What is a river in short. The largest waterways. The water content of the river is

I love to go to the sea, but the way to it is very long, but you can get out to the river every weekend. Best time- this morning on the bank of the river. Silence, the air is so clean that it is simply beyond words. It's great to spend time in nature with your family.

What is the river

There are a lot of rivers in our country, and they all differ significantly from each other. But, in general outline, the river is a stream of water that has made its way into the relief. Each river has:

• source;
• mouth;
• tributaries.

If you remember from school geography, then the source is the place where the river originates. The sources can be underground waters, springs or lakes. If the terrain is mountainous, then, as a rule, the river begins with glaciers. The river can flow into another river, as well as into a lake or sea. Just the place where it flows into another water body, and is called the mouth.

If you look at surveying the earth's surface with great height, then you can see that the river has many more branches. They are much shorter in length. These are the tributaries of the rivers. Together with the river itself, they form a river system. The rivers are very calm on the plains. But in those places where there are mountains, they change the nature of their course. They become very fast and violent.

How the water level in the river changes

Much changes in nature with the changing seasons. As for the rivers, the main thing for them is the change in the water level. Allocate:

• flood;
• floods;
• low water.

High water is typical for the spring period. The snow begins to melt abundantly, the water in the rivers becomes more, and therefore it gradually begins to leave its bed. Floods occur during the rainy season. Because of huge amount precipitation, the water level in the river rises markedly, but after their termination everything returns to normal.

Low water, on the contrary, speaks of a very small volume of water in the river. This situation can occur in very dry weather or during severe frosts. In hot summer period the river is real salvation. The beaches in our city are fully occupied, like in a seaside resort.

Water streams flowing in natural channels and feeding from surface and underground runoff from their basins. One of the branches of land hydrology, river hydrology, is engaged in the study of rivers. Rivers with their tributaries form a river system, ... ... Big Encyclopedic Dictionary

Modern encyclopedia

Rivers- RIVERS, water flows in natural channels, fed by surface and underground runoff from their basins. The river with its tributaries forms a river system. Mountain rivers are characterized by fast flow and usually narrow valleys; flat ... ... Illustrated Encyclopedic Dictionary

Encyclopedia of mythology

Water streams flowing in natural channels and fed by surface and underground runoff from their basins. One of the branches of land hydrology, river hydrology, is engaged in the study of rivers. The river with its tributaries forms a river system, ... ... encyclopedic Dictionary

Water that falls out in the form of rain immediately after it falls, and that falls out in the form of snow, grains, hail after they melt, flows partly along the soil surface, partly seeps into the soil and comes out in the form of springs (springs, springs). Both ... ... Encyclopedic Dictionary of F.A. Brockhaus and I.A. Efron

Water streams flowing in natural channels and fed by surface and underground runoff from their basins. R. are the subject of study of one of the sections of land hydrology, river hydrology. General information... In each district ... ... Great Soviet Encyclopedia

rivers- Reservoirs played a very prominent role among the Celts; thus, rivers were often considered the abode of their own spirits. The practice of throwing into rivers was widespread. expensive weapon, armor, coins and even jewelry as a sacrifice to the spirit of the river or ... ... Celtic mythology. Encyclopedia

Water. streams flowing into natures. channels and fed by surface and underground runoff from their basins. One of the branches of land hydrology, river hydrology, is engaged in the study of R. R. with its tributaries forms a river system, character and ... ... Natural science. encyclopedic Dictionary

Predictor. colloquial Evaluating the characteristics of moving crowds as endless and innumerable. Efremova's Explanatory Dictionary. T.F. Efremova. 2000 ... Modern explanatory dictionary of the Russian language by Efremova

Books

• Rivers, Evgeny Grishkovets. "Rivers" is the first story by Yevgeny Grishkovets. Like everything Grishkovets does, "Rivers" is a poignant and very warm work. For those who find reasons to live there, there was also for those who ...

River- directional flow fresh water, flowing in a certain relatively fixed channel and replenished mainly at the expense.

Source of the river- the place where the river originates. The source can be a spring, another body of water - a lake or swamp, a melting glacier. Occasionally, the source of a river may be the confluence of two other rivers.

Estuary- this is the place where the river ends, flowing into another, larger body of water: a river, lake, sea, ocean.

Bed- a path, a depression along which a water stream flows. The channel is relatively fixed, since the river can partially change its channel over time, leaving empty pits, depressions - meanders.

River valley- lowering of the relief from the source to the mouth. The river system is a river with all its tributaries.

River basin- the territory from which the river with all its tributaries collects water. Pools different rivers separated from each other by watersheds, often formed by hills or mountain ranges.

Rivers feeding- the flow of water into them. Different rivers have different sources of food, but in general they can be divided into four groups: snow, rain, glacial and underground. Many rivers are fed from various sources, in this case, they speak of a mixed diet.

