A river is a natural flowing watercourse freshwater, flowing towards an ocean, lake or another river. In some cases a river flows into the ground and becomes dry at the end of its course without reaching another body of water. Small rivers can be referred to using names such as stream, brook and rill. There are no official definitions for the generic term river as applied to geographic features, although in some countries or communities a stream is defined by its size. Many names for small rivers are specific to geographic location. Sometimes a river is defined as being larger than a creek, but not always: the language is vague. Rivers are part of the hydrological cycle. Potamology is the scientific study of rivers, while limnology is the study of inland waters in general. Most of the major cities of the world are situated on the banks of rivers, as they are, or were, used as a source of water, for obtaining food, for transport, as borders, as a defensive measure, as a source of hydropower to drive machinery, for bathing, as a means of disposing of waste.
A river begins at a source, follows a path called a course, ends at a mouth or mouths. The water in a river is confined to a channel, made up of a stream bed between banks. In larger rivers there is also a wider floodplain shaped by flood-waters over-topping the channel. Floodplains may be wide in relation to the size of the river channel; this distinction between river channel and floodplain can be blurred in urban areas where the floodplain of a river channel can become developed by housing and industry. Rivers can flow down mountains, through valleys or along plains, can create canyons or gorges; the term upriver refers to the direction towards the source of the river, i.e. against the direction of flow. The term downriver describes the direction towards the mouth of the river, in which the current flows; the term left bank refers to the left bank in the direction of right bank to the right. The river channel contains a single stream of water, but some rivers flow as several interconnecting streams of water, producing a braided river.
Extensive braided rivers are now found in only a few regions worldwide, such as the South Island of New Zealand. They occur on peneplains and some of the larger river deltas. Anastamosing rivers are quite rare, they have multiple sinuous channels carrying large volumes of sediment. There are rare cases of river bifurcation in which a river divides and the resultant flows ending in different seas. An example is the bifurcation of Nerodime River in Kosovo. A river flowing in its channel is a source of energy which acts on the river channel to change its shape and form. In 1757, the German hydrologist Albert Brahms empirically observed that the submerged weight of objects that may be carried away by a river is proportional to the sixth power of the river flow speed; this formulation is sometimes called Airy's law. Thus, if the speed of flow is doubled, the flow would dislodge objects with 64 times as much submerged weight. In mountainous torrential zones this can be seen as erosion channels through hard rocks and the creation of sands and gravels from the destruction of larger rocks.
A river valley, created from a U-shaped glaciated valley, can easily be identified by the V-shaped channel that it has carved. In the middle reaches where a river flows over flatter land, meanders may form through erosion of the river banks and deposition on the inside of bends. Sometimes the river will cut off a loop, shortening the channel and forming an oxbow lake or billabong. Rivers that carry large amounts of sediment may develop conspicuous deltas at their mouths. Rivers whose mouths are in saline tidal waters may form estuaries. Throughout the course of the river, the total volume of water transported downstream will be a combination of the free water flow together with a substantial volume flowing through sub-surface rocks and gravels that underlie the river and its floodplain. For many rivers in large valleys, this unseen component of flow may exceed the visible flow. Most but not all rivers flow on the surface. Subterranean rivers flow underground in caverns; such rivers are found in regions with limestone geologic formations.
Subglacial streams are the braided rivers that flow at the beds of glaciers and ice sheets, permitting meltwater to be discharged at the front of the glacier. Because of the gradient in pressure due to the overlying weight of the glacier, such streams can flow uphill. An intermittent river only flows and can be dry for several years at a time; these rivers are found in regions with limited or variable rainfall, or can occur because of geologic conditions such as a permeable river bed. Some ephemeral rivers flow during the summer months but not in the winter; such rivers are fed from chalk aquifers which recharge from winter rainfall. In England these rivers are called bournes and give their name to places such as Bournemouth and Eastbourne. In humid regions, the location where flow begins in the smallest tributary streams moves upstream in response to precipitation and downstream in its absence or when active summer vegetation diverts water for evapotrans
A tributary or affluent is a stream or river that flows into a larger stream or main stem river or a lake. A tributary does not flow directly into a ocean. Tributaries and the main stem river drain the surrounding drainage basin of its surface water and groundwater, leading the water out into an ocean. A confluence, where two or more bodies of water meet together refers to the joining of tributaries; the opposite to a tributary is a distributary, a river or stream that branches off from and flows away from the main stream. Distributaries are most found in river deltas. "Right tributary" and "left tributary" are terms stating the orientation of the tributary relative to the flow of the main stem river. These terms are defined from the perspective of looking downstream. In the United States, where tributaries sometimes have the same name as the river into which they feed, they are called forks; these are designated by compass direction. For example, the American River receives flow from its North and South forks.
