Saving England’s rarest rivers: the fight for chalk streams

UN World Water Day is held every year on 22 March and is an opportunity to celebrate water and inspire action to tackle the global water crisis. This year the theme is Glacier Preservation. We may not have glaciers in the Big Chalk domain but we do have chalk streams which David Attenborough described as some of the rarest and most precious types of freshwater system in the world.

Alison Matthews – Chalk Stream Restoration Strategy Programme Manager at The Rivers Trust – explains why he was right and tells us more about what is happening to help these amazing rivers.

Chalk streams are found flowing over a band of chalk that runs from the Dorset coast up to the Yorkshire coast, skirting around London and into the North and South Downs. While there is Chalk across much of Europe, it only surfaces like this in England and in a corner of France and Denmark. Which means that 85% of all the chalk streams in the world are English.

They come in many shapes and sizes, but all share the common characteristic of cool, clear, chalk groundwater upwelling through clean gravel beds, with a relatively small range of flows.

Chalk streams are special places for wildlife

Forming some of the most biodiverse ecosystems in the UK, chalk streams have a range of invertebrates such as the blue-winged olive or the winterbourne stonefly, in-river plants such as water crowfoot and starwort, and fish like trout and grayling. The wider stream corridor supports water voles, otters, kingfishers, egrets and herons.  When sympathetically managed, they form a vibrant habitat and are a home for iconic and endangered species such as water voles and salmon.  

People need chalk streams too

The cultural and social importance of chalk streams for people can’t be overlooked. I’ve visited rivers on farms who open their doors to people going through tough times, walked along chalk streams in the middle of cities and seen children delight in catching small fish in buckets. Grown-up fishermen have long enjoyed the challenge of fishing in chalk streams too: trout and salmon angling are an important part of chalk stream heritage.

Increasingly, people are also getting involved in practical work such as removal of non native plants and citizen science. Volunteering fosters a deeper connection with the local environment as well as bringing benefits to health and wellbeing.

The trinity of ecological health

To keep our chalk streams healthy they need good flow, good water quality and natural morphology. Our poor treatment of these gentle rivers has had a pronounced impact on them with only 12% of Chalk Streams considered to be at Good Ecological Status.

Analysis of data from the Environment Agency’s Catchment Data Explorer shows the factors causing the biggest impact.

The impact of poor water quality

Investment in improving water quality has generally led to a reduction in pollution but public concern is high about the effect of sewage discharges on rivers.

These concerns often relate to:

• overflows of partially treated sewage which happen too frequently
• small waste water treatment works discharging to chalk stream headwaters
• discharges where the permit conditions are not sufficiently protective
• bacterial contamination of recreational waters

Sediment pollution of chalk streams is also a big issue as clean gravels become smothered which has a big impact on invertebrate and fish life. This can often be combined with road run off where we are becoming increasingly aware of the potential risks associated with chemicals washing off the road surface.

Recent analysis of water quality data also shows an increasing array of chemicals to be found in our rivers, many with uncertain ecological impacts. No river in England meets good chemical status due to the presence of widespread toxic chemicals.

How we have shaped chalk streams

43% of chalk streams are considered to be artificial or heavily modified. The Romans first created mills and diverted rivers to harness river power. Modification of channels continued to support navigation and water meadows whilst many chalk streams were dredged to facilitate land drainage.

Modifications to chalk streams have many adverse impacts. Barriers prevent migrating fish from reaching their spawning grounds, fragment habitats and create areas of deep, slow flow where sediment builds up. Artificial banks and dredging disconnect rivers from their flood plains.

Our use of chalk water

In the south and east where the chalk outcrops in large areas, the majority of water supplies are derived from the chalk and the rivers that flow over it. In some places abstracting water has caused lasting damage – drying up streams and impacting on wetlands.

28% of chalk streams are reported by the Environment Agency as not having sufficient flow to support good ecological status. We urgently need both reductions in demand for water and investment in more sustainable water supplies to reduce abstraction pressure on chalk streams.

More challenges on the horizon

Modelling shows that rivers are likely to become warmer with lower flows and some of our classic chalk stream species are already in trouble. In some areas, water voles are declining at an alarming rate, native crayfish are under threat and non-native plants are impacting on the river environment.

The southern chalk stream salmon are on the verge of extinction with a mere 119 salmon ascending the River Itchen in 2021. Without healthy chalk streams, it is possible that some of the species dependent on them may go extinct.

What can we do?

There is hope. People have long cared about chalk streams. The Catchment Based Approach (CaBA) established a network of groups delivering actions to improve the water environment. At its heart are catchment partnerships who develop and implement catchment plans and work across sectors to deliver projects.

The CaBA Chalk Streams group was created in 2019 and published the Chalk streams strategy and Implementation plan. A vital component of the Strategy was the “One Big Wish” for proper recognition and protection of chalk streams as the rare and precious habitats that they are. Actions are underway to restore more sustainable abstraction, improve water quality and restore our rivers channels.

Some Big Chalk partners are at the forefront of this activity such as the Chilterns Chalk Streams Project and Big Chalk | River Thame Chalk Steam Strategy. There are also other projects such as Chalk Stream Flagship Projects and Landscape Recovery schemes which are intended to show how communities can work together to improve their local chalk streams – generating new sources of finance and finding new ways of working together.

The CaBA Chalk Streams Group want to build a community to share learning and expertise and build even greater ambition for protecting chalk streams. You can find out more about our work through our Chalk Stream Strategy - CaBA and taking a look at our webinars and resources.

Working with the Big Chalk partnership expands our network of people acting to protect chalk streams and enables us to pool expertise and knowledge. One example of that has been our recent collaboration to help the local groups producing Local Nature Recovery Strategies. We used our combined resources to collate and share suggested measures for protecting both chalk streams and chalk grassland.

The future for chalk streams

In short, there is a compelling case for the need to protect chalk streams and there is a growing community of people actively taking part in that work. However, as the climate changes and the population of England increases environmental pressure is only going one way. We must collaborate and work hard to protect this globally unique habitat.

Plans for 2025/26

The CaBA Chalk Streams Restoration Group has exciting plans for the coming year. Here are some of the things we aim to deliver:

• An updated map and inventory of chalk streams

• An annual review of chalk stream activity

• Help to Regional Water Resources groups in prioritising action to achieve sustainable abstraction

• Identification of future water company investment needs to improve water quality

• Development of approaches to help address highways and agricultural pollution

• Development of a Chalk Stream River Restoration Guide

You can find out more about our work through our website - Chalk Stream Strategy - CaBA

Alison Matthews – Chalk Stream Restoration Strategy Programme Manager at the Rivers Trust