Rivers, which originate in high-mountainous regions, are mainly fed by glaciers. Rain feeding distinguishes rivers located in tropical areas... Snow nutrition is typical for northern rivers, and rivers of the temperate strip often have mixed feeding.

River floods

Surely almost everyone watched with their own eyes the spring floods of the river, their strong decrease in the hot summer. This can be called spill and drain, but in general view such phenomena are called the water regime of rivers, that is, the change in time of the volume of water in the rivers, their levels and discharges.

River water regime manifests itself not only in spring or summer, there are also daily, ten-day, monthly and even long-term fluctuations. These fluctuations depend on the feeding regime of the rivers, that is, they receive water from the melting of snow and ice, precipitation and the intensity of water flow into the rivers from these phenomena. Both wind and human economic activity can affect the feeding of rivers.

The water regime of rivers has several main phases, called low water, flood and high water.

Low water- this is the state of the river, which is characterized by low water content, low water level for a long time. This is due to a decrease in the supply of the river. Distinguish between winter and summer low-water periods. In winter, all surface runoffs of rivers freeze, and in summer they dry up, and the river has only groundwater supply.

Flood Is a relatively short-term phenomenon caused by the rapid melting of snow and ice or heavy rainfall. This phenomenon is non-periodic and is characterized by a sharp rise in the water level in the river. This phenomenon can occur at any time of the year, and several floods in a row can cause floods.

High water- this is a phase of the river's water regime that occurs in the same season and is characterized by high level water and a long rise of this level. The flood is caused mainly by the melting of snow and glaciers. Distinguish between spring, spring-summer and summer floods.

Significance of rivers

It is very difficult to overestimate the importance of rivers in human life and the entire planet as a whole. It is enough just to estimate how much water humanity consumes per year to be convinced of this. And this volume exceeds 3.5 thousand cubic kilometers and increases annually.

In ancient times, rivers served as the most important communication route, so most cities were built precisely near large rivers. Today the river has lost its meaning of the main trade route but its significance remains enormous.

The river is the main source of fresh water needed in everyday life for Agriculture and industry.

The river remains an important transport route for transporting both people and goods.

When building hydroelectric power plants (hydroelectric power plants), giant dams block rivers, and huge turbines are generated by the movement of water necessary for a person electricity.

The river is essential recreational resource, which is used in the process of restoring and developing the physical and spiritual forces of a person, his ability to work and health. Most of the world's resorts are located near rivers or seas.

The river is a fishing spot.

Rivers of the world

The largest river, its length with the Missouri tributary 6400 km Mississippi originates in the mountains, flows to the southeast and flows into the Gulf of Mexico

Almost all continents (except Antarctica) are covered with a network of blue thread-arteries - rivers. In some places this network is denser, in other places it is less common. Rivers play a huge role in both maintaining ecological balance natural landscapes, and in the economic life of a person.

In this article, we will focus on many interesting questions. What is a river? What elements does it consist of? Why is a river called a river? And what are the names of the largest watercourses on the planet?

A river in a person's life. Man in the life of the river

There are at least 10 million rivers and streams in the world. They cover almost the entire Earth thick blue cobwebs. Most rivers in North America and Eurasia, least of all - in Africa and Australia. Interesting fact: 8 of the 10 largest rivers on Earth flow in the Northern Hemisphere.

Since ancient times, the river has become a great helper and reliable protector for humans. It was used and continues to be used for irrigating land, transporting goods, generating electricity. The first powerful civilizations arose in the valleys of such large watercourses as the Tigris, Nile and Euphrates.

At the same time, many rivers, as a result of active economic activity man was inflicted huge damage... This was especially pronounced in the second half of the twentieth century. Construction of huge dams and hydroelectric power plants, creation of huge reservoirs in area, discharge of tons of untreated industrial waste- all this negatively affected the ecosystems of the rivers of our planet.

What is a river? What elements does it consist of? And why is the river called a river? The answers to all these questions are later in our article.

Why is a river called a river? Origin of the word

In Polish - rzeka, in Ukrainian - rika, in Belarusian - cancer... It is believed that this word penetrated into the Slavic languages ​​as early as the 11th century. Scientists still do not really know the origin of the word "river". There are several versions worth considering. So why is a river called a river?

According to one of the assumptions, Slavic root"Rivers" was borrowed from the Old Irish language (in particular, from the word rian with a similar meaning). Another version connects it with the Gaulish word renos, from which, by the way, the name of the famous German river Rhine comes.

