The water regime of rivers is characterized by a cumulative change over time in the levels and volumes of water in the river. Water level ( H) - the height of the water surface of the river relative to the constant zero mark (ordinar or zero of the graph of the water meter). Among the fluctuations in water levels in the river, perennial, caused by secular climate changes, and periodic: seasonal and daily, are identified. In the annual cycle of the water regime of rivers, several characteristic periods are distinguished, 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. For example, the rivers of a temperate continental climate (Volga, Ob, etc.) have the following four phases: spring flood, summer low water, autumn water rise, winter low water. High water- a long-term increase in the water content of the river, which is repeated annually in the same season, causing a rise in the level. In temperate latitudes, it occurs in spring due to intense snow melting.

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

Floods- short-term non-periodic rises in water levels and an increase in the volume of water in the river. Unlike floods, they occur in all seasons of the year: in the warm half of the year they are caused by heavy or prolonged rains, in winter - by melting snow during thaws, in the mouths of some rivers - due to the surge of water from the seas where they flow. In temperate latitudes, the autumn rise of water in rivers is sometimes called a flood period; it 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 rainy weather is more common in autumn. Autumn floods on the Neva River in St. Petersburg are caused primarily by the surge of water from the Gulf of Finland by westerly winds; the highest flood of 410 cm occurred in St. Petersburg in 1824. Floods are usually short-lived, the rise in water level is lower, and the volume of water is less than during the flood.

One of the most important hydrological characteristics of rivers is the river runoff, which is formed due to the inflow of surface and ground waters from the catchment area. A number of indicators are used to quantify river runoff. The main one is the flow of water in the river - the amount of water that passes through the cross-section of the river in 1 second. It is calculated by the formula Q=v* ω, where Q- water consumption in m 3 / s, v Is the average river speed in m / s. ω is the area of ​​the free cross-section in m 2. According to the data of daily flow rates, a calendar (chronological) graph of fluctuations in water flow rates, called a hydrograph, is built.

A modification of the discharge is the volume of runoff (W in m 3 or km 3) - the amount of water flowing through the cross-section of the river for a long period (month, season, most often a year): W = Q * T, where T is the period of time. The volume of runoff varies from year to year; the average long-term runoff value is called the runoff rate. For example, the annual flow rate of the Amazon is about 6930 km 3, which is about> 5% of the total annual flow of all rivers in the world, the Volga - 255 km 3. The annual runoff volume is calculated not for a calendar year, but for a hydrological year, within which a full annual hydrological cycle of the water cycle ends. In regions with cold snowy winters, November 1 or October 1 is taken as the beginning of the hydrological year.

Drain module(M, l / s km 2) - the amount of water in liters flowing from 1 km 2 of the pool area (F) per second:

(10 3 is a multiplier for converting m 3 to liters).

The river flow module allows you to find out the degree of water saturation of the basin territory. It is zoned. The largest flow module at the Amazon is 30 641 l / s km 2; on the Volga it is 5670 l / s km 2, and on the Nile - 1010 l / s km 2.

Runoff layer (Y) - water layer (in mm), evenly distributed over the catchment area ( F) and flowing from it for certain time(annual runoff layer).

Runoff coefficient (TO) Is the ratio of the volume of water flow in the river ( W) to the amount of precipitation ( NS) falling on the basin area ( F) for the same time, or the ratio of the runoff layer ( Y) to the precipitation layer ( NS) that fell on the same area ( F) for the same period of time (the value is immeasurable or expressed in%):

K = W / (x * F) * 100%, or K = Y / x*100%.

The average runoff coefficient of all rivers on Earth is 34%. that is, only one third of the precipitation that falls on land flows into rivers. The runoff coefficient is zoned and varies from 75-65% in tundra and taiga zones to 6-4% in semi-deserts and deserts. For example, on the Neva it is 65%, and on the Nile - 4%.

The concept of flow regulation is associated with the water regime of rivers: the smaller the annual amplitude of water discharge in the river and the water levels in it, the more regulated the flow.

Rivers are the most mobile part of the hydrosphere. Their drain is an integral characteristic water balance land area.

The amount of river flow and its distribution throughout the year is influenced by a complex of natural factors and economic activity person. Among the natural conditions, the main one is the climate, especially precipitation and evaporation. With abundant precipitation, the river runoff is large, but it is necessary to take into account their type and nature of precipitation. For example, snow will produce more runoff than rain because there is less evaporation in winter. Heavy rainfall increases the runoff compared to overburden, with the same amount. Evaporation, especially intense evaporation, reduces runoff. In addition to high temperature, it is promoted by wind and lack of air humidity. The statement of the Russian climatologist A. I. Voeikov is true: “Rivers are a product of climate”.

Soils affect runoff through infiltration and structure. Clay increases surface runoff, sand reduces it, but increases underground runoff, being a moisture regulator. The strong granular structure of soils (for example, in chernozems) facilitates the penetration of water into the depths, and a crust often forms on unstructured sprayed loamy soils, which increases surface runoff.

The geological structure of the river basin is very important, especially the material composition of the rocks and the nature of their occurrence, since they determine the underground feeding of the rivers. Permeable rocks (thick sands, fractured rocks) serve as accumulators of moisture. The river runoff in such cases is greater, since a smaller proportion of precipitation is spent on evaporation. The runoff in the karst areas is peculiar: there are almost no rivers there, since the sediments are absorbed by funnels and cracks, but at their contact with clays or clay shales, powerful springs are observed that feed the rivers. For example, the karst Crimean Yaila itself is dry, but powerful springs gush at the foot of the mountains.

The influence of the relief (absolute height and slopes of the surface, density and depth of dissection) is large and varied. The runoff of mountain rivers is usually greater than that of flat rivers, since precipitation is more abundant in the mountains on the windward slopes, evaporation is less due to the lower temperature, due to the large slopes of the surface, the path and time for the precipitation to reach the river are shorter. Due to the deep erosional incision, there is more abundant underground recharge from several aquifers at once.

The influence of vegetation - different types of forests, meadows, crops, etc. - is ambiguous. In general, vegetation regulates runoff. For example, a forest, on the one hand, enhances transpiration, delays precipitation with tree crowns (especially coniferous forests, snow in winter), on the other hand, more precipitation usually falls over the forest, the temperature is lower under the canopy of trees and less evaporation, longer snow melting, better seepage of precipitation in forest floor. It is very difficult to reveal the influence of different types of vegetation in its pure form due to the joint compensating effect different factors especially within large river basins.

The influence of the lakes is unambiguous: they reduce the flow of rivers, since there is more evaporation from the water surface. However, lakes, like swamps, are powerful natural flow regulators.

The impact of economic activities on runoff is very significant. Moreover, a person influences both directly the flow (its size and distribution in a year, especially during the construction of reservoirs), and the conditions for its formation. When creating reservoirs, the regime of the river changes: during a period of excess water, they are accumulated in reservoirs, during a period of shortage, they are used for various needs, so that the flow of rivers is regulated. In addition, the runoff of such rivers generally decreases, because evaporation from the water surface increases, a significant part of the water is spent on water supply, irrigation, watering, and underground recharge decreases. But these inevitable costs are more than offset by the benefits of reservoirs.

When water is transferred from one river system to another, the runoff changes: in one river it decreases, in another it increases. For example, during the construction of the Moscow Canal (1937) in the Volga it decreased, in the Moscow River it increased. Other transport channels for the transfer of water are usually not used, for example Volga-Baltic, White Sea-Baltic, numerous channels Western Europe, China, etc.

Measures carried out in the river basin are of great importance for the regulation of river runoff, since its initial link is the slope runoff in the catchment. The main activities are as follows. Agroforestry - forest plantations, irrigation - dams and ponds in gullies and on streams, agronomic - autumn plowing, snow accumulation and snow retention, plowing across the slope or contouring on hills and ridges, tinning of slopes, etc.

In addition to the intra-annual variability of the runoff, its long-term fluctuations occur, apparently associated with 11-year cycles of solar activity. On most rivers, high-water and low-water periods of about 7 years are clearly traced: for 7 years, the river's water content exceeds the average values, floods and low-water periods are high, the same number of years the river's water content is less than the average annual values, and water discharge in all phases of the water regime is low.

Literature.

1. Lyubushkina S.G. General geography: Textbook. manual for university students enrolled in special. "Geography" / S.G. Lyubushkina, K.V. Pashkang, A.V. Chernov; Ed. A.V. Chernov. - M.: Education, 2004 .-- 288 p.

Intra-annual runoff distribution

Systematic ( daily) observations of water levels were started in our country about 100 years back. Initially, they were conducted in a small number of locations. At present, we have data on the river flow by 4000 hydrological posts. These materials are unique in nature, allowing you to trace changes in runoff over a long-term period, are widely used in calculating water resources, as well as in the design and construction of hydraulic and other industrial facilities on rivers, lakes and reservoirs. To solve practical issues, it is necessary to have observational data for hydrological phenomena for periods of time from 10 before 50 years and more.

