Ornette

The Ornette is small a French Rivière which runs in the departments of the Mayenne (53) and of the the Sarthe (72). It is an affluent of the the Sarthe out of Right Bank, therefore a tributary of a tributary of the the Loire by the Sarthe and the Maine.

Geography

Ornette takes its source in the heights of the north-eastern part of the department of the Mayenne, on the territory of Pre-in-Pail. It has its confluence with the the Sarthe in extreme cases between the communes of Saint-Pierre-of-Nests in Mayenne and Saint-Léonard-of-Wood in the department of the Sarthe.

Common crossings

Department of the Mayenne: Pre-in-Pail, Gesvres and Saint-Pierre-of-Nests.
Department of the the Sarthe: Saint-Léonard-of-Wood

Hydrology

Ornette is a well fed, but very irregular river. Its flow was observed during one 16 years period (1992-2007), with Saint-Pierre-of-Nests, locality of the department of the Mayenne located at little distance from its confluence with the the Sarthe. The catchment area of the river is there of 54 km ² (either its almost totality).

The interannual medium flow or module of the river with Saint-Pierre-of-Nests is of 0,536 m ³ a second.

Ornette presents seasonal fluctuations of flow very marked. The high waters take place in winter carrying the average monthly flow on a level located between 0,825 and 1,44 m ³ a second, from December to March included (with an in January maximum). As of March, the monthly flow decreases quickly to low waters of summer. Those rather long are held at the beginning of June with the beginning of October, accompanied by a fall of the monthly medium flow going up to 0,075 m ³ in September. But the fluctuations of flow are even more marked over moreover short periods or according to the years.

With the low water level, the VCN3 can fall until 0,002 m ³, in the event of dry period quinquennial, that is to say 2 small liters a second, which can be described as very severe, the course being then almost dry (see note).

As for the risings, they can be very important, taking into account the extremely modest size of the river and of its catchment area. The QIX 2 and QIX 5 are worth respectively 11 and 15 m ³ a second. The QIX 10 or calculated flow of decennial rising is of 18 m ³ a second, the QIX 20 of 20 m ³, while the QIX 50 was not calculated being given the insufficiency of the duration of observation of the flows (see note).

The recorded maximum instantaneous flow with Saint-Pierre-of-Nests during this 16 years period, was of 17,6 m ³ a second on February 25th, 1997, while the value maximum day laborer was of 11,9 m ³ a second on January 22nd, 1995. If one compares the first of these values on a QIX scale of the river, one notes that this rising was hardly of a decennial nature, and thus intended to rather frequently reproduce.

Ornette is an abundant river, well supplied with precipitations of its basin. The Lame of water past in its catchment area is of 314 millimetres annually, which is appreciably equivalent to the overall average of France all confused basins, and definitely higher than the average of the basin of the the Sarthe without the Loir (201 millimetres). The specific Flow of the river (or Qsp) reached the figure of 9,9 liters a second and per square kilometer of basin.

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