It is worth remembering another curious fact. So, in the ancient Indian book "Rigveda" the Russian Volga is mentioned under the name Rangha, which translates as the river Ra (possibly in honor of the pagan sun deity). With a fluent pronunciation, this word gradually transformed into "raha". Still later, the letter "x" turned into "k", and "a" - respectively, into "e". And so it arose Russian word The "river" we use today.

River in culture and folk art

The beauty of rivers and streams is described in numerous short stories, stories, poems, sung in songs. Volga, Don, Ob ​​and Neva - the names of these watercourses are most often found in Russian poetry and literature.

The river is an extremely photogenic natural site. She "looks" extremely well both in photographs and on the canvases of artists. Thus, the Volga can be seen in the famous painting "Barge Haulers on the Volga" by Ilya Repin. The mighty and majestic Kama is captured on the canvases of the famous master of landscape painting Ivan Shishkin. But one of the most famous works of Arkhip Kuindzhi depicts the night Dnieper. This picture is simple and ingenious at the same time!

Among other things, the river was reflected in folk art... There are dozens of proverbs, sayings and phraseological units about her. Here are just a few examples:

• "You cannot enter the same river twice!"
• "And you want to go across the river, but you stand on the bank."
• "Tears flow like a river."
• "Which river to float - that and water to drink."
• "The river is big and flows calmly."
• "The fast river erodes the banks."
• "The river is not the sea, longing is not grief."

What is a river: definition and main features

Rivers are one of the powerful exogenous (external) forces of the Earth. They perform colossal geological work, namely: they destroy, transport and accumulate masses in a new place. rocks.

What is a river? The definition of this natural object the following: this is a natural water flow that flows along the channel, which it also developed. We list key features rivers as a natural watercourse. So she:

• It flows from source to mouth under the influence of gravity.
• It feeds on underground, surface and (or) atmospheric waters.
• It has a length of at least 10 kilometers (if the watercourse is shorter, it is usually called a stream).
• It flows within the limits of an elongated and low relief form, referred to in geography as a river valley.
• It has its own catchment area, delineated by a clear boundary - the watershed.

The main elements of the river

Any river has a source (the place where it originates) and an estuary. The source is most often a source, lake or swamp. Mountain rivers often flow from the edge of glaciers. An estuary is where a watercourse flows into an ocean, sea, lake, or other river. It can be in the form of a delta or estuary. In the desert and arid regions of the Earth, so-called blind estuaries are quite common, when rivers do not carry their waters to the sea, being lost among the sands and salt marshes.

The lowest part of the river valley, which is constantly occupied by water flow, is called the river bed. Above is the floodplain (periodically flooded part of the valley), even higher - river terraces (former floodplains). In river beds, especially in mountainous ones, there are often rifts, stretches, rapids and waterfalls.

Many rivers have tributaries. At the same time, any natural watercourse can be a tributary of another, larger river. In hydrology, there is such a thing as a river system. It consists of one main river and all its tributaries. Sometimes their total amount reaches tens of thousands! Each natural watercourse is characterized by a number of specific parameters. Among them:

• Channel length.
• Channel width.
• Drainage area.
• The depth of the river.
• Fall and slope.
• Total water discharge (at the mouth).
• The chemical composition of water, etc.

River classification

All natural watercourses are classified by hydrologists according to a number of indicators. So, depending on the terrain, they are divided into mountain and plain. The former are characterized by large slopes, turbulent currents and extremely narrow, rocky valleys. The rivers of the flat type are characterized by a low flow rate and a significant tortuosity of the channel.

By age, rivers are young, mature and old, by channel stability - permanent and temporary (drying up), by ice regime- freezing and non-freezing.

According to the size and total length of watercourses in Russia, it is customary to distinguish three types of rivers:

1. Large (with a catchment area of ​​at least 50,000 sq. Km).
2. Medium (from 2,000 to 50,000 sq. Km.).
3. Small (up to 2000 sq. Km.).

Geography of rivers

On the surface of our planet, rivers are distributed extremely unevenly. The main watershed of the Earth distinguishes two main drainage basins: the Atlantic-Arctic and the Pacific. And the amount of river runoff from the first of these basins is much greater than from the second.

The density and "pattern" of the river network depend, first of all, on the climate of the territory. Secondly, from the terrain, and thirdly, from its geological history... The densest river network is typical for equatorial belt Earth. It is here that the largest and most full-flowing rivers of the planet - the Congo and the Amazon - flow. IN temperate latitudes the river network is more developed in mountainous areas. In tropical (desert) areas, deep and large watercourses are found as exceptions.

The largest rivers in the world and Russia (list)

Determining the length of a river channel is very difficult task... After all, you need to know exactly where the river begins and where it ends. As a rule, determining the location of the source causes a lot of controversy among geographers. Therefore, calculations of the length of certain rivers are often considered approximate.

