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Longer Reads

Monitoring water quality

A detailed look at our key water sampling activities

The monitoring of key parameters of river water in the Windrush and its tributaries provides valuable data and information to supply all of WASPs pillars of activity; communication and education, investigation and engagement.


The parameters selected for regular monitoring are those which are recognised as either relating to the permitted or unpermitted pollution activities of the water industry because they are identified in permits or because they can reveal pollution or the consequences of pollution events which may take days, weeks months and years to manifest themselves, particularly when involving lower level but chronic pollution.


The key monitoring activities involve the following:

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This is one of the key ‘nutrient’ substances recognised alongside nitrates as responsible for the eutrophication  of waters eutrophication | Definition, Types, Causes, & Effects | Britannica


As such it is controlled under the EU Water Framework Directive (transferred post Brexit) so that Sewage Treatment Works processing for a population equivalent of 10,000 or more must remove phosphate to a permitted level. The prevalence of the many  below 10k STWs on small rivers like the Windrush means that damage is common and often unaddressed, so that evidence gathering in this area is a vital part of WASP’s work.

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It is possible to force phosphate stripping by the industry if key points can be demonstrated and one of them is the presence of high inputs at damaging levels

Phosphate and nitrates are also sampled by Earthwatch, and Environmental charity which conducts biannual ‘Water Blitz’ events including on the Thames region but this data is very limited and can give only the most basic overview. WASP cooperates with and shares data and ideas with Earthwatch.

The WASP system for phosphate monitoring employs the Hanna low range pocket checker  (Price in 2020 @£75 ) which uses a reagent process to give a digital result to a colorimeter test, thereby avoiding subjective views, particularly in the difficult low definition range for phosphate tube/colour chart tests.

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The kit was selected as best of the type by the Environment Agency and in common with most WASP WQ monitoring kit was chosen in consultation with an Environment Agency specialist in this field. It actually measures orthophosphate so to convert to the phosphorus figures recorded by Earthwatch, the Hanna result is multiplied by 0.3261

Sampling started with one checker and was initially used to establish effectiveness and accuracy and to identify the key locations, relevance of point sources of pollution and the levels over a wide range of locations to provide an overview. That overview and key location data has been effectively used in TV and written media articles and in engagements with Thames Water and the Environment Agency. It has been of great value and there was no better way to enable WASP to have access to this vital field of knowledge.

With the addition of more equipment for more volunteers, the consistency of location and the frequency of sampling has increased and the database has grown. Results are logged by location and results using Epicollect 5 which is a free application hosted by the Big Data Institute.

Further development of phosphate sampling is our next step and that will bring in more coordinated sampling along with other parameters at key locations as well as the valuable random test option. Analysis of the available data is now viable with the volume reaching useful levels.

At present we have 8 pocket checkers deployed to volunteers who conduct consistent location as well as random or intelligence led tests.

The stand out piece of evidence obtained by WASP in this area is that the Defra SAGIS model for apportioning phosphate input from the water industry and agriculture appears to be highly inaccurate and that most of the phosphate recorded on the Windrush appears to be attributable to the water industry.


This is the second key nutrient contributing to eutrophication and its presence is often laid exclusively at the door of agriculture which is undoubtedly responsible for big inputs to the river, some of which are the consequence of now outdated and abandoned practices. However, it is clear that sewage works are also a contributor and the WASP testing program will help to establish the degree of input.

Background levels on the Windrush and most if not all local rivers are quite high as evidenced by the Earthwatch overview.


WASP monitoring has been limited in this area due to the high cost of the testing equipment and the practicalities of taking the readings at room temperature which is a requirement for this process.


Once again a Hanna meter has been used and has been of particular use recently in monitoring high levels in the upper catchment discovered, once again by spot sampling.

It has also been used in conjunction with an auto-sampler to obtain a 24-hour profile at a key location.


The development of this area is desirable at this stage of the investigation into the role of waste water wand water treatment in contributing to the high levels of nitrate in the catchment but at @ £500 per kit there is less opportunity to offer these to all of the P test team members.

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Ammonia is one of the core permit parameters required for most STWs, the others being Biochemical Oxygen Demand and Suspended Solids and it is relevant because it is not usually detectable in unpolluted water. STWs normally convert ammonia to nitrogen and many of the live industry monitoring is of the intermediate stage ammonium as an indicator of ammonia levels. This is measurable with live monitors rather than spot sample tests.

