Sarner Aa

Upper reaches of the Sarner Aa: Lauibach

The Sarner Aa (also: Sarneraa ) is a 28 km long tributary of Lake Lucerne in the canton of Obwalden in central Switzerland.

Course

During their run, the Sarner Aa changes its name several times. The source area is located on the eastern slope of the gums Höch ( 2,205 m above sea level. M. ) on the eastern edge of the Brienz Rothorn chain in the extended Alp Breitenfeld. Multiple source streams unite to Lauibach, the Sarner Aa is given in its upper reaches. This crashes with waterfalls down via steep steps to Lungernsee.

The water power in the area of ​​190 m high slope between the Lungernsee and Giswil is used by the power plant Lungerersee. Therefore, the outflow of the lake at Kaiser lounging chair is routed underground through a pressure tunnel. After the water power was used in the underground Kraftwerszentral Unteraa for generating electric current enters the river in Aaried, the valley floor south of Giswil, light again. From here it is called in its middle reaches Aa or Aawasser. It flows through Giswil and unites with the Giswiler Lauibach of the west and the water of the Little Melchaa from the east. When three water channel of the river flows north from Giswil to 2 km in the Sarnersee. For flood protection reasons, the running of the Little Melcha is changed so that it will flow directly into the Sarnersee from 2015.

Another major tributary is the Great Melchaa, which opens into the Sarnersee between Sachseln and Sarnen. Until the diversion of flood protection reasons, in 1880 the Big Melchaa did not drain into Lake Sarner but on the outskirts of Sarnen along and north of Sarnen culminated in the Sarner Aa.

In the lower reaches of the Sarnersee north of the river now called Sarner Aa. It flows channeled and straightened in Sarneraatal to North northeast by Sarnen and Wichelsee, which is under protection. From the barrage of the weighting Elsees the majority of the water flows through a 1860 m long pressure tunnel with 23 m net slope to the low -pressure rotor power plant Eichi and flows from there back into the river bed. Prior to taking the Sarner Aa left the water of the Great smear on. Then it flows to the west along the foot of the Mueterschwanderbergs and flows east from Alpnachstad in the Alpnachersee.

Flood

During the floods in August 2005, the Sarner Aa flooded below the Sarnersee large tracts of land. To prevent such events, the outflow of the Sarner Aa is to be increased to a capacity of 150 m³. To achieve this protection goal that the Obwalden people decided in a referendum on 26 September 2010 are that the two variants of the project " defined and broadened deeper Sarneraa » « Sarneraa with spillway tunnels East " and draw on the same planning status. End of July 2012 ended the tenders for the variant with the spillway tunnels east, the variant compared to to the Spring / Summer 2013 are available.