So, for example, only at the beginning of this century did hydrologists determine that the Amazon is the longest river on the planet. Prior to that, the record holder in this regard long time was considered the Nile. Thanks to modern methodology juxtaposition space images and computer processing of the initial data, the Amazon "outstripped" the Nile by as much as 140 kilometers in length.

There are 170 rivers in the world with a length of over 1000 kilometers. The following are the top ten from this list:

1. Amazon (6992 km).
2. Nile (6852 km).
3. Mississippi (6420 km).
4. Yangtze (5800 km).
5. Yellow River (5464 km).
6. Ob (5410 km).
7. Yenisei (5238 km).
8. Lena (5100 km).
9. Amur (5052 km).
10. Congo (4700 km).

But the Reprua in Abkhazia claims the title of the shortest river on the planet. Its length is only 18 meters.

The list of the largest rivers in Russia is as follows:

• Yenisei.
• Lena.
• Amur.
• Volga.
• Lower Tunguska.
• Vilyui.
• Kolyma.
• Ural.
• Deer.

The river as a symbol

The river is a dualistic symbol that simultaneously carries both creative (constructive) and destructive force nature. In a number of mythologies, it is presented in the form of a kind of "universal core" that connects the earthly with the divine. In many cultures, the river was perceived as a boundary that delimits world of the dead with the world of the living.

In ancient China, the river was a symbol eternal life and the well-being of the country. It was believed that if the river dries up, it will inevitably lead to the death of all state power.

Many peoples treat with special trepidation those rivers that flow through the territory of their compact residence. So, since ancient times, the "sacred" river for the Egyptians is the Nile. The Volga has about the same meaning for the Russians, the Dnieper for the Ukrainians, and the Ganges for the Indians.

River - natural water stream flowing in a worked-out depression. Its work is manifested in erosion, that is, in the destruction of rocks along which the river flows. As a result, river valleys are formed.

River valley

River valley- a linearly elongated depression, along the bottom of which a river flows. The following elements of a river valley can be distinguished: channel, floodplain, terraces, and a bedrock bank (Fig. 178).

Rice. 178. The structure of the river valley

A deepening in a river valley, but to which the waters of the river constantly flow, is called river bed.

The river bed is usually winding. Smooth bends of the river channel are called bends, or meanders(fig. 179).

At a certain stage of development, a river can straighten its course. The remains of the former river channels form oxbows - oblong, meandering or horseshoe-shaped lakes.

Rice. 179. Meander of rivers: a - initial stage; b - growth and displacement of the meander; c - straightening of the river bed and the formation of a residual reservoir - oxbow

Rice. 180. Fairway, reach and roll

Lines greatest depths river beds are called fairway(fig. 180).

The river bed is characterized by alternating deeper sections (plesov) with smaller (rolls)(see fig. 180). There may be waterfalls - the fall water flow from a pronounced ledge.

The place where the river originates, from which there is a constant flow of water in the channel, is called source. They can serve as a lake, swamp, glacier, spring.

The place where a river flows into another river, lake, sea or ocean is mouth. River mouths can be different in shape; For example, delta or estuary.

Delta - low-lying plain in the lower reaches of the river, composed of river alluvium and cut by a network of streams. It is formed near quietly flowing rivers that carry a large amount of solid precipitation into shallow seas.

Estuary- funnel-shaped bay narrowing towards the top, formed as a result of flooding of the lower reaches of the river valley under the influence of wave, river and tidal factors. Deserted rivers with little water sometimes end in blind mouths, that is, they do not reach the reservoir (Murghab, Tejent, Cooper Creek).

The part of the river valley that is filled with water during flood periods is floodplain. The width of the floodplains of lowland rivers can reach 40 km. The edge of the floodplain is often marked by a steep slope, on the edge of which there are sometimes alongshore shafts.

They rise above the floodplain river valley slopes. They may be high or low, steep or shallow. On the steepness, both slopes of the valley are the same or different (asymmetrical). In asymmetric valleys of the Northern Hemisphere, the right one is more often steep (action of the Coriolis force).

Valley slope often has a stepped shape. These steps are called terraces. Most often they arise as a result of the erosional activity of the river: the channel descends, cutting through the floodplain, which becomes a terrace. Occasionally, terraces appear when the earth's surface is skewed due to tectonic movements, as well as due to climatic changes.

The lowest river terrace is the floodplain, it is called floodplain terrace, other - above the floodplain.

Depending on the geological structure, the following terraces are distinguished:

• erosive(the alluvium forming the terrace has a low thickness);
• basement(there is a lot of alluvium, and bedrocks are exposed only in the lower part of the valley sides);
• accumulative(the river cuts through only ancient alluvium).

Terraces are also longitudinal, transverse and root.

The forms of river valleys can be varied, because many factors influence their formation: terrain relief; composition of rocks; erosion processes, etc.