Unlike phosphate and nitrate which cause harm through eutrophication, ammonia is damaging and lethal to aquatic life at varying levels influenced by temperature and the PH of the water.


Ammonia emanating from Witney STW in 2016 was responsible for killing around 1700 fish in the Colwell brook. That case was not prosecuted as the industry claimed without evidence that it was caused by a third party that was never identified.

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The WASP ammonia meters are less widespread and apart from at one location have not been used for routine sampling yet as most locations should and generally will reveal a zero or very low reading. They are used to monitor or identify suspected spilling events of to assess the contribution of suspicious outfalls, streams  or ditches.

The costs are similar to the phosphate kits and the recorded data is stored on the Windrush walk Epicollect 5 database.

Dissolved oxygen

Dissolved oxygen refers to the level of free, non-compound oxygen present in water or other liquids. It is an important parameter in assessing water quality because of its influence on the organisms living within a body of water.

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This is an important factor in understanding what is happening and why. It may provide useful information in understanding the role of algae and bacteria in turbidity through the seasons. On a very simple level it can show the temperature spikes that can come with untreated sewage impact or even the release of treated effluent. Constant monitoring provides a great background signature.

In Situ monitoring data showing a temperature rise during the night alongside a dissolved oxygen sag – likely to be a pollution event.

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Turbidity is a key area of work because it has been such a contentious topic with river campaigners for many years with the first rumblings of concern starting in the late 1970s with the observation of a summer ‘milkiness’ which has developed to an almost year round grey/brown murkiness with some clearer periods in winter.

The Environment Agency has tried to convince the public that this is a natural phenomenon and even that it is attributable to a geological fault which separated it from clearer rivers like the Coln. There was no scientific study conducted to back up that claim and the fact that the river Coln is now suffering similar turbidity problems after years of clear water appears to throw all of the Agency’s explanations into doubt.

One common feature of the rivers suffering turbidity issues is sewage pollution and a potential link with high phosphate inputs from STWs. The Environment Agency Slide used to explain the effects of high nutrient levels even identifies turbid water as a consequence of high nutrients.

Here is a simple guide to the effects of turbidity on aquatic life.

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WASP measures and gathers evidence about turbidity in two ways:

1. Situ Aqua Troll multi parameter meter. Using the In Situ Aqua Troll multi parameter meter which records data by the nephelometric turbidity unit which is an industry standard unit. This equipment is used for spot checks at points of interest and can be used to compare rivers and locations. It is particularly useful where levels are low or clarity is high so that alternative methods like Secchi discs and tubes are ineffective.

Sity Aqua Troll multi parameter

This is an example of a short study which was used to encourage the Environment Agency to engage in identifying the cause of high levels of turbidity seen in the river in early 2109.

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2. The WASP wand. This is a cheap and easily constructed device that was made to allow WASP to gather data during the Covid19 restricted periods. Here is how to make one: Wasp Turbidity Wand - YouTube

The data is once again stored on Epicollect 5 and gives a good indication of how turbidity has varied over the course of the year and can be viewed alongside rainfall and river level data to inform the debate about the causes of turbidity.

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Coliform bacteria

Coliform bacteria is the key measure for the assessment of bathing quality water under the Bathing Water Regulations 2013 and the development of a database on key locations on the Windrush is the starting point for an application for bathing water status which would be allied to a ‘safe for all’ recognition in a river which is often not appropriate for swimming but is a valuable asset in which to enjoy other recreation which involves direct contact with the water.

WASP has engaged in research and development work with a company called Palintest which is developing a field test for coliforms.

This led to the use of the currently recognized Colitag test which identifies the most probable number of bacteria colonies by adding water.

Epicollect 5 database

WASP has two projects; Windrush walk and Turbidity. Windrush walk holds entries from 556 sampling events (sometimes multiple samples) at sites of varying frequency.

The Turbidity project hold the WASP wand relative turbidity data which although set up as a temporary solution to Covd 19 restrictions, has yielded excellent comparative data and remains a cheap, useful and valid exercise. This holds 316 results at 6 key locations with some lesser tested spots added.

The analysis of all of our data is covered on the Analysis page as it extends way beyond the Citizen Science data.

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