Big Melchaa

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Big Melchaa
The Grosse Melchaa in Ranft, around 1825

The Grosse Melchaa in Ranft , around 1825

Data
Water code CH : 711
location Canton of Obwalden ; Switzerland
River system Rhine
Drain over Sarner Aa  → Reuss  → Aare  → Rhine  → North Sea
confluence from Cheselenbach and Bettenalpbach near Hugschwendi
46 ° 48 ′ 7 ″  N , 8 ° 17 ′ 6 ″  E
Source height 1026  m above sea level M.
muzzle between Sachseln and Sarnen in the Sarnersee Coordinates: 46 ° 52 ′ 52 "  N , 8 ° 14 ′ 29"  E ; CH1903:  661 195  /  192527 46 ° 52 '52 "  N , 8 ° 14' 29"  O
Mouth height 469  m above sea level M.
Height difference 557 m
Bottom slope 30 ‰
length 18.5 km
Catchment area 72.58 km²
Discharge  at the mouth of the
A Eo : 72.58 km²
MQ
Mq
3.49 m³ / s
48.1 l / (s km²)

The Grosse Melchaa (also Melchaa for short , Aa for Ache in Swiss German ) is an 18.5 km long tributary of the Sarnersee in the canton of Obwalden in central Switzerland .

course

The Melchaa arises as an outflow of the Melchsee in the summer and winter sports resort Melchsee-Frutt and flows through the Melchtal towards the north. At the level of the village of Flüeli-Ranft , the Melchtal narrows into the Ranft gorge . The Melchaa leads past the two Ranft chapels of Niklaus von Flüe . Shortly afterwards, the Melchaa flows under the Hohe Brücke at a depth of 100 m . The Melchaa finally follows an artificially displaced river bed and flows into the Sarnersee between Sachseln and Sarnen . Originally the Melchaa flowed along the outskirts of Sarnen and only north of Sarnen into the Sarner Aa . For reasons of flood protection, the course of the river was relocated in 1880.

Power generation

From the Melchsee , the water first flows through a pressure pipe into the Hugschwendi power plant 830 m below, where it drives two Pelton turbines with an output of 7 MW each to generate electricity. The power plant was commissioned in 1957. Previously (since 1904) the water from the Melchsee was used by the Stäubiloch turbine system . Originally the water flowed through the dust hole into a karst cave .

Information board at the dust hole

In the village of Melchtal , the Melchaa is slightly dammed by a small barrage (water catchment). Most of the water flows from here through an underground tunnel into the Kleiner Melchtal further south, and from there through a reservoir tunnel into the Marchgraben surge chamber and apparatus chamber. From there, the water reaches the Unteraa power station in Giswil via a pressure line , where it is turned into electricity by the Obwalden electricity station.

Flood

The flood in August 2005 caused considerable damage along the course of the Melchaa, for example a railway bridge was destroyed and a 16 kV line fell into the river. In the Acherlibach area, a large-scale, deep landslide of around 200,000 m³ occurred. The canton road was torn away over a length of around 30 m. Around a third of the material was pushed into the Melchaa, which accumulated accordingly.

Web links

Commons : Grosse Melchaa  - collection of pictures, videos and audio files

Individual evidence

  1. a b Geoserver of the Swiss Federal Administration ( information )
  2. a b Modeled mean annual discharge. In: Topographical catchment areas of Swiss waters: sub-catchment areas 2 km². Retrieved August 13, 2017 .
  3. Stäubiloch memorial plaque ( Memento of the original from May 18, 2015 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. Information page in the website of the Foundation “Natural Heritage Karst and Caves Obwalden” (NeKO) from September 29, 2004, accessed on September 17, 2012 @1@ 2Template: Webachiv / IABot / www.neko.ch
  4. Government Council of the Canton of Obwalden: Report on dealing with the flood disaster 2005 (PDF; 350 kB)