River and river valley. Meanders

In the last article I talked about what it is. In this article I will talk about individual elements of the river. This is what the fisherman encounters, the terms that the fisherman uses in. We are talking about such elements of the river as a channel, an island, a threshold, a riffle, a bank, a bottom, a spit, a creek, a whirlpool, a sandbar, a bank, a pool, a dam, a pressure and others.

Sometimes it happens that the river is divided into several parts, see the figure “Channel”. Usually one part of the river is smaller than the other. This is the part of the river that is smaller and is called - duct. In this case, between the river bed and the channel, a piece of land is formed, which is called - island. An island is a piece of land surrounded by water.

The river carries its waters from a higher place to a lower place, see the picture “Threshold”. This movement of water is uneven. In deep areas In slow-flowing rivers, this difference in height is not very noticeable. But, as a rule, after a deep section with a slow current there follows a shallow section with fast current. The bottom in such sections of the river is made of hard rocks that the river could not erode and destroy. Such sections of the river are called - threshold.

On small rivers such areas are more often called roll. But it's the same thing. Very often the river at the rapids is noticeably wider than usual. In principle waterfalls They are also rapids, only with a large difference in height along the river.

Sometimes on the river, to the side of the main channel, small lakes or lakes are formed on one side connected to the river. See the drawing “Braid”. Most often there is no current at all or it is circular and slow. Such sections of the river are called backwater. The backwater and the main channel of the river are separated by a strip of land, which is called - braid.

Sometimes the river flow shifts to one bank. See the drawing “Whirlpool”. And often, on the side of the other, flatter bank, a shallow section of the river with a slow current is formed. This section of the river is called - shallow. The deepest section of the river is called - whirlpool. Very often, whirlpools form after rapids.

Sometimes there is a slide at the bottom of the river, the top of which does not reach the surface of the water. The height difference between the top of this slide and the bottom of the river next to the slide can be very significant. See the picture “Bank”. Such slides are called -.

Various hydraulic structures are often erected on the river. Look drawing " Hydraulic structures" Such structures completely block the flow of the river, from one bank to the other. They are designed for a variety of purposes. On small rivers and streams they often build dams or dams for accumulating water for the purpose of arranging watering places for cattle. On large rivers it could be a hydroelectric power plant.

The part of the river near the dam towards the source of the river is called - headwater. Below the dam, the part of the river next to the dam is called - tailwater.

Water fills the river bed. See the picture “Shores”. Near the water, on one side and the other there is land. This land along the water flow is called -. It often happens that a river flows at the border of a mountain range and a plain. In such places, the banks on one side and the other are different. The higher bank is usually steep bank, and the lower one – gently sloping shore. Different banks of the river are also formed in places where the direction of the river flow changes.

Land waters make up only 3.5% of the waters of the entire hydrosphere. Of these, only about 0.5% are rivers. What is a river? This is a constant water flow that flows in a depression it has created in the surface. It has a beginning - a source and an ending - an mouth. A river can begin as a source of groundwater coming to the surface. The beginning of the river can also give mountain glacier, swamp or lake. This is what the source of the river is.

Bed

The water flow constantly moves in the depression filled with it - the channel. The direction of the river depends on the slope of the surface, i.e. from top to bottom. The speed of water movement in the channel is determined by the relief, the relative height of the surface along which it flows.

Throughout its entire journey, the river receives tributaries - streams that bring it their waters. Tributaries are right-handed if, when looking downstream, the tributary is on the right, and left-handed if it flows into main river left.

Estuary

What is a river mouth? This is the place where a river merges with another river or body of water. The length from source to mouth is the length of the river.

The main river with all its tributaries forms a river system.

A delta is a wide mouth. It occurs mainly near large rivers.

In addition to the question of what is the mouth of a river, the source of a river, another arises: what elements of a river valley exist?

River valley elements

The main reason for the flow of a river is gravity, so it flows along the slope of the surface. Most often, it cannot travel its way from source to mouth in a straight line due to natural obstacles. The river lays its bed from beginning to end along the most convenient sections for it - concave relief forms.

Another force that acts on the movement of the river is the Coriolis force. Therefore, the flow of all rivers in the Northern Hemisphere deviates to the right, and in the Southern Hemisphere - to the left. As a result of this phenomenon, a constant water flow erodes more of the bank towards which the deviation goes. The river bed increases in width and deepens with the force of the flow. This is how a valley is formed. The latter is a concave hollow, at the bottom of which there is a river bed. Over time, the channel deepens. The goal of the flow is to travel the path from top to bottom in the most shortcut, which means reducing the difference between the height of the source and the mouth to zero. Therefore, the watercourse will deepen its bed until it coincides with the water level of the reservoir into which it flows. This level is called the erosion base. The common basis of erosion for all rivers is the level of the World Ocean.