The following types of river valleys are distinguished by the shape of the transverse profile (Fig. 181): crevice (canyon), gorge, gorge, U-shaped valley, trough-shaped valley, trapezoidal valley, box-shaped valley, vaguely expressed valley. According to the outline in plan, lolines are subdivided into straight, meandering (meandering) and valleys with lake-like expansions (clear-like).

Rice. 181. Types of transverse profiles of river valleys: a - crevice (canyon); b - gorge, gorge; c - U-shaped valley; d - trough-shaped valley; d - trapezoidal valley; e - box-shaped valley; g - vaguely expressed valley

Strongly different from each other mountain and plain valleys. The former are characterized by a significant depth with a relatively small width and an uneven drop in the longitudinal profile. The latter, as a rule, are wide, have an insignificant depth and steepness of slopes, small slopes, etc.

The main river with tributaries form river system. The longest and most abundant river is usually considered the main one, however whole line the names of the main rivers have strengthened historically. In this case, the main river became the one that people knew earlier, longer and better. For example, the Missouri River is longer and fuller than the main Mississippi River. Along with the river, there are lake-river systems. They are formed by din where rivers flow through lakes, for example, r. The Neva flows through Lake Ladoga.

Each river has certain characteristics, including length, catchment area, annual flow, maximum and average water discharge, and a number of other indicators.

River length - the length of the river from source to mouth.

River basin

River basin (drainage basin rivers) - the territory of the earth's surface from which all surface and ground waters flow into the river with its tributaries. The river basin includes surface and underground catchments. Surface catchment is a section of the earth's surface from which water flows into a given river system or a specific river. The underground drainage basin is formed by strata of loose sediments, from which water enters the river network. But since it is very difficult to determine the boundaries of the underground catchment area, only the surface catchment area is taken as the size of the river basin.

Table 30. The largest rivers in the world

	Name	Length, km
	Neil (with Kagera)
	Amazon (with Ucayali)
	Mississippi - Missouri
	Ob (with Irtysh)
	Parana (from the origins of Paranaiba)
	Amur (from the sources of Argun and)

The largest drainage basin on Earth has a river. Amazon - 7.2 million km 2. Further in order are the basins of the Congo and Mississippi rivers (Table 31).

Table 31. The largest rivers in the world by basin area

	Name	Basin area, thousand km 2
	Amazon
	Mississippi

The basins of individual rivers are separated by watersheds.

Watershed - border between river basins. It is more pronounced in the mountains than in the plains.

River network density is determined by the ratio of the total length of all rivers to the area of ​​the drainage basin.

The fall - the difference in height between the source and the mouth.

River slope- the ratio of the fall to the length of the river, measured in meters per kilometer (m / km).

River runoff

River runoff(in a broad sense) is the movement of water in the form of a stream along river bed... It is influenced by many factors.

The statement of the Russian climatologist A. I. Voeikov is true: “Rivers are a product of climate”. So, with heavy precipitation, the runoff of rivers is large, but their type and nature of precipitation must be taken into account: snow gives a greater runoff than rain, heavy rainfall increases runoff compared to overburden with the same amount. But evaporation, especially intense evaporation, reduces runoff.

Very important geological structure the river basin, especially the chemical composition of rocks and the nature of their occurrence, since they determine the underground feeding of rivers. Permeable rocks (thick sands, fractured rocks) are moisture accumulators, river runoff in such cases is greater, since a smaller proportion of precipitation is spent on evaporation, and it is regulated.

Runoff in karst areas is peculiar: there are few rivers, since sediments are absorbed by funnels and cracks, but at their contact with clays or clay shales in river valleys and foothills, powerful springs are observed that feed the rivers. For example, the dry Crimean yayla, but powerful springs at the foot of the mountains.

Influence relief to the river runoff ( absolute height and surface slopes, density and depth of dissection) is large and varied. Stoke mountain rivers usually more than flatlands, since in the mountains on the windward slopes there is more rainfall, less evaporation due to lower temperatures, etc.

The flow of rivers is also influenced by human activities. First of all, this applies to rivers, the flow of water in which is regulated by the created reservoirs. The runoff of such rivers in general decreases, as evaporation from the water surface increases, a significant part of the water is spent on water supply, irrigation, watering, and underground recharge decreases.

When transferring water from one river system in another, the runoff is modified: in one river it decreases, in another it increases. For example, during the construction of the Moscow Canal (1937) in the river. It decreased in the Volga, and in the river. Moscow has increased.

To regulate the river flow, measures are carried out in the river basin, since its initial link is the slope flow in the catchment. The main activities carried out are as follows: agroforestry - forest plantations, etc., irrigation and drainage - dams and ponds on beams and streams, etc., agronomic - autumn plowing, snow accumulation and snow retention, plowing across the slope or plowing on hills and ridges, tinning of slopes, etc.

