Big River Watch Launch: A first look at the data

With over 3,600 surveys submitted for the first ever Big River Watch, our river experts have been busy exploring the data gathered by citizen scientists across the UK and Ireland.

Emma Brisdion


During our first Big River Watch in September 2023, an incredible 5,871 of you across the UK and Ireland came together and surveyed the health of your local river, and we’re so grateful for your time and effort. Our team of experts are exploring all the data that you gathered, and we’re excited to share some of the first insights from the event.

Where did you take part?

Over 3,600 surveys have been sent in, from individuals and families and teams, and we’re delighted to see that so many of you have been spotting wildlife, surveying river health and taking some mindful moments across the UK and Ireland. Can you spot your survey site on the map?

60% of you are new to citizen science

Data gathered by citizen scientists is an important tool for conservation charities. When members of the public and local communities help undertake surveys, we’re able to get a much bigger and better picture of the state of our rivers than if just our staff collected data. With technology, it is becoming increasingly easy to become a citizen scientist. In fact, 59.2% of you told us that you’d never taken part in a citizen science activity before – and we hope you’ll join us again for another Big River Watch in April!

👍 73% of you said your river looked healthy

While 17% said you thought it looked unhealthy at the spot where you were surveying, and 10% weren’t sure. Unfortunately, appearances can be deceptive – did you know that in England and Northern Ireland, not a single river is classed as in good overall condition? Chemical and nutrient pollution for example can be hard to identify when just observing the river, but can be very harmful to life in the river ecosystem.

👎 But 54% of you spotted a sign of pollution

Over half of all surveys submitted included at least one indicator of pollution. From signs of sewage to algae blooms and oily road runoff.

Sewage made an appearance

There were 322 total reports of sewage or sewage fungus in your surveys. 175 (5%) of you shared that you could see sewage pollution, and 147 (4%) reported seeing sewage fungus - a grey-brown filamentous fungus that grows in the water with high levels of organic matter and nutrients, that can indicate sites polluted with effluent.

What can we learn from this? Well, we know that rivers in the UK and Ireland are experiencing heavy pollution by sewage, so is it surprising that Big River Watch sewage sightings don't seem very high? Probably not! Sewage pollution isn't always easy to identify - so you may have been standing near some to survey your river, whether you spotted it or not. Other factors, like recent rainfall, also determine when CSOs are used. In other words, the sewage content in your river likely changes in accordance with the weather - that's why we also asked you about recent and current rainfall as part of the survey.

To paint an accurate picture of the problem of raw sewage in our rivers, we need reliable and up-to-date data from water companies, who can tell us where, when and for how long sewage has been released into rivers using Combined Sewer Overflows (CSOs). If you'd like to find out where your nearest CSOs are, and how many times water companies reported using them to spill sewage in 2022, head to our Sewage Map.

We also asked you how being by the river made you feel

Wild and healthy natural spaces are good for our mental health and wellbeing, and many of you shared that you felt calm and peaceful whilst taking part in Big River Watch. But we also took a look at how these answers changed depending on whether you reported that your river looked healthy or unhealthy. At spots where you felt the waterway was unhealthy, we saw an increase in words such as ‘disappointed’ and ‘concerned’.

How you felt when the river nearby looked healthy (left) and unhealthy (right)

What did you see?

We asked you to submit a photo or two of your local river, and you sent us the good, the bad, and the… bikes? From beautiful sunset riverside scenes, to dippers bobbing by the water’s edge and a variety of items that had been discarded in your local watercourses, you rose to the occasion and showed us the beauty of (and the problems faced by) your survey sites. At The Rivers Trust and at our local Trusts, we can look at these images combined with the pollution information that you’ve shared, to help identify problem hot-spots that need to be addressed and monitored.

A green river with lush vegetation Blue skies over a wide river Green river and trees A dipper bird sits by the water Geese swim through an algae filled river An autumnal riverside

What's next?

Join us for the next Spring Big River Watch, taking place from the 3rd May 2024.

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