Seyon

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Seyon
Seyon et moulin du Gor de Vauseyon.jpg
Data
Water code CH : 260
location Switzerland
River system Rhine
Drain over Zihl Canal  → Aare  → Rhine  → North Sea
source near Villiers on the western slope of the Grand Chaumont , in the extreme northeast of the basin of the Val de Ruz
47 ° 4 ′ 19 ″  N , 6 ° 58 ′ 47 ″  E
Source height 829  m above sea level M.
muzzle near Neuchâtel in Lake Neuchâtel Coordinates: 46 ° 59 ′ 18 "  N , 6 ° 55 ′ 20"  E ; CH1903:  560 717  /  204 275 46 ° 59 '18 "  N , 6 ° 55' 20"  O
Mouth height 429  m above sea level M.
Height difference 400 m
Bottom slope 28 ‰
length 14.3 km
Catchment area 114.9 km²
Discharge
A Eo : 114.9 km²
at the mouth 		MQ
Mq
 		2.71 m³ / s
23.6 l / (s km²)

The Seyon is a 14 km long northern tributary of Lake Neuchâtel in the Swiss canton of Neuchâtel . It drains the Val de Ruz and a section of the Neuchâtel Jura and belongs to the catchment area of ​​the Rhine . The catchment area of ​​the Seyon has an area of ​​about 120 km². The river was first mentioned in 1268 under the name Seion ; from 1402 the name Seon has been handed down.

geography

course

The small karst spring of the Seyon is located at about 830 m above sea level. M. on the parish grounds of Villiers on the western slope of the Grand Chaumont , in the extreme northeast of the basin of the Val de Ruz. The river Ruz de Chasseran belongs to the catchment area of ​​the Seyon . This rises with two source streams on the western slope of the Chasseral near Les Bugnenets and in the Combe Biosse . However, it seeps into the basin of Le Pâquier , although there is a direct connection to Villiers with the Klus von Chenau . This gorge, which today normally does not show an overground stream, was created by an earlier river during the folding of the Jura.

From Villiers the Seyon flows to the southwest through the wide valley basin of the Val de Ruz. Soon, however, it sinks into the tertiary sediments of the basin, with the Seyon Valley sunk a maximum of 50 m deep into the surrounding plateaus and always has a valley floor about 200 m wide. Short side streams and drainage channels bring more water to the Seyon, the most important of which is the concern that flows into Valangin . However, the Seyon also loses water in several places in the Val de Ruz through seepage in the porous limestone of the subsoil.

Below Valangin, the Seyon breaks through the anticline of the southernmost Jura chain in a narrow gorge, the Gorges du Seyon . When leaving this clus in the urban area of Neuchâtel , the river turns with a sharp curve to the east. The Seyon used to flow about 1.5 km parallel to the north bank of Lake Neuchâtel before flowing into the lake with an alluvial cone on which the lower town lies. However, frequent floods caused the city authorities to act. From 1839 to 1844 a tunnel was dug under the castle hill to lead the Seyon directly into Lake Neuchâtel.

The water that seeped into the Val de Ruz re-emerges with the source of the Serrière in a basin at the foot of the Jura on the western outskirts of Neuchâtel, below Peseux and also flows into Lake Neuchâtel after a 500 m run.

Catchment area

The catchment area of ​​the Seyon is 114.9 km² and consists of 40.6% forest land , 52.9% agricultural area and 6.3% settlement area .

The mean height of the catchment area is 972  m above sea level. M. , the minimum height is 481  m above sea level. M. and the maximum height at 1551  m above sea level. M.

Tributaries

  • Le Ruz Chasseran ( right )
  • Le Rin ( left )
  • Le Torrent ( right )
  • Le Ruisseau de St-Martin ( right )
  • Prés des Sauges ( right )
  • Le Ruz de Savagnier ( left )
  • Le Ruisseau les Vernets ( right )
  • Le Ruisseau les Lancinges ( right )
  • Le Chardonnet ( left )
  • Le Ruisseau les Quarrons des Sagnes ( left )
  • Le Morguenet ( right )
  • La Verchère ( right )
  • Landeyeux ( right )
  • Le Ruz d'Amont ( right )
  • La Sorge ( right )

Hydrology

In the Val de Ruz, the Seyon has an average gradient of just 1.4%. However, on the lowest section between Valangin and the mouth, the gradient is 5.5%. The Seyon is characterized by a nivopluvial discharge regime , with the mean discharge volume below Valangin being 20.7 m³ / s. However, the river has a very irregular flow of water, especially when the snow melts in combination with extensive rainfall, strong floods can occur.

Artificial and natural river sections alternate: the uppermost section of the Seyon - like various side streams - was developed into a drainage channel and completely straightened. In contrast, the middle course is designed close to nature with intact bank vegetation, the section in the Gorges du Seyon has even been preserved in a largely natural state.

use

The hydropower of the Seyon has been used in various places in the Val de Ruz for the operation of mills and sawmills since the Middle Ages . In Neuchâtel, too, the businesses that were dependent on hydropower settled along the Seyon. The main road between Neuchâtel and La Chaux-de-Fonds runs through the narrow ravine of the Seyon and is now a four-lane expressway; the downhill section was laid in a tunnel.

Individual evidence

  1. ↑ a b c Geoserver of the Swiss Federal Administration ( information )
  2. ↑ a b c Modeled mean annual discharge. In: Topographical catchment areas of Swiss waters: sub-catchment areas 2 km². Retrieved August 11, 2017 .