Chalk streams are characterised by clear water and a diverse flora. Only 210 are known globally, 85% of which are found in southern and eastern England.
The streams emerge from chalk aquifers. The very pure water is rich in minerals and remains at a fairly constant temperature year-round which lets diverse aquatic plants grow. The plant diversity and good water quality supports many invertebrate and fish species, including brown trout.
Simon Cooper in Life of a Chalkstream (published by William Collins 2014) says that “A chalkstream river valley today is a tamed version of how it started out. After the ice age it would have been little more than a vast, boggy marshland with no river to speak of but rather thousands of streams, rivulets and watercourses that randomly flowed this way and that. At some point, it is hard to say when, the early Britons must have started to use the valley for a purpose, initially farming, which involved draining the land. Inevitably drainage involved reducing the myriad streams to a few channels, which in turn became the rivers that have evolved into the chalkstreams we have today.”
Some headwaters of chalkstreams include ‘winterbournes’ (Anglo Saxon for a stream flowing from a spring), which naturally run dry in late summer when low winter rainfall has not recharged the aquifers. Excessive local abstraction will exacerbate this and is undoubtedly so for Exning where the level and flow is significantly less than 40 years ago. There are records of 4 water/corn mills on the New River in earlier times.
Other chalk streams
The Wild Trout Trust is a UK and Ireland-based conservation charity dedicated to safeguarding rivers, lakes, and their wildlife, notably wild trout.
chalkstreams.org is the website of Charles Rangeley-Wilson – a writer and conservationist with a passion for chalk-streams, and founder of the Wild Trout Society (which became the Wild Trout Trust).
The Rivers Trust is the umbrella organisation for 65 member Rivers Trusts across Britain, Northern Ireland, and Ireland, offering expertise in river and catchment conservation.
The River Lark Catchment Partnership is a group of organisations and individuals working to conserve and improve the River Lark and it’s catchment area.
The Bury Water Meadows Group works to conserve and improve the Rivers Lark and Linnet in Bury St Edmunds and the adjacent areas.