| Ardèche | |
| Map: | Ardèche.png |
| Source1 Coordinates: | 44.7°N 4.0447°W |
| Mouth Coordinates: | 44.2644°N 4.6481°W |
| Subdivision Type1: | Country |
| Length: | 125km (78miles) |
| Discharge1 Avg: | 65m3/s |
| Basin Size: | 2430km2 |
The Ardèche (in French aʁdɛʃ/; Occitan (post 1500);: Ardecha) is a 125km (78miles) long river in south-central France, a right-bank tributary of the River Rhône. Its source is in the Massif Central, near the village of Astet. It flows into the Rhône near Pont-Saint-Esprit, north-west of Orange. The river gives its name to the French department of Ardèche.
The valley of the Ardèche is very scenic, in particular a 30km (20miles) section known as the Ardèche Gorges. The walls of the river here are limestone cliffs up to 300m (1,000feet) high. A kayak and camping trip down the gorge is not technically difficult and is very popular in the summer. The most famous feature is a natural 60m (200feet) stone arch spanning the river known as the Pont d'Arc (arch bridge).
The source of the river lies at 1467m (4,813feet) above sea level in the Vivarais, near the Col de la Chavade, in the forest of Mazan in the commune of Astet. After the towns of Aubenas and Ruoms, it collects the Chassezac and the Beaume and plunges into its famous gorge below Vallon-Pont-d'Arc. It flows into the Rhône at Pont-Saint-Esprit.
The Ardèche flows through the following departments and communes:[1]
The most important tributaries and subtributaries to the Ardèche include:
The river has an average discharge of 65m3/s but experiences severe floods, called "coups de l'Ardèche" (Blows of the Ardèche), in spring and autumn and periods of very low water in summer. During flood events in 1827, 1890, and 1924, it reached 7800m3/s and the water level rose to a record 21.4m (70.2feet) in the gorge.
Despite the Ardèche's short length, the flow of the river at 65m3/s is relatively high—higher than the Gardon at 32m3/s, the Cèze (22 m3/s), the Hérault (44 m3/s), or the Agout (55 m3/s)—major rivers south of the Massif Central but much longer.
The inter-annual average flow of the Ardèche was observed and calculated over a period of 26 years at Saint-Martin d'Ardèche. It amounted to 63.4m3/s for a surface basin of 2240km2—i.e. the vast majority of its watershed of 2430km2. The river has seasonal fluctuations: a typical flow around the Cevennes, with high water in autumn and winter being double the normal, brings the average monthly flow at the first peak of 93m3/s in October then, after falling to 76m3/s in December, a new peak occurs from 96m3/s102m3/s in January–March (with a maximum in January). A rapid decline in flow rate follows ending in a dry period in July–August resulting in a decrease of the average monthly rate to the level of 12m3/s in July.[2] (See bar chart below.)
The VCN3 (minimum flow) can drop to 2.5m3/s in a dry year.
Floods can be extremely important (usually following storms in the Cevennes). The Qix 2 and Qix 5 are respectively 1800m3/s2600m3/s which is high. QIX 10 is 3100m3/s while QIX 20 and QIX 50 respectively rise to 3600m3/s4300m3/s.
The maximum instantaneous flow recorded in Saint-Martin d'Ardèche has been 4500m3/s (two-thirds of the average flow of the Danube), while the maximum recorded daily rate was 2506m3/s.
The runoff curve number flowing into the catchment of the river is 897mm annually, which is very high. The specific flow (Qs) reaches 28.3 litres per second per square kilometre of the catchment.
| Waterway | Location | Flows in m per second | Side max(m) | Max. instant | Max. journ. | Runoff Curve (mm) | Area (km) | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Module | VCN3 (low water) | QIX 2 | QIX 5 | QIX 10 | QIX 20 | QIX 50 | ||||||||
| Ardèche | Meyras | 3.52 | 0.090 | 150 | 230 | 280 | 330 | align="right" | - | 4.09 | 360 | 157 | 102 | |
| Ardèche | Pont-de-Labeaume | 16.30 | 0.550 | 400 | 590 | 710 | 830 | 980 | 7.00 | 1660 | 531 | 280 | ||
| Ardèche | Vogüé | 26.00 | 1.100 | 730 | 1100 | 1400 | 1600 | 1900 | 7.81 | 2200 | 890 | 1294 | 636 | |
| Ligne | Labeaume | 2.07 | 0.002 | 170 | 300 | 390 | 480 | align="right" | - | 4.14 | 622 | 162 | 586 | 112 |
| Beaume | 7.56 | 0.230 | 270 | 430 | 540 | 640 | align="right" | - | 5.73 | 683 | 348 | 994 | 241 | |
| Chassezac | Chambonas | 15.50 | 0.820 | 550 | 900 | 1100 | 1300 | 1600 | align="right" | - | 1800 | 878 | 965 | 507 |
| - from Borne | Saint-Laurent-les-Bains | 2.69 | 0.075 | 110 | 180 | 230 | 270 | 330 | align="right" | - | 694 | 174 | 1357 | 63 |
| - from Altier | Altier | 3.44 | 0.130 | 120 | 210 | 270 | 330 | 400 | 3.12 | 960 | 190 | 1056 | 103 | |
| Ardèche | Saint-Martin-d'Ardèche | 64.30 | 2.700 | 1800 | 2600 | 3100 | 3600 | 4300 | 8.12 | 4500 | 2510 | 908 | ||
The prefecture of Ardèche has provided a voice server since June 2005 whose objective is to regularly disseminate information messages to allow monitoring of any significant event that might trigger a civil security crisis or standby alert. Precise information on the evolution of any flood is provided.
The Ardèche receives water from the Loire river via the "La Palisse" flood barrier and the Lake d'Issarlès. Effectively, the water is collected to feed the EDF hydroelectric plant at Montpezat-sous-Bauzon and is subsequently piped into the Fontaulière river, a tributary of the Ardèche, near the town of Aubenas.
Several ancient inscriptions about a college of nautes (Boatmen) in associated rivers have been discovered in the Gard. It is possible that the two rivers concerned are the Ardèche and the Ouvèze.[3]
The identification of these two rivers is still pending. However, if it does involve the Ardèche river, the spellings Hentica (from 950), then Ardesca (in the Charta Vetus) have been attested.
The Ardèche is protected along almost all of its course. These protected areas are: