Saône

Saône (Sona)
River
The Saône in Lyon by night.
Countries France, Switzerland
Tributaries
 - left Doubs, Lanterne
 - right Azergues, Morgon
Source Vioménil
 - location Vosges
 - elevation 392 m (1,286 ft)
 - coordinates
Mouth Rhône
 - location Lyon, France
 - elevation 158 m (518 ft)
 - coordinates
Length 473 km (294 mi)
Area 29,950 km2 (11,564 sq mi)
Discharge
 - average 410 m3/s (14,479 cu ft/s)

The Saône (French pronunciation: [soːn][1]; Arpitan Sona) is a river of eastern France. It is a right tributary of the River Rhône. Rising at Vioménil in the Vosges department, it joins the Rhône in Lyon.

The name "Saône" derives from that of the Gallic river goddess Souconna, which has also been connected with a local Celtic tribe, the Sequanes. Monastic copyists progressively transformed "Souconna" to "Saoconna", which ultimately gave rise to "Saône". The other recorded ancient names for the river were Brigoulus and Arar.

Contents

Geography

The Saône rises at Vioménil at the foot of the cliff of the Faucilles in the Vosges at an altitude of 392 m, and flows into the Rhône at Lyon at an altitude of 158 m. Its length is 480 km[2]. Its largest tributary is the Doubs; upstream of receiving the Doubs at Verdun-sur-le-Doubs in Saône-et-Loire, the Saône is called the "Petite Saône" (lesser Saône), which reflects the large contribution of the Doubs to the Saône. In fact the Doubs' mean annual flow rate is slightly stronger than that of the Petite Saône (175 vs. 160 m³/s); some thus assert that it is in fact the Saône that flows into the Doubs. Nonetheless the Saône has a substantially larger watershed than the Doubs, at 11500 vs. 7500 km².

At 30,000 km² the Saône has the largest watershed of any French river which does not flow into the sea, covering approximately 1/18 of metropolitan France.

In pre-Roman times the river's name was "Arar", a doubling of the Indo-European root ar (water). According to Caesar's Gallic Wars this doubling reflected the idea that it was difficult to identify the direction of the river due to its slow rate of flow. Its current name came from a sacred spring, Sauc-Onna, located at Chalon, which was used by Roman legionnaries to refer to the entire river.

Departments and cities traversed by the Saône

Main tributaries of the Saône

R indicates a right tributary, L indicates a left tributary.

  • Vannon (R)
  • Salon (R)
  • Morthe or Morte (L)
  • Ecoulottes (R)
  • Ténise (L)
  • Vingeanne (R)
  • Ognon (L)
  • Bèze (R)
  • Tille (R)
  • Ouche (R)
  • Vouge (R)
  • Doubs (L)
  • Dheune (R)
  • Thalie (R)
  • Cosne (L)
  • Grosne (R)
  • Tenarre (L)
  • Seille (L)
  • Reyssouze (L)
  • Mouge (R)
  • Veyle (L)
  • l'Arlois (R)
  • Mauvaise (R)
  • Chalaronne (L)
  • Ardières (R)
  • Vauxonne (R)
  • Morgon (R)
  • Formans (L)
  • Azergues (R)

Navigation

The Saône is classed as navigable after its confluence with the Côney at Corre in the north of Haute-Saône all the way to its confluence with Rhône at la Mulatière, in Lyon. The navigable stretch is over 365 km long, of which 167 km is European large gauge (from Verdun-sur-le-Doubs to Lyon).

The Saône is linked with the Loire by the Canal du Centre, with the Yonne by the Canal de Bourgogne, with the Marne by the Canal entre Champagne et Bourgogne (previously the Canal de la Marne à la Saône), with the Meuse by the Canal de l'Est, whose southern branch has been renamed the Canal des Vosges, and with the Rhine by the Canal du Rhône au Rhin. All the canals are Freycinet gauge.

Also navigable are the small Canal de Pont-de-Vaux (3 km), the Seille, navigable in a 40 km stretch up to Louhans, and the lower part of the Doubs. None of these three connect the Saône to any other body of water.

Hydrology

The lesser Saône

The lesser Saône has a pluvial regime (sometimes influenced by snow), with a very strong oceanic effect. The soils are not susceptible to much infiltration, so that they saturate quickly which contributes to surface runoff. The flow rate grows very quickly, and after receiving the waters of the Lanterne, the Saône has already become a powerful river.

