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Gironde (estuary)

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Gironde
Lage der Gironde

Location of the Gironde

Data
Location France, Nouvelle-Aquitaine region
Origin Confluence of the Garonne and Dordogne rivers at Bec d’Ambès, near Bordeaux
45° 2′ 31″ N, 0° 36′ 26″ W
Source Height approx. 4 m[1]
Mouth into the Atlantic Ocean at RoyanCoordinates 45° 35′ 23″ N, 1° 2′ 57″ W
45° 35′ 23″ N, 1° 2′ 57″ W
Mouth height 0 m[1]
Height difference approx. 4 m
Bottom slope approx. 0.05 ‰
Length approx. 75 km(see individual references)
Small towns Pauillac, Saint-Georges-de-Didonne, Royan
Shipbar yes
Die Mündung der Gironde vom rechten Ufer aus gesehen

The mouth of the Gironde seen from the right bank

The Gironde is an estuary in southwestern France, stretching from the confluence of the Garonne and Dordogne rivers to the transition into the Atlantic Ocean in the Bay of Biscay. It is about 75[2] Kilometres long, up to 15 kilometres wide and runs in a north-northwesterly direction. With a surface area of 685 km², it is the largest estuary in Europe. The Gironde is named after the department of Gironde, which is mostly located on the left bank; opposite it on the right bank is the department of Charente-Maritime.

Geography

Location and course

The Gironde begins at the Bec d’Ambès, a peninsula about 15 kilometres downstream from Bordeaux, which the Garonne and Dordogne form just before their confluence. On the left bank, the entire length of the Gironde is covered by the Médoc wine-growing region, a low-lying, gently sloping landscape with sedimentary subsoil (gravel and pebbles) that is ideally suited to viticulture due to its permeability. The best sites are those that “see the water”, i.e. lie within the special microclimate shaped by the Gironde: Light is reflected by the large water surface and heat is stored, so that the conditions for grape ripening are optimal. These sites are home to the top wines of Margaux, Pauillac, Saint-Estèphe, Saint-Julien and several others. The right bank is initially dominated by a limestone escarpment (the Haute Gironde), on which the Côtes de Bourg and Côtes de Blaye appellations are located. In the Charente-Maritime area, the terrain gradually flattens out and viticulture disappears. The mouth of the Gironde is marked by the headland at Le Verdon-sur-Mer, the Pointe de Grave.

The course of the estuary rivers has changed slightly repeatedly over time. The town of Bourg-sur-Gironde, for example, is now on the Dordogne because the different levels of sediment transport over the centuries have shifted the course of sandbanks and islands, causing the Dordogne to veer northwards before flowing into the Gironde.

Catchment area and boundaries

The catchment area of the Gironde includes those of the two rivers that feed it: The Dordogne drains northern Guyenne and much of the southwestern Massif Central, the Garonne almost all of the rest of the Aquitaine basin. With the exception of the Basque Country and the coastal areas of the Landes, this covers a drainage basin bounded by the Pyrenees to the south, the watershed with the Mediterranean to the east, and the main watershed of the Massif Central to the north and northeast, encompassing nearly one-fifth of all of France. However, the freshwater discharge is exceeded 15 to 30 times by the volume of seawater flowing in at high tide.

The demarcation of the Gironde is controversial: in addition to the water area from the Bec d’Ambès, many include the lower reaches of the Garonne and Dordogne, as salinity and tidal range still manifest themselves clearly here. The considerable width of the two rivers has also led to the landscape between them being called Entre deux mers (Between two seas). The adjacent banks are also often counted as part of the estuary, especially the marshy lowlands on the left bank. The estuary itself is divided into an upper section (with numerous islands) and a lower section.

Climate

The Gironde lies in the temperate climate zone of oceanic character (maritime climate) with very mild winters, warm summers and frequent precipitation. Due to the enormous water surface, it moderates the climatic effects in the surrounding countryside even more, so that a very balanced temperature course prevails here. The winters are often frost-free, the summers still very bearable. The last icefall on the Gironde was recorded in the record winter of 1956.

Traffic

Car ferry entering the port of Le Verdon-sur-Mer

As the Gironde, due to its enormous width, is an obstacle to traffic, especially in the estuary, and there are no bridges to cross it, two car-ferry connections have been established. They connect the towns:

  • Blaye-Lamarque and
  • Royan-Le Verdon-sur-Mer.

Cities

Royan, seen from the Gironde estuary

If one adds the lower reaches of the estuaries, Bordeaux and its agglomeration is the all-dominant city of the Gironde. Inland on the Dordogne is Libourne, the other historically important river port, but in modern times it plays only a minor role compared to Bordeaux. On the Gironde itself, the seaside resort of Royan (Charente-Maritime) is the most important settlement, with just under 20,000 inhabitants (80,000 in the agglomeration). Well-known towns and villages on the right bank are Blaye, Bourg-sur-Gironde and Talmont-sur-Gironde, on the left bank Blanquefort, Pauillac and Margaux.

