Szczecin Lagoon
Szczecin Lagoon (, , since 1945 sometimes also "Oderhaff" (Oder lagoon) or "Pommersches Haff" (Pomeranian lagoon)) is a lagoon in the Oder estuary, shared by Germany and Poland. It is separated from the Pomeranian Bay of the Baltic Sea by the islands of Usedom and Wolin. The lagoon is subdivided into the "Kleines Haff" (, "small lagoon") in the West and the "Wielki Zalew" (, "great lagoon") in the East. An ambiguous historical German name was "Frisches Haff", which later exclusively referred to the Vistula Lagoon. Geography. From the South, the lagoon is fed by several arms of the Oder river and  smaller rivers like Ziese, Peene, Zarow, Uecker, and Ina. In the North, the lagoon is connected to the Baltic Sea's Bay of Pomerania with the three straits Peenestrom, Świna and Dziwna, which divide the mainland and the islands of Usedom and Wolin. The lagoon covers an area of 687 km, its natural depth is an average 3.8 metres, and 8.5 metres at maximum. The depth of shipping channels however can exceed 10.5 metres. Thus, the lagoon holds about 2.58 km of water. The annual average water temperature is 11 °C. 94% of the water loads discharged into the  lagoon are from the Oder river and its confluences, amounting to an average annual 17 km or 540 m per second. All other confluences contribute a combined annual 1 km. Since no reliable data for an inflow from the Baltic Sea exist, the combined inflow is an estimated 18 km from a catchment area of 129,000 km, residing in the lagoon for an average 55 days before being discharged into the Pomeranian Bay. The nutrients thereby transported into the lagoon have made it hyper(eu)trophic to eutrophic. The straits Peenestrom, Świna and Dziwna are responsible for 17%, 69%, and 14% of  the discharge, respectively. The average salinity is between 0.5 and 2 grams of salt per kilogram of water (approximately equivalent to 0.5 and 2 parts per thousand [ppt]). Occasionally northerly winds reverse the direction of the Świna, admitting sea water from the Baltic Sea into the lagoon, raising the local salinity to 6 ppt. History. The area became part of the emerging Polish state in the 10th century. Following Poland's fragmentation, it formed part of the Duchy of Pomerania. In the 17th century, it passed to Sweden. Later on, it gradually passed to the Kingdom of Prussia in the  18th and 19th century, and from 1871 it was also part of Germany. In 1880, the "Kaiserfahrt" ("Emperor's passage") channel on Usedom was opened, a water route with a depth of 10 metres connecting the lagoon with the Baltic Sea by bypassing the eastern part of the Swine, allowing large ships to enter the lagoon and the seaport of Stettin quicker and safer. The canal, approximately 12 km long and 10 metres deep, was dug by the German Empire between 1874 and 1880, during the reign of the first Kaiser Wilhelm (1797–1888) after whom it was named. Also, the  work resulted in a new island named Kaseburg (Karsibór) being cut off from Usedom. After the defeat of Nazi Germany in World War II in 1945, the eastern part of the lagoon became again part of Poland, while the western part became part of East Germany. The "Kaiserfahrt" was renamed "Piast Canal", after the Polish Piast dynasty, which first included the region to Poland in the 10th century. The German-Polish border also divides the bight called Neuwarper See near , Luckow. Economy. The lagoon has served as an important fishing grounds for centuries, as a major transportation pathway since the  18th century, and as a tourist destination since the 20th century. Heringsdorf Airport on Usedom island is located on the shores of the lagoon. Nature. The southern shore of the lagoon belongs to the Am Stettiner Haff Nature Park, its northern shore and the island of Usedom to the Usedom Island Nature Park. To the west is the Anklamer Stadtbruch Nature Reserve and, within it, the Anklamer Torfmoor, a protected wetland which is renaturalising after being used for peat extraction.