In the narrow sense, river runoff is the discharge of water in a river for a certain period (usually a year).

Water consumption- the amount of water that flows through the cross-section of the river per unit of time. Usually, the flow rate is usually expressed in cubic meters in one second (m 3 / s), and low flow rates (less than 0.1 m 3 / s) - in liters per second (l / s).

Living cross-section of the river - cross-sectional area of ​​the water flow.

Annual runoff- the amount of water flowing through the mouth of the river per year (Table 32).

Table 32.10 largest rivers in the world by annual flow

River name	The mainland on which the river is located	Annual runoff volume per year. Km 3
Amazon	South America
	South America
Mississippi	North America
	South America
Tocantins	South America

The movement of water in the river continuously changes in magnitude and direction, which leads to horizontal and vertical mixing of water. The flow of the river is characterized by speed. It can be determined by floats or special devices - hydrothermal spinners. It is expressed in meters per second.

With an open water surface in calm weather, the lowest velocities are observed near the banks and the bottom, which is due to friction, and increase towards the surface and the middle of the river. With a fair wind maximum speed happens on the surface, with a headwind and in winter with an ice cover, the maximum speed is observed at a certain depth.

Moving water is capable of doing work, that is, it has energy. They call her the living force of the river. It is directly proportional to the mass of the water and the speed.

In addition to water, rivers carry a large amount of solids. They are conventionally subdivided into suspended ones - moving together with water in the stream, and drawn ones - moving along the bottom by rolling and dragging.

The masses of suspended, entrained and dissolved chemical and biogenic substances, rocks that are carried away by surface runoff are called solid drain. Solid runoff is measured in tons carried by the river for a certain period of time (day, month, season, year) through the living (cross) section of the river. IN large rivers the volume of solid runoff reaches tens and even hundreds of millions of tons per year.

The first place in the world in terms of volume of solid runoff is occupied by the river. Yellow River (translated into Russian "yellow river"). Its name is associated with the abundance of portable solids that give the water a yellow tint (1300 million tons / year). The Chinese say that this water is too thick to drink, but too thin to be plowed. River bed The Yellow River is quickly silted up.

When a river reaches the sea or flows into another river, the solid runoff material forms fan or delta cones, usually with fertile land.

The turbidity of the water in the river depends on the magnitude of the solid runoff.

Turbidity of water - the amount of suspended particles contained in 1 m 3 of water (g / m 3) or in a liter of water (mg / l).

One of the most muddy rivers the world is p. Yangtze. This is facilitated by the weak stability of the rocks along which the river flows, the elevated and mountainous terrain, intense rains, deforestation and plowing of land.

Many rivers of Eurasia and Canada have a slight turbidity, where they are "strung" lakes-settlements, well-preserved natural vegetation, the grounds are bound by permafrost, low-lying coastal plains prevail.

In addition to solid particles, river waters contain a small amount of dissolved substances. They enter rivers through surface and underground runoff. In general, the salinity of river waters is low (usually less than 200 mg / l, but can reach up to 500 mg / l), since surface waters flow down from well-washed soils of interfluves, and a rapid change of water occurs in rivers. In areas of excessive moisture in the rivers, there are calcium waters. Sulfates appear in the waters of steppe rivers, chlorides appear in transit rivers of semi-deserts and deserts. The smallest mineralization is in mountain rivers fed by glacial and snowy waters, the largest is in rivers fed mainly by groundwater (for example, the rivers of Kazakhstan: Ishim - 12 g / l, Emba - 16 g / l, Turgai - 19 g / l) ... In addition to minerals, river water always contains nutrients necessary for life in the rivers themselves.

Thermal regime of rivers depends on climate and power sources. According to the thermal regime, there are three main types of rivers:

• with constantly warm water without seasonal fluctuations in temperature: Amazon, Congo, Niger, etc .;
• with seasonal fluctuations in water temperature, but not freezing in winter: Seine, Thames, etc .;
• with large seasonal temperature fluctuations, freezing in winter: Volga, Amur, Mackenzie and others in temperate and subarctic climatic zones.

In the warm half of the year, the temperature of the water across the free area differs little due to mixing. The change in temperature along the length of the river depends on the direction of the flow: it is less for latitudinal rivers than for rivers flowing in meridian direction... In rivers flowing from north to south, the temperature rises from source to mouth (Volga, etc.), in rivers flowing from south to north, on the contrary (Ob, Yenisei, Lena, Mackenzie). These rivers carry huge reserves of heat to the North Arctic Ocean, facilitating the ice situation there in spring, and shifting the boundaries of natural zones to the north.

In the winter period of frozen rivers, there are three main phases: freezing, freezing up, opening.