Hydrological stations and posts located on the territory of our country form the so-called state hydrometeorological network. It is run by Roskomhydromet and is designed to meet the needs of all industries. National economy according to data on the regime of water bodies. For the purpose of systematization, observation materials at posts are published in official reference publications.

For the first time, hydrological observation data were summarized in the State Water Cadastre USSR (GVK)... It included guides to water resources the USSR (regional, 18 volumes), information on water levels in rivers and lakes the USSR(1881-1935, 26 volumes), materials on the regime of rivers ( 1875-1935, 7 volumes). WITH 1936 g. materials of hydrological observations began to be published in Hydrological Yearbooks. Currently, there is a unified national system for accounting for all types of natural waters and their use on the territory of the Russian Federation.

Primary processing of data on daily water levels given in Hydrological Yearbooks consists in analyzing the intra-annual distribution of runoff and plotting water level fluctuations over the year.

The nature of the change in runoff during the year and the regime of water levels caused by these changes mainly depend on the conditions for feeding the river with water. According to the classification of B.D. Zaykova rivers are subdivided into three groups:

With spring floods resulting from melting snow on the plains and not high mountains;

With high water in the warmest part of the year, arising from the melting of seasonal and eternal mountain snows and glaciers;

With rain floods.

The most common are rivers with spring floods. For this group, the following phases of the water regime are characteristic: spring flood, summer low water, autumn water rise, winter low water.

During the period spring flood in the rivers of the first group, due to snow melting, the water discharge significantly increases, and its level rises. The amplitude of fluctuations in water levels and the duration of floods in the rivers of this group differ depending on the underlying surface factors and factors of a zonal nature. For example, the Eastern European type of intra-annual runoff distribution has a very high and sharp spring flood and low water discharges during the rest of the year. This is due to the insignificant amount of summer precipitation and strong evaporation from the surface of the steppe basins of the Southern Trans-Volga region.

Western European type distribution is characterized by a low and extended spring flood, which is a consequence of the flat relief and strong swampiness of the West Siberian lowland. The presence of lakes, marshes and vegetation within the catchment area leads to an even flow throughout the year. This group also includes the East Siberian type of runoff distribution. It is characterized by relatively high spring floods, rain floods in the summer-autumn period, and extremely low winter low-water periods. Due to this influence permafrost on the nature of the river's feeding.

The amplitude of fluctuations in water levels near medium and large rivers in Russia is quite significant. She reaches 18 m on the upper Oka and 20 m on the Yenisei. With such fillings of the channel, vast areas of river valleys are flooded.

The period of standing of low levels, changing little in time during the summer, is called the period summer low water, when the main source of water for rivers is groundwater.

In the autumn period, the surface runoff increases due to autumn rains, which leads to rising water and education summer-autumn rain flood. The decrease in evaporation during this period of time also contributes to the increase in runoff in autumn.

Phase winter low water in the river begins with the appearance of ice and ends with the beginning of the rise in water levels from spring snowmelt. During the winter low-water period, a very small runoff is observed in the rivers, since from the moment of the onset of stable negative temperatures, the river is fed only by groundwater.

The rivers of the second group stand out Far Eastern and Tien Shan types of intra-annual runoff distribution. The first of them has a low, highly extended, comb-like flood in the summer-autumn period and a low runoff in the cold part of the year. The Tien Shan type is distinguished by a lower amplitude of the flood wave and a secure runoff in the cold part of the year.

The rivers of the third group ( Black Sea type) rain floods are distributed evenly throughout the year. The amplitude of fluctuations in water levels is greatly smoothed out in rivers flowing from lakes. In these rivers, the boundary between high water and low water is hardly noticeable and the volume of runoff during high water is comparable to the volume of runoff during low water. All other rivers pass the main part of the annual runoff during floods.

The results of observations over the levels for a calendar year are presented in the form level fluctuation graph(fig. 3.5). In addition to the course of levels, the graphs show the phases of the ice regime with special symbols: autumn drift, freeze-up, spring drift, and also show the values ​​of the maximum and minimum navigational water levels.

Typically, the graphs of fluctuations in water levels at a hydrological station are combined for 3-5 years in one drawing. This makes it possible to analyze the river regime for low-water and high-water years and to trace the dynamics of the onset of the corresponding phases of the hydrological cycle for a given period of time.

River- a natural water flow constantly flowing in a depression (bed) formed by it.
In each river, a source, upper, middle, lower reaches and mouth are distinguished. Source- the beginning of the river. Rivers begin at the confluence of streams arising in places where groundwater flows out or collecting water from atmospheric precipitation that has fallen to the surface. They flow out of swamps (for example, the Volga), lakes and glaciers, feeding on the water accumulated in them. In most cases, the source of the river can be determined only conditionally.
Its upper course begins from the source of the river.
V upper In the course of the river flow, there is usually less abundant water than in the middle and lower reaches, the slope of the surface, on the contrary, is greater, and this is reflected in the speed of the current and on the erosion activity of the flow. V average In the course of the river, the river becomes abundant, but the speed of the current decreases, and the stream carries mainly the products of the erosion of the channel in the upper course. V lower during the slow movement of the flow, the deposition of sediments brought by it from above (accumulation) prevails. The lower course of the river ends with the mouth.
Estuary rivers - the place where it flows into the sea, lake, into another river. In a dry climate, where rivers consume a lot of water (for evaporation, irrigation, filtration), they can gradually dry up without bringing their waters to the sea or to another river. The mouths of such rivers are called "blind". All rivers flowing through a particular territory form it river network entering together with lakes, swamps and glaciers into hydrographic network.
The river network consists of river systems.
The river system includes the main river (which name it bears) and tributaries. In many river systems, the main river is clearly distinguished only in the lower reaches, in the middle and especially in the upper reaches it is very difficult to determine it. Length, water content, axial position in the river system, relative age of the river valley (the valley is older than that of the tributaries) can be taken as signs of the main river. The main rivers of most large river systems do not meet all these characteristics at once, for example: The Missouri is longer and fuller than the Mississippi; The Kama brings no less water to the Volga than the Volga carries at the mouth of the Kama; The Irtysh is longer than the Ob and its position is more consistent with the position of the main river of the river system. Historically, the main river of the river system was the one that people knew earlier and better than other rivers of this system.
The tributaries of the main river are called tributaries of the first order, their tributaries are called tributaries of the second order, etc.

The river system is characterized by the length of its constituent rivers, their tortuosity and the density of the river network. Length of rivers- the total length of all rivers in the system, measured on a large-scale map. The degree of tortuosity of the river is determined tortuosity coefficient(Fig. 87) - the ratio of the length of the river to the length of the straight line connecting the source and the mouth. River network density- the ratio of the total length of all rivers of the considered river network to the area it occupies (km / km2). On the map, even on a not very large scale, it can be seen that the density of the river network in various natural areas is not the same.
In the mountains, the density of the river network is greater than on the plains, for example: on the northern slopes of the Caucasian ridge it is 1.49 km / km2, and on the plains of the Ciscaucasia - 0.05 km / km2.
The area of ​​the surface from which water flows into the same river system is called the basin of this river system or its catchment. The basin of the river system consists of the basins of the tributaries of the first order, which in turn consist of the basins of the tributaries of the second order, etc. River basins are included in the basins of the seas and oceans. All land waters are divided between the main basins: 1) the Atlantic and Arctic oceans (area 67 359 thousand km2), 2) the Pacific and Indian oceans (area 49 419 thousand km2), 3) the area of ​​internal flow (area 32 035 thousand km2) km2).
River basins come in various sizes and shapes. There are symmetric basins (for example, the Volga basin) and asymmetric (for example, the Yenisei basin).
The size and shape of the basin largely determines the size and flow regime of the river. The position of the river basin is also important, which can be located in different climatic zones and can stretch in the latitudinal direction within the same zone.
Pools are bounded by watersheds. In mountainous countries, they can be lines that generally coincide with the crests of ridges. On plains, especially flat and swampy, watersheds are not clearly expressed.
In some places, watersheds cannot be drawn at all, since the mass of water of one river is divided into two parts, heading to different systems... This phenomenon is called bifurcation of the river (dividing it into two). A striking example of bifurcation is the division of the upper reaches of the Orinoco into two rivers. One of them, which retains the name Orinoco, flows into Atlantic Ocean, the other, the Casiquiare, flows into the Rio Negro, a tributary of the Amazon.
Watersheds limit the basins of rivers, seas, oceans. The main basins: the Atlantic and Arctic Ocean (Atlantic-Arctic), on the one hand, and the Pacific and Indian, on the other, are limited by the main (world) watershed of the Earth.
The position of the watersheds does not remain constant. Their movements are associated with the slow incision of the upper reaches of the rivers as a result of the development of river systems and with the restructuring of the river network, caused, for example, by tectonic movements of the earth's crust.
Riverbed. Water streams flow along the earth's surface in longitudinal depressions created by them - channels. There can be no river without a channel. The concept of "river" includes both a stream and a channel. In most rivers, the channel is cut into the surface along which the river flows. But there are many rivers, the channels of which rise above the plain they cross. These rivers have laid their channels in the sediments deposited by them. An example would be the Yellow River, Mississippi and Po rivers downstream. Such channels are easy to move, their lateral wall breaks often occur, threatening floods.
The cross section of a channel filled with water is called the water section of a river. If the entire water section is a section of a moving stream, it coincides with the so-called living section. If in the water section there are fixed sections (with a speed of movement not captured by the devices), they are called dead space. In this case, the free area will be less than the water one by the value equal area dead space. The channel cross-section is characterized by area, hydraulic radius, width, average and maximum depth.
The cross-sectional area (F) is determined as a result of depth measurements over the entire cross-section at certain intervals, taken depending on the width of the river. According to V.A. Appolov, the area of ​​the free cross-section is related to the width (B) and the greatest depth (H) by the equation: F = 2 / 3BH.
Hydraulic radius (R) is the ratio of the cross-sectional area to the wetted perimeter (P), i.e., to the length, of the line of contact of the flow with its bed:

