Nutrition and regime of the river: description of species. Feeding and regime of rivers Rivers have a rain source of food
Lecture #2
Rivers are fed by surface and underground waters. Surface food, in turn, is divided into snow, rain and glacial.
Snowy The rivers are fed by the melting of snow in the spring, which has accumulated during the winter. For most of the plain rivers of the ETS RF, the spring flood runoff is more than 50% of the total annual runoff.
The rain supply of the rivers occurs mainly due to the precipitation of heavy rains and showers. It has significant fluctuations throughout the year. For the rivers of the south of the Russian Federation and Far East rain supply can reach 70…80% or more of the annual runoff.
Glacial food occurs as a result of the melting of glaciers and eternal snows in the highlands. The greatest glacial runoff occurs during the hottest summer months of the year.
River feeding groundwater the most stable and uniform throughout the year. Almost all rivers have it. The share of underground recharge in the annual runoff varies within a very wide range: from 10 to 50…60% and depends on the geological conditions and the degree of drainage of the watershed.
The most widespread is mixed water food.
Depending on the nutritional conditions, it is formed hydrological regime of a water body, which is understood as a set of regularly repeating states of a water body, inherent in it and distinguishing it from other water bodies. It manifests itself in long-term, seasonal, monthly and daily fluctuations: water level, river water content, water temperature, ice phenomena, solid sediment runoff, composition and concentration of chemicals, etc.
In the hydrological regime, they emit three phases of the water regime (FVR): high water, floods and low water.
high water– River FVR, repeated annually in the data climatic conditions in the same season, characterized by the highest water content, high and prolonged rise in water level. It is caused on lowland rivers by snowmelt (spring flood), on high-mountain rivers - by melting snow and glaciers (summer flood), summer heavy rainfall in monsoonal and tropical zones (for example, summer flood on the rivers of the Far East).
high water– The river FVR, which can be repeated many times in different seasons of the year, is characterized by an intense, usually short-term increase in discharges and water levels caused by rains or snowmelt during thaws.
low water– FVR of the river, which is repeated annually in the same seasons and is characterized by low water content, long standing low water level and arising from a decrease in river nutrition. Underground food predominates. The summer (summer-autumn) low water period includes the period from the end of the flood to the autumn floods, and in their absence, to the beginning winter period. Winter low water usually coincides with the period of freezing. From the beginning of the freezing of rivers, water discharges gradually decrease, reaching a minimum before opening, which is associated with the depletion of groundwater reserves.
A general idea of the change in the FVR of the river is given by runoff hydrographs- a chronological graph of changes in water discharges during the year or season in this particular section of the watercourse. In hydrological calculations, one usually operates with a typical runoff hydrograph, i.e. with a hydrograph reflecting the general features of hydrographs over a number of years. Establishing patterns in the distribution of runoff within a year is of great practical importance for various water management purposes, for example, to determine the main parameters of reservoirs and hydraulic structures.
A typical runoff hydrograph for lowland rivers of the Russian Federation is shown in fig. 5. On it, you can highlight the volumes of runoff formed from various power sources.
We all know perfectly well that several largest rivers of our planet, the width of which reaches 50-60 kilometers.
But the source of even the largest river is a thin, inconspicuous stream. Only after running many hundreds of kilometers, having been saturated with the moisture of many large and small tributaries, the river becomes truly powerful and wide. Do you know what river nutrition is, and what are its sources? Yes, the river is also fed, but, of course, not by cutlets with mashed potatoes, but by water from its tributaries.
Nutrition and river regime
How to measure a river? You can measure its length, the width of the channel and the depth of the bottom. Another important characteristic is the water consumption, i.e. the amount of water that flows through a channel per unit of time. If you make these measurements throughout the year, you will find that the level and flow of water in different periods are not the same.
Continuing observations for several years in a row, you can see that in spring and autumn the river becomes more full-flowing, and in summer and winter the amount of water in it decreases. Scientists call these seasonal fluctuations the regime of the river.
