Thousands of dead fish washed up on banks of the River Wensum in Norwich last weekend, one of a rising number of mass fish kills being recorded due to this year’s record-breaking the drought.

Photos taken around the city centre last weekend show the banks of the Wensum littered with dead fish.

More than 3,000 dead fish were collected from the river by council and water company staff, however the total number dead is likely to be much higher.

Locals warn the situation could happen again due to the low flows in the river and pressures from pollution.

It comes as the Environment Agency (EA) warns it is dealing with a rapidly rising number of mass kill incidents due to the drought. The regulator has recorded 159 such cases so far this year.

Thousands of fish dead in Norwich

This summer the water levels have dropped exceptionally low as England experienced its driest July on record, as well as a succession of heatwaves. Half of England is now in drought with millions under hosepipe bans.

The River Wensum is a rare chalk stream and a Site of Special Scientific Interest, however, it is suffering due to sewage pollution and abstraction for drinking water, amongst other issues.

Sewage was discharged into the Wensum and a connecting watercourse following a short burst of rain last weekend. Shortly after locals began noticing dead fish washing up on the river banks.

The rain also washed pollutants from the road, such as oil and debris, being washed into the river.

The EA and Anglian Water are still investigating the incident and have said they believe the dry weather is the primary factor.

However, members of Wensum Riverkin, a group campaigning to protect the river, believe pollution is also likely to have played a part.

“Pollution in some shape or form, whether clogged and stagnant surface drains, sewage storm overflows, or both, was obviously a prime suspect in triggering this, even if the lethally low oxygen levels were considered the final killer,” said Tim Ellis, a member of the group.

He added: “The city of Norwich depends on a healthy, strongly flowing upper Wensum to keep its rivers in a decent state.”

A spokesperson for Anglian Water said: “The fish deaths have been linked to low dissolved oxygen levels in the river following a prolonged period of hot, dry weather and recent heavy rainfall. The Environment Agency is treating this as a wider weather-related environmental event rather than an Anglian Water pollution incident.”

A total of 134 drought-related environmental incidents have been recorded by the EA in waterways so far this year, the regulator told The i Paper.

As well as fish kill incidents, this figure also includes algal blooms in areas including East Anglia, Wessex, Lincolnshire and Northamptonshire, Cumbria and Lancashire and Hertfordshire and north London.

Algal blooms occur in warm temperatures when there is an excess of nutrients in the water, for example through sewage or agricultural pollution.

The total number of dry weather-related environment incidents (134) is lower than the same time last year (184), when large swathes of the country were also in the grips of drought.

However, the figure is far higher than in 2024 when just 12 such events were recorded.

It comes as parts of the UK brace for their another heatwave with temperatures as high as 36°C forecast in central and south-east England next week.

“Impacts of extreme heat such as rising water temperatures can damage river ecosystems and this year’s drought is putting tremendous stress on local fish populations,” a spokesperson for the EA warned.

The long-term forecast remains dry across southern England as the UK’s water supply continues to dwindle.