The hydraulic radius characterizes the cross-sectional shape of the channel, as it depends on the ratio of its width and depth. In shallow and wide rivers, the wetted perimeter is almost equal to the width; in this case, the hydraulic radius is almost equal to the average depth.
The average depth (Hcp) of the cross-section of the river is determined by dividing its area by the width (B): Hcp = S / B. Width and maximum depth are obtained by direct measurements.
All cross-sectional elements change along with the change in the position of the river level. The level of the river is subject to constant fluctuations, which are systematically monitored at special gauging stations.
The longitudinal profile of the river bed is characterized by a dip and a slope. Fall (Δh) - difference in heights of two points (h1-h2). The ratio of the fall to the length of the section (l) is called the slope (i):

The fall is expressed in meters, the slope is shown as a decimal fraction - in meters per kilometer of fall, or in thousandths (ppm - ‰).
The rivers of the plains have small slopes, the slopes of the mountain rivers are significant.
The greater the slope, the faster flow rivers (Table 23).

The longitudinal profile of the channel bottom and the longitudinal profile of the water surface are different: the first is always a wavy line, the second is a smooth line (Fig. 88).
River flow speed. The water flow is characterized by turbulent motion. Its speed at each point is continuously changing both in magnitude and in direction. This ensures constant mixing of the water and promotes erosion activity.
The speed of the river flow is not the same in different parts of the living section. Numerous measurements show that the highest speed is usually observed near the surface. As one approaches the bottom and the walls of the channel, the current velocity gradually decreases, and in the bottom layer of water, only a few tens of millimeters thick, it sharply decreases, reaching a value close to 0 at the very bottom.
Distribution lines equal speeds along the living section of the river - isotachs. The wind blowing with the current increases the speed on the surface; the wind blowing against the current slows it down. Slows down the speed of water movement on the surface and the ice cover of the river. The jet in the flow with the highest speed is called its dynamic axis, the jet of the highest speed on the surface of the flow is called the rod. Under some conditions, for example, when the wind is passing the current, the dynamic axis of the flow is on the surface and coincides with the rod.
The average speed in the living area (Vav) is calculated by the Shezy formula: V = C √Ri, where R is the hydraulic radius, i is the slope of the water surface at the observation site, C is a coefficient depending on the roughness and shape of the channel (the latter is determined using special tables).

The nature of the flow. Particles of water in the stream move under the action of gravity along the slope. Their movement is delayed by the friction force. In addition to gravity and friction, the nature of the flow is influenced by centrifugal force, arising at bends of the channel, and the deflecting force of the Earth's rotation. These forces cause cross and circular flow in the flow.
Under the action of centrifugal force at the bend, the stream is pressed against the concave bank. In this case, the greater the speed of the current, the greater the force of inertia that prevents the flow from changing the direction of movement and deviating from the concave coast. The current velocity at the bottom is less than on the surface, therefore the deviation of the bottom layers towards the coast opposite to the concave one is greater than surface layers... This contributes to the occurrence of a current across the channel. As the water is pressed against the concave bank, the surface of the stream receives a transverse slope from the concave to the convex bank. However, the movement of water on the surface along the slope from one bank to another does not occur. This is prevented by the centrifugal force, which forces water particles, overcoming the slope, to move towards the concave coast. In the bottom layers, due to the lower current velocity, the influence of the centrifugal force is less pronounced, and therefore the water moves in accordance with the slope from the concave to the convex bank. Particles of water moving across a river are simultaneously related downstream, and their trajectory resembles a spiral.
The deflecting force of the Earth's rotation forces the stream to press against the right bank (in the northern hemisphere), which is why its surface (as well as at a turn under the influence of centrifugal force) acquires a transverse slope. The slope and varying degrees of force on the water particles at the surface and at the bottom cause an internal counter-current flowing clockwise (in the northern hemisphere) when viewed downstream. Since this movement is also combined with the translational movement of particles, they move along the channel in a spiral.
On a straight section of the channel, where there are no centrifugal forces, the nature of the cross-flow is determined mainly by the action of the deflecting force of the Earth's rotation. At bends in the channel, the deflecting force of the Earth's rotation and the centrifugal force are either added or subtracted depending on where the river turns, and the lateral circulation is increased or decreased.
Cross-circulation can also occur under the influence of different temperatures (unequal density) of water in different parts of the cross-section, under the influence of the bottom topography and other reasons. Therefore, it is complex and varied. The influence of transverse circulation on channel formation, as we will see below, is very large.
River runoff and its characteristics. The amount of water passing through the flow area of ​​the river in 1 second is its consumption. The flow rate (Q) is equal to the product of the free area (F) and the average speed (Vcp): Q = FVcp m3 / sec.
Water flows in rivers are highly variable. They are more stable on rivers regulated by lakes and reservoirs. On rivers of the temperate zone, the highest water discharge occurs during the spring flood, the lowest - in the summer months. According to the data of daily expenditures, graphs of changes in expenditure are plotted - hydrographs.
The amount of water passing through the living section of the river for a more or less long time is the flow of the river. The runoff is determined by summing up the water consumption for the period of interest (day, month, season, year). The flow volume is expressed in either cubic meters or cubic kilometers. Calculation of the runoff over a number of years makes it possible to obtain its average long-term value (Table 24).

