Chalk Streams of Lincolnshire

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The Lincolnshire's chalk streams are a characteristic and attractive feature that has helped shape the Lincolnshire Wolds landscape over the past 10,000 years. Much of the rolling hills of the Lincolnshire Wolds has underlaying chalk that has been designated as an Area of Outstanding Natural Beauty. 

Rain that falls on the Wolds is filtered through the underlying chalk aquifer. An aquifer means that it is able to soak up and hold rainwater – a bit like a sponge. Water then moves through fissures (cracks) in the chalk. The water emerges at ground level, from springs and blow wells, crystal clear and with a constant temperature of 10°C. These typical characteristics make them ideal to provide drinking water to many and are home to some of the most rare and threatened plants and animals, such as water crowfoot, water vole, otter, European eel and Brown trout. 

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.