The River Evenlode catchment: a community’s ongoing fight against water pollution

28th August 2025

Our Freshwater Research Manager, Laura Bannatyne, shares the story of a local community’s ongoing fight against water pollution in the River Evenlode catchment in the Cotswolds.

A Cotswolds catchment

The Evenlode catchment lies in the heart of the Cotswolds, extending roughly 45 miles southeast from Moreton-in-Marsh in Gloucestershire to its confluence with the Thames near Cassington in Oxfordshire.

Its story shows the wider struggle to protect and restore the water quality of Britain’s waterways. This struggle is amidst the growing concern of communities, scientists, and organisations working for healthy rivers that will support wildlife, people’s wellbeing, food-production and water supply.

The Evenlode community’s fight is as much about their love and connection to the water as it is about the resources it provides.

Gradual decline

Over the past five years, Earthwatch Europe and other member organisations of the Evenlode Catchment Partnership (ECP) worked with and were funded by Thames Water. This was part of the Smarter Water Catchment initiative.

The aim was to return the waterbodies of the Evenlode catchment to ‘good ecological status’. Older community members recall that the Evenlode once ran crystal clear from its source to the confluence with the Thames.

It supported good fishing and opportunities for swimming and boating, abundant birdlife, and sightings of voles and otters.

Those days are gone, with river activities curtailed by reports of illness amongst participants, and fish numbers dropping to the point where fishing competitions were abandoned.

Gathering data

Supported by the FreshWater Watch team at Earthwatch Europe, ECP citizen scientists took monthly measurements of nitrates, phosphates, and turbidity throughout the catchment. This built on data gathered from 2014 onwards and extended the reach of the Environment Agency’s national monitoring programme.

These results were bolstered by regular surveys of aquatic invertebrates (which are the basis of healthy food chains for fish, birds and mammals). Near-continuous water quality data was also gathered from sophisticated equipment, known as sondes, installed by the ECP up- and downstream of sewage treatment works.

A robust body of data and information has been assembled thanks to these efforts, but it provides troubling insight into the issues in the Evenlode catchment. The full report is available here.

I’m part of this great body of citizen scientists who are concerned about our waterways, and who feel that it’s wrong for our rivers not to be in the healthy condition they were in our childhood.

John Pratt, Evenlode community volunteer

A troubling picture

As the Evenlode catchment is largely an agricultural area, there is a legacy of high nitrate concentrations in the waterways. The pollution from nitrates is exacerbated by elevated phosphate concentrations downstream of 19 sewage treatment works that serve the growing population of the catchment.

In summer, this is largely due to the failure of treated effluent permits to protect the reduced flow in headwaters and tributaries. In winter, it is because of the frequent and prolonged releases of untreated sewage from storm sewage overflows.

The impacts of this pollution can be seen in the falling fish numbers, murky flows, and algal blooms. It is measured by the twice-daily pattern of elevated phosphate, organic material, temperature and turbidity readings, and reduced dissolved oxygen concentrations in the water. These patterns are typical of sewage treatment works outflows.

Actions and consequences

Long-term mitigation of the impacts from agriculture are being addressed collaboratively by the ECP and landowners. This is through projects designed to retain run-off, sediment, and nutrients on farms, and to limit the use of natural and synthetic fertilisers.

At the same time, new connections to sewage treatment works from housing developments have increased sharply, placing more pressure on facilities that already lacked the capacity to deal with current volumes.

The scheduled upgrades intended to increase capacity and reduce the phosphate load from these works were systematically delayed or removed from planning cycles, with none of the promised phosphate reduction being implemented within the original timeframes.

ECP partner organisations and the community come together to monitor the waterways and raise awareness of the challenges facing the Evenlode. Despite all this work, as a result of the increased pressure on the area, there has been no measurable improvement in water quality in the River Evenlode and its tributaries during the five years of the Smarter Water Catchment initiative.

In fact, the situation has worsened in much of the catchment, with not one waterbody in the Evenlode achieving the Environment Agency’s criteria for “good” status in 2024.

Every single river heads into the ocean, and if things are in it like plastic, slurry and sewage, it will all float down the river into the sea. If we keep doing the river tests and not dropping litter that will help rivers and all bodies of water.

Pupils from Enstone Primary School

Government funding to address pollution and improve water quality

The ECP voted unanimously to step away from their funded relationship with Thames Water at the end of March 2025. They continue to strive for better water quality, sustainable land management, and do outreach with schools and community groups.

Earthwatch Europe are actively seeking funding to continue work with landowners and communities in the Evenlode and other catchments. Together we will put pressure on planning authorities, regulators, and water companies to ensure that sewage treatment works keep pace with development.

We also hope to see steps to remove phosphates (and other contaminants) more efficiently from sewage effluent.

As such, Earthwatch Europe welcomes the announcement by the Rt Hon Steve Reed (OBE, MP) that Government will reinvest water company fines into local projects across the country. It will fund projects to clean up our waters, including local programmes to address pollution and improve water quality.

We likewise urge Government to stand firm against calls for the easement of existing fines and penalties that have been imposed on water companies because of non-compliance.

Take action for your local river

Is the water quality in your catchment improving or declining? Find out by joining the Great UK WaterBlitz, a biannual campaign calling on everyone to test the quality of their local rivers, streams and lakes.

Help us understand the health of your local waterways and contribute to building a picture of water quality across the UK. This data will help us fight for change.