The flow of water is characterized by the water content of the river. River flow depends on the amount of water entering the river from the area of ​​its basin. To characterize the runoff, in addition to the flow rate, the runoff module, runoff layer, runoff coefficient are used.
Drain module(M) - the number of liters of water flowing down from a unit of pool area (1 sq. Km) per unit of time (in seconds). If the average flow rate in the river for a certain period of time is Q m3 / sec, and the area of ​​the basin is F sq. km, then the average runoff module for the same period of time is M = 1000 l / s * km2 (the factor 1000 is necessary, since Q is expressed in cubic meters, and M - in l). M Neva - 10 l / sec, Don - 9 l / sec, Amazon - 17 l / sec.
Runoff layer- a layer of water in millimeters that would cover the catchment area with an even distribution of the entire volume of runoff over it.
Runoff coefficient(h) - the ratio of the runoff layer to the amount of precipitation that fell on the same area over the same period of time, expressed as a percentage or in fractions of a unit, for example: the runoff coefficient of the Neva - 65%, the Don - 16%, the Nile - 4% , Amazon - 28%.
The runoff depends on the whole complex of physical and geographical conditions: on climate, soil, geological structure of the zone, active water exchange, vegetation, lakes and swamps, as well as on human activities.
Climate refers to the main factors in the formation of runoff. It determines the amount of moisture, which depends on the amount of precipitation (the main element of the input part of the water balance) and on evaporation (the main indicator of the expenditure part of the balance). The greater the amount of precipitation and the lower the evaporation, the higher the moisture should be and the more significant the runoff can be. Precipitation and volatility determine the potential for runoff. The actual flow depends on the whole complex of conditions.
The climate affects the runoff not only directly (through precipitation and evaporation), but also through other components of the geographic complex - through soils, vegetation, relief, which to one degree or another depend on the climate. The influence of climate on runoff, both directly and through other factors, manifests itself in zonal differences in the magnitude and nature of runoff. The deviation of the values ​​of the actually observed runoff from the zonal one is caused by local, intrazonal physical and geographical conditions.
A very important place among the factors determining the river runoff, its surface and underground components, is occupied by the soil cover, which plays the role of an intermediary between climate and runoff. The value of surface runoff, water consumption for evaporation, transpiration and recharge of groundwater depend on the properties of the soil cover. If the soil weakly absorbs water, the surface runoff is large, little moisture accumulates in the soil, the consumption for evaporation and transpiration cannot be large, and there is little groundwater supply. Under the same climatic conditions, but with a greater infiltration capacity of the soil, the surface runoff, on the contrary, is small, a lot of moisture accumulates in the soil, the consumption for evaporation and transpiration is large, and the supply of groundwater is abundant. In the second of the two described cases, the surface runoff is less than in the first, but due to underground recharge it is more uniform. Soil, absorbing water from atmospheric precipitation, can retain it and let it go deep beyond the zone available for evaporation. The ratio of water consumption for evaporation from the soil and for recharge of groundwater depends on the water-holding capacity of the soil. Soil, which holds water well, uses more water for evaporation and passes less water into the depths. As a result of waterlogging of the soil, which has a high water-holding capacity, the surface runoff increases. Soil properties are combined in different ways and this is reflected in the runoff.
Influence geological structure on river runoff is determined mainly by the water permeability of rocks and is generally similar to the effect of soil cover. The occurrence of waterproof layers in relation to the day surface is also important. The deep bedding of the seals contributes to the preservation of the infiltrated water from being consumed for evaporation. The geological structure influences the degree of flow regulation, the conditions of groundwater recharge.
The influence of geological factors least of all others depends on zonal conditions and in some cases overrides the influence of zonal factors.
Vegetation affects the amount of runoff both directly and through the soil cover. Its immediate effect is transpiration. River runoff depends on transpiration in the same way as it does on soil evaporation. The more transpiration, the less both components of the river flow. The crowns of trees retain up to 50% of the precipitation, which then evaporate from them. In winter, the forest protects the soil from freezing, in the spring it moderates the intensity of snow melting, which contributes to seepage melt water and replenishment of groundwater reserves. The influence of vegetation on runoff through the soil is due to the fact that vegetation is one of the factors of soil formation. Infiltration and water retention properties largely depend on the nature of vegetation. The infiltration capacity of the soil in the forest is extremely high.
The runoff in the forest and in the field generally differs little, but its structure is significantly different. In the forest, there is less surface runoff and more reserves of soil and groundwater (underground runoff), which are more valuable for the economy.
In the forest, a zonal regularity is found in the ratios between the components of the runoff (surface and underground). In the forests of the forest zone, the surface runoff is significant (higher moisture content), although less than in the field. In the forest-steppe and steppe zones in the forest, there is practically no surface runoff, and all the water assimilated by the soil is spent on evaporation and feeding of groundwater. In general, the influence of the forest on the runoff is water-regulating and water-protecting.
Relief affects the drain differently depending on the size of the molds. The influence of the mountains is especially great. The whole complex of physical and geographical conditions (altitudinal zonality) changes with height. In this regard, the runoff also changes. Since the change in the complex of conditions with height can occur very quickly, the overall picture of the formation of runoff in high mountains becomes more complicated. With altitude, the amount of precipitation increases to a certain limit, and the runoff generally increases. The increase in runoff on windward slopes is especially noticeable, for example, the runoff modulus on the western slopes of the Scandinavian mountains is 200 l / s * km2. In the inner, parts of the mountainous regions, the runoff is less than in the re-riper regions. The relief is of great importance for the formation of runoff in connection with the distribution of the snow cover. Significantly affects runoff and microrelief. Shallow depressions in the relief, in which water collects, contribute to its infiltration and evaporation.
The slope of the terrain and the steepness of the slopes affect the intensity of the runoff, its fluctuations, but do not significantly affect the amount of runoff.
Lakes by evaporating the water accumulating in them, they reduce the runoff and at the same time are its regulators. The role of large flowing lakes is especially great in this respect. The amount of water in the rivers flowing from such lakes hardly changes during the year. For example, the discharge of the Neva is 1000-5000 m3 / s, while the discharge of the Volga near Yaroslavl before its regulation fluctuated during the year from 200 to 11,000 m3 / s.
Has a strong effect on runoff economic activity people, making big changes in natural complexes. The impact of people on the soil cover is also of great importance. The more plowed areas, the more atmospheric precipitation seeps into the soil, moistens the soil and nourishes the groundwater, the smaller part of it flows down the surface. Primitive agriculture causes destructuring of soils, a decrease in their ability to assimilate moisture, and, consequently, an increase in surface runoff and a weakening of the underground soils. With rational farming, the infiltration capacity of soils increases with all the ensuing consequences.
Snow retention measures aimed at increasing the moisture entering the soil affect the runoff.
Artificial reservoirs have a regulating effect on the river runoff. Reduces runoff water consumption for irrigation and water supply.
Forecasting the water content and regime of rivers is important for planning the use of the country's water resources. In Russia, a special forecasting method has been developed, based on the experimental study of various methods of economic impact on the elements of the water balance.
The distribution of runoff in the territory can be shown using special maps, on which the isolines of runoff values ​​are plotted - modules or annual runoff. The map shows the manifestation of latitudinal zoning in the distribution of runoff, which is especially pronounced on the plains. The influence of the relief on the runoff is also clearly revealed.
Rivers feeding. There are four main sources of river power: rain, snow, glacial, underground. The role of this or that power source, their combination and distribution in time depend mainly on climatic conditions. For example, in countries with hot climates, snow supply is absent, rivers and deep-lying groundwater do not feed, and the only source of food is rainwater. In cold climates, melt water is of primary importance in the feeding of rivers, and groundwater in winter. In temperate climates, various food sources are combined (Fig. 89).

