What a river is, everyone knows. This is a reservoir that originates, as a rule, in the mountains or on hills and, having traveled from tens to hundreds of kilometers long, flows into a reservoir, lake or sea. That part of the river that departs from the main channel is called a branch. And a section with a fast current, running along the mountain slopes, is a threshold. So what is the river made of? What components can it be divided into? Let's take a closer look at what we mean by such a simple and familiar word as "river".
What is a river?
The first fundamental knowledge about animate and inanimate nature we get at school in the lessons of the world around us. Students are introduced to such concepts as a stream, river, lake, sea, ocean, and so on. Naturally, the teacher cannot but tell about what parts of the river are. Grade 2 is too early to remember a lot of terms and concepts. Therefore, children turn to their parents for help. And, I must say, putthem to a standstill. Because adults often cannot answer such simple questions. So, not everyone will be able to explain how the river delta differs from the channel, or how oxbow lakes are formed. Or here's another example - what is a river valley? Let's re-examine all these concepts.
A river is a constant flow of water. In arid regions of the Earth, such as Africa and Australia, it can dry up temporarily. Rivers feed on snow, underground, rain and glacial waters. This natural reservoir has a channel developed for centuries by its runoff. And the relationship between climate and the river is very clear. And it's easy to follow. The flow regime depends on the climate: it is far from being the same in different altitude, latitude and longitude zones.
The characteristics of the water resource we are considering also directly depend on the terrain and the area in which it is located. The map of the rivers shows that they can pass through the plains, down the mountain slopes. They can even be found underground. Plain rivers flow through flat, wide areas. Coastal erosion predominates here, that is, lateral erosion. The slopes of the reservoir are gentle, the channels are usually winding, the current has a weakly expressed character. Mountain rivers have completely different characteristics. Their channel is very narrow and rocky. The valleys are poorly developed, with steep slopes-banks. Usually such water arteries are not deep, but the speed of their flow is enormous.
Also distinguish lake rivers. They can either flow out of lakes or make their way through them. Such objects are characterized by higherrunoff in low water. Lake rivers have a long flood period. As a rule, they are not too long. Several other marsh rivers. They are, of course, less common. They have a more extended flood, frequent floods are noted due to the characteristic flat terrain of the area where the channel passes, which is constantly slowly replenished with water from the swamp.
Karst rivers deserve special attention. They almost always feed from groundwater, which fills the so-called karst voids. The low-water flow of these rivers is increased.
Source of the river
The beginning of the river is called the source. This is the place where a permanent channel is formed. The source can be different: a stream, a lake, a swamp. Large rivers often start from several smaller reservoirs. In this case, the source will be the place of their confluence. For example, the beginning of the Ob River is given by the waters of the Katun and Biya. Mountain rivers are almost always formed from the confluence of many streams. Well, the plains begin their journey from the lake. It is worth remembering that the geography of each reservoir is individual. And the source of each river is also unique in its own way.
River valleys
Before parsing the names of the parts of the river, we need to dwell on such a term as "river valley". In scientific terms, we are talking about elongated depressions created by watercourses. They have a certain bias towards the current. All parameters of river valleys (width, depth and complexity of the structure) are completely dependent on the degree of power of the watercourse. Values are also the duration of its existence, the nature of the surrounding relief. The stability of rocks and the degree of tectonic activity in the area are taken into account.
All river valleys have a flat bottom and slopes. But, again, their characteristics depend on the relief of the territory. Mountain rivers have steep slopes. They are deeper than flat ones. At the same time, their valleys are not wide, but narrow. Often they have a stepped bottom. The lowlands are completely different. They consist of a floodplain and a channel pitted by oxbow lakes. Young valleys are characterized by steep slopes, while older ones have stepped banks. Such slopes are called terraces. The older the river, the larger and wider its stepped banks.
Young rivers do not have terraces. Even the floodplain is not found everywhere. The bottom of such reservoirs is trough-shaped, often this is due to the fact that a glacier once passed through this territory. But there are exceptions.
