Our Fluidion Project

The aim of the ERA - Eco Rother Action Fluidion Project is to investigate E.coli levels in the River Rother and its tributaries as it flows from Petersfield to Midhurst. We use a Fluidion Alert One analyser to assess the E.coli levels in our water samples. These bacteria levels are an indicator of water quality, with high levels being a potential health risk and having the potential to be harmful to the environment.This information will be used to inform the Environment Agency (EA) when we record levels that are of concern to us, but, via this webpage, we also wish to make this information available to anyone who has an interest in knowing these levels, such as local river swimmers, anglers, or dog owners whose pets go in the river.

Although locals swim in the river at various different points, nowhere on this stretch of the Rother is a designated bathing site, which would then require more stringent monitoring by the EA.

We need to allow the River Rother to meet its own needs, plus those of people and the wider environment.

Water Quality Monitoring

In designated bathing waters, water quality is monitored regularly by the EA during the bathing season to help the public assess the risks of entering the water. These tests measure bacteria including E.coli (EC), with results for E.coli being reported in colony-forming units per 100ml (cfu/100ml). Bathing water quality is classified based on 4 years’ worth of samples from a site.

The Department for the Environment, Food and Rural Affairs (DEFRA) classifies water quality into the following categories:

🟢 Excellent – EC: ≤500 cfu/100ml

🟡 Sufficient – EC: ≤900 cfu/100ml

🔴 Poor – EC: >900 cfu/100ml (i.e. Sufficient standard not met)

See Understanding DEFRA data where it says ‘if water is classified as Poor, then the symbol for "poor" together with a sign showing advice against bathing must be displayed in the following year’.

While we quote DEFRA classifications here for reference, it’s important to note that official classifications are based on seasonal data, not single samples. DEFRA classifications also involve tests for Intestinal Enterococci.

Our test results so far

We are using our Fluidion Alert One to investigate E.coli levels in our section of the River Rother. Untreated wastewater discharges predominantly occur during and after heavy rains, and we will be monitoring river water downstream of such discharges. At other times we will be testing at various points along the Rother and its tributaries to develop our understanding of typical values and how they might fluctuate across the year. We are also checking phosphate levels whenever we test for E.coli to investigate the link between the two. Phosphates can occur naturally, or can come from sewage or from agricultural fertiliser run-off. Sewage related phosphates may come from Wastewater Treatment Works; privately owned septic tanks and small sewage treatment plants; or from animals including farm stock and pets.

Although our results look poor using the criteria above, it is too early to draw definite conclusions since the DEFRA criteria are expressed in terms of annual averages and using filtered samples. We test unfiltered samples.

Place	W3W location	Date	E.coli cfu/100ml	Phosphates ppm
River Rother, downstream of Rogate sewage works Rogate WTW - DS	huddled.easily.curiosity	040925	9734	0.41
Mizzards footbridge, upstream of Rogate sewage works Rogate WTW - US	comical.rifled.repeating	300825	2512	0.15
River Rother, downstream of Rogate sewage works Rogate WTW - DS	huddled.easily.curiosity	290825	4780	0.18
Elsted Stream, Dumpford, upstream of Trotton sewage works Trotton WTW - US	irrigated.frail.indirect	260825	4920	0.58
Elsted Stream, Dumpford, downstream of Trotton sewage works Trotton WTW - DS	tour.rooftop.harmlessly	250825	6703	0.80
Elsted Stream, upstream of Harting sewage works Harting WTW - US	shielding.strain.snuck	230825	260	0.37
Elsted Stream, downstream of Harting sewage works Harting WTW - DS	retain.simulator.dreams	220825	898	0.63
Mizzards footbridge, upstream of Rogate sewage works Rogate WTW - US	comical.rifled.repeating	070825	1427	0.25
River Rother, downstream of Rogate sewage works Rogate WTW - DS	huddled.easily.curiosity	060825	4779	0.23
Elsted Stream, upstream of Harting sewage works Harting WTW - US	shielding.strain.snuck	020825	1945	n/a
Elsted Stream, downstream of Harting sewage works Harting WTW - DS	retain.simulator.dreams	010825	5746	0.55 ppm
Elsted Stream, Dumpford, upstream of Trotton sewage works Trotton WTW - US	irrigated.frail.indirect	310725	3611	0.45
Elsted stream, upstream of Harting sewage works Harting WTW - US	shielding.strain.snuck	300725	355	0.55
Elsted Stream, downstream of Harting sewage works Harting WTW - DS	retain.simulator.dreams	280725	1665	0.55

Why this matters

The River Rother has many issues.

