Photographer's Note

Here I show you the Blautopf. It is a spring which serves as the source of the river Blau in the Karst landscape on the Swabian Alb. It is located in the city of Blaubeuren - about 16 kilometres west of Ulm where Blau river flows into Danube. This "spring" forms the drain for the Blau cave system. Because of its high water pressure, the spring has developed a funnel-like shape, which at its deepest point has a depth of 21 metres.
The entry to the Blau cave system lies at a depth of about 18 metres. Therefore, access is restricted to experienced and well-trained divers. In the 1980s, city authorities were forced to prohibit diving in the Blautopf after several accidents, including some fatal ones. Permission to dive in the Blautopf has only been granted to a few organizations, among them, the Arbeitsgemeinschaft Blautopf, a group of scientific speleologists. The first 1200 metres of the cave are filled with water and behind this part divers found a huge dry hall - 170 metres long, 50 metres high and 50 metres wide ...

One characteristic of a Karst environment is that water, which drains quickly through the limestone in one area, surfaces in another. Karst environments only have subterranean drainage, and there are no bodies of water above ground. Therefore, the size of the Blautopf depends greatly on the level of rainfall in its drainage area, though it never entirely dries out. The Blautopf is the second largest spring in Germany, after the nearby Aachtopf. Its delivery ranges between 310 litres and 32000 litres per second (!) - on an everage of 2000 litres per second.
The water's blue color is the result of chemical properties of limestone densely distributed in the water -and I can assure you that the here shown colour is in line with reality.

This is a stitch out of two photos.

In workshop you can see the drain of this "source" - a complete river.

Please also look HERE.

dta, papagolf21, jhm, chinchini, saxo042, ellelloo, jmcl, Kielia, thaprem has marked this note useful

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Additional Photos by Frank Kaiser (Buin) Gold Star Critiquer/Silver Workshop Editor/Gold Note Writer [C: 4250 W: 48 N: 10758] (42538)
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