November Water Quality findings summary

November Sampling Update

26/11/2025

This November, our water quality monitoring across the Dart catchment captured a mix of low, moderate, and high E. coli concentrations, reflecting the influence of rainfall, discharges from Combined Sewer Overflows (CSOs), and sewage treatment works (STWs) on the River and its tributaries.

6th November - First Wet Weather Sampling Round

Following 25.3mm of rain in the previous 48 hours, along with active spills from five CSOs (and a further five CSOs spilling in the 48 hours prior to sampling), we collected 16 samples across the Dart catchment. Our focus was on sites along the Old Mill Leat and the River Hems (including the western tributary and the Ambrook), as well as three small tributaries crossing the old Totnes to Buckfastleigh road.

• The three small tributaries (Old Road 1–3) showed relatively low E. coli levels, suggesting limited faecal inputs at the time of sampling.
  
  

• Sites on the Hems and Ambrook showed elevated E. coli, particularly upstream and downstream of Broadhempston STW, Torbryan, and along the Ambrook.
  
  

• Tripe’s Copse had extremely high E. coli levels, prompting us to raise an EIR with South West Water to investigate the upstream asset near Woodland.
  
  

• Interestingly, E. coli levels dropped between Ambrook DS and Littlehempston, suggesting some bacterial dilution.
  
  

E. coli concentrations (cfu/100ml):

 Old Road 1 — 700
Old Road 2 — 200
Old Road 3 — 600
Staverton Village — 0
Old Mill Leat DS — 1000
Staverton Bridge — 300
Broadhempston STW US — 2200
Broadhempston STW DS — 4300
Beaston Brook US — 2400
Beaston Brook DS — 3300
Torbryan — 2800
Torbryan #2 — 700
Tripes Copse — 13,500
Ambrook US — 3400
Ambrook DS — 8500
Littlehempston — 1300

11th November - Second Wet Weather Sampling Round & Lab Validation

Following 36.5mm of rainfall in the previous 48 hours, with three active CSO spills and eleven additional CSO spills in the previous 24 hours, we collected samples from Holne Weir down to Warfleet Creek in Dartmouth.

For seven of these samples, half of each was sent to an accredited laboratory for traditional culture analysis, while the other half was processed in-house using Petrifilms to measure E. coli. These quarterly validations ensure that the Petrifilm method accurately captures the pollution patterns observed in laboratory analysis.

• Sites upstream of Totnes Weir had relatively low E. coli (100–800 cfu/100ml), despite the rainfall.

• Downstream of Totnes Weir, levels were elevated at most sites, with Stoke Gabriel and Dittisham showing the highest readings of the year using Petrifilms.

• Overall, the lab results show a similar pattern of pollution across the catchment and confirm that the Petrifilms are effectively capturing these patterns. Petrifilms tend to slightly overestimate E. coli (by around 500 cfu/100ml), but they remain very useful for comparing bacterial loading between sites.

• The only sample that differed noticeably was from Dittisham. Petrifilms indicated a concentration between Steamer Quay and Stoke Gabriel, while the lab result was lower. This difference may be due to the natural uneven distribution of bacteria in water: by chance, the sample sent to the lab may have contained fewer E. coli than the one analysed in-house.
  
  

E. coli concentrations (cfu/100ml; lab results in brackets):
Holne Weir – 100 (340)
Ashburn – 500
Mardle – 200
Still Pool – 700
Dartington Beach – 800 (460)
Dartington Pontoon – 700 (410)
Steamer Quay – 1,800 (680)
Stoke Gabriel – 2,100 (760)
Dittisham – 1,900 (380)
Warfleet Creek, Dartmouth – 0 (61)

18th November - Dry Weather Sampling Round

Taking advantage of a break in wet weather, we collected samples at 14 sites across the Dart catchment. Despite the dry conditions, four CSOs had spilled in the previous 24 hours, and Harberton and Harbertonford STWs had been spilling continuously since 11th November. An EIR was raised with South West Water to understand the prolonged spills, which suggest that these assets may not be adequately coping with the demand placed on them.

• E. coli levels were low to moderate on the Ashburn River, Old Mill Leat, and some sites on the River Hems.
  
  

• Elevated concentrations were observed at Mardle, Tripe’s Copse, Torbryan, and the Ambrook, reflecting recent faecal pollution.
  
  

• As before, E. coli dropped between Ambrook DS and Littlehempston.
  
  

E. coli concentrations (cfu/100ml):
Ashburn — 400
Mardle — 2000
Old Mill Leet DS — 600
Staverton Bridge — 800
Beaston Brook US — 200
Beaston Brook DS — 300
Broadhempston STW US — 300
Broadhempston STW DS — 800
Tripes Copse — 2600
Torbryan #2 — 200
Torbryan — 1600
Ambrook US — 5200
Ambrook DS — 2400
Littlehempston — 0

24th November - Remaining Wet Weather Samples

Due to weekend rainfall, dry weather sampling was limited, so we focused on the Harbourne and Bow Creek, and an additional sample at Dartington Beach, which formed part of a new video project we are working on!

• Rainfall in the previous 48 hours was 26mm, with three CSOs actively spilling (including Harberton STW) and four additional CSO spills in the previous 24 hours (including Harbertonford STW).
  
  

• E. coli levels were moderate at Dartington Beach and elevated at the River Harbourne (downstream of both STWs) and Bow Creek, consistent with recent and ongoing spills. Responses to our EIR are awaited.
  
  

E. coli concentrations (cfu/100ml):
Dartington Beach — 1000
Harbourne — 1500
Bow Creek — 800

We’ll continue to monitor the Dart catchment closely over the coming months, tracking how rainfall, sewage discharges, and tributary flows affect water quality. Thank you for following our water quality monitoring and for your continued interest in the Dart catchment. Your support helps us keep a close eye on the River and its tributaries, and together we can better understand and respond to changes in water quality. We look forward to sharing more updates with you in December!