Depending on the nutrition, the amount of water in the river changes. These changes are manifested in fluctuations in the level of the river (the height of the water surface). Systematic observations of the level of rivers make it possible to find out the patterns in the changes in the amount of water in the rivers over time, their regime.
In the regime of rivers of a temperate cold climate, in the feeding of which important role melted snow waters play, four phases, or hydrological seasons, are clearly distinguished: spring flood, summer low water, autumn floods and winter low water. High water, high water, and low water are characteristic of the regime of rivers that are in other climatic conditions.
High water is a relatively long and significant increase in the amount of water in the river, which is repeated annually in the same season, accompanied by a rise in the level. It is caused by the spring melting of snow on the plains, the summer melting of snow and ice in the mountains, and heavy rains.
The onset and duration of floods are different in different conditions. High water caused by melting snow on the plains in temperate climates occurs in spring, in cold climates - in summer, in the mountains stretches into spring and summer. Floods caused by rains in monsoon climates include spring and summer, in equatorial climates they occur in autumn, and in Mediterranean climates they occur in winter. The runoff of some rivers during the flood period is up to 90% of the annual runoff.
Low water is the lowest water standing in the river with a predominance of underground recharge. Summer low water occurs as a result of high infiltration capacity of soils and strong evaporation, winter - as a result of lack of surface nutrition.
Floods are relatively short-term and non-periodic rises in the water level in the river, caused by the influx of rain and melt water into the river, as well as by the passage of water from reservoirs. The height of the flood depends on the intensity of rain or snowmelt. The flood can be seen as a wave caused by fast admission water into the channel.
A.I. Voeikov, who considered rivers as a “product of the climate” of their basins, created in 1884 a classification of rivers according to their feeding conditions.
The ideas underlying the Voeikov river classification were taken into account in a number of classifications. The most complete and precise classification was developed by M.I. Lvovich. Lvovich classifies rivers depending on the source of supply and on the nature of the distribution of flow throughout the year. Each of the four sources of food (rain, snow, glacial, underground) under certain conditions can be almost the only (almost exclusive), accounting for more than 80% of the total food supply, can have a predominant value in the river feeding (from 50 to 80%) and can prevail (> 50%) among other sources that also play a significant role in it. In the latter case, the river's feeding is called mixed.
The runoff is spring, summer, autumn and winter. At the same time, it can be concentrated almost exclusively (> 80%) or predominantly (from 50 to 80%) in one of the four seasons, or it can occur at all seasons, dominating (> 50%) in one of them.
Natural combinations of various combinations of power sources with different variants of runoff distribution throughout the year allowed Lvovich to identify the types of river water regime. Based on the main regularities of the water regime, its main zonal types are distinguished: polar, subarctic, temperate, subtropical, tropical and equatorial.
Rivers of the polar type are fed by melt water for a short period polar ice and snow, but they freeze over most of the year. Rivers of the subarctic type are fed by melted snow waters, their underground supply is very insignificant. Many, even significant rivers freeze over. Highest level these rivers have summer (summer flood). The reason is late spring and summer rains.
Rivers of the temperate type are divided into four subtypes: 1) with a predominance of feeding due to the spring melting of the snow cover; 2) with a predominance of rainwater supply with a small runoff in spring, both due to the abundance of rains and under the influence of snow melting; 3) with a predominance of rainfall in winter with a more or less uniform distribution of precipitation throughout the year; 4) with a predominance of rainfall in summer due to heavy monsoon rains.
Rivers of the subtropical type are fed mainly by rainwater in winter.
Rivers of the tropical type are characterized by low runoff. Summer rainfall predominates, with little precipitation in winter.
Rivers of the equatorial type have abundant rainfall throughout the year; the largest runoff occurs in the fall of the corresponding hemisphere.
The rivers of mountainous regions are characterized by regularities of vertical zonation.
Thermal regime of rivers. The thermal regime of the river is determined by the absorption of heat from direct solar radiation, the effective radiation of the water surface, the cost of heat for evaporation and its release during condensation, heat exchange with the atmosphere and the bed of the channel. The water temperature and its changes depend on the ratio of the incoming and outgoing parts of the heat balance.
In accordance with the thermal regime of rivers, they can be divided into three types: 1) rivers are very warm, without seasonal temperature fluctuations; 2) rivers are warm, with noticeable seasonal temperature fluctuations, not freezing in winter; 3) rivers with large seasonal temperature fluctuations, freezing in winter.
Since the thermal regime of rivers is primarily determined by the climate, large rivers flowing through different climatic regions have a different regime in different parts. Rivers of temperate latitudes have the most difficult thermal regime. In winter, when the water cools slightly below its freezing point, the process of ice formation begins. In a calmly flowing river, first of all, there are banks. Simultaneously with them or somewhat later, a thin layer of small ice crystals - lard - forms on the surface of the water. The fat and the banks freeze into the continuous ice cover of the river.
With the rapid movement of water, the freezing process is delayed by its stirring and the water can be supercooled by a few hundredths of a degree. In this case, ice crystals appear in the entire water column and intra-water and bottom ice is formed. Intra-bottom and bottom ice that has surfaced on the surface of the river is called sludge. Sludge accumulates under the ice and creates gaps. Sludge, fat, wet snow, broken ice floating on the river form an autumn ice drift. At the bends of the river, in the narrowing of the channel during ice drift, there are jams. The establishment of a continuous, stable ice cover on a river is called freeze-up. Small rivers freeze like poison earlier than large ones. The ice cover and the snow falling on it protect the water from further cooling. If heat loss continues, ice builds up from below. Since, as a result of freezing of water, the cross section of the river decreases, water under pressure can pour out onto the surface of the ice and freeze, increasing its capacity. The thickness of the ice cover on the flat rivers of Russia is from 0.25 to 1.5 m and more.
The freezing time of rivers and the length of the period during which the ice cover remains on the river are very different: Lena is covered with ice on average 270 days a year, Mezen - 200, Oka - 139, Dnieper - 98, Vistula near Warsaw - 60, Elbe near Hamburg - 39 days and even then not annually.
Under the influence of abundant groundwater outflows or as a result of the inflow of warmer lake water, ice holes can persist on some rivers throughout the winter (for example, on the Angara).
The opening of rivers begins near the banks under the influence of solar heat of the atmosphere and melt water entering the river. The influx of melt water causes the level to rise, the ice floats up, breaking away from the banks, and a strip of water without ice stretches along the banks - the rims. The entire mass of ice begins to move downstream and stops: first, the so-called ice movements occur, and then the spring ice drift begins. On rivers flowing from north to south, ice drift is more calm than on rivers flowing from south to north. In the latter case, the penetration begins from the upper reaches, while the middle and lower reaches of the river are ice-bound. A wave of spring floods moves down the river, with congestions formed, water level rises occur, ice, not yet starting to melt, breaks up and is thrown onto the shore, powerful ice drifts are created that destroy the banks.
On the rivers flowing from the lakes, two spring ice drifts are often observed: first there is river ice, then lake ice.
River water chemistry. River water is a solution with a very low salt concentration. The chemical characteristics of the water in the river depend on the sources of nutrition and on the hydrological regime. According to the dissolved minerals (according to the equivalent predominance of the main anions), river waters are divided (according to A.O. Alekin) into three classes: hydrocarbonate (CO3), sulfate (SO4) and chloride (Cl). The classes, in turn, are divided by the predominance of one of the cations (Ca, Mg or the sum of Na + K) into three groups. In each group, three types of waters are distinguished according to the ratio between total hardness and alkalinity. Most of the rivers belong to the hydrocarbonate class, to the group of calcium waters. Hydrocarbonate waters of the sodium group are rare, in Russia mainly in Central Asia and Siberia. Among carbonate waters, weakly mineralized waters (less than 200 mg / l) prevail, waters of medium mineralization (200-500 mg / l) are less common - in middle lane The European part of Russia, the South Caucasus and partly in Central Asia. Highly mineralized hydrocarbonate waters (> 1000 mg / l) are very rare. Rivers of the sulfate class are relatively rare. As an example, we can cite the rivers of the Azov region, some rivers North Caucasus, Kazakhstan and Central Asia. Chloride rivers are even less common. They flow in the space between the lower reaches of the Volga and the upper reaches of the Ob. The waters of rivers of this class are highly mineralized, for example, in the river. Turgai water mineralization reaches 19000 mg / l.
During the year due to changes in river flow chemical composition water changes so much that some rivers "pass" from one hydrochemical class to another (for example, the Tejen river belongs to the sulfate class in winter, and to the hydrocarbonate class in summer).
In areas of excessive moisture, the salinity of river waters is insignificant (for example, Pechora - 40 mg / l), in areas of insufficient moisture - high (for example, Emba - 1641 mg / l, Kalaus - 7904 mg / l). When passing from the zone of excess to the zone of insufficient moisture, the composition of salts changes, the amount of chlorine and sodium increases.
Thus, Chemical properties river waters show zonal character. The presence of readily soluble rocks (limestone, salt, gypsum) can lead to significant local features in the salinity of river water.
The amount of dissolved substances carried in 1 second through the flow area of ​​the river is the consumption of dissolved substances. The flow of dissolved substances, measured in tons (Table 25), is formed from the sum of expenditures.

The total amount of dissolved substances carried out by rivers from the territory of Russia is about 335 * 10-6 tons per year. About 73.7% of dissolved substances are carried out into the Ocean and about 26.3% - into the water bodies of the area of ​​internal flow.
Solid runoff. The solid mineral particles carried by the river flow are called river sediments. They are formed due to the drift of rock particles from the surface of the basin and erosion of the channel. Their number depends on the energy of the moving water and on the resistance of the rocks to erosion.
River sediments are divided into suspended and transported, or bottom. This division is arbitrary, since with a change in the speed of the current, one category of sediment quickly passes into another. The higher the flow rate, the larger the suspended particles can be. With a decrease in speed, larger particles sink to the bottom, becoming entrained (moving abruptly) sediments.
The amount of suspended sediment carried by the flow through the cross-section of the river per unit of time (second) is the suspended sediment discharge (R kg / m3). The amount of suspended sediment carried through the cross-section of the river over a long period of time is the runoff of suspended sediment.
Knowing the flow rate of suspended sediment and water flow in the river, it is possible to determine its turbidity - the number of grams of suspended matter in 1 m3 of water: P = 1000 R / Q g / m3. The stronger the erosion and the more particles are carried into the river, the greater its turbidity. The rivers of the Amu Darya basin are distinguished by the highest turbidity among the rivers of Russia - from 2500 to 4000 g / m3. Low turbidity is typical for northern rivers - 50 g / m3.
The average annual runoff of suspended sediment in some rivers is shown in Table 26.

During the year, the runoff of suspended sediments is distributed depending on the water runoff regime and is maximum on large rivers in Russia during the spring flood. For rivers in the northern part of Russia, spring runoff (suspended sediment is 70-75% of the annual runoff, and for rivers in the central part of the Russian Plain - 90%.
Traction (bottom) sediment is only 1-5% of the amount of suspended sediment.
According to Airy's law, the mass of particles transported by water along the bottom (M) is proportional to the speed (F) to the sixth power: M = AV6 (A is the coefficient). If the speed is increased by 3 times, the mass of particles that the river is capable of carrying will increase by 729 times. Hence, it is clear why calm flat rivers move only forests, while mountain rivers roll boulders.
At high speed, the drawn (bottom) sediments can move in a layer up to several tens of centimeters thick. Their movement is very uneven, since the speed at the bottom changes sharply. Therefore, sand waves are formed at the bottom of the river.
The total amount of sediment (suspended and bottom) carried through the flow area of ​​the river is called its solid runoff.
The sediments carried by the river undergo changes: they are processed (abraded, crushed, rolled), sorted by weight and size), and as a result, alluvium is formed.
Stream energy. The stream of water moving in the channel has energy and is capable of doing work. This ability depends on the mass of the moving water and on its speed. The energy of the river on a section L km long at a drop in Nm and at a flow rate of Q m3 / s is equal to 1000 Q * H kgm / s. Since one kilowatt is equal to 103 kgm / s, the capacity of the river in this section is 1000 QH / 103 = 9.7 QH kW. The rivers of the Earth carry 36,000 cubic meters to the Ocean annually. km of water. With an average land height of 875 m, the energy of all rivers, (A) is equal to 31.40 * 1000w6 kgm.

