Ru of Élancourt

The Ru of Élancourt is a French Rivière which runs in the department of the Yvelines (78). It is an affluent of the Mauldre out of Right Bank, therefore a tributary of a tributary of the the Seine.

Geography

The Ru of Élancourt is born on the territory from the commune of Élancourt, in Yvelines. Its course has an general orientation active of south-east towards the North-West. It joins the Mauldre (Right Bank) with Jouars-Pontchartrain.

Common crossings

The Ru of Élancourt crosses the communes of Élancourt, It Tremblay-on-Mauldre and Jouars-Pontchartrain, all located in the department of the Yvelines.

Hydrology

The flow of the Ru of Élancourt was observed for one 27 years period (1978-2004), at the hydrometric station of Chenevières, commune of Jouars-Pontchartrain, locality located at the level of its confluence with Mauldre (ref.: ). The catchment area of the river is of 23 km ².

The interannual medium flow or module of the river with Jouars-Pontchartrain is of 0,339 m ³ a second. Let us note that this flow is largely inflated by the rejections of increasingly important urban populations, in the agglomerations of Versailles and Saint-Quentin-in-Yvelines. This water is rejected into the river after treatment in the purification plants. This phenomenon tends to increase with the passing of years.

The Ru of Élancourt presents seasonal fluctuations of flow very little important. The high waters are held in autumn and winter and are characterized by average monthly flows going from 0,35 to 0,40 m ³ a second, from October at March included (with a very light maximum from December to February). As of April, the flow drops very gently to the low waters which take place in summer from June to August, with a fall of the monthly medium flow going until 0,25 m ³ in August, which remains very abundant. But the variations of flow can be more important according to the years.

Thus the VCN3 can fall until 0,062 m ³, in the event of dry period quinquennial, that is to say 62 liters a second, which must be regarded as rather comfortable remainder (see note).

However the risings can be rather important, taking into account the extreme exiguity of the catchment area. The QIX 2 and QIX 5 or calculated flows of biennial and quinquennial rising are worth respectively 2,8 and 4,2 m ³. The QIX 10 or calculated flow of decennial rising is worth 5,1 m ³ a second, while the QIX 20 is assembled to 6,0 m ³ a second. As for the QIX 50, it was not calculated (see note). The recorded maximum instantaneous flow with Jouars-Pontchartrain, during the period of observation, was of 7,86 m ³ a second on July 5th, 1983, while the value maximum day laborer was of 2,95 m ³ a second on October 26th, 1981. By comparing the first of these figures with the values of the various QIX of the river, it appears that this rising was largely higher than that envisaged by the QIX 20, and was at least cinquantennale, and thus completely exceptional.

On the whole, the Ru of Élancourt is an abundant river, overfed by important purified urban rejections. The Lame of water past in its catchment area is of 466 millimetres annually, which is high, definitely higher than the overall average of France, and of course than the totality of the basin of the the Seine (approximately 240 millimetres). The specific Flow (or Qsp) reached of this fact the solid figure of 14,7 liters a second and per square kilometer of basin.

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