The mean annual flow rate, or discharge, of the Saône has been measured over 44 years (as of 2007) at the Ray-sur-Saône hydrological station, situated about 30 km after the Lanterne confluence between Port-sur-Saône and Gray. The figure is 59.7 m³/s for a watershed area of 3,740 km² (the upper basin of the lesser Saône), and has an annual maximum of 64.5 and minimum of 54.8 m³/s.

The river exhibits seasonal variations in flow rate, with winter floods from 84 to 108 m³/s from December to March inclusive, and summer reductions in July/August/September falling to a monthly average of 16.9 m³/s in August[3].

The runoff curve number in the upper basin of the lesser Saône is 505 mm annually (cf. 687 mm for the Lanterne), an elevated figure resulting from the very high rainfall in the Vosgian part of its watershed. The specific flow rate rises to 16.0 litres per second per square kilometre of watershed.

The maximum instantaneous recorded flow rate was 930 m³/s on 19 December 1982.

The greater Saône

The greater Saône is formed by the confluence of the Doubs and the lesser Saône at Verdun-sur-le-Doubs. The Doubs brings a mean annual flow rate of 175 m³/s, and the lesser Saône, 160 m³/s.

The greater Saône has only modest tributaries which have little effect on floods or other hydrological properties. It flows in a vast plain approximately 3 km wide as far as Lyon in the basin of the former Bressan lake. The slope is very weak, and without hydraulic projects up to the north of Chalon aimed at guaranteeing a deep navigation channel, overflows would be more frequent.

At the Couzon-au-Mont-d'Or hydrological station, located where the river enters the Lyon area, measurements taken between 1969 and 1986 revealed a mean annual flow rate of 473 m³/s, with a 100-year flood flow rate of 3,180 m³/s[4]. The runoff curve number from the river's entire watershed is 501 mm, and the specific flow rate rises to 15.8 litres per second per square kilometre of watershed.

Average flow rate

Mean monthly discharge (in m3/s)
Hydrological station : Couzon-au-Mont-d'Or (date unknown)


Source : Banque Hydro - Station U4710010

Overall, the average flow rate in Lyon is 475 m³/s, with a minimum of 153 m³/s, in August, and a maximum of 954 m³, in February[5].

Historic floods

When the Saône floods, the impact varies considerably over the course of the river. A large flood with a strong flow rate upstream can be largely attenuated in the Bressan plain so as to have only moderate impact at Mâcon, particularly if it carries a limited volume of water. By contrast, a medium-sized flood of the lesser Saône can turn into a significant flood downstream, if the Doubs brings in a similar contribution at about the same time.

Historic floods include:

The reference flood in town planning is the 100-year event, meaning that which has a probability of 1/100 of occurring each year. This reference was in the course of being modified as maps linked to modelling the 1840 flood in modern town planning conditions were distributed to local mayors in December 2008, and as new prevention plans were ordered for 2012.

Management

From September 1 2004 until 31 August 2009, a river contract specific to the flood-prone Saône valley operated through the Etablissement Public Territorial du Bassin (EPTB) Saône et Doubs, in partnership with the various water agencies of the area, including:

  • Agence de l'Eau Rhône, Méditerranée et Corse
  • Collectivités régionales et départementales
  • Chambres d'agriculture
  • Voies Navigables de France
  • Fédérations de pêches

This contract, the Contrat de vallée inondable de la Saône provided for the implementation of significant procedures for water quality improvement, for the preservation and rehabilitation of aquatic and natural habitats, for flood risk management and for the maintenance of the river and its banks. A new contractual approach was being developed for the following five years.

Related articles

References

  1. ^ (French) Jean-Marie Pierret, Phonétique historique du français et notions de phonétique générale, Peeters, Louvain-la-Neuve, 1994, p. 104.
  2. ^ (French) Sandre. "Fiche rivière la saône (U---0000)". http://sandre.eaufrance.fr/app/chainage/courdo/htm/U---0000.php?cg=U---0000. Retrieved 19 July 2008. 
  3. ^ (French) Banque Hydro - Station U0610010 - La Saône à Ray-sur-Saône (Synthèse) (Do not tick the box "Station en service")
  4. ^ (French) Drainage basin of the Saône
  5. ^ (French) Banque Hydro - Station U4710010 - La Saône à Couzon-au-Mont-d'Or (Do not tick the box "Station en service")
  6. ^ (French) Floods of the Rhône and all its tributaries, Volume 4

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