It is customary to distinguish three main periods in the regime of any river:
- - a long period when the amount of water reaches a maximum, as a rule, due to the spring melting of snow;
- - periods of lowering the water level, usually occur in summer and winter;
- - short-term and sharp, lasting only a few days, rise in water level due to heavy rains or sudden snowmelt.
It is easy to see that fluctuations in the water level in the river are caused by an increase or decrease in its supply, i.e. water entering the river from tributaries, streams and underground sources. Hydrologists (specialists who study the "behavior" natural waters and reservoirs) distinguish four main sources of river nutrition - snow, glacier, rain and underground. One of them is usually predominant, but the river does not refuse the rest either.
Rain, snow supply
Rivers fed exclusively by rain are characterized by frequent and sudden floods. As a rule, these are tropical and subtropical rivers flowing from peaks or hills. 
In our country, there are also rivers with a predominantly rain source of food. They flow from the peaks of Altai, the Caucasus, the Baikal region and other similar regions. But for our rivers, no less powerful source than rain is snow, or rather, its spring melting. "Snowy" rivers, as a rule, are distinguished by the softness of the water and the low content of salts in it. In spring, they are characterized by abundant floods, after which the river enters its usual banks. A similar picture is observed after heavy rains.
Glacial nutrition
The main source of water in the river may be a mountain glacier, the melting of which replenishes the water level in the channel. Such rivers originate on the high peaks of the mountains, covered with a multi-meter layer of ice. In summer, when the glacier actively melts, the water level in them rises, the flow becomes turbulent and erodes the banks, carrying down fertile soil.
Therefore, as a rule, glacial rivers are not popular with the population, and their banks are deserted and barren. Sometimes a glacial river flowing down from a mountain peak, for many centuries, carves a deep gorge in the rocks, the bottom of which becomes its channel.
underground food
On the plains and in the lowlands there are rivers that feed mainly from underground sources. There are not so many of them, and their diet is still not well understood. It has been established that underground power can be ground, i.e. coming from the upper aquifer, in which rainwater absorbed into the soil accumulates, or artesian, coming from natural artesian well.
Underground feeding is typical for small streams, but large water flows are supplied mainly from tributaries.
The runoff of rivers and their water regime during the year bears the stamp of zonality, since they are determined primarily by the conditions of nutrition. The first classification of rivers according to feeding conditions and water regime was created by A.I. Voeikov in 1884. Later, it was improved by M.I. Lvovich by quantifying the role of individual sources of river nutrition and the seasonal distribution of runoff. Under certain conditions, each of the food sources can be almost exclusive if its share is more than 80%; may have a predominant value (50-80%) or prevail over others (less than 50%). The same gradations are used by him for the flow of rivers according to the seasons of the year. According to the combination of food sources (rain, snow, underground, glacial) and the seasonal distribution of runoff, they identified six zonal types of the water regime of rivers on Earth, well expressed on the plains.
Rivers of the equatorial type have abundant rain supply, a large and relatively uniform flow throughout the year, its increase is observed in the autumn of the corresponding hemisphere. Rivers: Amazon. Congo etc.
Tropical rivers. The flow of these rivers is formed due to monsoonal summer rains in the subequatorial climate zone and predominantly summer rains on the eastern coasts tropical zone, so the flood is summer. Rivers: Zambezi, Orinoco, etc.
Subtropical rivers in general, they are predominantly rain-fed, but two subtypes are distinguished according to the seasonal distribution of runoff: on the western coasts of the continents in the mediterranean maritime climate the main runoff is winter (Guadiana, Guadalquivir, Duero, Tajo, etc.), on the eastern coasts in a monsoon climate, summer runoff (tributaries of the Yangtze, Huang He).