The water level is not constant, it depends on many factors: features geological structure surface, volume of incoming water, economic use etc. The strength and speed of the flow also constantly changes. After some time, the valley created by the river at the very beginning widens and deepens. The development of the valley occurs unevenly; terraces are formed on its sides - the remains of the channel in which the stream was located at previous stages of its development.

Due to seasonal floods, the river overflows its banks, overflows the bed and floods part of the valley. The section that is filled with water during a flood is called the floodplain of the river.

River feeding

What is a river with a certain type food? By feeding a river we mean the source from which it receives water. Water can come from several sources:

From the atmosphere . In the form of precipitation (liquid or solid).
From the glaciers . As a result of melting.
From underground sources.

Thus, the rivers can be fed as follows: atmospheric, glacial and underground.

It is very rare for a river to be fed from only one source; it often has mixed type nutrition. This is especially true for large objects.

On Earth, there is a certain pattern in the distribution of river nutrition. Thus, in tropical, subtropical, subequatorial and equatorial latitudes, as well as on the eastern and western coasts of the temperate zone near rivers, it is common atmospheric type nutrition.

Among the rivers feeding precipitation, a subtype is distinguished as snow. What is a snow-fed river? It feeds on melted snow waters. This type has permanent watercourses in the temperate and subarctic zones.

The rivers of the subarctic zone have a glacial type of feeding.

River mode

River regime is a periodic change in water level throughout the year. Maximum level- high water, minimal - low water. Flood is a short-term sharp increase in water level. High water can turn into a flood; this is when water floods not only the floodplain, but also the part of the valley above the floodplain. Such phenomena are typical for rivers monsoon regions in summer. Rivers temperate latitudes throughout the year they have a very unstable water regime with frequent floods.

The rivers of temperate continental regions are fed by the waters of melted snow in the spring, overflowing with floods. They have two low water periods - in summer and winter. In summer, floods may occur during heavy rainfalls.

Rivers of continental regions tropical zone, originating in the mountains, are fed by melted snow waters, so their peak floods are observed in the summer.

Rivers with underground type food dries up in summer.

From all the above facts we can conclude what a river is. The definition will sound like this: this is a natural watercourse sufficiently large size, which flows down the mined out channel, from the source to the mouth, has a certain regime and is fed by underground or surface runoff.

River- a watercourse that has a clearly defined channel and is fed by precipitation and groundwater from its catchment.

River terms:

Source of the river- the place where the river begins, from which the constant flow of water begins. The source can be a spring, swamp, lake, glacier.
river valley- lower part earth's surface, through which the river flows. The formation of river valleys is associated with geological processes, deformations earth's crust, the action of glaciers and erosion of the banks by the river itself.
Bed- a lowered part of a river valley through which water flows at its lowest levels (without flooding the floodplain).
Strezhen- a conditional line connecting points on the water surface of the river with the greatest depth of the channel and maximum flow speeds.
Floodplain- part of a river valley that is periodically flooded during high rises in water levels (high water, flood).
Indigenous shores- areas of the earth's surface that border the river valley from the sides.
oxbow- an old channel, a former bend, straightened by a new channel and isolated from it. Over time, the oxbow lake becomes shallow, silts up, becomes overgrown with bushes, or turns into a swamp.
Island- a small area of land covered with vegetation, washed on all sides by water.
Middle- an alluvial (without vegetation) formation in a riverbed, washed by water from all sides.
Top- the upstream part of the island, the middle.
Ear- the downstream part of the island, the middle.
Sleeve- part of the river that was formed when the channel was divided by an island.
Move- part of the river that was formed when the channel was divided into a middle.
Duct- a branch running along the floodplain away from the main channel.
Water's edge- line of intersection of the water surface with the shore
Splash- a narrow strip of sloping shore adjacent to the water.

