The importance of our chalk streams and how we can help them

Several of the world’s most precious chalk streams are found here in the North Wessex Downs Area of Outstanding Natural Beauty, including The River Kennet, Letcombe Brook and The River Lambourn. See links below to latest information from ARK (Action for the River Kennet) and the Letcombe Brook Project.

What is so special about chalk streams?

Chalk streams are rivers that rise from springs in landscapes with chalk bedrock. There are only 200 in the world and most of the are in the UK. Their bedrock is in a sponge formation, allowing rainwater to percolate easily down to the underground aquifer or water table. Chalk streams therefore receive little surface runoff. As a result, their flow contains little organic matter and sediment and is generally very clear. The beds of challk streams are generally clean, compacted graveland flints, which are good spawning areas for trout and grayling. Many of the chalk stream springs have also been used as sites for watercress production, due to their constant temperature and clean, alkaline, mineral-rich spring water.

Water sharing

There is a finite amount of water on the planet and it is shared between human consumption and our natural waterways.

Water companies extract water from chalk stream aquifers and if too much is taken, it exacerbates the tendency of streams to run dry (like the River Lambourn is a winterbourne flowing only part of the year) and can seriously affect wildlife in the stream.

The more water we use in our homes and businesses, the more is tied up in pipes and sewage systems and the less remains in our rivers and waterways. The more chemicals we use in our homes and businesses, the more toxic our rivers become as the sewage system doesn’t filter them all out before the water is returned to the rivers.

Why does this matter?

Rivers are home not only to fish but to many species at the bottom of the food chain for birds qne mammals like water voles. They are also vital for many insects that have an aquatic stage of development. The reduction in our insect population is partly because of the drop in clean aquatic habitat. 

Rivers and their banks are also vital wildlife corridors, in the same way that hedgerows are.

What can we do to help our rivers?

Talk by Anna Forbes from ARK (Action for the River Kennet) – 19 January 2022

Anna explains the wonderful work ARK is doing to protect the Rivers Kennet and its tributaries including the Lambourn and the Shalbourne Rivers. Over winter  trout are laying their eggs in mounds and depressions of gravel so please try not to disturb the eggs as only 5 in 100 trout survive their first year.

Invasive Himalayan Balsam needs to be removed from banks for instance at Weston and fallen trees left in situ for Kingfishers to nest in.

There is exciting evidence of otters in Newbury from their poo/spraint (which doesn’t smell bad and is full of fish scales and crayfish shells).

There have been mink sightings on the river and they must be despatched as they are vicious predators of smaller, native wildlife.

Interview with Letcombe Brook Project Officer Mark Bradfield – April 2021


Mark Bradfield (above) looks after the Letcombe Brook which is 12 kilometres of chalk stream that rises in Letcombe Regis and flows north through Wantage and Grove. Mark explains how the river is home to otters, water voles and trout, the problems of mink and crayfish, the power of ponds and how to garden along the river.

Listen here from 4 min 20 sec:


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Penny Post


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Covering: Newbury, Thatcham, Hungerford, Marlborough, Wantage, Lambourn, Compton, Swindon & Theale