Estéron

The Estéron is a river of France, Affluent of the Var out of Right Bank. It runs in the departments of the Alp-of-High-Provence and the the Alpes-Maritimes. Its length is of 66,7 kilometers.

Geography

Estéron is born on the territory from the commune of Soleilhas in the department from the Alp-of-High-Provence to six or seven kilometers with the east-north-east from Castellane, and takes almost from the start the direction of the east. It quickly crosses the limit with the department of the the Alpes-Maritimes, and continuous in this direction to its confluence with the Var on the level of the commune of the Broc, a few kilometers upstream of Nice.

Hydrology

Estéron is a rather abundant river all the year. Its flow was observed over one period of 97 years (1911-2007), with the Broc, very close to its confluence with the VAr. The catchment area of the river is there of 451 km ², i.e. its quasi totality.

The interannual medium flow or module of the river to the Pitcher is of 6,96 m ³ a second.

Estéron presents typical seasonal fluctuations of the Mediterranean rain mode. One distinguishes indeed there two periods of rising related to the equinoxes. The high waters of autumn carry the average monthly flow on a level located at 10,1 m ³ a second, in November and are followed of a very light fall of flow to 8,84 m ³ a second in January. A second rise of the flow follows then leading to a second top in March (10,3 m ³) and April (9,34 m ³). Consequently starts a regular fall which leads to low waters of summer from July to September included, with the low water level in August (monthly average of 2,16 m ³ a second), which is still enough strapping man in Provence. On the whole, the seasonal oscillations are relatively not very important. However the fluctuations of flow can be much more marked over short periods.

The VCN3 can fall until 0,82 m ³, in the event of dry period quinquennial, which is still not too severe. The VCN3 is the past minimal quantity or minimal flow over three days consecutive.

The risings can be very important for a small river with reduced basin. The QIX 2 or calculated flow of biennial rising and QIX 5 (calculated flow of quinquennial rising) are worth respectively 160 and 270 m ³. The QIX 10 or calculated flow of decennial rising is of 340 m ³ a second and the QIX 20 of 400 m ³. As for the QIX 50 or computed value of the flow of raw cinquantennale, it is assembled to 490 m ³ (see note). That means that, for example, every two years, one must expect a rising of about 160 cubic meters, and every twenty years a rising of 400 cubic meters must occur, statistically at least.

The recorded maximum instantaneous flow was of 464 m ³ a second on December 20th, 1997. By comparing this value with the scale of the QIX of the river, it appears that this believed was more important than vicennial, undoubtedly of order of forty years, and thus relatively rare.

On the whole, Estéron is an abundant river. The Lame of water past in its catchment area is of 488 millimetres annually (against 746 for Tinée), which is high, being worth definitely more than the average overall of France all confused basins, but lower than the blade of the totality of the basin of the VAr (553 millimetres). The specific Flow of the river (or Qsp) reached the figure of 15,4 liters a second and per square kilometer of basin.

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