Durance

The Durance (; ''Durença'' in the Occitan classical norm or ''Durènço'' in the Mistralian norm) is a major river in Southeastern France. A left tributary of the Rhône, it is long. Its drainage basin is .Bassin versant : Durance (La)
Observatoire Régional Eau et Milieux Aquatiques en PACA

Its source is in the southwestern part of the Alps, in the Montgenèvre ski resort near Briançon; it flows southwest through the following departments and cities:
* Hautes-Alpes: Briançon, Embrun.
* Alpes-de-Haute-Provence: Sisteron, Manosque.
* Vaucluse: Cavaillon, Avignon.
* Bouches-du-Rhône.

The Durance's largest tributary is the Verdon. The Durance itself is a tributary of the Rhône and flows into the Rhône near Avignon. The Durance is the second longest (after the Saône) of the tributaries of the Rhône and the third largest in terms of its flow (after the Saône and Isère).

Etymology

The Durance is documented as (1st c. AD), (Δρουέντιος; 2nd c. AD), (854) and (1127). The name ''Dru-ent-ia'' probably means 'the flowing one', stemming from the Proto-Indo-European root *''dreu''- ('to run, walk fast').

Similar names are found in the names of many rivers in the Western Alps and further: Dora in Italy, Dranse in Haute-Savoie, and the Drôme in south-eastern France. All these rivers have their sources in mountains, and are fast-running.

The Durance retains its name rather than either the Clarée or Guisane, even though the latter two are longer than the Durance when they each merge. The Durance is better known than the other two rivers because the Durance valley is an old and important trade route, whereas the valleys of the Clarée and Guisane are effectively dead ends.

Hydrography

The Durance is long from its source at the foot of Sommet des Anges, at high, above Montgenèvre, to its confluence with the Rhône. However, a longer route is traced by the Clarée-Durance system with a length of . Its descent is unusually rapid at 81 m/km (165 ft/mi) in its first , then 15 m/km (30 ft/mi) to its confluence with the ,Clébert & Rouyer, ''Durance'', p.35. and then still nearly 8 m/km (16 ft/mi) to the confluence with the Ubaye. This descent stays relatively steep after this confluence, then shallows to approximately 0.33% in its middle course (to the Mirabeau bridge), then 0.24% in its lower course. For comparison, at approximately from its source, the Isère is at altitude and the Durance at , which contributes partially to its fast-flowing nature, including in the lower part of the river. It drops from its source to Mirabeau and approximately from its source to the confluence with the Rhône.

Departments and main towns crossed

The river only runs through the towns of Briançon and Sisteron — built where the banks are very steep — the other towns are built on slopes close to the river:

* Hautes-Alpes
**Briançon
** Embrun
*Alpes-de-Haute-Provence
** Sisteron
** Château-Arnoux-Saint-Auban
*Vaucluse
**Pertuis
** Cadenet
**Cavaillon
*Bouches-du-Rhône
**left bank of the Durance.

The Durance catchment area extends to three other departments: Var, Drôme and Alpes-Maritimes. The Durance is the longest river in Metropolitan France without a department named after it.

Source to Serre-Ponçon

The source of La Durance is on the northern slope of the , where the first small streams combine into a river. This runs near to Montgenèvre and then flows into the larger Clarée river, and then passes through Briançon before the Guisane joins it. It then continues south combining with the Gyronde  — the Écrins glacial stream — at L'Argentière-la-Bessée. The confluence with the Guil occurs below Guillestre and Mont-Dauphin. The Durance then flows south-south-west and flows into the Lac de Serre-Ponçon just downstream of Embrun. The confluence with the Ubaye was flooded as the lake filled.

Middle section: from Serre-Ponçon to Mirabeau

The middle part of the Durance runs through a landscape that changes as the valley increasingly widens. The river itself becomes steeply banked by terraces, and carves a channel, sometimes a few metres deep, sometimes tens of metres deep. In its middle and lower reaches the Durance is affected by the Mediterranean climate: flooding after autumnal rains, with low water levels in summer. Just before the narrow gap in the mountains at Sisteron, the Durance joins Buëch and the . Water also flows in from the EDF Canal.

Beyond Sisteron further rivers and streams join the Durance: Jabron, Vançon, Bléone near Les Mées and from the Asse (river) a few kilometres to the south of Oraison. The Verdon flows into the Durance near Cadarache. The valley widens still further into an alluvial plain several kilometres wide ( near Manosque). Here the river was diverted for the development of modern agriculture and the construction of the A51 motorway.

There are several dams along the middle part of the Durance. In addition to main dam at Serre-Ponçon, there are dams at Espinasses, Sisteron, L'Escale and Cadarache. There are small canals whose primary purpose is to draw water from the river into the EDF Canal which in turn feeds the hydroelectric power stations. Some of the water diverted by the dams is used for irrigation.

Mirabeau to Avignon

The valley narrows for a few kilometres until the water gap at Mirabeau, at a depth of , then widens again into an even broader plain until the confluence with the Rhône south of Avignon. Its direction changes from southerly to westerly then northwesterly, aligning with the small Provençal mountain ranges between which it flows (Alpilles and Luberon). The Durance receives only one significant tributary on this last part of its course: the Calavon

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