Spring Big River Watch: your river health survey results

In May, we ran our second ever Big River Watch – a citizen science event where we invite everyone in the UK and Ireland to be part of a free and easy survey of river health.

Emma Brisdion



In May, we ran our second ever Big River Watch – a citizen science event where we invite everyone in the UK and Ireland to be part of a free and easy survey of river health.

The ask is simple; spend 15 minutes or so near your local river and tell us what you see by filling out a short survey in the Big River Watch app. All surveys recorded on Friday 3rd May until midnight on Thursday 9th May 2024 are included in our Spring Big River Watch analysis and on our interactive data explorer. The app itself remains open for data collection year-round, though, so if you’d like to keep adding to our data set at any time, you can.

During the Spring Big River Watch, around 2,400 of you got involved to submit 1,500 surveys, covering all corners of the UK and Ireland. If we were to combine all of our surveys, together we spent over 25 days river watching!

Here's what you saw:


Spring Big River Watch included a bank holiday, and the survey results indicate that plenty of wildlife was out and about enjoying the sunshine that some parts of the UK and Ireland enjoyed; 702 surveys reported seeing ducks, 367 recorded fish, 282 spotted swans and 227 saw herons. 8 surveys even reported seeing beavers, and one lucky citizen scientist even sent us a photo of a water vole that had made an appearance during their survey!

Riverfly numbers are affected by poor water quality and loss of available habitat. Their presence (or absence!) is a key indicator of the health of a river. At this time of year, with warmer weather and longer days, many of the nymphs – particularly of mayflies – that have been living in the river will emerge as adults and embark on their adult life stage above the water as beautiful, winged adults. 26% of surveys in the Spring Big River Watch recorded seeing riverflies, while just 11% recorded them in the Autumn Big River Watch which took place in September 2023.

Some of the photos you submitted included the wildlife spotted.

a small yellow mayfly sits atop an outstretched finger A white adult swan swims next to several baby swans

How we perceive river health

In our State of Our Rivers Report, published earlier this year, we shared the official WFD data on river health, and the results weren’t good – in England alone, no single stretch of river achieved good overall status, and just 15% reached good ecological status.

So why, then, did 63% of Big River Watchers report that they felt their river looked healthy, and only 25% feel they were looking at an unhealthy river? It’s unlikely that many of the rivers surveyed were indeed ‘healthy’. This partly comes down to us not always being able to see what’s going on in our rivers. Big River Watch is a visual survey in which participants record what they see, while many of the issues that our rivers face lie hidden under the surface. Not all contaminants are visible from the riverbanks; chemical pollution, for example, is present in all of our rivers, yet we have to rely on water sample testing and monitoring equipment to identify it. Some signs – sewage pollution and litter, for example – are often spotted or easier to see after heavy rains, during which they are more likely to be washed into our rivers and be visible during a survey.

Big River Watch asks participants whether they believe the river at their survey location looks healthy or unhealthy, and later asks them to describe how they feel in one word. We collected up some of the most common feelings, and took a look at whether there might be a link with the perceived health of the river. We spotted the same trend that came from the Autumn Big River Watch; positive feelings (calm, peaceful, relaxed etc.) were more likely to be recorded by users stood observing a healthy-looking river, and negative feelings (sad, disappointed, frustrated) were felt far more often by users surveying an unhealthy-looking river.

If you want to take a deeper dive into this disconnect, you can do so using our interactive data explorer. On the map, each survey point is marked blue or red for surveyor perception of healthy or unhealthy river status, but each river stretch is also marked with blue or red (best seen when zoomed in) to correspond with its official Water Framework Directive assessment of ecological health.

While we provide a handy ID guide to common pollutants in the app, not all signs of pollution are easy to identify or appear obviously, and these results also underscore the room for further education to help communities better identify problems with their local rivers.


That being said, 61% of surveys recorded at least one sign of pollution. Silt was the most commonly reported pollutant in 33% of all surveys, followed by livestock (15%). 112 (7.6%) of surveys reported sewage, and 110 (7.5%) reported sewage fungus.

Many of us will, unfortunately, be all-too familiar with the sight of a plastic bottle bobbing at the surface of a river, or of wet wipes tangled in the bankside vegetation, so the survey also asks about visible litter. In the Spring Big River Watch, 53% of surveys reported some kind of litter, and in the photographs that you submitted, we spotted shopping trolleys and cartons.

Below are some of the photos of pollution that you saw during this Big River Watch.

A traffic cone sits amongst junk in a clogged up urban river plastic and cans sit atop a polluted river white and brown scum seen on the surface of the water vibrant green algae fills the water at the edge of a river

Further Citizen Science

This time, around 38% of you said you were new to citizen science! If you enjoyed being part of the Big River Watch, this survey by no means needs to be the end of your citizen science journey. Big River Watch takes place twice a year, so we’ll see you in September for the next one.

Each of our local Trusts (find yours here) also offers different opportunities to get involved as a volunteer or take part in activities which gather information on the health of our rivers. Get in touch with your local team and you could, for example, become a riverfly monitor and sample freshwater invertebrates, or sign up to regular WaterBlitz events to test small water samples for phosphates and nitrates. In June, our friends at EarthWatch are running the Great UK WaterBlitz, during which you can test water quality with a kit that they send you.

In fact, we were delighted to see that some Big River Watch-ers paired their survey with other forms of citizen science, including sending in photos of bacteria water testing, and water quality spot measurements with an EXO25 multi-parameter sonde! Some of you also took part in litter picks, or joined our local Trusts at kick-sampling events to explore life in the river.

Citizen science equipment in front of a river bank insects from river water samples sit in small shallow dishes next to an ID guide

What you told us

It’s also been wonderful to see your Big River Watch experiences on social media. Thank you for tagging us in your photos and sharing what you’ve seen or how you felt during your surveys.

“Just completed the #BigRiverWatch survey on the lower Spey. It was super simple and quick to do, plus I got to spend 10 idyllic minutes listening to the sounds of nature and looking out for wildlife on the banks of my favourite river”

- Spey Catchment Initiative

“Took part in the Big River Watch today, for the first time. So glad I did. In my busy life campaigning for nature and animals, just that 15 minutes of standing still and observing my local river reminded me why I do what I do. I came back relaxed and refreshed.”

- Anne-Marie, via X

“The Rivers Trust #BigRiverWatch complete for Spring 2024 on the River Meon. Even had a ‘Yellow May’ Mayfly land on my hand... Heptagenia suplhurea. Lots of marginal vegetation growing with the high flows looking lush with the sound of evening birdsong.”

- Kerry, via X

“We loved taking part in the Big River Watch this weekend with The Rivers Trust! Great way to engage kids in the environment, rain and all.”

- Anonymous, via Instagram

Want to know more?

We’ve created an interactive data explorer that allows you to explore the survey data.

If you’d like to download the full dataset or have any further enquiries, please contact [email protected].

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