Oka (Russian: Ока́) is a great river in Russia, the biggest right confluent of the Volga. It flows through the Oblasts of Oryol, Tula, Kaluga, Moscow, Ryazan, Vladimir and Nizhny Novgorod. Its length exceeds 1500 km. The Volga river in Western Russia, Europes longest river, with a length of 3,690 km (2,293 miles), provides the core of the largest river system in Europe. ... A watershed is a region of land where water drains downhill into a specified body of water, such as a river, lake, sea, ocean or wetland. ... The source of a river or stream may be a lake, a spring, or a collection of headwaters. ... In hydrology, the discharge of a river is the volume of water transported by it in a certain amount of time. ... A watershed is a region of land where water drains downhill into a specified body of water, such as a river, lake, sea, ocean or wetland. ... A tributary (or affluent or confluent) is a contributory stream, a river that does not reach the sea, but joins another major river (a parent river), to which it contributes its waters, swelling its discharge. ... For other meanings of the word Volga see Volga (disambiguation) Волга Length 3,690 km Elevation of the source 225 m Average discharge  ? m³/s Area watershed 1. ... Oblast (Czech: oblast, Slovak: oblasÅ¥, Russian and Ukrainian: , Belarusian: , Bulgarian: о́бласт) refers to a subnational entity in some countries. ... Oryol Oblast (Орловская область) is a regional subdivision of Russia. ... Tula Oblast (Russian: ) is a federal subject of Russia (an oblast). ... Kaluga Oblast (Russian: ) (29,900 km², pop. ... Moscow oblast (Моско́вская о́бласть) is an administrative subdivision of Russia officially established on January 14, 1929. ... Ryazan Oblast (Russian: ) is a federal subject of Russia (an oblast). ... Vladimir Oblast (Russian: ) is a federal subject of Russia (an oblast). ... Nizhny Novgorod Oblast (Russian: ) is a federal subject of Russia (an oblast). ...

The name of Oka is cognate to aqua, the Latin word for water, and to the name of the Aa River in Switzerland. Historically, the river gave its name to the Upper Oka Principalities, situated upstream from Tarusa. One of the largest Russian cities, Nizhny Novgorod, was founded to protect the Oka's confluence with the Volga. The Russian capital, Moscow, sits on one of the Oka's tributaries - the Moskva River. Latin is an ancient Indo-European language originally spoken in the region around Rome called Latium. ... Aa is the name of a large number of small European rivers. ... The Upper Principalities (Russian: Верховские княжества) is a term traditionally applied in Russian historiography to about dozen tiny and ephemeral polities situated along the upper course of the Oka River at the turn of the 14th and 15th centuries. ... Tarusa (Таруса in Russian) is a town in the Kaluga Oblast in Russia. ... Nizhny Novgorod (Russian: Ни́жний Но́вгород), colloquially shortened as Nizhny and also transliterated into English as Nizhniy Novgorod or Nizhni Novgorod, is the fourth largest city of the Russian Federation, ranking after Moscow, Saint Petersburg and Novosibirsk. ... Moscow (Russian: Москва́, Moskva, IPA: (help· info)) is the capital of Russia and the countrys principal political, economic, financial, educational and transportation center, located on the river Moskva. ... Moskva River near the Moscow Kremlin. ...

Cities and towns on Oka

• Orel
• Kaluga
• Serpukhov
• Pushchino
• Kolomna
• Ryazan
• Murom
• Dzerzhinsk
• Nizhny Novgorod