Choisille

The Choisille is a French Rivière which runs in Touraine, in the department of Indre-et-Loire (37). It is a direct affluent of the the Loire out of Right Bank.

Geography

Choisille takes its source with Nouzilly in the department of Indre-et-Loire, in a wooded area comprising of many ponds (Wood of the Mortar, Bois of Nouzilly). Shortly after its birth, it takes the direction of south-west, orientation which it will maintain until the accesses of Turns. At this place, it transfers towards the south, and thus, after a course of 25 kilometers, it joined the the Loire on the level of Saint-Cyr-sur-Loire, in the agglomeration of Turns, a little downstream from the downtown area.

Common crossings

Choisille crosses the communes of Nouzilly, Cerelles, Chanceaux-on-Choisille, Saint-Antoine-of-Rock, Mettray, It Membrolle-on-Choisille, Fondettes and Saint-Cyr-sur-Loire, all located in the department of Indre-et-Loire.

Hydrology

Choisille is a river rather not very abundant, like the majority of the rivers of Touraine (department of Indre-et-Loire). The hydrometric station of Mettray, locality located at little distance from its confluence, raised, on a portion of basin of 174 square kilometers (more than 95% of the catchment area), a module or interannual medium flow of 0,845 m ³ a second. The observations were made during one 16 years period going from 1970 to 1985.

Choisille presents seasonal fluctuations of flow rather little marked. The high waters are held in winter and are characterized by monthly flows going from 1,09 to 1,59 m ³ a second, from January to April included (with a maximum extremely marked in February). The low waters take place in summer, of at the end of July at the beginning of October, involving a fall of the monthly medium flow going up to 0,372 m ³ in August, which is far from being weak in the area. But the fluctuations are much more marked over moreover short periods, or according to the years.

With the low water level, the VCN3 can fall until 0,093 m ³, in the event of dry period quinquennial, that is to say 93 liters a second, which is not at all severe for such a small river. Let us recall that the VCN3 is a measurement of the severity of the low water levels which gives the past minimal quantity or minimal flow over three days consecutive.

As for the risings, they are usually moderated, at least in the context ligérien. The QIX 2 and QIX 5 are worth indeed respectively 8,5 and 13 m ³. The QIX 10 or calculated flow of decennial rising is of 16 m ³ a second and the QIX 20 of 19 m ³. As for the QIX 50 it was not calculated, for lack of duration of sufficient observation (see note).

The recorded maximum instantaneous flow with Mettray was of 23,9 m ³ a second on March 1st, 1980, while the value maximum day laborer was of 15,4 m ³ a second on November 24th, 1984. If one compares the first of these values on a QIX scale, one notes that this rising was much more important than the vicennial rising defined by the QIX 20, undoubtedly of order cinquantennal even more, and thus very exceptional. On the whole, Choisille is a river very little abundant, like the majority of the rivers of plain of the basin of the Loire. The Lame of water past in its basin is of 153 millimetres annually, which is much lower than the overall average of France all confused basins, and also to the average of the basin of the the Loire (more or less 244 millimetres). The specific Débit of the river (or Qsp) is assembled consequently at weak 4,9 liters a second and per square kilometer of basin.

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