Сена: Река Парижа и Северной Франции

Major river in northern France

The Seine (/s//eɪ//n//, //s//ɛ//n/ sayn, sen, sɛn) is a river in northern France. Its drainage basin is in the Paris Basin (a geological relative lowland) covering most of northern France. It rises at Source Seine, northwest of Dijon in northeastern France in the Langres plateau, flowing through Paris and into the English Channel at Le Havre (and Honfleur on the left bank). It is navigable by ocean going vessels as far as Rouen, from the sea. Over 60 percent of its length, as far as Burgundy, is negotiable by large barges and most tour boats, and nearly its whole length is available for recreational boating; excursion boats offer sightseeing tours of the river banks in the capital city, Paris. There are 37 bridges in Paris across the Seine (the most famous of which are the Pont Alexandre III and the Pont Neuf) and dozens more outside the city. A notable bridge, which is also the last along the course of the river, is the Pont de Normandie, the ninth longest cable stayed bridge in the world, which links Le Havre and Honfleur.

The Seine rises in the commune of Source Seine, about northwest of Dijon. The source has been owned by the city of Paris since 1864. A number of closely associated small ditches or depressions provide the source waters, with an artificial grotto laid out to highlight and contain a deemed main source. The grotto includes a statue of a nymph, a dog, and a dragon. On the same site are the buried remains of a Gallo Roman temple. Small statues of the dea Sequana "Seine goddess" and other ex votos found at the same place are now exhibited in the Dijon archaeological museum.

The Seine is dredged and ocean going vessels can dock at Rouen, from the sea. Commercial craft (barges and push tows) can use the river beginning at Marcilly sur Seine, to its mouth. At Paris, there are 37 bridges. The river is only above sea level from its mouth, making it slow flowing and thus easily navigable. The Seine Maritime, from the English Channel at Le Havre to Rouen, is the only portion of the Seine used by ocean going craft. The tidal section of the Seine Maritime is followed by a canalized section (Basse Seine) with four large multiple locks until the mouth of the Oise at Conflans Sainte Honorine Smaller locks at Bougival and at Suresnes lift the vessels to the level of the river in Paris, where the junction with the Canal Saint Martin is located. The distance from the mouth of the Oise is
The Haute Seine, from Paris to Montereau Fault Yonne, is long and has 8 locks. At Charenton le Pont is the mouth of the Marne. Upstream from Paris seven locks ensure navigation to Saint Mammès, where the Loing mouth is situated. Through an eighth lock the river Yonne is reached at Montereau Fault Yonne. From the mouth of the Yonne, larger ships can continue upstream to Nogent sur Seine (, 7 locks). From there on, the river is navigable only by small craft to Marcilly sur Seine (, 4 locks). At Marcilly sur Seine the 19th century Canal de la Haute Seine used to allow vessels to continue all the way to Troyes. This canal has been abandoned since 1957. The average depth of the Seine today at Paris is about Until locks were installed to raise the level in the 1800s, the river was much shallower within the city, and consisted of a small channel of continuous flow bordered by sandy banks (depicted in many illustrations of the period). Today the depth is tightly controlled and the entire width of the river between the built up banks on either side is normally filled with water. The average flow of the river is very low, only a few cubic metres per second, but much higher flows are possible during periods of heavy runoff.

Four large storage reservoirs have been built since 1950 on the Seine as well as its tributaries Yonne, Marne, and Aube. These help in maintaining a constant level for the river through the city, but cannot prevent significant increases in river level during periods of extreme runoff. The dams are Lac d’Orient, Lac des Settons, Lake Der Chantecoq, and Auzon Temple and Amance, respectively.

A very severe period of high water in January 1910 resulted in extensive flooding throughout the city of Paris. The Seine again rose to threatening levels in 1924, 1955, 1982, 1999–2000, June 2016, and January 2018. After a first level flood alert in 2003, about 100,000 works of art were moved out of Paris, the largest relocation of art since World War II. Much of the art in Paris is kept in underground storage rooms that would have been flooded. A 2002 report by the French government stated the worst case Seine flood scenario would cost 10 billion euros and cut telephone service for a million Parisians, leaving 200,000 without electricity and 100,000 without gas.

In January 2018 the Seine again flooded, reaching a flood level of on 29 January. An official warning was issued on 24 January that heavy rainfall was likely to cause the river to flood. By 27 January, the river was rising. The Deputy Mayor of Paris Colombe Brossel warned that the heavy rain was caused by climate change. He added that "We have to understand that climatic change is not a word, it's a reality."