Flowing through sandy soils it is said to be the most erodible river in the UK, which leads to high sedimentation levels. There are a number of Invasive Non-Native Species present, including mink and Himalayan Balsam, as well as there being species that are absent but would have been here previously such as water voles and beavers. Local agriculture introduces the possibility of agricultural run-off. Water is extracted both for agricultural and human use. There are many weirs and other human constructions across the flow of the river making it difficult for fish to move freely along the river. There are chemicals from road run-off ending up in the river, as well as litter.

And. of course, there is the issue of untreated wastewater, including sewage, being discharged into our waterways, known as ‘spills’, especially during times of heavy, persistent rain. The public do now have access to real near time data about whether any Southern Water Wastewater Treatment Works are spilling via their Rivers and Seas Watch page, and more widely via Rivers Trusts’ Sewage Map.

How much untreated wastewater ends up in the River Rother in our area?

River Rother Combined Sewage Overflows from source to Midhurst

Total hours of discharge of untreated sewage
(FYI there are 8760 hours in a year)



2020
2021
2022
2023
2024

Liss Waste Water Treatment Works, Southern Water
611
607
542.90
1439.85
878.05

College St., Petersfield, CSO, Southern Water
3
7
0
0
2.93

Chapel St., Petersfield, CSO, Southern Water
151
28
4.97
15.43
44.89

Petersfield Waste Water Treatment Works, Southern Water
233
330
328.97
543
331.24

Buriton, Sewage Treatment Works, Southern Water
975
284
128.55 
2394.95
2284.80

Rogate, Waste Water Treatment Works, Southern Water
705
323
259.98
772.99
627.20

South Harting, Waste Water Treatment Works, Southern Water
4146
3406
3154.83
2164.12
3,583.98

Totals
6824 hours
4985 hours
4420.20 hours
7330.34 hours
7753.09

The Rother needs all the friends it can get!

Terms and Conditions

Water testing disclaimer

The terms ERA and ERA - Eco Rother Action are defined as including the organisation itself, all volunteers, any sponsors, advisers, affiliated organisations and/or people in any way connected with ERA or advising ERA.

These tests by ERA are performed in good faith, at irregular intervals and with limited resources for testing, analysis and publication.

The Environment Agency (EA) is the regulator and it is the relevant authority for supervising water quality, pollution and sewage levels on the River Rother in the Rother Valley. EA is also responsible with respect to public safety issues in relation to the latter. ERA is not responsible and cannot be held liable for any of these matters.

ERA is a voluntary organisation run by volunteers.

Limitations of liability

The information is provided by ERA without any guarantees, warranties or liability of any kind whatsoever and howsoever arising. This includes but is not limited to any acts or omissions, any inaccuracies and/or any relevancy as to time frame.

ERA excludes any and all liabilities, to the fullest extent permitted by law, for any of these limitations of liability, any actions taken or not taken based on any information provided by ERA or any lack of information.

Neither ERA - Eco Rother Action, its volunteers, nor any affiliated organisations can be held liable for:

• Errors by ERA in conducting or processing tests

• Delays by ERA in obtaining or publishing test results

• Any reliance on the information provided

ERA shares test results to help river users make informed decisions. However, these results are only a general guide and may not reflect real-time conditions. By using our data you acknowledge that:

• ERA, its volunteers, and affiliated organisations are not liable for any harm or damage suffered due to reliance on our data.

• The information is provided without guarantees, conditions, or warranties regarding accuracy.

• We exclude all liability to the fullest extent permitted by law for actions taken or not taken based on our content.

User Responsibility

All users of the River Rother must assess all and every risk in interactions of any kind that they have with the River Rother including, but not limited to, any pollution, sewage, chemicals and/or run-off. Users are responsible for themselves, their children and animals in these and all other respects and in particular if entering the River Rother or its tributaries or streams for any purpose including, but not limited to, swimming or paddling. Users are to supervise closely their children, any vulnerable adults or non or poor swimmers and/or their animals. Any health problems are to be reported to the relevant authorities and are not the responsibility of ERA - Eco Rother Action in any respect. Water quality can change rapidly, and test results may not reflect current conditions.

Third-party links and data

This webpage may reference third-party organisations or external data sources. We are not responsible for the accuracy, availability, or reliability of external information.

Changes to these terms

We reserve the right to update these Terms and Conditions. Continued use of this webpage constitutes acceptance of any changes.