Bulbourne river at Berkhamsted

   Chalk Stream

The water flow of chalk streams is dependent on the height of the underground water table in the chalk bed rock. Historically this level was high-- requiring an overflow in the form of marshy flood meadows. This all changed when the Grand Union Canal was built and began to pump water from the underground water table with pumps at Northchurch and Dudswell. Later still, as the town grew, the public utilities increased their take. Gradually the flood meadows dried out and the Bulbourne, like the other Chiltern Chalk streams, became a “low flow” river, often drying out completely during the summer months.

Rainfall from October -March would see a temporary return of water, but the combined abstraction of the Water Companies and the canal would reduce the water table to the no-flow state.

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