Auron (river)

Hydrography

It takes its source in the oriental party of the Forêt of Tronçais, with Couleuvre, small town of the north of the Département Allier. It bathes the towns of Dun-on-Auron and Bourges. Its course is in general carried out south-east towards the North-West. It joins the Yèvre, with Bourges, after having traversed 77 kilometers.

Principal affluents

Sagonin

Hydrology

Auron is a fairly abundant river, hardly more than the majority of the rivers of plain of the catchment area of the Loire. Its flow was observed over one 41 years period (1966-2007), with Bourges, chief town of the Département of Expensive the located at its confluence with the Yèvre. The catchment area of the river is there of 585 km ², that is to say the totality of this last.

Interannual medium flow or module of the river in Bourges east of 3,73 m ³ a second.

Auron presents seasonal fluctuations of flow little marked, with high waters of winter carrying the average monthly flow on a level located between 5,0 and 8,0 m ³ a second, from December to March included (with an in February maximum). An intermediate period of spring follows then when the monthly flows drop, but remain abundant (April-May). As of at the end of June are held low waters of summer, from July to October included, with a fall of the monthly medium flow up to 1,0 m ³ in August, which remains very consistent, it should be underlined. But the fluctuations of flow can be larger according to the years, and over moreover short periods.

With the low water level, the VCN3 can fall until 0,110 m ³, in the event of dry quinquennial period, that is to say 110 liters a second, which can be regarded as severe. The VCN3 is the past minimal quantity or minimal flow over three days consecutive.

As for the risings, they can be rather important certainly, but absolutely without common measurement with the risings of the affluents of the Loire located at the west of the basin of the latter (Creuse, Gartempe, Mayenne, Sèvre Nantes or Oudon and Anglin).

Thus the QIX 2 and QIX 5 or calculated flows of biennial and quinquennial rising are worth respectively 31 and 46 m ³ a second. The QIX 10 or calculated flow of decennial rising is of 55 m ³ a second, the QIX 20 of 65 m ³, while the QIX 50 is worth 77 m ³ a second (see note).

It can be interesting to compare the QIX 2, QIX 10 and QIX 50 of Auron to those of the Grand Morin river with dreaded risings and affluent of the Marne upstream of Paris. Whereas the QIX 2 of Auron is assembled to 31 m ³ a second, that of Large Morin in is worth 54 (for a higher medium flow of 57%, and a surface of upstream reservoir from more or less 32% than those of Auron). For the QIX 10, that of Auron being of 55 m ³ a second, it is assembled to 93 m ³ for Large Morin. As for the QIX 50, whereas that of Auron is assembled to 77 m ³ a second, that of Large Morin amplifies its advantage, since it is worth 130 m ³, that is to say close to the double of that of Auron. One concludes from it that the risings of Auron are proportionally weaker than those of Large Morin. This shows how much the behavior Auron diverges from the average behavior from the rivers from the basin ligérien.

The maximum instantaneous flow recorded in Bourges during the period of observation, was of 83,8 m ³ a second on May 6th, 2001, while the value maximum day laborer was of 75 m ³ a second on May 7th of the same year. By comparing the first of these values on a QIX scale of the river, one notes that this rising was more than cinquantennale and thus completely exceptional.

Auron is not a very abundant river. The Lame of water past in its catchment area is of 202 millimetres annually, which is definitely lower than the overall average of France all confused basins, and also to the average of the basins of the Cher (223 millimetres with Tours), and of the the Loire (244 millimetres). The specific Débit of the river (or Qsp) posts of this fact a rather weak figure: 6,4 liters a second and per square kilometer of basin.

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