Freezing of rivers begins at an air temperature slightly below 0 ° C with the appearance of crystals - needles, then lard and pancake ice... With heavy snowfalls, the water forms snezhura. At the same time, streaks of ice appear off the coast - take it away. Bottom ice may appear on the rifts (rapids), which then floats up, forming, together with pancake ice, snow cover and ice floes detached from the banks, an autumn ice drift.

Ice cover on rivers is established mainly as a result of congestion - the accumulation of ice floes in shallow waters, in winding and narrow places and their freezing with each other and with banks. Small rivers freeze before large ones.

The duration of the freeze-up and the thickness of the ice are different and depend on the climatic conditions. For example, p. The Volga in the middle reaches is covered with ice for 4-5 months and the ice thickness is up to 1 m, r. Lena in the middle reaches - 6-7 months with an ice thickness of up to 1.5-2 m. The thickness and strength of the ice determine the possibility and duration of river crossings and movement on their ice - on winter roads. With freeze-up on rivers, phenomena such as polynyas can be observed: dynamic - on the rapids of the channel, thermal - in places where warm groundwater or discharge of industrial water.

In areas with permafrost and severe frosts, river ice is frequent - ice build-ups in the form of flat-convex ice bodies at the outpouring river water to the surface due to the narrowing of the free flow area. The thickness of the ice is on average 3-5 m. Along the length of the river, they are usually arranged in chains for tens of kilometers, sometimes narrowing, then expanding depending on the shape of the river valley. There are known cases when the ice "took prisoner" of the village. The largest ice in the world (according to V. M. Kotlyakov) - Bolshaya Momskaya (more than 100 km 3) exists in the valley of the river. Moma, the right tributary of the Indigirka. It has a length of 40 km and a thickness of 3-8 m. The flow of groundwater participates in its formation. Quite often on the rivers you can see side by side seemingly antagonistic phenomena - ice holes and ice. In fact, they are closely related to each other: the ice cover with its upper edge adjoins the polynyas in the places where comparatively powerful warm springs emerge.

On the rivers there are zazory - blockage of the living section of the river by the mass of in-water and bottom broken ice... They impede the operation of the hydroelectric power station, as ice clogs the water intake openings of the dams. Finally, complete freezing of rivers is also possible (in the north-east of Siberia and Alaska).

The rivers open up in spring 1.5-2 weeks after the air temperature passes O ° C due to solar heat and the arrival warm air... Melting of ice begins under the influence of melted snow water entering the river, streaks of water appear near the coast - flanges, and when snow melts on the ice surface - thawed patches. Then ice moves, it collapses, spring ice drift and floods are observed. On the rivers flowing from the lakes, in addition to the main river, there is a secondary ice drift caused by the removal of lake ice. The height of the flood depends on annual quantity snow reserves on the catchment, the intensity of spring snowmelt and rain during this period. On the rivers flowing from north to south, ice drift and floods in different sections occur at different times, starting from the lower reaches, there are several peaks of floods, and in general everything is calm, but stretched out in time (Dnieper, Volga, etc.).

River water regime characterized by the cumulative change over time in the levels and volumes of water in the river.

Water level- the height of the water surface of the river relative to a certain zero mark.

The characteristic periods with certain levels and volumes of water in the river are called phases of the water regime. They are different for different rivers and depend on climatic conditions and the ratio of food sources: rain, snow, underground and glacial.

The main phases of the water regime are flood and low water.

High water - a high and prolonged rise in the water level in the river, repeated annually in the same season, accompanied by flooding of the floodplain. During this period, the rivers have the highest water content. The flood falls most of annual river flow (up to 60-80%). High water is caused by the spring melting of snow in the plains, the summer melting of snow and ice in the mountains and in polar regions, long heavy rains in the warm season. Depending on what is the cause of the flood, this period on different rivers happens in different seasons of the year, for example, in the summer on the river. Ganges, Indus, Yangtze, Mekong due to monsoon summer rains and melting of glaciers in the mountains; in winter on the rivers of the Mediterranean (Guadiana, Guadalquivir, etc.) due to winter rains.

Table 33. Distribution of the main types of river power sources by continents and parts of the world

The predominant power source	Prevailing stock	Continents and parts of the world
				North America	South America		Australia
Snow
Rain
Underground
Glacial
Internal flow areas

e - the areas of internal drainage are large.

Low water(low water) - a period of long lower levels and water discharge in the river with the predominance of underground recharge. Summer low water is caused by intense evaporation and seepage of water into the ground, despite the greatest amount of precipitation at this time. Winter low water is the result of a lack of superficial nutrition. At this time, rivers exist only at the expense of groundwater.

