This is a summary of the work undertaken by local citizen scientists to test our stretch of the river for harmful bacteria, including E. Coli, which are well known to be the cause of some serious gastro-intestinal symptoms affecting swimmers and other recreational users of the river.
This study looked at the biological pollution of faecal bacteria, which primarily affects human health and was planned to be a Goring-only project. However, we had a request to become a partner in a slightly larger study, which extends downstream to Pangbourne, and join forces with another environmental charity, Thames21. They were gathering bacterial data for a potential future application to the Environment Agency (EA) for Pangbourne Meadows to be given designated Bathing Water status. This required bacterial data collected upstream to beyond Goring’s sewage treatment works.
Pollution in our rivers, especially in the Thames, has been making headline news for several years now and has shown many rivers are not fit for safe recreational activity. Plus, much of the aquatic wildlife is in decline. The latest State of Our Rivers Report 2024, published by The Rivers Trust shows the full year’s data from 2023. It reveals that 0% of English rivers are in good overall status, 23% are in poor or bad overall status and 85% of river stretches fall below good ecological standards. Only 15% achieved good or above ecological health status. Of these poor results, 62% are attributed to agricultural and rural land management (e.g. pollution from fertilizers or livestock) and 54% attributed to the activities of the water industry (including discharges of untreated sewage, especially in periods of heavy rainfall). At the time of writing (8 Oct 2024), the latest Ofwat annual report has been published showing water companies must pay £157.6 million in poor performance fines due to falling behind on key Ofwat targets. This includes managing only a 2% reduction of their commitment of a 30% reduction target in pollution incidents, with Thames Water required to pay out about a third (£56.8m) of their 17 total fines.
About 20 GGEO volunteers from Goring and Streatley were trained to take part in the Water Quality Monitoring study to determine the level of faecal bacterial pollution present in our stretch of the Thames. The two bacteria to be monitored are those which most affect human health, namely Escherichia coli (E. Coli) and Intestinal Enterococci (IE). These are used as ‘indicators’ by the EA when they make their classification of water quality for ‘Designated Bathing Waters’.
On specific days, every week for 20 weeks between 16 May and 24 September 2024, river water was sampled from four sites between South Stoke and Beale Park. Three sites were located downstream from the Sewage Treatment Works in Goring, Streatley and Lower Basildon: at The Leatherne Bottel car park, Ferry Lane and Beale Park, respectively. The fourth location was on the Berkshire bank across the river from South Stoke and served as a ‘Control site’, being well upstream of the discharge pipe from the Goring STW, and therefore would give a baseline level for any pollution coming into the Goring Gap from Benson, Wallingford and above.
View a live sewage discharge map.
Samplers always worked in pairs. The person sampling wore a life vest, with the other person holding on to it when necessary, working according to the risk assessment. They were trained to collect samples according to a strict aseptic protocol and sterilised all the equipment before using it, including the stainless steel pivoting beaker and the end section of the telescopic rod used to collect the water. They used protective gloves at all times, and poured 500 ml of river water into the pre-printed sterile bottles supplied by the laboratory who analysed the samples. To avoid the bacteria multiplying after the samples were taken, the filled bottles were kept in the dark in a rucksack with an ice pack until they were dropped off to a cool box at the collection point in Goring. From there, an overnight courier delivered the samples to the UKAS government-approved microbiology lab for analysis the next morning.
There are three stand-out results from our work:
The EA has the convention of presenting the various levels of bacteria in river water to the public as four band designations from ‘Excellent’ (the highest, cleanest water quality), ‘Good’ (generally good water quality), ‘Sufficient’ (water meets the minimum standard) to ‘Poor’ (does not met the minimum standard). For E. Coli, ‘Good’ is <1,000 bacteria/100ml and ‘Poor is >1,000. For IE it’s different with ‘Good’ being <400 and ‘Poor’ >400.
As you can see in the bar chart below, the vertical axes had to be broken to change scales in order to accommodate all the date. Interestingly, the highest levels of E. Coli recorded on that day was at site A, the green control location upstream of Goring STW, showing that the bacterial pollution didn’t come from discharges from the overflow storm pipes at our two local treatment works downstream of this point. However, Cholsey STW, 4.5km upstream of sample point A, was spilling for 30.25 hours prior to sampling, and Benson STW, further upstream, was spilling for 38.3 hours during the same period.
The EA’s Monthly Water Situation Report for September 2024 states, "The Thames area experienced its wettest month since records began in 1871. Overall, the Thames area received 193mm of rainfall during the month and over a third of this fell on just two days, 22 and 23 September." Also, the highest rainfall recorded during this period by the EA’s Cleeve Lock rainfall monitor was on 22 September at 38.21mm, two days before the last samples were collected on week 20 on the 24 September. (Goring STW has one storm tank with a capacity of 345,000 litres. Streatley STW has no storm tank).
(NB: The rainfall line on the bar chart shows the average rainfall over the preceding 7 days so doesn’t show this three-day dry period).
The reason for these relatively high spikes is currently the subject of an investigation we are conducting with Thames Water. One possible explanation is that the samples were taken about two metres downstream from the footbridge over the confluence of the mill stream which runs past the Ferry Lane sewage pumping station. This is documented as having a discharge outlet, but unlike sewage treatment works, pumping stations are not fitted with real-time flow sensors which record the start and stop times of all spills. Later this year we are planning follow-up study when we will periodically test the water quality up and downstream of this pumping station to check if we can prove if this the source of the pollution or not.
Overall, the rainfall for week 19 was generally unremarkable for this period of the year. Heavy rainfall has been shown to increase bacterial pollution in rivers, and it also increase agricultural chemical pollutants (e.g. nitrates and phosphates) due to run-off, which is accentuated when the river runs through a valley. We, however, are unable to determine the source of bacteria we collected, although this is now possible with more sophisticated techniques.
At present, sewage is legally only treated to environmental and not public health standards under the conditions of the Bathing Water designation. Climate change is likely to continue to trigger extreme and sporadic weather events, such as heavy rainfall, so improvements to sewage treatment works and storm storage capacity are needed urgently. Goring STW is listed by Thames Water as being due to meet all government targets for storm overflows by 2035 – 2040. Streatley STW is not on the list.
GGEO is planning a follow-up study to try to identify the sources of the biological pollution mentioned above and also to monitor and identify various sources of chemical and other types of pollution in this stretch of the Thames.
Acknowledgments:
This monitoring programme was part-funded by Mend the Gap and conducted in partnership with Thames21 led by Aggie Hodges, who has produced a 29-page technical report of the whole study. The trustees of GGEO would like to thank the 20 or so local volunteers who underwent training and collected 80 water samples over the five months and particularly GGEO’s scientific water quality team of Dr Lotte Meteyard, Jonathan Dewsbury and Steve Rock for undertaking the statistical analysis of the samples from GGEO’s four sites and creating the bar chart above.
