Sestra River is a river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 in Saint Petersburg

Saint Petersburg

Saint Petersburg is a city and a federal subject of Russia located on the Neva River at the head of the Gulf of Finland on the Baltic Sea...

 and Leningrad Oblast

Leningrad Oblast

Leningrad Oblast is a federal subject of Russia . It was established on August 1, 1927, although it was not until 1946 that the oblast's borders had been mostly settled in their present position...

, Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

.

The length of the river is 74 km (46 mi). The area of its basin

Drainage basin

A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...

 is 393 km² (152 mi²). The Sestra River flows over the Karelian Isthmus

Karelian Isthmus

The Karelian Isthmus is the approximately 45–110 km wide stretch of land, situated between the Gulf of Finland and Lake Ladoga in northwestern Russia, to the north of the River Neva . Its northwestern boundary is the relatively narrow area between the Bay of Vyborg and Lake Ladoga...

. It used to fall into the Gulf of Finland

Gulf of Finland

The Gulf of Finland is the easternmost arm of the Baltic Sea. It extends between Finland and Estonia all the way to Saint Petersburg in Russia, where the river Neva drains into it. Other major cities around the gulf include Helsinki and Tallinn...

 until the early 18th century. After the construction of a dam

Dam

A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

 for the needs of the munitions factory in Sestroretsk

Sestroretsk

Sestroretsk is a municipal town in Kurortny District of the federal city of St. Petersburg, Russia, located on the shores of the Gulf of Finland, the Sestra River and the Sestroretskiy Lake northwest of St. Petersburg...

, a part of the river was turned into a reservoir called Sestroretsky Razliv (Sestroretsk Overflow) two meters (six feet) in depth with an area of 10.6 km² (4 mi²). Since then, the Sestra River has been flowing into this reservoir. The Sestroretsk Overflow is separated from the Gulf of Finland with a ridge of artificial sand dunes. Excess water is dumped into the Gulf of Finland through a canal

Canal

Canals are man-made channels for water. There are two types of canal:#Waterways: navigable transportation canals used for carrying ships and boats shipping goods and conveying people, further subdivided into two kinds:...

, which is 4.8 km (3 mi) long. The Sestra River served as a natural border between Russia and Sweden

Sweden

Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

 1323–1617 and between Russia and Finland

Finland

Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

in 1812–1940.