| Birs | |
|---|---|
 The Birs inLaufen | |
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| Location | |
| Country | Switzerland |
| Physical characteristics | |
| Mouth | Rhine |
• coordinates | 47°33′28″N7°37′04″E / 47.5579°N 7.6177°E /47.5579; 7.6177 |
| Length | 73 km (45 mi) |
| Basin features | |
| Progression | Rhine→North Sea |
TheBirs (French:Birse) is a 73-kilometre (45 mi) long river in Switzerland that flows through theJura region and ends as a tributary to theRhine betweenBasel andBirsfelden. It is the most important river of theSwiss Jura.
The Birs has its source in a spring near theCol de Pierre Pertuis at 762 metres (2,500 ft) above sea level a little southwest ofTavannes in theJura bernois. It starts as a proper river; the large amount of water is the product of an extended underground river system.
The Birs runs through wider valleys (Vallée de Tavannes) and narrow gorges. NearDelémont, the capital of the canton of Jura, it joins theSorne and theScheulte. BetweenSoyhières andLiesberg, it leaves the French-speaking part of Switzerland, enters the canton ofBasel-Landschaft and receives theLützel from the left. InLaufen it forms a waterfall, which was the source of power and of the name of the city.
At the gorge ofAngenstein, the river runs into theBirseck, the lowland byAesch. Between Aesch andDornach, the Birs is rich in fresh-water crabs, the native species of which are now threatened by the American red crab. Earlier, the Birs was polluted and dammed, but it has largely been restored to its original state.
TheReinacherheide is a wildlife preserve with 83 species of bird.
The mouth of the Birs was hardly settled until the 18th century. Today, the city ofBirsfelden stands there. The lower stretches of the Birs form the border betweenBasel-Stadt and Basel-Landschaft. In 2004, it was restored from a concrete canal to a more natural river. Beavers have even been sighted along the river. The Birs also forms the border between the cities ofBasel andBirsfelden. It flows into the Rhine atBirskopf after 73 kilometres (45 mi).
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