Chalk stream

"Chalk river" redirects here. For the village in Ontario, Canada, see Chalk River.
The River Bourne at Winterbourne Gunner, a typical chalk stream

Chalk streams are rivers that rise from springs in landscapes with chalk bedrock. Since chalk is permeable, water percolates easily through the ground to the water table and chalk streams therefore receive little surface runoff. As a result, the water in the streams contains little organic matter and sediment and is generally very clear. [c]

The beds of the rivers are generally composed of clean, compacted gravel and flints, which are good spawning areas for Salmonidae fish species.[3] Since they are fed primarily by aquifers, the flow rate, mineral content and temperature range of chalk streams exhibit less seasonal variation than other rivers.[3][4] They are mildly alkaline[5] and contain high levels of nitrate, phosphate, potassium and silicate.[3] In addition to algae and diatoms, the streams provide a suitable habitat for macrophytes (including water crowfoot)[6] and oxygen levels are generally supportive of coarse fish populations.[3]

Of the 210 rivers classified as chalk streams globally, 160 are in England.[5]

A list of chalk streams in England gives a total of 224.[g]

  1. ^ a b *"WWF-UK (2014) The State of England's Chalk Streams" (PDF). This report has been written by Rose O’Neill and Kathy Hughes on behalf of WWF-UK. Retrieved 2 April 2023.
  2. ^ *"UK Rivers and Chalk Streams". WWF-UK. Retrieved 2 April 2023.
  3. ^ a b c d Berrie AD (1992). "The chalk-stream environment". Hydrobiologia. 248: 3–9. doi:10.1007/BF00008881.
  4. ^ Casey H (1969). "The chemical composition of some southern English chalk streams and its relation to discharge". Yearbook of the Association of River Authorities: 100–103.
  5. ^ a b Pearce, Fred (24 July 2014). "The threat to chalk streams, our unique contribution to global ecology". The Guardian. London. Retrieved 19 August 2020.
  6. ^ Dawson FH (1979). "Ranunculus calcareus and its role in lowland streams". Annual Reports of the Freshwater Biologists' Association. 47: 60–69.


Cite error: There are <ref group=lower-alpha> tags or {{efn}} templates on this page, but the references will not show without a {{reflist|group=lower-alpha}} template or {{notelist}} template (see the help page).