Sunday, September 7, 2008

The Origin of the Rhume river/Die Rhumequelle

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During my five week long stay in the Harz mountains I managed to undertake a few geology related tours. One of those took me and a friend to the Rhumequelle - the largest karst spring of Lower Saxony with a diameter of 20 m. Besides the main spring there are dozens of minor springs in the immediate vicinity of the Rhumequelle. Together with the main spring they have an average discharge rate of around 2.200 l/s with a maximum discharge of 5.900 l/s in rainy times and a minimum of 900 l/s in dry seasons. Only a small amount of the water derives from precipation. The largest amount comes from underground supply derived from the rivers Siebe and Oder who lose a significant amount of their water to karst ground water aquifers.



The spring itself is situated in the Zechstein-Dolomite (Upper Permian) that is jammed inbetween Lower Buntsandstein (Lower Triassic) clastic sediments by a major fault.



A small portion is used for drinking water. The water is of pure drinking water quality and aside from removing an excess of natural sulfate from it, it is directly pumped to the costumers. It is generally low on nutrients and other impurities but exhibits a fascinating blue colour that makes a wonderful constrast to the green of the surrounding trees.


View across the main spring of the Rhume with typical water colour.

If any of you should be close to it. It is well worth a visit!


References:
  • Grimmelmann, W. (1992): Hydrogeologisches Gutachten Trinkwasserschutzgebiet "Pölder Becken", NLfB Archiv Nr. 100277, unpublished.
  • Hermann, A. (1969): Die geologische und hydrogeologische Situation der Rhumequelle am Südharz, Jh. Karst u. Höhlenk., H. 9: 107 - 112, München.
  • Röhling, H.-G. (2003): Die Rhumequelle im Eichsfeld - eine der größten Karstquellen in Mitteleuropa, Eichsfeld Jahrbuch, 11. Jahrg., 329 - 357, Duderstadt.

6 comments :

Silver Fox said...

Very interesting post. Is it just sulfate that is coloring the water, or is there some extra copper present, also? [And fyi, you would use "excess" not "access" - although they sound very similar in english! - english can be a terrible language!]

Lost Geologist said...

Actually I am not totally sure what is causing the coloring. However, there is definitly no copper in the water. So what remains is the sulfate, minute amounts of dissolution left-overs in the form of clay particles and organic substances from the few aquatic plants. I was trying to find a source commenting on the color but I was not successful. Now that I think of it I could have taken a bottle of it with me and tried to test it myself. *sigh*

Silver Fox said...

Does the silt or clay in the water have a glacial source? The color is similar, though stronger, to glacial meltwater.

Lost Geologist said...

I cannot answer your question. I can only assume that is comes from the impurities of the gypsum and dolomite and the clay rich clastic sediments that are sealing the aquifer towards the hanging wall.
The literatur on this spring is not very large. Besides the 3 I listed I can only find one other article dating from 1913. In my UNI-library there is only one of the 3 mentioned articles and it does not discuss the substances in the water in any detail. It only mentions their presence. It reminds a lot of glacial meltwater though. You are right. If there is any connection or perhaps just a similiar mechanism behind it is beyond my current knowledge. I assume though that it is simply the suspended load that is respondsible for the color. That again is mainly Calciumsulfate and the minor amounts of clay particles.

Lost Geologist said...

I was in the library again today and also used the chance to look up the color issue a bit more. However, none of the articles are explaining it. Only one talks about how the color changes to brown if there is a lot of heavy rain. The original glacial blue color is not explained though.

Silver Fox said...

It might just be a sulfate thing then, like you said - it's a pretty color - maybe that's the artist in me!