Rivers of a moderate type. Within the temperate climate zone, four subtypes of rivers are distinguished according to their sources of food and the seasonal distribution of runoff. On the western coasts, in a maritime climate near rivers, it is predominantly rain fed with a uniform distribution of runoff throughout the year with some increase in winter due to reduced evaporation (Seine, Thames, etc.); in areas with transitional climate from sea to continental near rivers, mixed feeding with a predominance of rain over snow, with a low spring flood (Elbe, Oder, Vistula, etc.); in areas continental climate the rivers are mostly fed by snow and spring floods (Volga, Ob, Yenisei, Lena, etc.); on the eastern coasts with a monsoon climate near the rivers, it is mainly rain fed and summer floods (Amur).
Scheme of classification of rivers by sources of food (according to M.I. Lvovich).
Rivers of the subarctic type They are mainly fed by snow with an almost complete absence of underground due to permafrost. Therefore, many small rivers freeze to the bottom in winter and have no flow. High water on the rivers is mainly summer, as they break up in late May - early June (Yana, Indigirka, Khatanga, etc.).
Polar type rivers in a short period of summer they have glacial nutrition and runoff, but for most of the year they are frozen.
Similar types and subtypes of the water regime are characteristic of lowland rivers, the flow of which is formed in more or less the same type of climatic conditions. The regime of large transit rivers crossing several climatic zones is more complicated.
The rivers of mountain regions are characterized by vertical zonality patterns. With an increase in the height of the mountains near the rivers, the share of snow, and then glacial nutrition, increases. Moreover, in an arid climate near rivers, glacial nutrition is the main one (Amu Darya and others), in a humid climate, along with glacial climate, rain nutrition is also carried out (Ron and others). Mountain, especially high-mountain, rivers are characterized by summer floods.
The most intense and even catastrophic summer floods are on rivers that begin high in the mountains, and in the middle and lower reaches are abundantly fed from monsoon rains: the Indus, the Ganges, the Brahmaputra, the Mekong, the Irrawaddy, the Yangtze, the Huang He, and others.
Classification of rivers by B. D. Zaikov
Along with the classification of rivers by M. I. Lvovich, typification of rivers according to the hydrological regime of B. D. Zaikov is popular in Russia. Under hydrological regime in this case, we understand the distribution and nature of the passage of various phases of the water regime: high water, low water, floods, etc. According to this typification, all rivers in Russia and the CIS are divided into three groups:
- with spring flood;
- with summer floods and floods;
- with flood regime.
Within these groups, according to the nature of the hydrograph, rivers with various types mode.
Among the rivers with spring flood rivers stand out: Kazakhstani type (sharply pronounced short flood and almost dry low water for most of the year); Eastern European type (high short flood, summer and winter low water); West Siberian type (low extended flood, increased runoff in summer, low water in winter); East Siberian type (high flood, summer low water with rain floods, very low winter low water); Altai type (low uneven stretched flood, increased summer runoff, winter low water).
Among the rivers with summer flood rivers are distinguished: the Far Eastern type (low extended flood with floods of monsoon genesis, low winter low water); Tien Shan type (low extended flood of glacial genesis).
WITH flood regime rivers stand out: Black Sea type (floods throughout the year); Crimean type (floods in winter and spring, summer and autumn low water); North Caucasian type (floods in summer, low water in winter).
The forecast of the water content of rivers and their regime during the year has great importance to address issues of wise use of countries' water resources. The forecast of runoff during floods is very important, which in individual years are extremely high (for example, on the rivers of Primorsky Krai in August 2000) and lead to negative consequences.
1. Climate classification A.I.VOEIKOVA (1884)
Having studied the influence of climatic conditions, the intra-annual distribution of runoff A.I. Voeikov concluded: "ceteris paribus, the country will be the richer in flowing waters, the more precipitation and less evaporation."
The classification is based on the thesis: “rivers are a product of the climate”. He divides rivers into 4 groups and 9 types.
Let's take a closer look at a brief description of all types of rivers in the world.
1 group – MELT FEED – 3 types.