The Chicago River's North Branch has the East and Middle Fork. Forks are sometimes left. Here, the "handedness" is from the point of view of an observer facing upstream. For instance, Steer Creek has a left tributary, called Right Fork Steer Creek. Tributaries are sometimes listed starting with those nearest to the source of the river and ending with those nearest to the mouth of the river; the Strahler Stream Order examines the arrangement of tributaries in a hierarchy of first, second and higher orders, with the first-order tributary being the least in size. For example, a second-order tributary would be the result of two or more first-order tributaries combining to form the second-order tributary. Another method is to list tributaries from mouth to source, in the form of a tree structure, stored as a tree data structure. A gallery of major river basins with tributaries Estuary
A river mouth is the part of a river where the river debouches into another river, a lake, a reservoir, a sea, or an ocean. The water from a river can enter the receiving body in a variety of different ways; the motion of a river is influenced by the relative density of the river compared to the receiving water, the rotation of the earth, any ambient motion in the receiving water, such as tides or seiches. If the river water has a higher density than the surface of the receiving water, the river water will plunge below the surface; the river water will either form an underflow or an interflow within the lake. However, if the river water is lighter than the receiving water, as is the case when fresh river water flows into the sea, the river water will float along the surface of the receiving water as an overflow. Alongside these advective transports, inflowing water will diffuse. At the mouth of a river, the change in flow condition can cause the river to drop any sediment it is carrying; this sediment deposition can generate a variety of landforms, such as deltas, sand bars and tie channels.
Many places in the United Kingdom take their names from their positions at the mouths of rivers, such as Plymouth and Great Yarmouth. Confluence River delta Estuary Liman
The Republic of Sakha is a federal Russian republic. It had a population of 958,528 at the 2010 Census ethnic Yakuts and Russians. Comprising half the Far Eastern Federal District, it is the largest subnational governing body by area in the world at 3,083,523 square kilometers, its capital is the city of Yakutsk. It is known for its extreme and severe climate, with the lowest temperatures in the Northern Hemisphere being recorded in Verkhoyansk and Delyankir, regular winter averages being below −35 °C in Yakutsk; the hypercontinental tendencies result in warm summers for much of the republic. Borders: internal: Chukotka Autonomous Okrug, Magadan Oblast, Khabarovsk Krai, Amur Oblast, Zabaykalsky Krai, Irkutsk Oblast, Krasnoyarsk Krai. Water: Arctic Ocean. Highest point: Peak Pobeda, Mus-Khaya Mountain Peak Maximum N->S distance: 2,500 km Maximum E->W distance: 2,000 km Sakha stretches to the Henrietta Island in the far north and is washed by the Laptev and Eastern Siberian Seas of the Arctic Ocean.
These waters, the coldest and iciest of all seas in the Northern Hemisphere, are covered by ice for 9–10 months of the year. New Siberian Islands are a part of the republic's territory. After Nunavut was separated from Canada's Northwest Territories, Sakha became the largest subnational entity in the world, with an area of 3,083,523 square kilometers smaller than the territory of India. Sakha can be divided into three great vegetation belts. About 40% of Sakha lies above the Arctic circle and all of it is covered by permafrost which influences the region's ecology and limits forests in the southern region. Arctic and subarctic tundra define the middle region, where lichen and moss grow as great green carpets and are favorite pastures for reindeer. In the southern part of the tundra belt, scattered stands of dwarf Siberian pine and larch grow along the rivers. Below the tundra is the vast taiga forest region. Larch trees dominate in the north and stands of fir and pine begin to appear in the south.
Taiga forests cover about 47% of Sakha and 90% of the cover is larch. The Sakha Republic is the site of Pleistocene Park, a project directed at recreating Pleistocene tundra grasslands by stimulating the growth of grass with the introduction of animals which thrived in the region during the late Pleistocene — early Holocene period. Sakha Republic is the only subject of Russia. Sakha spans three time zones: Yakutsk Time Zone. Covers the republic's territory to the west of the Lena River as well as the territories of the districts located on both sides of the Lena River. Vladivostok Time Zone. Covers most of the republic's territory located between 140 ° E longitude. Districts: Oymyakonsky, Ust-Yansky, Verkhoyansky. Magadan Time Zone. Covers most of the republic's territory located east of 140°E longitude. Districts: Abyysky, Momsky, Srednekolymsky, Verkhnekolymsky. Navigable Lena River, as it moves northward, includes hundreds of small tributaries located in the Verkhoyansk Range. Other major rivers include: Vilyuy River Lena River tributary Olenyok River Aldan River Lena River tributary Kolyma River Indigirka River Alazeya River Amga River Aldan River tributary Olyokma River Lena River tributary Markha River Vilyuy River tributary Tyung River Vilyuy River tributary Maya River Aldan River tributary Anabar River Yana River Morkoka River Markha River tributary Uchur River Aldan River tributary Linde River Lena River tributary Nyuya River Lena River tributary Selennyakh River Indigirka River tributary There are over 800,000 lakes in the republic.
