Bienne (river)

Geography

Bienne takes its source around Russet-red the with 1 000m of altitude. It passes then to Morez and Saint-Claude.

Hydrology

Bienne is the most important affluent of the Ain, with a medium flow of more than 30 m ² a second.

Its flow was observed during one 37 years period (1971-2007), with Jeurre, locality of the department of the the Jura, located at little distance from its confluence with Ain. At this place the catchment area of the river is of 650 km ² on a total from more or less 700 for the whole of the basin, that is to say more than 90% of totality.

The interannual medium flow or module of the river with Jeurre is of 30,0 m ³ a second. It is of 32 on the level of the confluence with Ain.

Bienne presents seasonal fluctuations of flow not too important. The high waters are held autome at the beginning of spring and are characterized by average monthly flows from 30 to 44,2 m ³ a second, from October at May included. One can distinguish two maximum there; the first in December, the second, corresponding to the snow melt, in spring, in March and in April. The low waters take place in summer, from June to September, with a fall of the monthly medium flow going up to the level of 11,1 m ³ in August. But beyond this seasonal rate/rhythm, there exist fluctuations much fuller over moreover short periods, as testify some to strong periodic risings and the very depressed low water levels.

The VCN3 can fall until 1,3 m ³, in the event of quinquennial dries, which is very low, without being really severe (see note).

In addition the risings can be extremely important. Indeed, the recorded maximum instantaneous flow was of 822 m ³ a second on December 22nd, 1991, while the value maximum day laborer was of 680 m ³ a second on February 15th, 1990. The QIX 2 and QIX 5 or flows calculated for a biennial and quinquennial rising are worth respectively 400 and 520 m ³ a second. The QIX 10, or calculated flow of decennial rising, is of 590 m ³ and the QIX 20 of 660 m ³ a second. As for the QIX 50, it is of 760 m ³, that is to say more of the three quarter of that of the Yonne for example, river however famous for its excesses (see note). To notice that the flow of 822 m ³ raised in 1991 was higher than the QIX 50 of the river and undoubtedly constituted the peak of a centennial rising.

As comparison, let us recall that the QIX 10 of the Marne to Gournay-sur-Marne, at the entry of Paris, is worth 510 m ³ a second, while its QIX 50 is of 650 m ³. Thus the risings of this river badly known and locked up in a very small basin are higher than those from the Marne in Paris.

The Lame of water past in the basin of Bienne is of 1 460 millimetres annually, which is extrèmement high, among highest raised in France, and also much higher than that of the whole of the area catchment of the the Rhone (670 millimetres with Valence for a surface of basin of 66 450 km ²). The specific Débit (or Qsp) is assembled at 46,2 liters a second and per square kilometer of basin.

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