The main parts of the river - the channel and floodplain - are formed in different ways. In rocks susceptible to rapid erosion, they are much wider than in crystalline soils. Also, the main feature of river valleys is that they always gradually expand towards the mouths. Their slopes become gentler, and the terraces widen.
River valleys also have a special practical significance. This is the most convenient place for the construction of settlements. As a rule, cities and towns stand on terraces, and floodplains serve as excellent grazing land.
Floodplain
Literally translated, “floodplain” is what water fills. And this is an absolutely correct definition. This is part of the rivervalleys, which during floods and floods are completely flooded with water. The floodplain has its own unique landscape. Often it is divided into two levels. The lower floodplain is flooded regularly, from year to year. The upper part is only in those years when the water level is high.
Each flood leaves its mark on the river floodplain. It erodes surface soils, creates gullies and forms oxbow lakes. Every year, sand, pebbles and loams remain on the surface of the earth. This leads to an increase in the level of the floodplain. At the same time, the process of deepening the channel is going on. Over time, the low floodplain turns into a high floodplain, and terraces above the floodplain are formed. They are stepwise. The floodplain has coastal cliffs several meters high. Often gullies and oxbow lakes form on it.
Floodplains of flat rivers are wide. For example, at the Ob, the width reaches 30 kilometers, and in some areas even more. Mountain rivers cannot boast of floodplain territories. Such areas are found only in fragments, and they can be found on one side, then on the other.
The value of floodplain lands is great. Such valuable lands are used as pastures and hay meadows. The floodplain of almost any large river in the steppe, forest-steppe or taiga zone is a stable area for the development of animal husbandry.
River bed
The lowest part of the river, or rather the valley, is called the channel. It is formed by continuous water flow. Runoff and most of the bottom sediments constantly move along it. The channel usually has manybranches. It is rarely straight, except perhaps near mountain streams.
The channel, as it approaches the mouth, forms many channels and branches. Especially a lot of them in the delta. The channel in the floodplain of the river is formed during periods of high water, but in the hot summer months it can dry up. The branches of lowland rivers have a winding relief. They show mobile accumulations of fine clastic sediments. In mountain rivers, channels are formed extremely rarely, and the branches are more straight. Often you can find sections of rapids and different heights of waterfalls. They can be cluttered with pebbles and large boulders. The stretches - deep sections of the sleeves - alternate with rifts. Often such transitions are noted in the lower reaches. The width of the branches of full-flowing rivers, for example, such as the Yenisei, Lena, Volga, Ob, can reach several tens of kilometers.
Thresholds
The flow of the river often forms rapids. Especially often they are found in the channel of mountain rivers. The threshold is a shallow area littered with pebbles or boulders. It is formed in places where hard-to-erode rocks occur. There are large current fluctuations here. The rapids, due to their relief, make navigation impossible and make rafting very difficult. Sometimes, because of them, a person is forced to build bypass channels. Hydroelectric power stations are often built downstream of the rapids. At the same time, the fall of the river and significant slopes are used with maximum benefit. An example is the Ust-Ilimskaya HPP on the Angara River.
What is a river delta?
Delta islowland of the river. It is almost always characterized by numerous branched ducts and sleeves. The delta is formed exclusively in the lower reaches. It is also important to note that a special mini-ecosystem is formed in this section of the reservoir. Each river is unique and unrepeatable.
Most of the major rivers in Russia have extensive deltas with well-developed alluvial activity. Volga and Lena are always cited as classic examples. Their deltas are huge and branch out into a whole network of branches. In addition to them, one can also note the Kuban, Terek and Neva. A distinctive feature of the deltas located in the southern regions are developed floodplains. A lush variety of vegetation is noted here, various mammals, amphibians and reptiles find shelter along the banks. Many species of birds build their nests in forests and thickets near the water. But these areas are especially valuable for fishery resources. Noting the question of what a river delta is, we can say with confidence that this is a unique microcosm with its own nature.