The energy of the rivers is spent on overcoming friction, on erosion, on the transfer of material in a dissolved, suspended and entrained state.
As a result of the processes of erosion (erosion), transfer (transportation) and deposition (accumulation) of sediments, a river bed is formed.
River channel formation. The stream constantly and directly cuts into the rocks through which it flows. At the same time, it seeks to develop a longitudinal profile, in which its kinetic force (mv2 / 2) will be the same throughout the river, and an equilibrium will be established between erosion, transfer and sedimentation in the channel. This channel profile is called the equilibrium profile. With a uniform increase in the amount of water in the river downstream, the equilibrium profile should be a concave curve. It has the greatest slope in the upper part, where the mass of water is the smallest; downstream, with an increase in the amount of water, the slope decreases (Fig. 90). In the rivers of the desert, which are fed in the mountains, and in the lower reaches that lose a lot of water for evaporation and filtration, an equilibrium profile is formed, which is convex in the lower part. Due to the fact that the amount of water, the amount and nature of sediments, the speed along the course of the river change (for example, under the influence of tributaries), the equilibrium profile of rivers has unequal curvature in different sections, it can be broken, stepwise, depending on specific conditions.
The river can develop an equilibrium profile only under conditions of prolonged tectonic rest and unchanged position of the erosion base. Any violation of these conditions leads to a violation of the balance profile and to the resumption of work on its creation. Therefore, in practice, the equilibrium profile of a river is not achievable.
Unworked longitudinal profiles of rivers have many irregularities. The river intensively erodes the ledges, fills the depressions in the channel with sediments, trying to level it. At the same time, the channel is incised according to the position of the base of erosion, spreading up the river (retreating, regressive erosion). Due to the irregularities of the longitudinal profile of the river, waterfalls and rapids often appear in it.
Waterfall- the fall of the river flow from a pronounced ledge or from several ledges (cascade of waterfalls). There are two types of waterfalls: Niagara and Yosemite. The width of the Niagara-type waterfalls exceeds their height. Niagara Falls is divided by the island into two parts: the width of the Canadian part is about 800 m, the height is 40 m; the width of the American part is about 300 m, the height is 51 m. Waterfalls of the Yosemite type are high in height and relatively small in width. Yosemite Falls (Merced River) is a narrow stream of water falling from a height of 727.5 m. This type includes the highest waterfall on Earth - Angel (Angela) - 1054 m (South America, Churun ​​River).
The ledge of the waterfall is continuously collapsing and receding up the river. In the upper part it is washed away by the flowing water, in the lower part it is vigorously destroyed by the water falling from above. Waterfalls recede especially quickly in cases where the ledge is composed of easily eroded rocks, covered only from above with layers of persistent rocks. It is precisely such a structure that the Niagara ledge has, retreating at a rate of 0.08 m per year in the American part and 1.5 m per year in the Canadian part.
In some areas there are “waterfall lines” associated with long-distance ledges. Often, "waterfall lines" are associated with fault lines. At the foot of the Appalachians, when passing from mountains to plains, all rivers form waterfalls and rapids, the energy of which is widely used in industry. In Russia, the line of waterfalls runs in the Baltics (the precipice of the Silurian plateau).
Thresholds- sections of the longitudinal river bed, in which the fall of the river increases and, accordingly, the speed of the river flow increases. Rapids are formed for the same reasons as waterfalls, but at a lower ledge height. They can occur at the site of a waterfall.
Developing a longitudinal profile, the river cuts into its upper reaches, pushing back the watershed. Its basin increases, an additional amount of water begins to flow into the river, which contributes to cutting. As a result, the upper reaches of one river can come close to another river and, if the latter is located higher, capture it and include it in its own system (Fig. 91). The inclusion of a new river in the river system will change the length of the river, its flow and affect the process of channel formation.

River interceptions- the phenomenon is not uncommon, for example r. Pinega (the right tributary of the Northern Dvina) was an independent river and was one with the r. Kuloi, which flows into the Mezen Bay. One of the tributaries of the Northern Dvina intercepted most of the Pinega and diverted its waters to the Northern Dvina. The Psel River (a tributary of the Dnieper) intercepted another tributary of the Dnieper - Khorol, r. Merty - upstream p. Moselle (belonging to the river Meuse), Rhone and Rhine - parts of the upper Danube. It is planned to intercept the Danube by the rivers Neckar and Rutach, etc.
Until the river develops an equilibrium profile, it intensively erodes the bottom of the channel (deep erosion). The less energy is spent on erosion of the bottom, the more the river erodes the banks of the channel (lateral erosion). Both of these processes, which determine the formation of the channel, occur simultaneously, but each of them becomes leading at different stages.
The river very rarely flows straight. The initial deviation may be due to local obstacles due to geological structure and terrain. The meanders formed by the river remain unchanged for a long time only when certain conditions, which are difficult to erode rocks, a small amount of sediment.
As a rule, gyri, regardless of the cause of their occurrence, continuously change and move downstream. This process is called meandering, and the convolutions formed as a result of this process - meanders.
The water flow, which for whatever reason (for example, due to the emergence of bedrock on its way), the direction of movement, approaches at an angle to the channel wall and, intensively eroding it, leads to a gradual retreat. Reflecting at the same time downstream, the stream hits the opposite bank, erodes it, is reflected again, etc. As a result, the eroded areas "pass" from one side of the channel to the other. Between two concave (eroded) sections of the coast, there is a convex section - the place where the bottom cross current, coming from the opposite shore, deposits the erosion products carried by it.
As the tortuosity increases, the meandering process intensifies, however, up to a certain limit (Fig. 92). An increase in tortuosity means an increase in the length of the river and a decrease in the slope, which means a decrease in the speed of the current. The river loses its energy and can no longer erode the banks.
The curvature of the meanders can be so great that a breakthrough of the isthmus occurs. The ends of the severed gyrus are filled with loose deposits, and it turns into an oxbow.
The strip within which the river meanders is called the meander belt. Big rivers, meandering, form large meanders, and their meander belt is wider than that of small rivers.
Since the stream, eroding the coast, approaches it at an angle, the meanders do not just increase, but gradually move downstream. Over a long period of time, they can move so much that the concave section of the channel will be in place of the convex one, and vice versa.

Moving in the meander belt, the river erodes rocks and deposits sediments, resulting in a flat depression lined with alluvium, along which the riverbed meanders. During floods, the water overflows the channel and fills the depression. This is how a floodplain is formed - a part of a river valley that is flooded.
During floods, the river is less meandering, its slope increases, the depth increases, the speed becomes greater, the erosion activity intensifies, large meanders are formed, which do not correspond to the meanders formed during the low-water period. There are many reasons for eliminating the tortuosity of the river, and therefore meanders often have a very complex shape.
The relief of the bottom of the channel of a meandering river is determined by the distribution of the current. The longitudinal flow, due to the force of gravity, is the main factor in bottom erosion, while the lateral flow determines the transfer of erosion products. At the washed-out concave bank, the stream washes out a depression - a stretch, and the cross current carries mineral particles to the convex bank, creating a sandbank. Therefore, the cross-sectional profile of the channel at the bend of the river is asymmetric. On a straight section of the channel, located between two streams and called a roll, the depths are relatively shallow, and there are no sharp fluctuations in depth in the transverse profile of the channel.
The line connecting the deepest places along the channel - the fairway - runs from stretch to stretch through the middle part of the rift. If a roll crosses the fairways that do not deviate from the main direction, and if its line runs smoothly, it is called normal (good); a roll, in which the fairway makes a sharp bend, will be shifted (bad) (Fig. 93). Bad rifts make navigation difficult.
The formation of the channel topography (formation of streams and rifts) occurs mainly in spring during floods.

