A karst spring is a spring that is part of a karst system. That includes the underground drainage of a much larger area, which means that karst springs often have a very large discharge. Because of their often conical or bowl shape, such water sources are also known in German-speaking lands as a Topf ("pot") which is reflected in names such as Aachtopf (the source of the Radolfzeller Aach) or Blautopf (the source of the Blau river in Blaubeuren).
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The main feature of karst springs results from the fact that water is rapidly transported by underground caverns. This means that there is minimal filtering of the water and little separation of different sediments. Groundwater emerges at the spring within a few days. Storms, snowmelt and general seasonal changes in rainfall have a very noticeable and rapid effect on karst springs.
Many karst springs dry up during the driest part of the year and are then known as intermittent springs. Still others are dry most of the year round and only flow after heavy rain. Sources that only flow during wet years are often known in German as Hungerbrunnen ("hunger springs"), the reason being that folklore sees a connection between the flow rate of a spring and poor yield in a wet year. It is however more of a culturally related superstition. Scientific studies on various Hungerbrunnen have not confirmed such a relationship. An example is the Hungerbrunnen in the parish of Heuchlingen near Gerstetten.
The properties of karst springs are unsuitable for the supply of drinking water. Their uneven flow rate does not support steady rates of consumption, especially in summer when there is lower discharge but higher demand. In addition, poor filtering and high hardness mean that the water quality is poor. For these reasons, karst springs are nowadays rarely used for drinking water.
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- Whittow, John (1984). Dictionary of Physical Geography. London: Penguin, 1984, p. 291. ISBN 0-14-051094-X.
- Elmer LaMoreaux, Philip (2001). "Geologic/Hydrogeologic Setting and Classification of Springs". Springs and Bottled Waters of the World: Ancient History, Source, Occurrence, Quality and Use. Springer. p. 57. ISBN 978-3-540-61841-6.