Dadou

The Dadou is a river south of the France. It is one of the most important affluents of the Agout, therefore tributary of a tributary of the Tarn and the the Garonne.

Geography

It takes its source in the Monts of Lacaune on the commune of Masnau-Massuguiès in the Tarn and is thrown in the Agout out of Right Bank, close to Ambres, after having crossed of is in west the totality of the Département of the Tarn

Principal affluents

the Ambias
the Oulas
the Dadounet
the Lézert
the Nandou
the Agros

Hydrology

minimal Flow (with Montdragon): 0,78 m ³ /s
maximum Flow (with Graulhet): 293 m ³ /s (rising of December 14th, 1981)

The flow of Dadou was observed during 13 years (1973-1986), with Graulhet, locality of the Département of the Tarn, located not far from the confluence with the Agout. The surface taken into account is of 762 km ², that is to say 89% of total area catchment river which makes 858 of them.

The interannual medium flow or module of the river with Graulhet is of 10,8 m ³ a second.

Dadou presents seasonal fluctuations of flow extremely marked, with high waters of winter carrying the average monthly flow on a level located between 17,4 and 24,0 m ³ a second, from December to March included (with a maximum well Net in February). In April, the flow strongly decreases, and it constitutes a kind of intermediate plate with very a small rebound in May (13,6 m ³ a second in May). In June however the medium flow crumbles (5,39 m ³) what leads quickly to the low waters of summer which take place from July to September, with a fall of the monthly medium flow going until 2,52 m ³ a second in August, which remains still rather consistent.

However, the VCN3 can fall until 0,510 m ³, in the event of dry period quinquennial, that is to say 510 liters a second, which becomes severe (see note).

In addition the risings can be important. The QIX 2 and QIX 5 or calculated flows of biennial and quinquennial rising are worth respectively 150 and 210 m ³ a second. The QIX 10 or calculated flow of decennial rising is worth 240 m ³ a second, while the QIX 20 is assembled to 280 m ³. The QIX 50 was not calculated fault one duration of sufficient observation to do it (see note). It is however estimated at 320 m ³ a second. The recorded maximum instantaneous flow with Graulhet was of 293 m ³ a second on December 14th, 1981, while the value maximum day laborer was of 234 m ³ a second the same day. By comparing the first of these figures with the values of the various QIX of the river, it appears that this rising was intermediate between a vicennial rising and a rising cinquantennale and thus intended to repeat the every approximately 35-40 years.

The Lame of water past in the basin of Dadou is of 449 millimetres annually, which is high, very definitely higher than the overall average of France, all confused basins, and also to that of the area catchment of the the Garonne (385 millimetres with Farmhouse-with Agenais). It is however lower than the whole of the basin of the Agout (565 millimetres). The specific flow (or Qsp) is assembled consequently to the solid figure of 14,2 liters a second and per square kilometer of basin.

Departments and crossed cities

Tarn: Montdragon, Graulhet, Briatexte.

References

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