Shipping terminology:

Ship's passage (fairway)- a body of water on an inland waterway (river), intended for the movement of vessels and marked on the ground and (or) map.
Navigation axis- a conventional line passing in the middle part of the channel or indicated by navigational signs.
Channel edge- a conventional line limiting the width of the ship's passage.
Lane- part of the ship's channel between its axis and the right or left edge.
Main navigation route- a ship passage that is the main one in relation to other ship passages in a given area.
Ship's pass- transition of a ship's passage from one shore to another.
Backwater- a part of the river that has become shallow at the upper end of the bend, equipped for mooring ships.
Raid- part of the river bed allocated for the mooring of ships.
Water area- water space within a roadstead, backwater, port.

Fluctuations in water levels in the river.

Water level is the height of the water surface in a water body above the conventional horizontal comparison plane.
High water- phase water regime river, repeating in these climatic conditions annually (almost at the same time of year) with the most high level water. Floods are caused by snowmelt and melting glaciers. Depending on the climatic zone and conditions, the flood can be spring, spring-summer and summer. The duration of the flood varies from two to three weeks to two months.
Low water- phase of the river’s water regime, characterized by a long period of low water level. The beginning of the low water period is taken to be the end of the flood, and the end is the onset of rising water during the autumn rains. During low-water periods, rivers are fed mainly by groundwater and this phase of the water regime is characteristic of summer months(usually July-August).
Flood- a phase of the river’s water regime, characterized by short-term and irregular rises in water level caused by rain or snowmelt during thaws. The duration of the flood is from a week to a month. In addition to the listed water regimes, it should be noted that characteristic phenomenon for a number of areas, like flooding.
Flood- flooding of territories with water for various reasons, usually during periods of high water and floods, which is a natural disaster. Regulation of the water regime during the navigation period is carried out using dams and reservoirs built on rivers.

A river is a natural permanent water stream (watercourse) of significant size with a natural flow along the channel (the natural depression it has created) from the source down to the mouth and fed by surface and underground runoff from its basin.

The rivers are integral part hydrological cycle. Water in the river is usually collected from surface runoff resulting from atmospheric precipitation With a certain area limited by the watershed (river basin), as well as from other sources, such as groundwater reserves, moisture stored in natural ice(during the melting of glaciers) and snow cover.

In places of natural or artificial obstacles to the flow of a river, reservoirs (flowing lakes or artificial seas) appear. Limnology (Greek λίμνε - lake, λόγος - study) or lake science is a branch of hydrology, the science of the physical, chemical and biological aspects of lakes and other fresh water bodies, including reservoirs. In turn, rivers are the subject of one of the largest sections of land hydrology - river hydrology or potamology (from ancient Greek ποταμός - river, λόγος - study - literally the science of rivers), which studies the structure of river networks, river flow, morphometry of rivers swimming pools and so on. As a rule, rivers make their way and flow through zones of least stress and resistance - along tectonic faults.

For a long time, the energy of fast rivers and waterfalls has been widely used in human economic activity as a source of renewable energy for the operation of water mills and turbines of hydroelectric power stations.

General information

In each river, a distinction is made between its place of origin - the source and the place (section) where it flows into the sea, lake or confluence with another river - the mouth.

Rivers that directly flow into oceans, seas, lakes or are lost in sands and swamps are called main; flowing into main rivers - tributaries.

The main river with all its tributaries forms a river system characterized by density.

The land surface from which a river system collects its waters is called a catchment, or drainage area. The drainage area together with top layers the earth's crust, which includes a given river system and is separated from others river systems watersheds is called a river basin.

Rivers usually flow in elongated low forms of relief - valleys, the lowest part of which is called a channel, and the part of the valley bottom flooded with high river waters is called a floodplain, or floodplain terrace.

The channels alternate between deeper places - reaches and shallow areas - rifts. Line greatest depths the channel is called thalweg, close to which the shipping channel or fairway usually passes; line highest speeds flow is called a core.

The boundary of a river's watercourse is the bank; depending on its location along the stream relative to the center line of the watercourse's bed, the right and left banks of the watercourse are distinguished.

The difference in height between the source and the mouth of a river is called the fall of the river; The ratio of the fall of a river or its individual sections to their length is called the slope of the river (section) and is expressed as a percentage (%) or in ppm (‰).

On the surface globe The rivers are distributed extremely unevenly. On each continent, it is possible to outline the main watersheds - the boundaries of the areas of runoff entering various oceans. The main watershed of the Earth divides the surface of the continents into 2 main basins: the Atlantic-Arctic (the flow from the area of which flows into the Atlantic and Arctic oceans) and the Pacific (the flow into the Pacific and Indian oceans). The volume of runoff from the area of the first of these basins is significantly greater than from the area of the second.

