Chalk Streams of Lincolnshire

Rain that falls on the
Since ground water levels in the chalk vary according to rainfall and seasons, chalk streams can be quite intermittent in their flow. Some chalk streams have ‘winterbourne' stretches at their headwaters. During the winter when rainfall is at its greatest levels the aquifer will be well topped up. The head of the stream moves up the valley as the water table rises. In summer, lower levels of rainfall soaks into the chalk and the water table drops. The head of the stream moves down the valley, leaving the top section of the stream dry. This dry section is what we call the ‘winterbourne' stretch because it only flows after the winter rains. A characteristic range of invertebrates are adapted to these conditions.