Hot summer takes toll on chalk stream ecosystems

A summer of consistently low rainfall and high temperatures has damaged the fragile ecosystems of chalk streams, conservationists have warned.

On the River Pang in Berkshire, stretches of the waterway have dried up in places where residents and anglers say they have never previously seen.

The chalk stream was also rated as poor by the Environment Agency this summer after failing a test for hazardous substances.

Chalk streams are a globally rare habitat, with about 85% of the world's examples found in the UK, and they support species including water voles, white-clawed crayfish, brown trout and kingfishers.

Chalk streams are fed by groundwater stored in aquifers, where porous chalk acts like a giant sponge, absorbing rainfall and slowly releasing it into rivers.

And as part of emergency drought conditions, Thames Water has been permitted to pump from the river's aquifer to boost drinking supplies.

Some conservationists argue that this slows the recovery of chalk streams as they rely on the aquifer as a reserve.

Liz Elmore-Elkin, who lives near the Pang in Bucklebury, said she had never seen water levels so low.

"Normally, you'd have this flowing through at a minimum of a foot.

"In all the years I've been coming here, I've never seen it less than this."

For the first time since she has lived there, Elmore-Elkin has been able to stand on the riverbed at the village ford.

The area between Frilsham and Upper Bucklebury received just 66.1mm of rain over the three summer months, 59.4% below the long-term average for 1991 to 2020.

While lower water levels are not unusual after summer, conservationists said exceptionally low rainfall this year had left the aquifers that feed chalk streams unusually depleted.

Peter Devery, from the Angling Trust, said: "The River Pang has suffered exceptionally low water levels this year.

"Anglers who have known and fished the river for decades have seen stretches dry up that they have never previously known to run dry."

He said the impact on fish and other wildlife could be severe and warned recovery could take several seasons, or even years, after water levels returned.

In 2022, Thames Water launched the Pang Flagship Chalk Stream Partnership, which it said would deliver restoration projects between 2025 and 2035.

Charlotte Hitchmough, chief executive of Action for the River Kennet, said: "This is a bit of a wake-up call for the state of our rivers.

"[The Pang is] of poor ecological status, its fish populations are terrible - it's a river that's been messed around with over hundreds and hundreds of years and we've got a number of projects, as part of the flagship project, that are starting to address that."

A Thames Water spokesperson said: "Drought has put significant strain on water resources across Thames Water's region.

"Chalk fed rivers are known to demonstrate changes in flow as the water table rises and falls.

"During hot and dry periods, the source of these rivers can move downstream, leaving some stretches of the river bed dry.

"These natural cycles of wetting and drying are characteristic of chalk streams."

The company said autumn and winter rainfall would be vital to replenishing groundwater levels, adding that ground and soil conditions were the driest since its records began in 2001.

A spokesperson from the Environment Agency said: "Chalk streams such as the River Pang are a valuable natural resource that the Environment Agency is working hard to restore and protect.

"The Pang Flagship project will see £2m of investment to help restore and improve the river."