Ecosystem

Reeds and fishing hut on the left bank in Pauillac

Like many brackish water reservoirs, the Gironde is a species-poor but individual-rich body of water. As a result, it has been a rich fishing ground throughout the ages. The individual species vary according to the salinity of the surrounding water.

The food chain is based on phytoplankton, which is not present in the middle reaches due to tidal turbulence, and zooplankton, which is mainly formed by millimetre-sized crabs. White crabs are more numerous than anywhere else in France. The fish species are either marine, which can swim inland to a certain point, or migratory, adapted to both fresh and salt water. The former include sole, skate and anchovy, the latter eel, roach and lamprey.

The Gironde is home to the European sturgeon, which has its last refuge in the world here. It has been protected since 1982, when the species was almost extinct, and has since been selectively bred and released. For some time now, caviar has even been produced again on a modest scale.

As it lies on the migration route of many migratory birds, the area is also a preferred breeding and resting place for about 130 bird species. The cormorant, black-headed gull and white stork are found here as native species, as well as periodic ducks, buzzards and many others.

The ecosystem of the Gironde is very fragile due to the muddy subsoil, which absorbs significantly more pollutants than other soils. In particular, the presence of zinc and cadmium has made it illegal to consume wild oysters because of the accumulation of heavy metals in their flesh. A certain problem is also posed by exotics, which can affect the original fauna through exposure or introduction. A particularly illustrious example of this is a piranha caught in the Gironde in 2004.

Since 2015, the Gironde has been part of the Estuaire de la Gironde et Mer des Pertuis Marine Nature Park.

History

Already in the Bronze Age, but at the latest since Roman times, the Gironde has played an outstanding strategic and economic role. Bordeaux, then Burdigala, already had a seaport accessible via the Gironde, which laid the foundation for trade and long-lasting prosperity. Roman remains, as well as a Gallic boar standard, have been found in Soulac-sur-Mer. The ground plans of patrician villas suggest that there must have been a summer resort here, right at the mouth of the Gironde, to which the wealthy citizens of Burdigala went. The fact that a strategically important access to the sea also has its disadvantages was demonstrated by the Norman invasions that swept across the Gironde after the fall of the Roman Empire and devastated Bordeaux.

In the late Middle Ages, the area was in English hands: trade between Aquitaine and the British Isles was conducted via the Gironde. In particular, Bordeaux exported the wine cultivated in the region, which was called claret in England and was very much appreciated. Other exports included dyes, salt, and weapons. Stockfish, leather, cloth and metals were imported from England. The shipping route was not only important from a commercial point of view: It was also used to move most of the troop contingents provided by the English during the Hundred Years’ War. Due to the conflict between England and France, but also due to pirates, the sea trade was disturbed again and again, so that at times powerful fleet units were formed for mutual protection.

Estuary of the Gironde 1634, copper engraving by Christophe Tassin

In the early modern period, when the French had regained control of the territory, Bordeaux was the nation’s largest and most important port, through which much of the Atlantic maritime trade with Africa and the Antilles passed. The Gironde therefore took on paramount strategic importance and was purposefully fortified with fortifications and garrison sites. In the 17th century, Vauban built the large fortress of Blaye on the right bank, which received a – less spectacular – counterpart, Fort Médoc on the left bank. An additional post was established on an island so that the Gironde could not be navigated without permission or military confrontation. This precaution also secured the economic concept of mercantilism in terms of military strategy.

In June 1940, the Wehrmacht conquered large parts of France (“Western Campaign”). Hitler ordered the construction of the Atlantic Wall, the southern end of which was formed by the Garonne. In “Führerweisung No. 50”, Hitler ordered all river mouths to be developed into strong “defensive areas” to secure them against an Allied invasion. In January 1944, Hitler declared some defensive areas to be “fortresses” that had to be defended “to the last cartridge” (see Fester Platz (Wehrmacht)). On the headland between the Atlantic and the Gironde, the fortress Gironde-South was built on an area of 170 square kilometres

In the 20th century, as the city port of Bordeaux was gradually abandoned, the Gironde acquired particular economic importance. Much of the goods handling was transferred downstream, among other things the special needs of handling ocean liners, which could not sail up to the Garonne, had to be taken into account. A container terminal was therefore set up at Le Verdon, which could also handle oil loading. Between Le Verdon and Bordeaux, a refinery was built in Pauillac. This led to a certain industrialisation along the Gironde.

Web links

Commons: Gironde– Collection of images, videos and audio files

Individual references

  1. a b geoportail.gouv.fr (1:16.000)
  2. The Gironde is not included in the French water database sandre.fr, because according to the logic there, as an estuary, it is already counted among the marine waters. The information on the dimensions of the Gironde was therefore taken from fr.wiki.