It started with a morning of pulling Himalayan balsam along the River Chelt.

As volunteers (including from the Guardians of the River Chelt) worked their way along Chelt Walk as part of a session organised by Cheltenham Borough Council, they came across something worrying. In the shallow water were two tiny dead bullheads – small, bottom-dwelling fish that are particularly sensitive to changes in water quality. Nearby, the riverbed was coated in thick brown algae. On their own, neither sight tells the whole story. But together they raised an important question.

Was the river trying to tell us something?

Rather than making assumptions, the group did exactly what they encourage everyone to do: they asked questions, checked the evidence and reported what they had found.

Every report helps build the bigger picture

After seeking advice from Conservation Officer for the Wild Trout Trust Ed Noyes, the dead fish were reported to the Environment Agency.

Although there were only two fish, the advice from the Environment Agency was clear:

Report every incident of dead fish, even if it’s only one or two.

Each report helps build a picture of what’s happening across our rivers and can help identify problems much earlier. At around the same time, another resident shared a photograph of what looked alarmingly like sewage entering the River Chelt near a storm overflow. The image was quickly passed to Severn Trent’s River Rangers.

Within hours, both Severn Trent and the Environment Agency had visited the site. Their investigation found no evidence that the storm overflow had discharged, ammonia levels were low, and there were no signs of sewage pollution. Instead, the culprit appeared to be something much more natural.

When algae looks like sewage

The brown scum floating on the surface wasn’t sewage at all. It was dying brown algae.

During long periods of hot, dry weather, algae can grow rapidly in rivers. As it dies back it breaks away, floats downstream and can collect in thick brown mats that look remarkably like pollution.

It can be alarming to see, but appearances can sometimes be deceptive. That doesn’t mean people shouldn’t report it. Quite the opposite.

The rapid response from Severn Trent and the Environment Agency shows just how seriously reports are taken. If something doesn’t look right, it’s always worth letting them know. It’s far better to investigate a natural event than to miss a genuine pollution incident.

Heat brings hidden challenges

While the algae itself wasn’t pollution, the prolonged hot weather is creating real challenges for river wildlife.

Warm water holds less dissolved oxygen than cool water, making it harder for fish and other aquatic life to breathe. When algae grows quickly and then dies, the natural process of decomposition uses even more oxygen, putting additional pressure on wildlife.

This is especially difficult for species such as bullheads, which live on the riverbed and are among the first fish to be affected when oxygen levels fall.

Recent water quality monitoring carried out by volunteers has also shown warmer-than-usual river temperatures and elevated phosphate levels. On their own these figures don’t necessarily indicate pollution, but when combined with observations from the river they help build a much clearer understanding of what’s happening. This is exactly why regular monitoring matters.

What should you do if you see something?

If you notice dead fish, suspected pollution or anything else that doesn’t look right on the River Chelt:

• Report environmental incidents to the Environment Agency Incident Hotline: 0800 80 70 60
• Report suspected pollution involving Severn Trent related watercourses: 0800 783 4444

You don’t need to know exactly what’s happened. Simply reporting what you’ve seen, where you saw it and when it occurred can help experts investigate and, if necessary, protect the river.

Looking after the River Chelt together

The Guardians of the River Chelt have always believed that everyone can play a part in caring for our local river. Sometimes that’s by removing invasive Himalayan balsam. Sometimes it’s by collecting water quality data. Sometimes it’s simply by noticing when something doesn’t seem right. Every observation helps. Every report adds to our understanding. And every person who takes the time to care becomes another guardian of the River Chelt.