5th October 2026 River Deben Environment Monitoring Results
The weather in September and into early October continued to be warm and mostly dry with minimal rainfall - a fraction of the seasonal average. River levels and flow are still extremely low for this time of year, illustrated by the fact that at Debenham 9 of the 16 sampling sites were dry. Hence for the non-tidal section, with ditches and feeder streams dried out, pollution levels were much the same as in August and July.
1. E.coli
In the non-tidal section, there were low E.coli levels in much of the main River Deben away from the Anglian Water STW's and only at Charsfield and Wickham Market was there any significant downstream effect from these treatment works. The section above Easton continues to show almost no E.coli pollution.
For the Fynn and Lark tributaries, the picture is broadly similar with the Anglian Water works at Henley, Tuddenham and Grundisburgh having a significant impact. However, E.coli levels in a few locations notably in Grundisburgh village were higher than expected; it is possible that, with low flow in small streams, dog-fouling may be one cause.
In the tidal section, it is good to report that there were low E.coli levels across the river and estuary, although as usual both Kirton and Martlesham Creek STWs continue to vie for "Top of the Poops" status!
At Debenham and above it, where the river is narrow with many source streams joining, there was a record number of dry sites reported. E.coli levels, at those where water was present, were however lower than in previous months perhaps due to the impact of sunshine breaking down E.coli in exposed pools.
2. Phosphate
The position for phosphates is a little more complex as low flow and record low river levels tend to concentrate this chemical pollutant. That said, the section below Debenham and to Easton continues to show minimal phosphate levels and almost all sites are within the WTD / Natural England healthy river target of 0.1 mg/litre. Further downstream in the main River Deben, phosphate levels rise somewhat although these are still not far off "healthy river" levels; this is probably in large part due to the lack of rainfall/ little run-off and the installation of Anglian Water phosphate removal technology. However, it is clear that the Charsfield STW continues to have problems with PO4 removal within its new stripping installation.
In the Fynn/Lark section, phosphate levels are somewhat higher due, in part, we think, to the Anglian Water STW's not having had any investment. For example, the Henley STW at 13.03 mg/litre is emitting 130 times the "healthy river" level which is record from our studies
In the tidal section, phosphate pollution in Woodbridge/ Melton is above WTD/ Natural England guidelines even at high tide although down towards Bawdsey levels are minimal. The inland Kirton STW continues to be a high emitter and recent one-off tests in the non-tidal backwaters at Falkenham shows phosphate pollution over 15 times the acceptable level
In the Debenham area, phosphate levels were lower than reported in September. Even at the Debenham STW outfall the 0.23 mg/ litre reading is lower, showing the positive impact of phosphate removal investment - the comparator figure in August 2023 (prior to investment) was 6.58 mg/ litre, a 30 fold decrease. This figure demonstrates the case for investment in all the smaller STWs in our catchment.
3. Nitrate
Nitrate levels continue to be relatively low for the time of year due to little rainfall and almost no run-off from agricultural land and highways. For much of the non-tidal Deben, nitrate spikes are only evident at and just below the Anglian Water STWs, although like phosphates the levels tend to increase further towards the tidal junction at Ufford/ Wilford Bridge. Above the Debenham STW and towards Aspall, levels are very low still.
On the Fynn/Lark, there is a similar picture but with, in several cases, elevated levels up to 100 ppm even where there is no nearby STW outfall. The tidal section shows levels between 0 and 10 ppm, due in large part to tidal dilution. Only at Martlesham Creek STW is the nitrate above this with a 100 ppm reading.
4. Ammonia
Across the Deben catchment, ammonia levels are below 0.5 ppm in most places indicating relatively good river health. However close to and at the Anglian Water STWs there are expected spikes above 1.00 ppm, notably at Martlesham Creek (8.16) and Kirton (6.52). A tidal spike at Wilford Bridge (1.07 ppm) is concerning as this is some way from any pollution emitter; this may be due to a local point source as one of our volunteers noted a smelly ditch in Bromeswell area. This has yet to be investigated.
5. Other News
Charsfield Oil Spill - A recent oil spill pollution incident took place at Charsfield on Friday 25th September when a builder's van came off the road and ended upside down in Potsford Brook. Oil from the sump flowed out into the dry ditch creating a sizable spill. Action by our volunteers and local Parish Council in reporting the incident to the Environment Agency resulted in a "clean-up" being started just before the 7th October rainfall. The time taken from incident report to clean up was however rather too long and appears to suggest that the EA Hotline reporting and follow up needs improvement as volunteers had to make multiple calls and send emails to prompt timely action.
OurRivers.TV - 1st October saw the launch of the Deben Climate Centre OurRiversTV channel which features short video news items about the Four Rivers Recovery Project. You can see the news items featuring water quality work and a number of the initiatives underway as part of this wider East Suffolk project. A weekly flow of news items and features is planned.
Ufford Breach Recovery - Earlier this year, the weir at Ufford Bridge collapsed and water levels dropped by almost 1 metre, lowering levels upstream too. The popular circular walk to Melton was closed due to the collapse of the footbridge and the main channel to Old Melton Mill dried out completely, stranding many fish and with a loss of all aquatic life. A joint recovery project was set up with the landowner, Lower Deben Owners Group (LDOG) and Parish Councils in Ufford, Melton and Bromeswell working alongside agencies including the Environment Agency, Water Management Alliance and Suffolk CC Rights of Way. The first recovery action in early September was to clear the main channel, reintroducing water to this section. The photo shows the digger just after the water started to flow down the channel which had previously been almost completely blocked with silt, weeds and reeds. The work was featured on BBC Look East and received very positive support from the local community.
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