Major lakes and reservoirs include: Lake Mogotoyevo Lake Nedzheli Lake Nerpichye Vilyuyskoye Reservoir Sakha's greatest mountain range, the Verkhoyansk Range, runs parallel and east of the Lena River, forming a great arc that begins in the Sea of Okhotsk and ends in the Laptev Sea. The Chersky Range has the highest peak in Sakha, Peak Pobeda; the second highest peak is Peak Mus-Khaya reaching 3,011 m. The Stanovoi Range borders Sakha in the south; the Republic's extensive coastline contains a number of peninsulas. The soil contains large reserves of oil, coal, gold, tin and many others. Sakha p
Russia the Russian Federation, is a transcontinental country in Eastern Europe and North Asia. At 17,125,200 square kilometres, Russia is by far or by a considerable margin the largest country in the world by area, covering more than one-eighth of the Earth's inhabited land area, the ninth most populous, with about 146.77 million people as of 2019, including Crimea. About 77 % of the population live in the European part of the country. Russia's capital, Moscow, is one of the largest cities in the world and the second largest city in Europe. Extending across the entirety of Northern Asia and much of Eastern Europe, Russia spans eleven time zones and incorporates a wide range of environments and landforms. From northwest to southeast, Russia shares land borders with Norway, Estonia, Latvia and Poland, Ukraine, Azerbaijan, China and North Korea, it shares maritime borders with Japan by the Sea of Okhotsk and the U. S. state of Alaska across the Bering Strait. However, Russia recognises two more countries that border it, Abkhazia and South Ossetia, both of which are internationally recognized as parts of Georgia.
The East Slavs emerged as a recognizable group in Europe between the 3rd and 8th centuries AD. Founded and ruled by a Varangian warrior elite and their descendants, the medieval state of Rus arose in the 9th century. In 988 it adopted Orthodox Christianity from the Byzantine Empire, beginning the synthesis of Byzantine and Slavic cultures that defined Russian culture for the next millennium. Rus' disintegrated into a number of smaller states; the Grand Duchy of Moscow reunified the surrounding Russian principalities and achieved independence from the Golden Horde. By the 18th century, the nation had expanded through conquest and exploration to become the Russian Empire, the third largest empire in history, stretching from Poland on the west to Alaska on the east. Following the Russian Revolution, the Russian Soviet Federative Socialist Republic became the largest and leading constituent of the Union of Soviet Socialist Republics, the world's first constitutionally socialist state; the Soviet Union played a decisive role in the Allied victory in World War II, emerged as a recognized superpower and rival to the United States during the Cold War.
The Soviet era saw some of the most significant technological achievements of the 20th century, including the world's first human-made satellite and the launching of the first humans in space. By the end of 1990, the Soviet Union had the world's second largest economy, largest standing military in the world and the largest stockpile of weapons of mass destruction. Following the dissolution of the Soviet Union in 1991, twelve independent republics emerged from the USSR: Russia, Belarus, Uzbekistan, Azerbaijan, Kyrgyzstan, Tajikistan and the Baltic states regained independence: Estonia, Lithuania, it is governed as a federal semi-presidential republic. Russia's economy ranks as the twelfth largest by nominal GDP and sixth largest by purchasing power parity in 2018. Russia's extensive mineral and energy resources are the largest such reserves in the world, making it one of the leading producers of oil and natural gas globally; the country is one of the five recognized nuclear weapons states and possesses the largest stockpile of weapons of mass destruction.
Russia is a great power as well as a regional power and has been characterised as a potential superpower. It is a permanent member of the United Nations Security Council and an active global partner of ASEAN, as well as a member of the Shanghai Cooperation Organisation, the G20, the Council of Europe, the Asia-Pacific Economic Cooperation, the Organization for Security and Co-operation in Europe, the World Trade Organization, as well as being the leading member of the Commonwealth of Independent States, the Collective Security Treaty Organization and one of the five members of the Eurasian Economic Union, along with Armenia, Belarus and Kyrgyzstan; the name Russia is derived from Rus', a medieval state populated by the East Slavs. However, this proper name became more prominent in the history, the country was called by its inhabitants "Русская Земля", which can be translated as "Russian Land" or "Land of Rus'". In order to distinguish this state from other states derived from it, it is denoted as Kievan Rus' by modern historiography.
The name Rus itself comes from the early medieval Rus' people, Swedish merchants and warriors who relocated from across the Baltic Sea and founded a state centered on Novgorod that became Kievan Rus. An old Latin version of the name Rus' was Ruthenia applied to the western and southern regions of Rus' that were adjacent to Catholic Europe; the current name of the country, Россия, comes from the Byzantine Greek designation of the Rus', Ρωσσία Rossía—spelled Ρωσία in Modern Greek. The standard way to refer to citizens of Russia is rossiyane in Russian. There are two Russian words which are commonly