Thinning

Thinning
The Dünnern near Herbetswil
Data
Water code	CH : 436
location	Switzerland Canton of Solothurn
River system	Rhine
Drain over	Aare  → Rhine  → North Sea
source	between the white stone chain in the south and whales Matt in the north (Chaltbach) 47 ° 15 '56 "  N , 7 ° 29' 22"  O
Source height	approx.  760  m above sea level M.
muzzle	near Olten in the Aare Coordinates: 47 ° 20 ′ 57 ″  N , 7 ° 54 ′ 16 ″  E ; CH1903:  635 188  /  244357 47 ° 20 '57 "  N , 7 ° 54' 16"  O
Mouth height	389  m above sea level M.
Height difference	approx. 371 m
Bottom slope	approx. 10 ‰
length	36 km
Catchment area	234 km²
Outflow A Eo : 234 km² at the mouth	MQ Mq	4.28 m³ / s 18.3 l / (s km²)

source muzzle

Source and Mündungsort the Dünnern

The Dünnern is a 36 km long left tributary of the Aare in the Swiss canton of Solothurn . It drains a section of the Solothurn Jura and belongs to the catchment area of ​​the Rhine . The catchment area of ​​the Dünnern has an area of ​​about 230 km².

geography

The source area of ​​the Dünnern is at around 760 m above sea level. M. on the parish grounds of Gänsbrunnen in the syncline between the Weissenstein chain in the south and the Walenmatt in the north. The Dünner now flows east-northeast through the valley of Welschenrohr and receives tributaries from several small streams that arise on the slopes of the surrounding Jura heights and have in some cases carved deep erosion valleys into the hard limestone layers of the anticlines of the Jura chains.

East of Welschenrohr, the Dünnern flows through a narrow valley and overcomes a height difference of around 100 m over a distance of 2 km. Afterwards it reaches the wide valley level of the Balsthaler Tal (also called Dünnerntal), the longest valley in the Folded Jura located furthest to the east . The width of the flat valley floor varies between 0.5 and 1 km. In Balsthal opens with the Augstbach the most important page of Bach Dünnern which drains the eastern part of Balsthaler Valley.

The Dünnern characterized in Balsthal an arc southeast and breaks through the first Jura chain with the Balsthaler Klus , a characteristic Jura transverse valley in which the stratigraphic structure of the anticline with soft and hard layers of rock (striking rock walls) is well exposed. A comparison of the height conditions shows that the Balsthaler Klus could not have been created solely due to erosion of the thin ones: The height line 800 m above sea level. M. is higher here than the source area of ​​760 meters (see above), which runs counter to gravity . Rather, it can be assumed that there was a geological disturbance in the form of a cut between approx. 1000 m above sea level before the river took effect. M. and 700 m above sea level. M. existed, which then through the thin to less than 500 m above sea level. M. was deepened. The original disorder is due to the Jura folding .

In Oensingen the Klus opens and the Dünnern enters the Swiss Plateau addition. Here it turns again to the east-northeast and flows parallel to the Jura chain and the Aare. She uses the gravel plain of the Gäus , which is rich in groundwater . This section served as a river valley before the Aare ice ages. However, it was modulated as a result of debris and moraine deposits from the Ice Age glaciers, which is why the Aare had to look for a new route further out into the Swiss Plateau.

In the area of Hägendorf , where the Cholersbach flows into it, the plain narrows; The lowermost section of the Dünnern is flanked by the Jura range in the north and by the ridge of the Born in the south .

At Olten , the Dünnern flows down steps in the rock from the Gäu Plain to the Aareniederung; Since the Middle Ages, the considerable gradient has been used to drive waterworks for several businesses. The river flows south of the old town of Olten at 395 m above sea level. M. in the Aare.

Hydrology

The confluence of the Augstbach and Dünnern in the Klus in Balsthal

In the middle and lower reaches, the slope of the thin is just 0.5%. The Dünnern is characterized by a pluvial runoff regime , with the mean runoff volume at Olten being 3.9 m³ / s. Flood events can occur in spring during the snowmelt in combination with copious rain or in the case of long-lasting precipitation in the catchment area also in the other seasons.

From 1933 to 1944, the course of the Dünnern was corrected, straightened and squeezed into a natural canal bed in a large-scale improvement in the Gäu. Before, the course of the river had numerous meanders here and often overflowed its banks. The entire middle course between Herbetswil and Oensingen is also largely canalised and straightened. In near-natural to natural condition there are only a few sections on the upper reaches of the municipality of Welschenrohr.

use

Since the Middle Ages , the water power of the Dünnern has been used in various places for the operation of mills , sawmills and forges . In Olten, the hydropower-dependent trade (mills and especially hammer forges ) has developed almost exclusively along the Dünnern since the 14th century . Recently there have been ideas from the Alpiq company to use the Dünnern gradient for small hydropower plants . Finally, on December 14, 2015, the ADEV Energiegenossenschaft's power plant started operations in Olten. The new 370 kW hydropower plant was built into an existing concrete sewer that was being renovated at the same time.

literature

• Urs Wiesli: Geography of the Canton of Solothurn. Kantonaler Lehrmittel-Verlag, Solothurn 1969.

Web links

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

• Hydrological data of the Dünnern on the FOEN website

Individual evidence

1. ↑ ^{a b c} Geoserver of the Swiss Federal Administration ( information )
2. ↑ ^{a b} Topographical catchment areas of Swiss waters: area outlets. Retrieved May 30, 2019 . 
3. ↑ City small hydropower plant in Olten on the network! ADEV Energiegenossenschaft, December 18, 2015, accessed on March 5, 2018.