1. Rivers fed by melting snow, on the plains and in low mountains up to 1000 meters. These are the rivers of the North-East of Siberia, the northern part North America. The rivers flow in the area of permafrost, the filtration is insignificant, the snow cover is established for 8-10 months. There are spring floods caused by melt water.
2. Powered by melting snow in the mountains. These are the rivers Central Asia. Regular floods are observed on these rivers, the size of which depends on the amount of snow (snow reserves) and the course of summer air temperatures ( fast growth- intensive snowmelt).
3. Powered by melting snow in spring and early summer. These are the rivers of countries with severe and snowy winters. They have a well-defined flood in the spring from melting snow. (European part of Russia, Western Siberia, Scandinavia, Belarus, East Germany, northern part of the USA).
2 group – RAIN FEEDING – 4 types.
4. From rains with high water in the warm season (summer). These are the rivers of areas where tropical and monsoon rains fall. Precipitation is unevenly distributed throughout the year. They fall mainly in the summer and create significant floods. In winter, the rivers are shallow - they are fed mainly by groundwater (the Amur, Selenga, Amazon, Congo, Nile rivers).
5. Rivers fed by winter rains. Precipitation is relatively evenly distributed throughout the year. The water content of these rivers increases during the cold season, but in general, river level fluctuations are small. Summer precipitation does not cause an increase due to evaporative losses (rivers of Central and Western Europe).
6. Rivers fed by abundant winter rains during the cold season. There is little precipitation in summer, the rivers dry up (Southern Europe, the northern coast of Africa, California, Chile).
7. The absence of rivers due to the dryness of the climate (rivers of the largest deserts in the world - the Sahara, the Arabian Peninsula, Central Asia). With large amounts of precipitation, temporary streams appear along the depressions of the eolian relief, along the gullies. Water flows into the basins.
3 group – TALO-RAIN NUTRITION – 1 type.
8. Drying rivers that are fed by rains for a short time of the year, and in the rest of the year the rivers are drying up or turned into separate lakes-puddles along the hollows in the channel (the rivers of the Steppe Crimea, the lower reaches of the Kura, the Araks, part of Mongolia, the northern part of Kazakhstan ).
4 group – SUB-GLACY NUTRITION -1 type.
9. Rivers fed from under the continental ice, when it melts in the summer. The water mass of the World Ocean warms up in the summer, then it warms up the coastal part of the continents, which causes melting of the continental ice at the bottom (streams of Antarctica, Greenland, the northern coast of the Arctic).
Classification by M.I. LVOVICH (for the CIS rivers).
The classification is based on two criteria:
power supplies;
· intra-annual flow distribution.
They characterize the origin of the river runoff (its genesis) and the zonal geographical regularities of the water regime of the rivers. The classification uses the method of quantifying the share of individual food sources in the annual runoff, which makes it possible to genetically analyze the water regime of rivers and classify them according to food sources.
For a quantitative assessment of each source of food, M.I. Lvovich used the method of dividing the hydrograph and identifying types of food, taking into account the course of air temperatures and precipitation precipitation(snow, rain, hail, etc.).
This classification of the water regime of rivers according to the predominant type of food and seasons of the year with a predominant runoff can be represented as follows:
M.I. Lvovich identified 20 types of water regime and 4 main areas for the CIS territory: snow, rain, predominantly glacial and mixed nutrition. An index was given for each of the 20 types. For example, when writing D 3 L this means - exclusively rain food in summer; C 2 V- mostly snowy in spring, etc.
His typological scheme is based on combinations of food sources with the distribution of runoff according to the seasons of the year.
The distribution of rivers on the territory of the CIS by sources of food is subject to a certain pattern. Most of the territory of the CIS is occupied by river basins of snow, mainly snow and mixed with a predominance of snow supply. On the plains it wears zonal character.
In the extreme south, there are areas of pure snow supply ( From 3), because rains do not give runoff due to the dryness of the climate, groundwater lies deep and does not take part in the feeding of rivers (the rivers Bol. and Mal. Uzen, Eruslan, rivers of northern Kazakhstan, etc.).