The basin area, including a part of Belgium, is , 2 percent of which is forest and 78 percent cultivated land. In addition to Paris, three other cities with a population over 100,000 are in the Seine watershed: Le Havre at the estuary, Rouen in the Seine valley and Reims at the northern limit—with an annual urban growth rate of 0.2 percent. At the beginning of the 20th century, most domestic sewage was used as fertilizer for nearby croplands. As populations grew, the agricultural capacity to absorb those wastewaters was exceeded. Large scale construction of waste water treatment plants (WWTPs) began in 1940 to meet demand; however, by 1970, about 60% of urban sewage was allowed to flow into the river untreated. The resulting oxygen depletion reduced the number of fish species to three. Measures taken in the early 2000s due to the Water Framework Directive led to significant reductions of organic carbon, phosphorus and ammonium, which in turn decreased the occurrence and severity of phytoplankton blooms. Continued WWTP construction and new treatment methods improved environmental conditions. In 2009, it was announced that Atlantic salmon had returned to the Seine. By the early 2020s, the number of fish species near Paris had rebounded to 32. The resulting oxygen deficit is principally caused by allochthonous bacteria larger than one micrometre in size. The specific activity of these sewage bacteria is typically three to four times greater than that of the autochthonous (background) bacterial population. Heavy metal concentrations in the Seine are relatively high. The pH level of the Seine at Pont Neuf has been measured to be 8.46. Despite this, the water quality has improved significantly over what several historians at various times in the past called an "open sewer". In 2018, a €1.4 billion ($1.55 billion) cleanup programme called the "Swimming Plan" was launched with the aim of making the river safe to use for the 2024 Summer Olympics. The project includes constructing a basin to store rainwater, which would then be slowly released into the sewer system, preventing overflow. Plans also call for several public swimming areas to be made available by 2025, ending a 102 year ban instituted in 1923 due to the polluted water. Efforts have been successful, with the fish population surging from just 2 species to over 30. However, E. coli levels are still far higher than what is safe to swim in, though this could depend on the season. On 28 or 29 March 845, an army of Vikings led by a chieftain named Reginherus, which is possibly another name for Ragnar Lothbrok, sailed up the River Seine with siege towers and sacked Paris. On 25 November 885, another Viking expedition led by Rollo was sent up the River Seine to attack Paris again. In March 1314, King Philip IV of France had Jacques de Molay, last Grand Master of the Knights Templar, burned on a scaffold on an island in the River Seine in front of Notre Dame de Paris. After the burning at the stake of Joan of Arc in 1431, her ashes were thrown into the Seine from the medieval stone Mathilde Bridge at Rouen, though unserious counter claims persist. On 9 August 1803 Robert Fulton, American painter and marine engineer, made his first successful test of his steamboat in the Seine beside the Tuileries Garden. Having a length of sixty six feet and an eight foot beam Fulton's steamboat attained speeds of three to four miles per hour against the Seine's current.

At the 1900 Summer Olympics, the river hosted the rowing, swimming, and water polo events. Twenty four years later, it hosted the rowing events again at Bassin d'Argenteuil, along the Seine north of Paris.

The Seine was one of the original objectives of Operation Overlord in 1944. The Allies' intention was to reach the Seine by 90 days after D Day. That objective was met. An anticipated assault crossing of the river never materialized as German resistance in France crumbled by early September 1944. However, the First Canadian Army did encounter resistance immediately west of the Seine and fighting occurred in the Forêt de la Londe as Allied troops attempted to cut off the escape across the river of parts of the German 7th Army in the closing phases of the Battle of Normandy. Some of the Algerian victims of the Paris massacre of 1961 drowned in the Seine after being thrown by French policemen from the Pont Saint Michel and other locations in Paris.

Dredging in the 1960s mostly eliminated tidal bores on the lower river, known in French as "le mascaret."

In 1991 UNESCO added the banks of the Seine in Paris—the Rive Gauche and Rive Droite—to its list of World Heritage Sites in Europe. In 2007 55 bodies were retrieved from its waters; in February 2008, the body of supermodel turned activist Katoucha Niane was found there.

In 2024, the River is set to be host to a boat parade with boats for each national delegation during the opening ceremony of the 2024 Summer Olympics.