It takes its source in the the Alsatian Jura, with Winkel with a Résurgence with Ligsdorf. It circumvents then Ferrette by the east, forks towards north and is thrown in the the Rhine downstream from Strasbourg after the fall of Gambsheim.
223 km length, it sprinkles successively Altkirch, Mulhouse, Colmar and Sélestat. In the crossing of Strasbourg, it is divided into several arms and contributes to the tourist fame of the district of the Petite France .
The name of the city It comes from this river crossing it.
Its principal affluents reach him out of left bank, resulting from the Vosgean massive : the Releases, the Doller, the the Thur, the Lauch, the Fecht, the Giessen (and its affluent the Liepvrette), the Andlau, the Ehn, the Bruche and the Souffel. It is also fed from the right-sided by the Ground water Rhenish which brings small affluents to him of which the Blind, which gives him its water with Ehnwihr between the confluences of Fecht and Giessen.
The mode of It pluvio-oceanic, is characterized by high waters in winter and at the beginning of spring, and low waters in summer like at the beginning of the autumn. To the level of Erstein, it is connected to an outfall channel and a feeder canal which make it possible to control of it the flow at the entry of Strasbourg.
The flow of It was observed for one 34 years period (1974-2007), at the hydrometric station of Hunter-Cold, commune of Strasbourg, chief town of the department, was located little before the confluence of It with the the Rhine. The catchment area of the river is of 4 600 km ² are nearly 97% of its totality which is of 4 760,5 km ².
Interannual medium flow or module of the river in Strasbourg east of 58 m ³ a second.
It presents seasonal fluctuations of flow very little important. The high waters are held in winter and are characterized by average monthly flows going from 65,6 to 68,7 m ³ a second, from December to March included (with a very light in February maximum). As of April, the flow drops very gently to the low waters which take place in summer from July to October, with a fall of the monthly medium flow going until 48,10 m ³ in September and August, which remains very abundant. But the variations of flow can be more important according to the years.
Thus the VCN3 can fall until 29 m ³, in the event of dry quinquennial period, that is to say 29 000 liters a second, which must be more regarded as remainder than comfortable (see note).
However the risings can be rather important, without being really devastators, more especially as outfall channels exist (before Strasbourg in particular). The QIX 2 and QIX 5 or calculated flows of biennial and quinquennial rising are worth respectively 140 and 170 m ³. The QIX 10 or calculated flow of decennial rising is worth 200 m ³ a second, while the QIX 20 is assembled to 220 m ³ and the QIX 50 to 250 m ³ a second (see note). The maximum instantaneous flow recorded in Strasbourg, since 1974, was of 280 m ³ a second on February 17th, 1990, while the value maximum day laborer had been of 236 m ³ a second the previous day, February 16th. By comparing the first of these figures with the values of the various QIX of the river, it appears that this rising of February 1990 was higher than that envisaged by the QIX 50, and was thus completely exceptional.
On the whole, it is an abundant river, strongly supplied with the strong Vosgean precipitations, partially compensated however by the weakness of precipitations on the plain of Alsace. The Lame of water past in the area catchment of It is of 398 millimetres annually, which is however rather high, definitely higher than the average overall of France, and even higher than the totality of the basin of the the Rhine (approximately 375 millimetres) profiting from very important alpine precipitations. The specific Flow (or Qsp) reached of this fact the solid figure of 12,6 liters a second and per square kilometer of basin.
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