Upper Parrett and Yeo Phosphate Pollution Study
A citizen science investigation



Cartgate2020Cartgate pond, Martock, May 2020. Consistently free of excessive phosphate despite being fed by very phosphate-rich run-off.


These pages will be under constant development throughout 2022

Measuring phosphate pollution in the Somerset Levels catchment

This is a report of an ongoing Citizen Science Project looking at phosphate levels in tributaries of the River Parrett in and around Martock Parish. It started early 2021.


Emerging messages from this study

A rather surprising conclusion emerging from this fine-grain local study of phosphate pollution is that a number proven solutions have long existed and that much of contamination results from failures in the two main industries concerned to put them into practice and the failure of government to enforce its own regulations.

1 The phosphate concentration in the Parrett downstream could probably be reduced by 30% or more if (a) Witcombe Dairy in Ash and Martock parishes observed DEFRA rules for farming near water (more..) and if (b) Wessex Water removed phosphate from the outflows from Crewkerne, Martock and South Petherton Sewage Treatment Works

2 The study shows that where farmers do elect to follow DEFRA guidance, often at a cost to themselves, phosphate levels in watercourses are reduced considerably (more..).

3 Although DEFRA rules for farming near water (link on the right) are shown to be effective in limiting phosphate nutrient pollution, the Environment Agency has seemingly been unable to enforce them adequately mainly, it seems, because of lack of conclusive evidence. In this area there is some evidence that the phasing out of the EU Basic Support grant may have led, either knowingly or inadvertantly, to a disregard of the DEFRA rules. Agricultural run-off seems to be now the main cause of high phosphate levels in this part of the Parrett catchment and a significant reason seems to be that farmers are able to cultivate field margins, including those adjacent to waterways, more intensively..

4 Farmers in the parishes have not yet wholeheartedly adopted practices, widespread elsewhere where flash storms are more common, that resist sudden surface run-off carrying nutrient-rich fine topsoil particles during storms. Typical practices common in other countries are contour ploughing and undersowing. While most farmers in the area have recently adopted maintaining a ground cover over winter, this is not universal and former maize fields left untouched are a significant cause of run-off.

5 Wessex Water has shown that it is well able to reduce phosphate very effectively in the outflow from umanned sewage treatment works, none yet has been installed in the Parrett Catchment. Further, Wessex water adds phosphate to domestic supplies to counter lead poisoning from old pipes and corrosion of old cast iron piping. This is estimated to account for about 5% of the anthoprogenic phosphate entering our water courses.

6 Many countries, such as Canada and many US states, have long banned the the inessential use of phosphates as water softeners in detergents which accounts for over 10% of sewage-generated phosphate. The UK overruled such a ban passed in 2013 by the European Parliament.

7 There is some evidence that the Hills to Levels Scheme (Somerset River Authority and FWAG South West) as it is emerging in Martock, could be a potentially useful example of a mechanism for limiting the amount of phosphate entering the downstream watercourses (more..).

Andrew Clegg
12 February 2022


Somerset County phosphate briefing letter, 2021
South Somerset phosphate briefing letter, 2021

Natural England reports, letters and press releases
-Press release downgrading the environmental status of the Levels due to phosphate levels
- Letter to Somerset and Dorset Councils on developments affecting the levels catchment area
- Somerset levels Profile. Somerset Moors and Levels National Cgaracter Area Profile.
- Somerset Levels Conservation Objectives (2019)

Environment Agency reports, letters and press releases
Phosphorus and Freshwater Eutrophication Pressure Narrative (2019)

DEFRA guidlines on farming near watercourses.
Rules for farmersand land managers to prevent water pollution

Parish phosphate data from the Environment Agency
The Environment Agency collects monthly data in the Parish. Those for the last decade are here (xls files).
Parrett data.
Hinton Meads Brook and Mill Brook .

Environment Agency data - all rivers
The Environment Agency publishes data for many solutes on all rivers here on the DEFRA site
Extracts from the 2021 phosphate sampling of nearby stretches of the Yeo and Parrett are here

[Note that the Environment Agency sampling is expressed as 'total phosphate as P', the convention now used; I have converted this in the data to the older convention of orthophosphate used elsewhere in this document, to facilitate comparisons. The conversion multiplier is 3.06. See experimental pages for more details]

The Ramsar Convention
The Ramsar Convention on Wetlands is an intergovernmental treaty that provides the framework for national action and international cooperation for the conservation and wise use of wetlands and their resources.www.ramsar.org

About Hills to Levels
This is a Somerset catchment management approach to slowing river flow at times of greatest flood risk. It is funded by the Somerset Rive authority and managed by Farming and Management Group, South West (FWAGSW)



Why I set up these pages
I set up these pages as a one-stop repository of evidence around the matter of nutrient pollution of the Somerset Moors and Levels.

This is a decades long story of declining biodiversity in the area that came to a head at the end of 2020 when Natural England initiated a ban of all development in the Somerset Levels catchment area that was not accompanied by a statement showing that it would not generate a net increase in phosphate in teh catchment. This website focuses on the phosphate in the upper catchment of the river Parrett, most partcularly in Martock and neigbouring parishes. This focus spread also to the Whitcombe area of Ash Parish following reports of significant algal blooms in the area.

Navigating these pages
The right columns contain links to more information, sources and data relevant to the discussion in the main columns
The Menu bar gives access to different parts of the study
Sources - A summary account, with photigraphs, of where the excess phosphate is coming from
Experimental - Technical details of the experimental procedures
2021 and 2022 Data - Results, discussion and emerging detailed conclusions.

Existing phosphate monitoring in the upper Parrett catchment area
Phosphate in the watercourses of the Levals catchment is measured routinely by the Environment Agency and Wessex Water monitors the impact of their sewage plants. Both organisations have been helpful in sharing their data (follow links on the right). Both organisations, however, only sample the main watercourses which provides useful information about the extent of the problem but very little about its causes. I therefore decided to rectify this through a programme of sampling of some of the tributaries and rhynes feeding the river Parrett upstream of Langport, concentrating mainly on those in my Parish of Martock and the river Yeo in Ash Parish. The initial work is largely a scoping excercise to allow the design of more f ocussed subsequent studies. The three study areas are described below.

In 2022 the study area will widen with the help of more volunteers and will include West Sedgemoor

The 2021 Study Areas
1 The River Parrett and minor tributaries In Martock Parish
2 The Wellhams Brook Catchment Area between Martock and Yeovil
3 The Witcombe Area of Ash Parish and the River Yeo

The 2022 Study Areas
1 The upper Parrett above the A303 bridge at Martock
2 The Parrett from Martock to Thorney
3 The Hills-to-Levels flood protection scheme in Wellhams Brook
4 The Parrett and tributaries around Langport
5 West Sedgemoor and tributaries
6 The Sowy and Moors around Middlezoy

The Somerset Levels European Court Case
This action by Natural England followed a European Court Case that noted that the UK government was falling short of its obligations under the Ramsar Wetlands Convention in allowing excessive pollution by phosphate of the Somerset Levels Ramsar sites. The government was ordered to address the issue and its first step was to stop all development as an interim intervention until a satisfactory solution was developed.