Further north, the proportion of snow supply decreases ( From 2) , because underground runoff and precipitation increase. With advancement to the north, the share of ground food decreases and the share of rain food increases (Asian part of Russia, Vilyuy River).
In the north-west of the European part of Russia, mixed-flow rivers flow ( From 1).
There are fewer rain-fed rivers. They flow through the Colchis and Lankaran lowlands, in the Far East.
In mountainous regions, above the border of eternal snows (nival zone), rivers are fed by glaciers.
Classification by B.D.ZAYKOV.
This classification is based on the characteristics of the water regime of the rivers B.D. Zaikov divided all the rivers of the CIS into 3 groups and 10 types.
The most common rivers in the CIS with spring floods, but depending on the nature of the flood, its duration and the regime of the rivers in the rest of the year, the groups are divided into the following types:
1 group– rivers with SPRING FLOW
Types : 1. Kazakh;
2. Eastern European;
3. West Siberian;
4. East Siberian;
5. Altai.
2 group
Types: 6. Far East;
7. Tien Shan.
3 group– rivers with FLOOD REGIME
Types: 8. Black Sea;
9. Crimean;
10. North Caucasian.
a brief description of types of rivers by the nature of the water regime
1 group– rivers with SPRING FLOW
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1. Kazakh
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Has a pronounced spring flood lasting less than 1 month, rare and short floods during the spring and autumn periods. Low flow in spring, summer and autumn (rivers of the Aral-Caspian basin and the southern Trans-Volga region). |
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2. Eastern European . It has a high, longer flood lasting 1-3 months. Rain floods in summer, heavy rains in autumn (rivers of the Russian Plain). |
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3. West Siberian . It has a low, stretched spring flood lasting up to 4 months. In autumn - low rain floods (rivers Ob, Ket, Vasyugan, etc.). |
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4. East Siberian . It has a high spring flood, summer-autumn floods, low winter low water, freezing in winter to the east of the Yenisei (Vitim, Indigirka, Kolyma, etc.). |
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5. Altai . It has a low, stretched comb-type flood, increased summer-autumn runoff, low winter low water (rivers of Altai and Central Asia). |
2 group– rivers with FLOOD IN SUMMER TIME
3 group– rivers with FLOOD REGIME
For large and largest rivers (Ob, Yenisei, Lena), the features of the water regime change in different climatic zones.
Genetic classification of P.S.KUZIN.
This is a classification of the rivers of the CIS according to the main phases of the water regime, based on geographical zoning. The essence of this classification lies in the connection of the main types of water regime with hydrological zones, which are a reflection on earth's surface belts. Moreover, not only individual elements of the river regime, but also the main phases of the water regime are subject to geographical zonality.
The classification is based on the following principles:
type of river feeding and phases of the water regime;
the nature of the relief;
geographic areas.
Kuzin P.S. divides all the rivers of the CIS into 3 types that have a zonal character.
Kuzin P.S. considered the selected types of river regime as categories expressing the main features of the water regime of the CIS rivers.
By the nature of the relief rivers are divided into:
1) mountainous (with the manifestation of altitudinal zonality in the distribution of elements of the water regime);
2) flat (with the manifestation of latitudinal zonality of the elements of the water regime).
Hydrological zones allocated in accordance with geographical zonality, the boundaries of hydrological zones coincide with the boundaries of geographical zones. Kuzin P.S. 6 hydrological zones have been identified: arctic, tundra, forest, steppe, semi-desert and desert.
This classification made it possible to bring into a system disparate information on rivers and to explain the regularities in the change in the main phases of the water regime across the territory and to establish the boundaries of hydrological zones and regions.
Remember:
Question: In what parts of the hydrosphere are the main reserves concentrated? fresh water?