Life in the rivers. Living conditions in fresh waters differ significantly from living conditions in oceans and seas. In a river great importance for life have fresh water, constant turbulent mixing of water and relatively shallow depths accessible to the sun's rays.
The flow has a mechanical effect on organisms, provides an inflow of dissolved gases and the removal of decay products of organisms.
According to the living conditions, the river can be divided into three sections, corresponding to its upper, middle and lower reaches.
In the upper reaches of mountain rivers, water moves at the highest speed. There are often waterfalls and rapids here. The bottom is usually rocky, with almost no silty deposits. The water temperature is lowered due to the absolute height of the place. V general conditions less favorable for the life of organisms than in other parts of the river. Aquatic vegetation is usually absent, plankton is poor, invertebrate fauna is very scarce, fish food is not provided. The upper reaches of the rivers are poor in fish both in the number of species and in the number of individuals. Only some fish can live here, for example, trout, grayling, marinka.
In the middle reaches of mountain rivers, as well as in the upper and middle reaches of plain rivers, the speed of water movement is less than in the upper reaches of mountain rivers. The water temperature is higher. Sand and pebbles appear at the bottom, and silt in the backwaters. Living conditions here are more favorable, but far from optimal. The number of individuals and species of fish is greater than in the upper reaches, in the mountains; common fish such as ruff, eel, burbot, barbel, roach, etc.
The most favorable living conditions in the lower reaches of rivers: low flow velocity, muddy bottom, a large number of nutrients... Mainly fish such as smelt, stickleback, river flounder, sturgeon, bream, crucian carp, carp are found here. Fish that live in the sea, into which rivers flow: sea flounder, sharks, etc., penetrate. Not all fish find conditions for all stages of their development in one place, the breeding and habitats of many fish do not coincide, and fish migrate (spawning, forage and wintering migrations).
Channels. The canals are artificial rivers with a peculiar regulated regime, created for irrigation, water supply and navigation. The peculiarity of the channel mode is small fluctuations in the level, but if necessary, the water from the channel can be completely drained.
The movement of water in the canal has the same laws as the movement of water in the river. The canal water to a large extent (up to 60% of all water consumed by it) is used for infiltration through its bottom. Therefore, the creation of anti-infiltration conditions is of great importance. This task has not yet been solved.
Possible average flow rates and bottom velocities should not exceed certain limits, depending on the resistance of the soil to erosion. For ships moving along the channel, the average current speed of more than 1.5 m / s is already unacceptable.
The depth of the canals should be 0.5 m more than the draft of the vessels, the width should not be less than the width of two vessels + 6 m.
Rivers like natural resource. Rivers are one of the most important water resources that have been used by people for a variety of purposes for a long time.
Shipping was the branch of the national economy for which the study of rivers was required first of all. Connecting rivers with canals allows you to create complex transport systems... Length river routes in Russia currently exceeds the length of the railways. Rivers have long been used for timber rafting. The importance of rivers in the water supply of the population (drinking and household), industry, Agriculture... All major cities are on the rivers. The population and urban economy consume a lot of water (on average 60 liters per day per person). Any industrial product cannot do without irretrievable consumption of a certain amount of water. For example, for the production of 1 ton of pig iron, 2.4 m3 of water is needed, for the production of 1 ton of paper - 10.5 m3 of water, for the production of 1 g of fabric from some polymer synthetic materials - more than 3000 m3 of water. On average, one head of cattle has 40 liters of water per day. The fish wealth of the rivers has always been of great importance. Their use contributed to the emergence of settlements along the banks. Nowadays rivers are used as a source of valuable and nutritious product - fish are not used enough; much more important marine fishing... In Russia great attention paid to the organization of fisheries with the creation of artificial reservoirs (ponds, reservoirs).
In areas with a large amount of heat and a lack of atmospheric moisture, river water is used in large quantities for irrigation (UAR, India, Russia - Central Asia). The energy of rivers is being used more and more widely. The total hydropower resources on Earth are estimated at 3,750 million kW, of which Asia accounts for 35.7%, Africa - 18.7%, North America - 18.7%, South America - 16.0%, Europe - 6. 4%, Australia - 4.5%. The degree of use of these resources in different countries, on different continents is very different.
The use of rivers is currently very large and will undoubtedly increase in the future. This is due to the progressive growth of production and culture, with the continuously increasing demand of industrial production for water (this is especially true for the chemical industry), with an increasing consumption of water for the needs of agriculture (an increase in productivity is associated with an increase in water consumption). All this raises the question not only of the protection of river resources, but also of the need for their expanded reproduction.

Distribution of annual river flow.

Stock yavl. element of geogr. shell. It is regarded as a large natural complex. All components of geogr. landscape due to the integrity and indissolubility of nature are interconnected. Nature water, being an element of geogr. landscape, yavl. connecting link of all geogr. processes.

Consideration of runoff as an element of geogr. environment assumes its study on a wide geogr. basis. Exactly this approach is stock à environment. environment was developed by V.G. Glushkov in the form of a geographer-hydrol. method. This method establishes a causal relationship of all waters of a given area with the geographical landscape as a whole, including, in addition to climate, geology, geomorphology, soil and vegetation, and on the basis of these relationships established. characteristics of sv-in the waters themselves.

Thus, Glushkov for the first time in the history of father. hydrology formulated the need to study waters for genetic. basis depending on nature. conditions in the cat. these waters are found. This way of research (dialectical) is closely related to the doctrine of Dokuchaev about geogr. zonality of soils with the research of L.S. Berg on landscapes, Voeikov on the relationship of natural waters and climate, Vernadsky on the unity of natural waters, Trigoriev on physical. geogr. the process of development of the natural environment. According to Kuzin (1960), dep. unity. attempt in hydrology, where the need is clearly and clearly formulated. genetic study of land waters in dependent. from those nat. conditions in the cat. these waters are found. This definition very important. In hydrology, geosystem analysis, the comparison method, and others are used. Statistical methods are also widely used. Research. river runoff to genetic. basis allows you to select geogr. regularities of spaces. variability of river flow characteristics.

Space distribution characteristic of the river runoff are most clearly represented by the maps of the isolines of the annual runoff. The runoff map has the great advantage that it very informatively shows the territorial changes of the mapped characteristic. Let us consider the river flow maps for the territory of b. USSR and certain regions of the country.

Isolines of the annual runoff (maps of the annual runoff)

The first map was compiled by D.I.Kocherin in 1927. It covered the European part of the USSR. It was based on observations on 34 points. Scientific significance of the map: for the first time, the role of climate was clearly shown when building a map. zonality and dependence of the river. runoff from the climate. The doctrine of A.I. Voeikov was confirmed that rivers are a product of climate, and E.M: Oldekov that the chief phys.-geogr. factor - the climate that determines the river. stock by 75-85%. The latitudinal direction of the isolines, felt by the author intuitively, subsequently received practical confirmation. The card was practical. value, because from 1927 to 1936, until the appearance. next maps, it was the basis for the substantiation of tens and hundreds of hydraulic engineering. objects. The map was used to determine aq. resources of unexplored basins.

Subsequently, the work continued. In 1936. a flow map of the European part of the USSR was compiled. On it we see the latitudinal arrangement of the river runoff isolines (in the Urals - meridional). The authors of the map are B.D. Zaikov and S.Yu. Belenkov. 1280 points were used for plotting. outlines were made for building a map of the Asian territory. The map was updated in 1946 by Zaikov.

After 1946 in hydrol. mapping was calm. Only in 1961 there was a production. new map (K.P. Voskresensky, 5690 observation points).

In 1980, another map was drawn up (A.V. Rozhdestvensky with colleagues). This map was included in SNiP 2.01.14-83., As well as in the manual for the definition of hydrol. characteristics. The average long-term runoff was calculated from the beginning of the discovery of hydrol. and up to 1975 inclusive. The scale of the map is 1:10 000 000. There are no fundamental differences between this map and the previous one. The number of observations is the same as in the previous map. Annual river map flow is compiled in flow modules M (l / s.km 2). Also possible is the unit of measurement H mm = W / A. For the flat part of Europe. territory of the country, the amplitude of fluctuations in the modulus is average per year. runoff is between 10-12 l / s.km 2 in the North. Dvina, Pechora, on the rivers of Karelia up to 0.5-1.0 in the south in the Azov region. On the plains. ter. the course of isolines reflects latitudinal zoning. In the foothills and mountains obs. means. increase in runoff. So in the Khibiny, the drain module was taken away. up to 18, in the North. Urals up to 20, in the Carpathians - up to 25-30, in the south-west. slope of the Caucasus - up to 75-80 l / s.km 2. In the Caucasus, the largest runoff is at the river. Ukhalta, a tributary of the r. Kodori - 88 l / s.km 2. On a hill, for example. the isolines tend to the meridional, the flow modulus from the foot of the mountains to the peaks. Negative. landforms cause a pronounced decrease. Vametny minimum in the Lovatsko-Ilmenskaya nizm (6 l / s.km 2). More complex distribution in the Asian part of the USSR, variable. flow to the West. - Sib. nizm. the same as in Vost.-Europe. plain. From north to south, there is a decrease in runoff. Security Zap. - Sib. nizm. Ural from the west. atlantic. air masses and the proximity of the desert regions of Central Asia determine a greater dryness of the climate compared to comparison. with Europe. Flow module M ↓ from 8 l / s.km 2 on the Yamal, Gydansky peninsula, most of the West. Sib. nizm. up to 0.2 - 0.1 l / s.km 2 in the upper reaches of the Irtysh, Inshma. So arr. , the difference in flow modules at the same latitude in front of and behind the Urals reaches 2 l / s.km 2. In Vost. Siberia, Primorsky Territory, Yakutia and Kamchatka for example. isolines changes with latitude. to the meridian. Along the coast of the Bering Sea, the amplitude of the meas. from 25-30 l / s.km 2 in the Pamirs, Altai, Sayan Mountains up to 2 l / s.km 2 in the Yana, Indshirka basin, up to 0.1 l / s.km 2 in the deserts of Kazakhstan. On the polar islands of Wrangel, Novosibirsk, Severnaya Zemlya, Franz Josef Land, the flow module M varies from 2 to 8 l / s.km 2 in the named sequence. In the modern borders of Russia, the magnitude of the modulus ranges from 75 to 0.1 (75 - in Kamchatka, 0.1 - in the Azov region). A map of the average annual runoff layer in mm and river water content is available in the textbook of Mikhailov, Dobrovolsky 1991. Fluctuations of years. runoff on the territory. Rossi ranges from 1800 mm on Kamchatka and 1000 mm on Sakhalin to 5 mm or less in the Caspian and Azov regions. On the plains of Europe. parts of the runoff layer ↓ from north to south from 400 to 10-20 mm. In the mountains, the runoff increases on the Kola Peninsula - 400-600, North. Caucasus - 1000 mm, in the West. Siberia - from 300 to 10 mm from the North. South. In Vost. In Siberia, Yakutia, Primorye and Kamchatka, the latitudinal direction turns into the meridional one, the runoff layer ranges from 1800 m in the mountains to 10-20 mm in the Lena basin. for terr. Russia, on the average, the runoff layer was. 198 mm. To the Center. Black earth - 105 mm. Uneven distribution runoff is not accidental due to the variability of DOS. factors that determine the river. stock. River differentiation runoff over the territory is associated with the variability of the atm. precipitation and relief. Acc. with these 2 main natures. factors are formed by geogr. patterns, i.e. latitudinal zoning in the plain, high-altitude - in the mountains.

