Chalk streams, explained

Published
Wood in the river
To improve the river Cray’s health and boost its biodiversity, we introduced large wood and flow deflectors, creating faster and slower flows and providing habitat niches for plants and wildlife.

If you watched the BBC series Wild Isles, chances are that you were mesmerised by the scenes of England’s chalk streams. Crystal-clear water, idyllic landscapes and a wide range of wildlife make these watercourses some of the most beautiful and special ones. Chalk streams are extremely rare and we’re lucky enough to have 85% of them in our backyard. There are around 224 running through the English countryside but, sadly, about three-quarters aren’t in good health.

What is a chalk stream?

Chalk streams are fed from underground water and rise through chalk bedrock. This filter process ensures the water is clear, pure, and nutrient-rich. These characteristics, along with the constant water temperature throughout the year, allow a great diversity of aquatic plants to thrive, supporting many fishes, invertebrates, and other species.

These habitats are extremely important for biodiversity as well as our culture. They provide fresh water and leisure spaces for people and are a quintessential part of the English countryside. It’s our duty to protect them and ensure they’re healthy. Unfortunately, there are many issues stressing our chalk streams.

Key challenges affecting the chalk streams

A 2014 Chalk Stream report conducted by WWF, found that 75% of chalk streams have been significantly modified from their natural state. These man-made modifications leave fewer habitats for wildlife and decrease the stream’s resilience to pollution, flooding, and droughts.

Abstraction also puts a key pressure on these ecosystems. As populations increase, so does the need for water supply. Since 1985, the demand has soared by 70%, leading water companies to abstract more water from rivers and aquifers such as the chalk streams in the Chilterns. More than half of England’s chalk streams are at risk from over-abstraction, which could result in ecological damage.

Sewage pollution and agricultural run-off also contribute to the poor health of the streams, killing wildlife and stressing already damaged ecosystems. Extreme weather events caused by climate change such as heatwaves are leading to the drying out of rivers and streams, amounting to the pressure they’re already facing.

On a positive note, there are many organisations and initiatives that are currently helping restore our chalk streams. One of our projects, the Craywatch, funded by Enovert Community Trust, the London Borough of Bexley and the Environment Agency, helped to restore stretches of the River Cray.

The River Cray is a chalk stream that rises from springs in Orpington, near Bromley and joins the River Darent near Dartford and then the Thames. Pollution, abstraction, and invasive species were some of the problems facing the Cray. To improve the river’s health and boost its biodiversity, we introduced large wood and flow deflectors, creating faster and slower flows and providing habitat niches for plants and wildlife. We have also trained citizen scientists to monitor the river’s condition.

Protecting our aquatic environments requires multi-stakeholder action. We can only tackle the modification, abstraction, pollution, and climate change issues if we work together.