Answer: Of the total amount of water on Earth, fresh water makes up a little more than 2% of the total volume of the hydrosphere. The main fresh water reserves are glaciers, the fresh water sources used include the water of rivers, lakes, groundwater reserves.
Question: What are the sources of food for rivers and lakes?
Answer: Depending on the sources of nutrition, rain, snow glacial and underground nutrition are distinguished.
Rain feeding prevails in the warm zone and in areas of the temperate zone with a monsoonal climate. The proportion of runoff rainfall increases when it falls on moist soil.
Snow nutrition prevails in cold and temperate zones. The runoff of snow water is facilitated by the increased intensity of snowmelt, winter freezing of the soil, and especially the presence of an ice crust on the soil.
Glacial nutrition occurs as a result of the melting of glaciers. The main factors are the catchment area occupied by glaciers and air temperature.
Underground feeding is the flow of groundwater and interstratal waters into the river (flow into the rivers of soil waters and perched waters conditionally refers to surface feeding). Underground power depends on geological structure, distribution in the basin of permeable soils, fissured rocks, from forest cover.
Question: What is the regime of a river, how is it determined?
Answer: Depending on the conditions of nutrition in the regime of rivers, there are: high water, floods and low water.
High water is a phase of the water regime of the river, which is repeated annually in the same climatic conditions in the same season, characterized by the highest water content, high and prolonged rise in the water level. On lowland rivers, floods are caused by snowmelt (spring flood), on high-mountain rivers - by melting snow and glaciers (summer flood), in monsoonal and tropical zones- Summer rainfall.
Flood is a phase of the water regime of the river, which can be repeated many times in different seasons of the year, is characterized by an intense, usually short-term, increase in flow and water levels and is caused by rain or snowmelt during thaws. A flood of outstanding magnitude and rare in frequency of occurrence, which can cause casualties and destruction, is called a catastrophic flood. In engineering practice, the term "flood" is often replaced by the term "flood".
Low water is a phase of the water regime of the river, which is repeated annually in the same seasons, characterized by low water content, a long standing low level and arising as a result of a decrease in river nutrition. The summer (summer-autumn) low water period includes the period from the end of the flood to the autumn floods, and in their absence - until the beginning of the winter period, that is, before the appearance of ice phenomena on the river.
Summer low water can be stable, long, as well as intermittent, unstable (periodically disturbed by rains). Winter low water usually coincides with the period of freezing. Water discharges from the beginning of freezing of rivers gradually decrease, reaching a minimum before opening; this is due to the depletion of underground (ground) water reserves.
Summer low water is typical for the rivers of the steppe and semi-desert zones, during this period the river is fed mainly by groundwater.
Winter low water is typical for rivers with a continental climate, often coinciding with the period of freezing. During this period, the river is fed by groundwater. In areas with a harsh climate, small rivers sometimes freeze to the bottom.
Question: What waters are called groundwater, and which are called interstratal?
Answer: Ground water. Water that accumulates in the process of filtration on the first water-resistant layer from the surface of the earth is called groundwater. It does not have protection from waterproof layers; the area of water supply coincides with the area of their distribution. The depth of groundwater varies from 2-3 m to several tens of meters.
Interstratal underground waters. Interstratal waters lie between two water-resistant layers, are isolated from atmospheric precipitation and surface groundwater by a waterproof roof, due to which they have the greatest sanitary reliability. Depending on the conditions of occurrence, they can be pressure (artesian) or non-pressure. Their distinguishing feature is the occurrence below one, two or more layers of water-resistant rocks and the absence of nutrition from the surface directly above them.
My geographical research:
Question: What is the difference between the feeding of rivers in the temperate climatic zone of the equatorial and tropical?
Answer: The feeding of rivers depends on the source of replenishment. water resource rivers and is due to the climate of the area where the river flows.
In areas with a temperate climate, rivers are mostly fed by snow and rain sources; in tropical and equatorial climates, rivers are mainly fed by a rain source, since there is no snow source, and underground sources are smaller in volume than in the temperate climate zone.
