Vandelogne

The Vandelogne or Vendelogne is a French Rivière which runs in the departments of the Two-Sevres (79) and of the Vienna (86). It is an affluent of the Auxances out of left bank, therefore a tributary of a tributary of the the Loire by Auxances, then the Clain, then the Vienna.

Geography

Vandelogne takes its source between the localities of Saint-Martin-of-Fouilloux the and of Would know, in the department of the Two-Sevres. It has a course directed since the west towards the east. It is thrown in the Auxances (left bank) with Chiré-in-Montreuil a little upstream of Vouillé, in the department of the Vienna.

Common crossings

Vandelogne crosses the following communes (of upstream downstream):

department of the Two-Sevres: Saint-Martin-of-Fouilloux the, Would know, and Tool bag-in-Parthenay.

department of the Vienna: Chalandray, Ayron, Frozes and Chiré-in-Montreuil.

Hydrology

Vandelogne is a very irregular river, as many river of the west of the basin of the Loire. Its flow was observed during one 19 years period (1976-1994), with Ayron, locality of the department of the Vienna located at the level of its confluence with the Auxances. Surface thus studied there is of 62 km ², that is to say almost the totality of the catchment area of the river.

The interannual medium flow or module of the river with Ayron is of 0,324 m ³ a second.

Vandelogne presents seasonal fluctuations of flow extremely marked, like very often in the Western basin of the Loire. The high waters are held in winter and are characterized by average monthly flows going from 0,572 to 0,775 m ³ a second, from December to February included (with a maximum very Net in February). In March, the flow strongly drops. It is formed initially a transitional period, in March - April, with very a small rebound in April, then the reduction is accentuated to the low waters of summer which take place from July to September included, involving a fall of the average monthly flow up to 0,045 m ³ in August. But these monthly averages are only averages and hide fluctuations much more marked over short periods or according to the years.

With the low water levels, the VCN3 can fall until 0,001 m ³ a second, that is to say a small liter a second, in the event of dry period quinquennial, which is very severe, the river being then tiny room to a thin filament of water. But this fact is frequent among the rivers of the Western area of the basin ligérien (see note).

As for the risings, they can be relatively important, taking into account the exiguity of the catchment area, but are far from reaching the tops met more in the west among the rivers running on the oriental party of the old impermeable Armorican base (Sèvre Nantes, Hyrôme, etc). The QIX 2 and QIX 5 are worth respectively 5,2 and 8,2 m ³ a second. The QIX 10 or calculated flow of decennial rising is of 10 m ³ a second, the QIX 20 of 12 m ³, while the QIX 50 was not calculated, for lack of one duration of sufficiently long observation (see note).

The recorded maximum instantaneous flow with Ayron was of 9,15 m ³ a second on January 1st 1994, while the value maximum day laborer was of 7,8 m ³ a second on January 6th of the same year. 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 completely banal.

Vandelogne is a river rather not very abundant. The Lame of water past in its catchment area is of 166 millimetres annually, which is half less than the overall average of France, and is also lower than the average of the basin of the the Loire (more or less 245 millimetres) and of the Clain (223 millimetres). The specific Flow (or Qsp) reached the rather poor figure of 5,2 liters a second and per square kilometer of basin.

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