The density of the river network and the direction of flow depend on the complex of modern natural conditions, but often, to one degree or another, retain the features of previous geological eras. The river network reaches its greatest density in equatorial belt where they flow greatest rivers world - Amazon, Congo; in tropical and temperate zones it can also be high, especially in mountainous regions (Alps, Caucasus, Rocky Mountains, etc.). Occasional in desert areas flowing rivers, which occasionally turn into powerful streams during snowmelt or intense rainfall (rivers of lowland Kazakhstan, oueds of the Sahara, Creek (a drying up river) and Australia, and others).

Classification

Classification of rivers by size

Large rivers are lowland rivers with a basin area of more than 50,000 km2, as well as predominantly mountain rivers with a drainage area of more than 30,000 km2. As a rule, their basins are located in several geographical zones, and the hydrological regime is not typical for each river geographical area separately.
Middle rivers are lowland rivers, the basins of which are located in the same hydrographic zone, having an area from 2000 to 50,000 km2, the hydrological regime of which is characteristic of rivers in this zone.
Small rivers are rivers whose basins are located in the same hydrographic zone, have an area of no more than 2000 km2 and whose hydrological regime, under the influence of local factors, may not be typical for rivers in this zone.

Topographic classification

Depending on the topography of the area within which the rivers flow, they are divided into mountainous and flat. Many rivers alternate between mountainous and flat areas.

Mountain rivers, as a rule, are distinguished by large slopes, rapid currents, and flow in narrow valleys; erosion processes predominate.
Lowland rivers are characterized by the presence of channel meanders, or meanders, formed as a result of channel processes. On lowland rivers There are alternating areas of erosion of the channel and accumulation of sediment on it, as a result of which rifts and riffles are formed, and deltas are formed at the mouths. Sometimes branches that branch off from a river merge with another river.

Hydrobiological classification

Classification according to the possibility of water sports

According to the International River Difficulty Scale, there are six levels of difficulty.

Classification by tributary network configuration

There are 12 classes of rivers based on the nature of the network of tributaries, determined by the Strahler Number. The headwaters of the rivers according to this system belong to the first class, and the Amazon River to the twelfth.

Use of rivers

Since ancient times, rivers have been used as a source fresh water, for obtaining food (fishing), for transport purposes, as a protective measure, demarcation of territories, as a source of inexhaustible (renewable energy (rotation of machines (for example, a water mill) or hydroelectric turbines), for bathing, irrigation of agricultural land and as a means of disposal from waste.

Rivers have been used for navigation purposes for thousands of years. The earliest evidence of river navigation dates back to the Indus Valley Civilization, which existed in the northwest of modern Pakistan around 3300 BC. The use of river navigation in human economic activities provides cheap (water) transport, and is still widely used on the world's largest rivers, such as the Amazon, Indus, Ganges, Nile and Mississippi (river). The amount of harmful emissions produced by river boats around the world is not clearly regulated or regulated, which contributes to the constant release into the Earth's atmosphere large quantity greenhouse gases, as well as an increase in the incidence of malignant neoplasms in the local population as a result of the constant inhalation of harmful particles emitted into the air by water transport.

Rivers play an important role in determining political boundaries and protecting the country from the invasion of external enemies. For example, the Danube was part of the ancient border of the Roman Empire, and today the river forms much of the border between Bulgaria and Romania. The Mississippi in North America and the Rhine in Europe are the main borders dividing the east and west of countries located on their respective continents. In southern Africa, the Orange and Limpopo rivers form the boundaries between provinces and countries along their routes.

Flood

A flood (or flood) is part of the natural cycle of a river - one of the phases of the river’s water regime, repeating annually in the same season of the year - a relatively long and significant increase in the river’s water content, causing its level to rise. Usually accompanied by the release of water from the low-water channel and flooding of the floodplain.

Flood is a phase of the water regime of a river - a relatively short-term and non-periodic rise in the water level in the river, caused by increased melting of snow, glaciers or an abundance of rain. Unlike a flood, a flood does not recur periodically and can occur at any time of the year. Significant flooding may cause flooding. As the flood moves along the river, a flood wave is formed.

Flood - flooding of an area as a result of rising water levels in rivers, lakes, seas due to rain, rapid snow melting, wind surge of water to the coast and other reasons, which damages people's health and even leads to their death, and also causes material damage . Wind surges of water in sea estuaries and on windy areas of the coast of seas, large lakes, and reservoirs. Possible at any time of the year. They are characterized by a lack of periodicity and a significant rise in water levels.