Regional maps of river flow.

River contour maps drain, made up. for macro areas, allow you to select geogr. regularity of space. variability of the river. flow, but the water resource estimate may be very low. In 1965, a map of the annual runoff for the Central Black Earth Region appeared.

When constructing river flow maps, anomalous flow values ​​are not considered.

Water Fund of Russia.

These are 2.5 million rivers; 2.8 million lakes, over 30,000 reservoirs and ponds.

Glaciers have cover and mountain distribution.

Russian rivers belong to the basins of 12 seas: the Barents, Baltic, Kara, Laptev Sea, East Siberian Sea, White Sea, Chukchi, Bering, Okhotsk, Japanese, Azov, Black seas.

To the Basin North. Arctic Ocean rel. 80% of the catchment area, Atlantic and Pacific 10% each. The Volga forms the largest empty basin. On its territory there are 39 constituent entities of the Russian Federation. The Volga is the largest waterway, the most important international transport corridor. Within Russia, there are 5 rivers with a catchment area of ​​over 1 million km 2: the Ob, Yenia, Lena, Volga, Amur and 50 rivers with a catchment area of ​​over 100,000 km 2. The density of the river network varies significantly from North to South and when moving from plains to mountains. The density of the river network is greater in the North and in the mountains than in the South and on the plains. The largest rivers: Don, Pechora, North. Dvina, Yenisei, Yana, Indigirka, Taz, Kolyma, Ural, Amur form the national heritage of the country. These rivers form the water resources of Russia. The quantity and quality of water determines the quality of life.

Naturally. pov. water bodies include lakes. They are found most often in the Northwest. There are 60,000 lakes in Karelia. The largest freshwater reservoir is Baikal. this is the deepest lake. The vast majority of lakes in Russia are fresh, but there are also salt lakes - Elton, Baskunchak. Many lakes are of great water management and recreational importance. These include Lake Ladoga, Eliger, Kronotskoye Lake and others. water bodies also include swamps. It is known that the area is bog massifs.

Glaciers in the country are mostly found in the mountains. Glacier areas are common on Novaya Zemlya, Franz Josef Land. There are glaciers in the Caucasus, Sayan Mountains, Altai, Urals, Stanovoy ridge.

Huge reserves of water are contained in the arts. reservoirs. There are 2290 reservoirs, the largest volume is over 100 million km 3 - the southwest reservoir. 363 reservoirs are large.

All reservoirs with a volume of more than 1 million m 3 are a reservoir, which is less - a pond.

Water Fund of the Central Black Earth Region.

The water bodies of the Central Churches belong to the basins of the Black, Azov and Caspian Seas. The entire territory under consideration is divided by watersheds of 3 rivers. basins: Don, Volga, and Dnieper. On the territory. CC flows from the named Don only. and the Volga and the Dnieper are represented by their tributaries. 2/3 of the territory falls on the Don basin, 1/3 - on the Volga and Dnieper basins. Rechn. sist. Don is represented. rivers Sosna, Voronezh, Khoper, Bityug, Vorona, Seversky Donets and others, flowing within Lipetsk, Tambov, Voronezh, Belgorod, Kursk. Volga basin: Tsna with tributaries (Tambov region). Dnieper basin: Diet with tributaries, Vorskla, Psel (Kursk and Belgorod regions). Hydro the network is represented by brooks, rivers and temporary streams, runoff cat. occurs only in spring or summer. The rivers' hydrography is complemented by lakes and marshes. Both those and others are small in terms of the area of ​​the water mirror, their distribution. on terr. does not exceed 1% of the total area. On the territory. TsCHR - 5164 watercourses. over 35,000 km. They are comp. a small part of the total number of rivers in Russia. River density the network is small, but varies: 0.27 km / km 2 in Tamb. region, in the Lipetsk region. - 0.23 km / km 2; in the Voronezh region. - 0.18 km / km 2; to Belg. region - 0.11.

Naib. the number of lakes in the bass. Tsny, Ravens, Dona, Bityuga. They are disposed. in the floodplains of rivers, have an elongated shape, which indicates their ancient origin. In the floodplain of the Don lakes Tygonovo, Kremenchug, Takhta and others. In the bass. Tsny Svyatovskoe, Prince and others. In the bass. Seim linenevo. The largest lake is Ilmen in the bass. Khopra.

Swamps on the territory. The Central Black Earth Region is small, they are in the basin of the Vorona, Usman, Savala, Voronezh. The most famous swamp is Cranberry (near Voronezh). Underground sources are a special group of objects. They give rise to many rivers. There are many spring rivers in the Lipetsk region. In the present. time obs. rise in the level of groundwater. The largest springs are Nizhnekislyai and Belaya Torka. Mineral springs - Lipetsk, Uglyansky, Ikoretsky. Sanatoriums function on the basis of them. A large number of ponds and reservoirs are present on the territory of the Central Black Earth Region. At the beginning. 60s, there were several. thousand ponds. The largest reservoir is Voronezh, followed by Matyrskoe, Starooskolskoe, Kurchatovskoe, Ilushpanskoe. When using water for human needs, the question of water supply arises.

2.13. When determining the calculated hydrological characteristics of the annual flow of river water, the requirements set forth in paragraphs. 2.1 - 2.12.

2.14. To determine the intra-annual distribution of water runoff in the presence of hydrometric observation data for a period of at least 15 years, the following methods are adopted:

runoff distribution according to analogous rivers;

method of composing seasons.

2.15. The intra-annual runoff distribution should be calculated by water management years, starting with a high-water season. Season boundaries are assigned the same for all years, rounded to the nearest month.

2.16. The division of the year into periods and seasons is made depending on the type of river regime and the prevailing type of use of the flow. The duration of the high-water period should be set so that its accepted boundaries include the high water for all years. The period of the year and the season in which natural runoff can limit water consumption are taken as the limiting period and limiting season. The limiting period includes two adjacent seasons, one of which is the most unfavorable in terms of runoff use (limiting season).

For rivers with spring floods, two dry seasons are taken as the limiting period: summer - autumn and winter. If water consumption for agricultural needs predominates, summer-autumn should be taken as the limiting season, and winter for hydropower and for water supply.

2.17. For alpine rivers with summer floods and mainly irrigated runoff, the limiting period is taken to be autumn - winter and spring, and the limiting season is spring.

When designing the diversion of excess water for flood control or when draining swamps and wetlands, the limiting period is taken to be the high-water part of the year (for example, spring and summer - autumn), and the limiting season is the most abundant season (for example, spring).

The calculated probability of exceeding the runoff value for the year, for the limiting season and period is determined by the distribution curves of the annual probability of exceeding (empirical or analytical).

2.18. The intra-annual runoff distribution for a specific observation year is taken as a calculated one if the probability of excess runoff for this year and for the limiting period and season are close to each other and correspond to the annual probability of excess specified according to the design conditions.

2.19. The intra-annual runoff distribution when calculating by the layout method is determined from the conditions of equality of the probabilities of exceeding the runoff for the year, runoff for the limiting period and within it for the limiting season.

The runoff value of a season that is not included in the limiting period is determined by the difference between the annual runoff and the runoff for this period, and the runoff value for the non-limiting season included in the limiting period is determined by the difference between the runoff of this period and the season.

2.20. With similar values ​​of the coefficients of variation and asymmetry of river runoff for the year and the limiting period and season, the calculated intra-annual distribution is determined as the average for all years distribution of water runoff by months (decades) as a percentage of the annual water runoff of the river under study.

2.21. With a slight change in water consumption during the year, it is allowed to change the calendar distribution of water runoff by seasons and months of the curve of the duration of daily water consumption for the year.

2.22. If the water flow changes under the influence of economic activity, it is necessary to bring it to the natural river flow in accordance with the requirements of clause 1.6. Based on these data, the calculated intra-annual distribution of the river water flow is determined and the corresponding changes are made to the calculation results.