Sempachersee

Sempachersee
Sempachersee
Geographical location	Central Switzerland
Tributaries	Grosse Aa , Kleine Aa , ippenrütibach , Röllbach , Greuelbach , Rotbach , Nottwiler Dorfbach , Eybach
Drain	Sure
Places on the shore	Sursee , Sempach , Nottwil , Eich
Data
Coordinates	654 084  /  221742 coordinates: 47 ° 8 '40 "  N , 8 ° 9' 6"  O ; CH1903:  654,084  /  221742
Altitude above sea level	504  m above sea level M.
surface	14.5 km²
scope	19.657 km
Maximum depth	87 m

The Sempachersee is a lake near Sursee in the Swiss canton of Lucerne . It has an area of ​​14.5 km², its water level is 504  m above sea level. M. , it holds 0.66 km³ and is 87 m deep at the deepest point. Its length is 7.5 km, the circumference 19.7 km and the mean discharge 1.28 m³ / s.

In contrast to most Swiss lakes, large parts of the lake shore are not accessible to the public, but are closed off by fenced-off private property. The bathing ban for the entire Sempach promenade dates from the 1960s.

Seven municipalities border Lake Sempach: Sursee , Sempach , Oberkirch , Nottwil , Eich , Schenkon and Neuenkirch . A total of around 30,000 people live in these.

history

The Reuss Glacier , which retreated towards the end of the Würme Ice Age, left behind several moraines around 12,000 years ago, including the one from Mariazell, which dams Lake Sempach at its northern end. Several pile dwellings found during excavations show Neolithic and Bronze Age settlement on the lake.

In 1806 the lake was lowered by about 1.7 meters, which freed up a lot of land and reduced the risk of flooding. Since then, the altitude at the outlet of the Sure (in the Aargau Suhre ) in Oberkirch has been artificially regulated.

Water quality

The intensification of agriculture around the lake and the increased discharge of untreated municipal sewage led to a massively higher nutrient input in the 1970s, which caused algae to flourish excessively. After they died, they drew a lot of oxygen from the lake when they decomposed in the deep water, which culminated in fish deaths in 1984 .

During this time, several measures were taken to improve the oxygen levels in the lake. On the one hand, attempts were made to curb the nutrient input, for example through improved wastewater treatment, by restricting fertilization and the use of areas directly on the lake, or by motivating farmers to make voluntary ecological contributions in return for compensation. In 1999, these efforts were intensified with the 10-year phosphorus project .

On the other hand, since 1984 the lake has been artificially ventilated at a depth of about 80 meters. From 1984 to 1996 considerable amounts of pure oxygen were brought into the lake in the summer (maximum 1986: 580 tons). In winter, the water circulation in the lake was supported with compressed air. From 1997, the lake's renovation had an effect and the pure oxygen could be replaced by normal, fine-bubble pumped air due to the progressive recovery of the lake.

The significantly better phosphorus values ​​allowed the duration of the daily ventilation to be gradually reduced, but the lake cannot be left entirely to itself for the time being. In addition, the Sempachersee is based on its size the most productive lake in Switzerland for fishing. The Swiss Air Force used the lake as a firing range, where they practiced dropping bombs and using on-board cannons.

Regular events

The Sempachersee Triathlon takes place every year at the beginning of July. During the annual lake crossing in August, swimmers cover a distance of 2.1 km to the other bank. The "Stage at the Lake" takes place every year in the lido Sursee. The yacht club Sempachersee organizes regular sailing competitions. In autumn the rowing club Seeclub Sursee organizes a regatta.

Drunkard

Sempachersee Triechter Sursee

The Triechter is a bay surrounded by two peninsulas at the northern end of the lake. On the western peninsula a hiking trail leads past the ruins of a Romanesque church, on the eastern peninsula there are private properties. In between there is the old location of the Mariazell chapel , marked with a stone cross, as well as boat places, the lido of Sursee and the Seeclub Sursee. The water is not considered to be particularly clean here because the water drain has no drain.

societies

The lake is used as a training area by the Seeclub Sursee, the Seeclub Sempach, the SLRG Sempachersee, the Windsurfclub Eich, the Surfclub Sempachersee and the Yachtclub Sempachersee.

Bathing establishments

With the exception of Oberkirch, every municipality on Lake Sempach has a bathing establishment (Badi). In Oberkirch, the entire lake access is a nature reserve or privately owned. The attempt to create a public lake access with a bathing establishment was unsuccessful, despite the collection of signatures. In Schenkon there is a second, unguarded access to the lake next to the swimming pool at the Seepark. However, bathing is prohibited there because of the jetty. Neuenkirch has a small unguarded bathing resort, the so-called Rossbadi. Nottwil has a small, public and unguarded lake access. In the summer there is a restaurant by the lake. Sursee at the northern end and Sempach at the southern end of the lake each have a public bathing establishment.

See also

• List of lakes in the canton of Lucerne

Web links

Commons : Sempachersee  - collection of images, videos and audio files

• Environment & Energy Lucerne: Lake Sempach
• Community association of Sempachersee: lake aeration, phosphor project, place of learning
• Association Pro Sempachersee
• Excavations of the University of Bern in Zellmoos (PDF file; 573 kB)
• Waltraud Hörsch: Lake Sempach. In: Historical Lexicon of Switzerland .

Individual evidence

1. ↑ ^{a b c d} Seen (Federal Office for the Environment FOEN). Retrieved January 18, 2020 . 
2. ^ Marc Benedetti: Fisherman's survey: whitefish and perch dominate in Lake Sempach. In: zofingertagblatt.ch . July 22, 2019, accessed on July 23, 2019 : "The negative climax was 1984, when 26 tons of fish perished in the great fish death."