Much of the process of erosion of river beds and deposition of eroded rocks on the corresponding floodplains occurs during floods. In many developed areas of the world economic activity humans have changed the shape of river beds, influencing the magnitude (intensity) and frequency of floods. Examples of human impacts on the natural state of rivers include the construction (creation) of dams, straightening of riverbeds (construction of canals), and drainage of natural wetlands. In most cases, human mismanagement in floodplains leads to a sharp increase in the risk of floods:

artificially straightening a river bed allows water to flow faster downstream, increasing the risk of flooding in areas downstream;
changing the nature of the river floodplain (straightening) removes natural flood control reservoirs, thereby increasing the risk of floods in the lower reaches of rivers;
creating an artificial embankment or dam can only protect the area downstream of the river (behind the dam), and not those areas that are located upstream;
The presence of a dam, as well as straightening and strengthening of banks (for example, the creation of embankments, etc.) can also increase the risk of flooding in areas located upstream of the river. As a result, there is a difficulty in outflow and an increase in pressure exerted on the downward flow, associated with an obstacle to the normal outflow of water due to the narrowness of the channel enclosed between the reinforced banks.

underground river

Most, but not all rivers flow on the surface of the Earth. Underground rivers flow underground in caves. Rivers of this kind are often found in regions with limestone (karst) deposits in geological formations. In addition, there are caves formed in the body of glaciers by melt water. Such caves are found on many glaciers. Melted glacial waters are absorbed by the body of the glacier along large cracks or at the intersection of cracks, forming passages that are sometimes passable for humans. The length of such caves can be several hundred meters, depth - up to 100 m or more. In 1993, a giant glacial well “Isortog” with a depth of 173 m was discovered and explored in Greenland; the influx of water into it in summer was 30 m3 or more. Due to the presence of a “roof” formed from geological rocks that are impermeable to water (or ice) and high pressure, directed towards the overlying massifs of the glacier, a so-called topographic gradient is created - such streams can even flow uphill. Another type of glacial caves are caves formed in a glacier at the point of release of intraglacial and subglacial waters at the edge of the glaciers. Meltwater in such caves can flow both along the glacier bed and over glacial ice.

Water is usually found in many caves, and karst caves owe their origin to it. In caves you can find condensation films, drops, streams and rivers, lakes and waterfalls. Siphons in caves significantly complicate passage and require special equipment and special training. Underwater caves are often found. In the entrance areas of caves, water is often present in a frozen state, in the form of ice deposits, often very significant and perennial.

Puerto Princesa Underground River is an underground river near the Philippine city of Puerto Princesa, on the island of Palawan (Philippines). This river, about 8 km long, flows underground, in a cave, towards the South China Sea. Created in the area where it is located National Park underground river of the city of Puerto Princesa (Puerto Princesa Subterranean River National Park) - a nature reserve located 50 km from the city. The park is located in the St. Paul Mountain Range in the northern part of the island and is bounded by St. Paul Bay and the Babuyan River. A similar river is known on the Yucatan Peninsula in Mexico, but this one is recognized as the largest. Both underground rivers owe their existence to karst terrain. The water in these rivers changed direction, finding its way down, thanks to the dissolution of carbonate rocks and the formation of a vast underground river system.

The Hamza River (port. Rio Hamza) is the unofficial name for the underground flow under the Amazon. The opening of the “river” was announced in 2011. The unofficial name is given in honor of the Indian scientist Walia Hamza, who spent more than 45 years researching the Amazon.

Largest rivers in the world

The Greatest Rivers of the World

№	Name	Length (km)	Basin area (thousand km²)	Average water flow at the mouth (thousand m³/s)	Highest water flow at the mouth (thousand m³/s)	Solid waste (million tons/year)
1.	Amazon
2.	Nile
3.	Yangtze
4.	Mississippi - Missouri
5.	Yellow River
6.	Ob (with Irtysh)
7.	Parana (from the origins of Paranaiba)
8.	Mekong
9.	Amur (from the sources of Arguni)
10.	Lena
11.	Kongo (with Lualaba)
12.	Mackenzie (from the headwaters of the Peace River)
13.	Niger
14.	Yenisei (from the origins of the Small Yenisei)
15.	Volga
16.	Indus
17.	Yukon
18.	Danube
19.	Orinoco
20.	Ganges (with Brahmaputra)
21.	Zambezi
22.	Murray
23.	Dnieper