1st June 2026 River Deben Environment Monitoring Results

Our recent sampling safari took place just before the weather broke after a prolonged dry spell through May. The contrast between Monday's sampling weather and the thunderstorms on Tuesday this week means that there will now be more water in our rivers and probably higher levels of nutrients in some areas.

We have added a number of new locations notably two around Kirton where there is an Anglian Water Sewage Treatment Works (STWs) which drains into the tidal estuary at Falkenham and a couple on the Fynn. During the past month, the Rendlesham phosphate stripping plant has been commissioned by Anglian Water and we are seeing the first signs of reduced pollution there.

1. E.coli

Levels of E.coli bacterial pollution in large sections of the non-tidal Deben were stable at the start of June with only the Anglian Water STW's having elevated concentrations. On the Fynn and Lark, the position is quite different with several hotspots again showing up - in part due to new sites being sampled. Two small streams in Playford and at Run Meadow in Martlesham showed very high E.coli pollution with 342 colonies per 1ml and 170 Colonies per 1ml. respectively. Both these streams are used for paddling by children and the Environment Agency (EA) are being informed to investigate.

In the tidal section, the Woodbridge/ Melton area was clean but further down towards the sea, we recorded worrying per 1ml levels of E.coli at Kyson Point (15), Waldringfield (21), Ramsholt (14) and Bawdsey (8) - all taken on a falling tide. The Waldringfield E.coli level if confirmed by the EA would be a breach of the "safe bathing" status which is the first one in 2025 and 2026. The Bawdsey result is equally concerning as it is the highest we have recorded in 3 years. There may be a Martlesham Creek effect here or more likely another pollution source.

The new STW site at Kirton showed very high E.coli levels although the Falkenham seaward side was clear - samples here were taken on a rising tide however. Our new samplers there have previously seen wet wipes and paper on the beach so we will keep an eye on this location.

At Debenham, 8 of the 16 sampling sites were dry due to the prolonged high temperatures and the lack of rain. The other sites showed similar levels of E.coli to previous months, including the area around the Anglian Water STW.

2. Phosphate

This month showed similar low levels of phosphate in the upper reaches of the Deben from just below Debenham down to Easton. Further downstream the Anglian Water STW's continue to the prime source of phosphate pollution. However, it is noteworthy that the Wickham Market phosphate level is back within its EA permit after the April and May problems. We are pleased to see the Rendlesham phosphate levels dropping from 7.42 mg/litre in May to 1.92 mg/ litre this month. This is clear evidence of phosphate reduction plant commissioning - we are going to test weekly through June here; it's been a long wait requiring sustained lobbying to see this being implemented.

By contrast, the Fynn/Lark levels remain high with Henley, Witnesham and Tuddenham STW's all well above the Deben numbers. There are no immediate Anglian Water plans to invest in PO4 removal here or at Martlesham. The new Kirton STW location now takes over as the highest phosphate pollution source in the catchment.

At Debenham, phosphate levels are generally lower than elsewhere although low/no flow and dry weather have made concentrations higher than in previous months.

3. Nitrate

Levels of nitrate pollution across the Deben catchment are broadly similar to those in April and May except at the notable hotspots close to Anglian Water STW's. The two charts below show low levels of nitrate in the upper Deben whilst those in the lower reaches of the Fynn levels remain stubbornly high. There may be some farming practice differences at work here and more analysis covering a whole year is needed.

4. Ammonia

Ammonia pollution in the Deben is restricted to a few sites close to or at the outfalls from Anglian Water STW's. Our new ammonia dipstick methodology although quicker and safer to use, may under-report some of the higher levels. However, we still use the Hanna Ammonia MR tests where there are indications of significant ammonia presence

Thank you as always to all our volunteers for their continued support to the Deben Climate Centre citizen science efforts.

Check out our River Deben Water Quality Dashboard for detailed results by

location.