The Durance - SpeedyLook encyclopedia

Etymology

The Durance is documented in the old forms Druentia (1st century), Drouentios potamos (2nd century), Durantia (854, 1271) or Durentia (1127)… The traditional forms are probably deteriorations of *Dūrantia , based on the hydronyme Dur- that one finds in the name of many rivers of the Western Alps (Dora in Italy, Dranse in Haute-Savoie, Drome), associated with the rental suffix - antia .

Hydrography

Of its source above the Montgenèvre with the confluence with the Rhone, the Durance traverses 305 km. However, more the long course is traced by the system the Clarée-Durance and has a 325 km length. The originality of the course is its slope, which remains relatively high in the lower part (approximately 0.3%), since to approximately 100 K of the source, Isere runs to 330 m of altitude and the Durance with 700 Mr. This fact contributes partially to the torrential character of the river, including in the lower course.

Departments and crossed main cities

Hautes-Alpes (05): Briançon, Spray;
Alp-of-High-Provence (04): Sisteron, Castle-Arnoux-Saint-Auban;
Vaucluse (84): Sluice, Cadenet, Cavaillon.

Source with Greenhouse-Ponçon

To the lake of Greenhouse-Ponçon, the Durance circulates in a more or less broad valley surrounded by high mountains. It is an alpine river with the nival mode, with high-water in June and a flow supported even in summer. The torrent of Montgenèvre is thrown in Clarée, crosses Briançon then receives Guisane. It moves then towards the south, receives water of Gyronde (glacial torrent of the Jewel cases), of Guil and is thrown in the lake of Greenhouse-Ponçon a little downstream from Embrun. The confluence with Ubaye was drowned during the filling of the lake.

Of Greenhouse-Ponçon with Castle-Arnoux

The landscape changes radically, because the mountains deviate and of the increasingly vast plates replace them. The bed itself becomes again boxed, digging in the terraces around a furrow of a few meters to a few tens of meters of depth. Right before the clue of Sisteron, the Durance joins the Buëch, which recovered water of the channel EDF. Many minor affluents with the rain mode also flow close to Sisteron (Sifts, Jabron, Vançon). It happens that the latter are dry in summer.

Of Castle-Arnoux in Avignon

As upstream, the Durance remains surrounded by hills or plates, but the valley widens in an alluvial plain several kilometers of width (5 km with Manosque), recently arranged with the development of a modern agriculture and the construction of the highway A 51.

The river receives water of the Bléone close to the Mées, the Asse a few kilometers in the south of Oraison and the the Verdon in the lake of Cadarache. The valley is tightened on a few kilometers with the crossing of the procession of Mirabeau, then réélargit in a plain even vaster to the confluence with the Rhone. The river does not receive any more any important affluent downstream from Cadarache

List affluents

(D) the Clarée;
(D) the Guisane;
(D) the Wave;
(D) the Gyronde;
(D) the Biaysse;
(G) the Guil;
(G) the Ubaye;
(D) the Advance;
(D) the Luye;
(D) the Rousine;
(G) the Sifts;
(D) the Buëch;
(D) the Jabron;
(G) the Vançon;
(G) the Bléone;
(G) the Rancure;
(G) the Adze;
(D) the Bush hammer;
(G) the the Verdon;
(D) the Eze;
(D) the Coulon.

Hydrology

Capricious river, formerly dreaded for its risings as well as for its low water levels, the Durance is an at the same time alpine and Mediterranean river with quite particular morphology.

Flow

With the confluence with the Rhone, the average natural flow of the Durance is approximately 190 m ³ /s, with a strong annual variability. It can vary between 40m ³ /s (the most severe low water levels) and 6000 m ³ /s (risings millénales). With the outlet in the lake of Greenhouse-Ponçon, the medium flow is of approximately 80 m ³ /s; on the level of Oraison it is approximately 120 m ³ /s and after reception of the Verdon 175 m ³ /s. downstream the contribution of water of the affluents reaches is very weak. The annual maximum generally occurs in May or in June, but the most violent risings occur in autumn. The low water level takes place in winter in the high valley and summer in the average and lower part of the course.

