoke Gabriel, Dittisham, and Warfleet Creek—will shift to monthly sampling.
Rain-responsive tributaries with high variability—such as Rattery Stream and Old Road sites—will be included in expanded wet-weather sampling rounds.
This refined winter strategy ensures that Friends of the Dart continues to focus on the areas most in need while maintaining a strong long-term dataset. These actions will help build evidence for the 2026 bathing season and strengthen collaboration with regulators and local partners to protect the health of the River Dart year-round.
This data review was carried about by Eliza Boyacigiller, our water technician. You can read her full and detailed report here.