Friends of the River Mimram - protect this rare chalk stream

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Unique to England

There are only 200 chalk streams in the world and 180 of these are in England. It is England’s unique habitat - like our version of the rain forest.

Chalk: the ideal water course and a unique ecosystem

The underground journey of water from rain to river is the key to what

 shapes a chalk stream. Rainwater dissolves chalk and so becomes alkaline and rich in nutrients. It is cooled by its journey through the chalk, and springs from the ground at a constant temperature whether summer or winter. Under natural circumstances, chalk aquifers buffer the impacts of flood and drought so that chalk stream flows are constant and equable.

Perfect conditions for wildlife

These fertile flows creates perfect conditions for thriving wildlife. These lush rivers provide a gentle habitat in which everything grows to abundance – insects, water plants, fish, crayfish, birds and mammals like the water vole and the otter (Kenneth Grahame’s The Wind in the Willows was, after all, written beside a chalk stream).

Under threat

The chalk aquifer makes the perfect underground reservoir, so as populations have grown water companies have dug deeper boreholes to extract more water. As more water is abstracted, the river flows become slower, affecting the purity of the water, the trout and greyling, the water voles, etc. If they dry out through taking too much water...... All is lost.

Dr Charlie Bell, Living Rivers Officer from Herts Middx Wildlife Trust, explains the importance of chalk streams and why they are under threat

Watch the video >>>>