A mixed mode

The catchment area of the Durance gathers territories going of the eternal snow to the hills and plates with the Mediterranean Climat. Thus, the river is subjected to a nival mode in its higher course (to Greenhouse-Ponçon), with winter low water levels and risings each year from May to July. Downstream, its many affluents of medium mountains or the plates to the Mediterranean primarily rain mode bring water only in winter, in spring and at the time of the risings of autumn, with a low and very irregular flow in summer. It follows a shift of the natural maximum of spring from June to May while descending the course.

Believed

Hydro-electric installation

Channel EDF of the Durance runs on more than 250 km, of the stopping of Greenhouse-Ponçon in the High Alps with the Pond of Berre. It was arranged following the realization of the stopping of Greenhouse-Ponçon to convey water necessary to the hydroelectric production, the irrigation and drinking water of Provence.

The channel feeds out of water the fifteen hydroelectric stations quoted below and allows them to start and function simultaneously. A power of 2000 MW (the equivalent of 2 nuclear reactors) can thus be mobilized in less than 10 minutes. The whole of installation produces each year approximately 6 billion kWh, that is to say 10% of the whole of the hydraulic production of Électricité de France.

The channel also makes it possible to convey the water stored in the stoppings of Greenhouse-Ponçon and the Verdon towards the Low-Durance. Thanks to the channel, agriculture in Provence east safe from the dryness. Each year, the channel transports several billion m3 of water which irrigate 150.000 hectares of cultivated grounds. But moreover, it is the source of supply of the Canal of Marseilles and also feeds out of water the networks and from the Company of the Canal of Provence.

Impact of installations

The Durance had an average natural flow of 188 m ³ /s and a river mode of Mediterranean type, but hydraulic installations modified its course. Separately a very low reserved flow, the mass of water circulates from now on in a “channel usinier” which skirts the natural bed of the large river in order to make them pass by a series of hydro-electric factories. This channel usinier can contain until 250 m ³ /s. So at the time of the great risings, the surplus waters borrow the natural bed again, the tanks being largely insufficient to store similar water masses (they are especially Greenhouse-Ponçon, but also the large tanks of the the Verdon, his principal affluent).

Hydroelectric installations

Channels EDF;
Stopping-factory of Greenhouse-Ponçon;
Factory of Sisteron - St-Lazare dam;
Factory of Salignac;
Stopping of the Stopover;
Factory of Speech;
Factory of Brillanne;
Factory of Manosque;
Factory of Holy-Tulle;
Stopping of Cadarache;
Factory of Jouques;
Stopping of Mallemort.

History

The Durance played a very important part in the history of Provence, and largely contributed to the economic growth and demographic of the Marseilles area, after having been an obstacle with circulation during centuries.

Antiquity

During the Antiquity, and until the 19th century, the Durance was famous for its difficult crossing, its brutal risings and its inconstant flow. The width of its bed, the force and low depth of its current, and the changes of course after the risings also made the river navigation very difficult in spite of the flow relatively important, in particular in period of high-water.

At the time préromaine, the Durance was the border between various people celto-Ligurians established along his bed, like the Cavares (Cavaillon) and the Salyens (Rhone delta). vats were to make it possible to cross it, in particular with the height of Pertuis, city whose name preserves the memory of this function.

The Middle Ages and modern times

12th at the 19th century, the Rivière was employed with the Flottage of wood, crossed in the Alps and used in the towns of plain and the shipyards. The bridge of Sisteron, set up with the Middle Ages, remained until the middle of the 19th century the only passage into hard from one bank to another of the Durance. An important canal system of irrigation develops, with in particular the construction of channels deviating a small portion of the flow towards Arles and Crau. The construction of the channel of Provence in the middle of the 19th century made it possible the Marseilles agglomeration to develop very quickly.

20th century: hydroelectric installations

Hydroelectric installations, with the construction of the chain of stoppings on the Durance, the Verdon like on Buëch and Bléone, had the most important economic impacts and most visible in the landscape. The major part of the flow was diverted in channels downstream from Greenhouse-Ponçon, and only circulates in the natural bed a reserved flow from 2 to 5 m ³ /s, corresponding to 1/40 of the natural flow. The bed was gradually fixed and of the vegetation starts to push there, where water does not run any more. Thanks to the tanks of Greenhouse-Ponçon and Holy-Crosses, which can retain a total of more than 2 billion tons water, the irrigation remains possible in summer during the driest years, and around the water levels the economy could develop around estival tourism.

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