Estudies
When a river flows into the sea, shallow bays often form. They are called estuaries. Such a bay in the lower reaches of the river is a very unusual and picturesque place. The estuary occurs when the lowland rivers are flooded by the sea. It can be open - then it is called a lip. At the same time, the bay does not have to be connected to the sea at all. There are also closed estuaries, that is, separated from sea water by a strip of land - a narrow embankment. As a rule, the water of estuaries is s alty, but not to such an extent asmarine. True, with a small influx of fresh water, it can become very saline. The bay in the lower reaches of the river is not always formed. Many of them are located on the coast of the Sea of \u200b\u200bAzov. There are estuaries near the Dniester and Kuban rivers.
River mouth
The place where a river flows into a lake, reservoir, sea or other body of water is called a mouth. It may be different. For example, in the territory adjacent to the mouth, an estuary, a bay, or a wide delta may form. But river water may disappear, and there are several reasons for this - withdrawal for irrigation of agricultural plantations or simply evaporation. In this case, they speak of a blind mouth, that is, the river does not flow anywhere. It often happens that at the end of its path, the waters simply go into the ground, and the flow disappears. Therefore, it cannot be said that every river has a well-defined mouth. For example, the Okavango riverbed disappears into swamps in the Kalahari Desert. Thus, the source of the river and the mouth are not necessarily clearly defined, and it is not always possible to find them.
River tributaries
A tributary is a stream that flows into a larger river. It usually differs from the latter in smaller volumes of water and in length. But, as studies conducted in recent decades show, this is not always the case. There are several rivers that violate this established law. For example, the Oka flows into the Volga, which is inferior to it in terms of water volume. At the same time, the Kama also flows into this great water artery, which is also more full-flowing. But on the Volga, all known exceptions do not end there. The Angara is recognized as a tributary of the Yenisei. At the same time, the part of the river that merges with the second object has twice the volume of water. That is, we can say with confidence that the Angara is larger. As a rule, the tributary has differences in the direction of the valley, so you can accurately determine what flows into what.
But rivers don't always merge with each other. Sometimes they flow into lakes or other bodies of water. The tributaries are divided into right and left, depending on which side they approach the channel. They are of different order: primary and secondary. Some of them flow directly into the channel of the main drain. These are major tributaries. All rivers that connect with them will be secondary. For example, the Zhizdra is a primary tributary for the Oka and a secondary tributary for the Volga.
Backwater
The sleeve is also part of the river. It can be a branch or "split" of the channel. Note that the sleeve must necessarily flow back into the river. Sometimes this happens after a few tens of meters, but more often it stretches for several kilometers. The sleeve is formed as a result of sediment deposition. At the same time, an island is formed in the channel. The sleeves have many local names. On the Volga they are called "volozhki". On the Northern Dvina River they are designated by the word "hollow". On the Don, the locals call them Starodone. On the Danube River - "girlo". Sleeves can be secondary. Then they are usually called ducts. Almost all branches and ducts become oxbow lakes after some time. As the mainstream changes, they disconnect.
Staritsa
Staritsa is an elongated lake or section of a river that has detached from the main channel. Starks can be found in the floodplain or on the lower terrace. They occur when the branches are blocked by sand or clay shoals, as well as when the necks of the meanders break through. Old women always have a characteristic horseshoe shape. They connect with the waters of the main channel only at the time of the spill. Most of the time they are separate reservoirs. Often they are called floodplain lakes. The diagram of a part of the river, on which all the oxbow lakes are marked, can give an idea of how the channel looked before. Over time, this object changes - it overgrows, its shape changes. The old woman turns into a swamp, and then completely into a damp meadow. After some time, there is no trace of her.
River levels
River level is the height of the water surface. This concept is used for almost all natural and artificial reservoirs. Each river has low and high values mentioned. The maximum water level is observed during floods, usually in spring and summer. Floods also occur in autumn. The reason for this is torrential downpours. In winter, the water level drops to a minimum. Often the river becomes less full-flowing even in summer - during long droughts, when the streams flowing into the channel dry up. The regime of each river is strictly individual. The decrease and increase in the water level always depends on climatic and relief features.