Question: What causes changes in river runoff by seasons in different climatic zones?
Answer: river flow is the amount of water flowing through the cross section of a river flow in a given time. The annual river flow is usually measured. The most important indicator of river flow is the flow of water, i.e. the volume of water flowing through the cross section of the river flow per unit time (usually measured in m³ / s). In a broad sense, river runoff is the movement of water flow along a river channel.
Among natural conditions the main one is climate, especially precipitation and evaporation. With heavy rainfall, the flow of rivers is large, but one must take into account their type and the nature of the fallout. For example, snow will provide more runoff than rain because there is less evaporation in winter. Heavy precipitation increases the runoff compared to continuous precipitation with the same amount. Evaporation, especially intense, reduces runoff. Apart from high temperature, it is promoted by wind and lack of air humidity.
Economic activity - in the warm season, more intensive water intake than in the cold season
Question: Give examples of rivers whose characteristics may correspond to the data in the table.
Rivers of the equatorial type have abundant rainfall, a large and relatively uniform flow throughout the year, its increase is observed in the autumn of the corresponding hemisphere. Rivers: Amazon. Congo.
Tropical rivers. The feeding of these rivers is formed by monsoonal summer rains in the subequatorial climatic zone and mainly summer rains on the eastern coasts of the tropical zone, the flood is summer, and therefore the largest runoff is in summer. Rivers: Zambezi, Orinoco.
The rivers of the subtropical type as a whole are predominantly rain-fed, but according to the seasonal distribution of the runoff, two subtypes are distinguished: on the western coasts of the continents in the Mediterranean climate, the main runoff is winter (Guadiana, Guadalquivir, Duero, Tajo, etc.), on the eastern coasts in the monsoon climate, the runoff is summer (tributaries of the Yangtze, Huang He).
Rivers of a moderate type. Within the temperate climate zone, four subtypes of rivers are distinguished according to their sources of food and the seasonal distribution of runoff. On the western coasts in a temperate maritime climate, the rivers are predominantly fed by rain with a uniform distribution of runoff throughout the year with some increase in winter due to reduced evaporation (Seine, Thames, etc.); in areas with a transitional climate from maritime to continental near rivers, mixed feeding with a predominance of rain over snow, with a low spring flood (Elbe, Oder, Vistula, etc.); in regions of a temperate continental climate near rivers, snow is predominantly fed and spring floods (Volga, Ob, Yenisei, Lena, etc.); on the eastern coasts with a monsoon climate near the rivers, it is mainly rain fed and summer floods (Amur).
Questions and tasks:
Question: How and why does the value of the annual runoff layer on the earth's surface change?
Answer: The value of the annual runoff is the difference between the values of the annual layer of precipitation (in mm) and evaporation in any territory. The size of the runoff layer depends on the climate and varies from the equator to the poles
Question: On which continent is the density of the river network the greatest, why?
Answer: The densest river network in South America, because South America has the largest annual runoff layer. - 580mm.
Question: In which climatic zone and why is the annual flow of rivers the most uniform?
Answer: Rivers of the equatorial type have abundant rainfall, a large and relatively uniform flow throughout the year, its increase is observed in the autumn of the corresponding hemisphere. Rivers: Amazon, Congo.
Question: What are the factors affecting the number of lakes?
Answer: The location of lakes on the continents depends on the presence of natural depressions (hollows) and climate. In humid climate there are many full-flowing sewage lakes with fresh water, in an arid climate (tropical) there are few lakes, mostly saline drainless ones.
The main location of the lakes is the north of North America and Eurasia, where there are many tectonic faults and depressions.
Question: Tell us about the significance of glaciers and groundwater for nature and man.
Answer: Glaciers are a supply of fresh water, groundwater is a source of nutrition for rivers and lakes, a source of fresh water for humans, where there are no large lakes and rivers with the possibility of domestic water intake, the therapeutic effect of mineral groundwater on healing.