Harling Drove, Norfolk
|Guided tours:||self guided|
|As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
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The Devil’s Punchbowl is a circular depression with no inflow and no outflow, nevertheless it contains a small circular lake. One of the strange things related to this lake is, that the level rises and falls independent from the weather.
The explanation is rather simple, this is a so-called seasonal lake or karst lake, which is simply a visible part of the karst ground water. The underground is composed of chalk, which is karstified. The cracks and caves are filled with water to a certain level, which is called karst ground water or karst aquifer. Inflow and outflow influences the level of the ground water, so it rises in times of snow melt and heavy rains, and falls in very dry periods. However, the whole water body reacts slower than a surface stream, so after a heavy rain it takes hours or days until the level rises, and it may take weeks until it falls again.
The lake itself is located inside a doline, we guess its a solutional doline, where the water vanished into the ground through a crack, widening the crack and dissolving the rock around the swallow hole. This created a shallow circular depression. When the doline became deeper it reached the water table and if the water table rises, the water in the doline rises and vice versa.
The Devil’s Punchbowl and nearby Ringmere and Langmere, are designated Sites of Special Scientific Interest (SSSI), called Breckland meres. However, there are marked differences in water level between the Devil’s Punchbowl and nearby Ringmere and Langmere, showing that they have separate hydrological systems.