Méchet

The Méchet is a small French river which runs in the Département of Saône-et-Loire (71). It is an affluent of the Arroux out of Right Bank, therefore a tributary of a tributary of the the Loire.

Geography

Méchet is born in the solid mass from Morvan on the territory from the commune of Saint-Price, in the south of the forests of Saint-Price and Glenne. Initially directed towards the south, it goes up towards the North-West on the level of Saint-Leger-under-Beuvray, after having received water of the oriental party of the Mont Beuvray. On the level of the commune of Large-Glass the, it carries out a news and last buckles which directs it towards south-east. It ends up being thrown in Arroux in extreme cases between the communes of Laizy and Monthelon.

Most of its catchment area belonged to the Regional natural park of Morvan.

Common crossings

The river crosses or skirts the following communes (of upstream downstream): Saint-Price, Saint-Leger-under-Beuvray, Large-Glass the, Laizy and Monthelon, all located in the Department of Saône-et-Loire.

Hydrology

Méchet is a rather irregular river, following the example its neighbors resulting from the north-eastern edge of the Massif Central, and above all the Arroux and the Aron. Its flow was observed during one 13 years period (1983-1995), with Monthelon, locality of the Département of Saône-et-Loire located at the level of its confluence with Arroux. Surface thus studied is of 89 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 Monthelon is of 2,20 m ³ a second.

Méchet presents seasonal fluctuations of flow extremely marked, like very often in the basin of the Loire. The high waters are held in winter and are characterized by average monthly flows going from 2,88 to 4,78 m ³ a second, from December to April included (with a maximum very Net in January). In March however, the flow drops rather extremely and it occurs a plate, with light increase of the flow in April (3,12 m ³ a second). In May the flow crumbles (1,74 m ³ then 1,16 m ³ in June), which leads quickly to the low waters of summer which take place from July to September included, involving a fall of the average monthly flow up to 0,328 m ³ in August. But these monthly averages occult fluctuations much more marked according to the years or over short periods.

With the low water level, the VCN3 can fall until 0,088 m ³ a second (88 liters), in the event of dry period quinquennial, which becomes severe. But this fact is frequent among the rivers of the area of Morvan (see note).

As for the risings, they can be rather important, taking into account the smallness of the catchment area. The QIX 2 and QIX 5 are worth respectively 18 and 22 m ³ a second. The QIX 10 or calculated flow of decennial rising is of 24 m ³ a second, the QIX 20 of 26 m ³, while the QIX 50 was not calculated fault one duration of sufficient observation to determine it (see note).

The recorded maximum instantaneous flow with Monthelon was of 26,4 m ³ a second on February 14th, 1990, while the value maximum day laborer was of 24,5 m ³ a second the same day. If one compares the first of these values on a QIX scale of the river, one notes that this rising was of a vicennial nature, and thus intended to repeat itself every 20 years on average.

Méchet is an extremely abundant river. The Lame of water past in its area catchment of 783 millimetres annually, which is more or less twice and half superior with the overall average of France, and more is still compared with the average of the basin of the the Loire (more or less 245 millimetres). The specific Flow (or Qsp) reached of this fact the very high figure of 24,7 liters a second and per square kilometer of basin.

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