Rivers Trust seeks help in mapping precious chalk streams

Environmentalists, conservationists and nature lovers across south-east England are being asked to help compile the first comprehensive list of the area’s chalk streams, many of which have never been categorised.

Chalking one up: the River Wandle, with its source in Croydon, is one of just 200 chalk streams in the world

The South East Rivers Trust is seeking the help of anglers, ramblers, river users, conservation groups or individuals who love their local river to help.

The ambitious citizen science exercise has been created to map out lost, hidden or as yet undefined chalk streams as part of the charity’s Chalk Stream Review.

It is estimated that 95per cent of all the world’s pure chalk stream water exists in southern England, and most are feared to be under threat from pollution and water extraction.

Chalk streams are any stream or river that has a flow dominated by natural discharges from a chalk aquifer. In south-east England, there are also many rivers and streams that rise from greensand aquifers, as well as chalk.

Charting the flow: SERT wants the public’s help in recognising chalk streams

On these landscapes, the ground is highly permeable, which results in little surface run-off and rivers are formed instead where water springs from the ground. Due to the filtering nature of the rocks, this water is very high quality and has high alkalinity (it is very “hard” water) because of the dissolved minerals from the rocks it passes through.

There are only about 200 chalk streams worldwide, making them one of the world’s rarest and most precious habitats.

With SERT’s area stretching from Berkshire through Surrey and south London to Kent and down through the Weald to Sussex, the charity is ideally placed to capture complete details about chalk streams – with the public’s help.

The public can upload information via a web portal until December 15, with contributions analysed by SERT’s experts, and potentially added to national databases. Click here to go to SERT’s chalk stream portal

The map of chalk streams to check stretches from Basingstoke, Farnham and Guildford, through Kingston and Sutton across to Dartford and Maidstone and on as far as Folkestone. Another band runs across the South Downs National Park, from Eastbourne to Berwick.

The River Wandle, with its source in South Croydon, and the Hogsmill, in Sutton and Kingston, are both regarded as chalk streams.

City stream: culverted and urbanised, the Hogsmill is another chalk stream that rises in south London

Dr Chris Gardner, the head of science and partnerships at the South East Rivers Trust, said: “Chalk streams are so rare they are often referred to as the equivalent of England’s rain forests or the Great Barrier Reef.

“They are hotspots for biodiversity, as aquatic animals have adapted to the characteristics of these unique habitats.

“This makes it vital we understand where they all are and protect them. However, while a lot is known about the classic chalk streams of Hampshire, the smaller chalk springs and streams of the North Downs and South Downs have been overlooked.

“There is not a definitive list of them – and there is no better way of gaining that information than by asking local people, who know their rivers best. We’re looking for your help. Checking out your local stretch of chalk stream will make a real difference as we categorise these rare habitats, in order to put together plans to protect them.”

Chalk streams are characterised by having high-quality, clear water and low sediment, meaning a wider variety of wildlife can thrive in and alongside them. This makes them as popular for fly-fishing as they are for herons and other wild birds.

Salmon and brown trout typically thrive in them, as do a huge variety of invertebrates such as mayfly and plants like watercress and the white-flowering water crowfoot, the vegetation made famous by 19th Century artist Sir John Everett Millais, who used the River Hogsmill at Ewell as his setting for the painting “Ophelia”.

The South East Rivers Trust is celebrating its 20th anniversary in 2022.

Working in 12 river catchments across the South East, the Trust connects communities and mobilises citizen scientists to educate and engage people on the importance of rivers, and supports and challenges stakeholders, businesses and individuals to protect them.

For more information about its chalk stream survey and other activities, visit www.southeastriverstrust.org/

Read more: River from Tory Philp’s constituency runs brown with sewage


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News, views and analysis about the people of Croydon, their lives and political times in the diverse and most-populated borough in London. Based in Croydon and edited by Steven Downes. To contact us, please email inside.croydon@btinternet.com
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