A sudden short-term non-periodic rise in the water level in the river is called flood. In contrast to floods, floods occur in all seasons of the year: in summer they can be caused by heavy rains; in winter - melting snow during thaws; at the mouths of some rivers due to the surge of water from the seas (the autumn floods on the Neva River in St. Petersburg are caused by the surge of water from the Gulf of Finland by westerly winds).

Autumn rise of water in rivers, sometimes called leash period, is associated with a decrease in temperature and a decrease in evaporation, and not with an increase in precipitation - there are less of them than in summer, although cloudy weather is more often in autumn.

Forecasting the water content of rivers and their regime throughout the year is of great importance for resolving issues of rational use. water resources countries. It is very important to forecast runoff during floods, which in some years are extremely high and lead to negative consequences.

According to the feeding conditions and water regime, the rivers are subdivided into separate groups. The first such classification was created by A. I. Voeikov(1842-1916) in 1884. Later it was improved by M.I. Lvovich in 1964 at the expense of quantify the role of individual sources of river feeding and the seasonal distribution of runoff. He identified six zonal types of water regime of lowland rivers.

Equatorial rivers type have abundant rainfall, large and relatively uniform runoff throughout the year, some increase is observed in the fall of the corresponding hemisphere. These are the Amazon, Congo and others.

Rivers tropical type. The runoff of these rivers is formed by monsoon summer rains in the subequatorial climatic zone and mainly summer rains on east coasts tropical belt, therefore, the summer flood. This type includes the Niger, Orinoco, and Nile rivers.

Rivers subtropical type in general, they are mainly fed by rain, but according to the seasonal distribution of runoff, two subtypes are distinguished: on the western coasts of the continents in the Mediterranean maritime climate the main runoff is winter (Guadiana, Guadalquivir, Duero, Tahoe, etc.), on the eastern coasts in a monsoon climate, summer (tributaries of the Yangtze, Yellow River).

Rivers moderate type. Within the temperate climatic zone, four subtypes of rivers are distinguished according to their sources of supply and seasonal distribution of runoff. On the western coasts in the maritime climate near the rivers, it is predominantly rain fed with an even distribution of runoff throughout the year, with a slight increase in winter due to a decrease in evaporation (Seine, Thames, etc.); in areas with a transitional climate from maritime to contin-
the mental diet near the rivers is mixed with a predominance of rain over snow, with a low spring flood (Elbe, Oder, Vistula); in areas continental climate near rivers, mainly snow and spring floods (Volga, Ob, Yenisei, Lena); on the east coasts with monsoon climate the rivers are mainly fed by rain and summer floods.

Rivers subarctic type have predominantly snow supply with an almost complete absence of subsurface due to permafrost. These rivers in cold period years (8-9 months) freeze to the bottom and have no runoff. High water on rivers of this type is summer, since they open up in late May - early June (Yana, Indigirka, Khatanga, etc.).

Rivers polar type in short period the summers are fed by snow and glaciers and runoff, while most of the year they are frozen.

Such types and subtypes of the water regime are characteristic of rivers, the flow of which is formed in more or less of the same type. climatic conditions... The regime of large transit rivers crossing several natural and climatic zones is more complicated. It is all the more difficult for rivers mountain areas, which are characterized by the patterns of vertical zonality. As the height of the mountains near the rivers increases, the share of snow and then glacier nutrition also increases. Therefore, rivers that begin in the mountains and have additional snow and glacier nutrition are characterized by summer floods (Amu Darya, Syrdarya, etc.). Summer floods are especially intense and even catastrophic on rivers that begin high in the mountains, and in the middle and lower reaches are abundant monsoon rains: Indus, Ganges, Brahmaputra, Mekong, Irrawaddy, Yangtze, Yellow River, etc.

Economic importance and protection of rivers

Rivers have great economic value... Formation and development are associated with them. human society... Since historical times, rivers have been used as sources of fresh drinking water, communication routes, for fishing and fish farming, timber rafting, irrigation and watering of lands, water supply for the population. They are used to supply water industrial enterprises receiving electricity.

Rivers are of great aesthetic and recreational importance, being places of recreation and various sports activities. They serve as collectors, water receivers for drainage reclamation of wetlands.

The widespread involvement of rivers in economic circulation has become disastrous for them. Unfortunately, many rivers are heavily polluted with industrial and domestic wastewater, pesticides and mineral fertilizers from fields and runoff from livestock enterprises. Water protection zones are far from everywhere along river banks. Many of the rivers, especially those flowing in the southern regions, where there is a great need for irrigation, are highly understandable. For this reason, the Amu Darya and Syr Darya practically do not flow into the Aral Sea, and it is rapidly drying up. Rivers need protection and support of their natural water regime and its reasonable improvement by creating reservoirs, canals and carrying various works in the channel and basin of the river.