§ 1. The concept of the hydrosphere

Hydrosphere- water shell of the Earth. It includes all chemically unbound water, regardless of its state of aggregation. The hydrosphere consists of the World Ocean and land waters. The total volume of the hydrosphere is about 1400 million km 3, with the main mass of water - 96.5% - in the waters of the World Ocean, salty, undrinkable. The continental waters account for only 3.5%, of which more than 1.7% is contained in the form of ice and only 1.71% in the liquid state (rivers, lakes, groundwater). The remaining volume of the Earth's water shell, or hydrosphere, is in a bound state in the earth's crust, in living organisms and in the atmosphere (approximately 0.29%).

Water is a good solvent, a powerful vehicle. It moves huge masses of substances. Water is the cradle of life, without it the existence and development of plants, animals and man, his economic activity is impossible. Hydrosphere - battery solar heat on Earth, a huge pantry of mineral and human food resources.

The hydrosphere is one. Its unity lies in the common origin of all natural waters from the Earth's mantle, in the unity of their development, in spatial continuity, in the interconnection of all natural waters in the system of the World Water Cycle (Fig. V .1).

World water cycle- this is a process of continuous movement of water under the influence of solar energy and gravity, covering the hydrosphere, atmosphere, lithosphere and living organisms. From the earth's surface, under the influence of solar heat, water evaporates, and most of it (about 86%) evaporates from the surface of the oceans. Once in the atmosphere, water vapor condenses upon cooling, and under the influence of gravity, the water returns to earth's surface in the form of precipitation. A significant amount of precipitation falls back into the ocean. The water cycle, in which only the ocean and atmosphere take part, is called small, or oceanic, the water cycle. AT global, or big, the water cycle involves land: the evaporation of water from the surface of the ocean and land, the transfer of water vapor from the ocean to land, the condensation of vapor, the formation of clouds and precipitation on the surface of the ocean and land. Next is the surface and underground runoff of land waters into the ocean (Fig. V.1). Thus, the water cycle, in which, in addition to the ocean and atmosphere, land also takes part, is called global the water cycle.

Rice. V.1. World water cycle

In the process of the world water cycle, its gradual renewal takes place in all parts of the hydrosphere. So, underground waters are updated for hundreds of thousands and millions of years; polar glaciers for 8-15 thousand years; waters of the World Ocean - for 2.5-3 thousand years; closed, drainless lakes - for 200-300 years, flowing - for several years; rivers - 12-14 days; atmospheric water vapor - for 8 days; water in the body - in a few hours. The global water cycle connects all the outer shells of the Earth and organisms.

At the same time, land is part of the water shell of the Earth. These include underground water, rivers, lakes, glaciers and swamps. Land waters contain only 3.5% of the total world water reserves. Of these, only 2.5% are insipid water.

§ 2. Modern ideas about the world water cycle

The observed change in the level of the World Ocean by many researchers is explained by climate change. It is believed that the current level rise is due to the redistribution of water from continental blocks to the ocean due to river runoff, evaporation and deglaciation. In the schemes of the general circulation, the volume of water evaporated over the ocean is assumed to be equal to the volume of water received from the continents in the form of river runoff, precipitation and melting of glaciers:

where E is evaporation, P is precipitation, R is regional, underground, and other types of runoff controlled by precipitation. However, this scheme is correct only in the first approximation and is implemented under the condition that the total mass of water on the Earth's surface is constant and the capacity of oceanic and sea basins is unchanged. If we consider the planet as an open thermodynamic system, then it is necessary to take into account the endogenous inputs of water and its losses during photolysis. In other words, at least four more items must be present in the balance of the global water cycle on the Earth's surface:

Without taking into account these factors, the real picture of the change in the level of the World Ocean will be displayed incorrectly, especially in the paleogeographical aspect and in the forecast for the future.

For a long time in the Earth sciences there have been ideas about the great antiquity of the modern volume of the hydrosphere and its extremely slow changes in the present and future. It is assumed that water on Earth was formed by condensation immediately after the accretion of protoplanetary matter or accumulated in the process of degassing and volcanism. From this, a conclusion is made about the antiquity of the World Ocean, the modern size and depth, which it acquired back in the Precambrian (600-1000 million years ago). The theory of evolution built on such a foundation earth's crust and the face of the Earth as a whole looks “waterless”, since the hydrosphere was either given to the planet initially, or acquired by it approximately in the middle of the Precambrian.

As a result of many years of research into the materials of deep-sea drilling by the American vessel "Glomar Challenger" (1968-1989) on uneven-aged shallow-water formations found in the section of sediments and basalts of the bottom of the Atlantic, Indian and Pacific oceans (DSDP, 1969-1989), it was first made theoretical background quantitative determination of the average rate and mass of annual inflows of endogenous water to the Earth's surface in the modern period and the last 160 million years. The boundary of their rapid (by more than an order of magnitude) increase was found, and a regularity describing this phenomenon was obtained.

V(t) = a exp (-t/c) + v (mm/1000 years),

where a = 580 mm/1000 years; c = 25 mm/1000 years; c = 14.65 million years; t - time in million years (Fig. V.2).

Since the rate of endogenous free water inflows in the obtained empirical graph V(t) and its approximation is determined in mm/1000 years, this allows us to quantify average weight annually taken out during the dehydration of free water on the Earth's surface during the last 160 million years and the historical period of the Holocene.

Instrumental observations at water measuring posts from 1880 to 1980 established that the sea level is rising at an average rate of 1.5 mm/year. This rise is not due to climate warming, as is commonly believed, but consists of the following items: 0.7 mm/year due to the melting of 250 km 3 of the Antarctic and Greenland ice shelves; 0.02 mm/year due to the accumulation of 7 km3 of precipitation. The remaining part (0.78 mm/year) is mainly endogenous water inflows with volcanic products, along deep faults, solfataras, fumaroles and by conduction. And this is the lower limit of the recorded outflow of endogenous water, since the level rise occurs against the background of the continuing deepening of the bottom of the World Ocean in the zones of rift ridges, the continental margin Pacific Ocean, along island arc trenches and the Mediterranean region marked by Pliocene-Quaternary seismicity and volcanism. It should also be taken into account that almost 20% of the water removed from the bowels is used to moisten marine sediments. Thus, the value obtained is 0.78 mm/year - s with good reason can be rounded up to 1.0 mm/yr. This value, determined in a way independent of drilling data, nevertheless fits well with the general course of the V(t) plot (Fig. V.2). This serves as an additional confirmation of the general trend of an exponential increase in the rate and mass of endogenous water outflow since the end of the Cretaceous.

Rice. V.2. Graph characterizing the rate of sinking of the Earth's oceanic segments ( right part) and the inflow of endogenous water in the last 160 million years and in the future, calculated according to the data on modern hypsometry of uneven-aged shallow-water sediments of the Glomar Challenger: 1 - from the wells of the Pacific, 2 - Atlantic, 3 - Indian oceans; 4 - water, 5 - deep water sediments, 6 - shallow water sediments, 7 - basalts.

The left part of the graph characterizes the rate of water inflow in the future, the shading shows confidence intervals calculated with a probability of 0.95%

Thus, up to an order of magnitude, the annual inflow of free water to the Earth's surface in the historical period of the Holocene was 3.6 × 10 17 g.

The average rate of water inflow over the past 160 million years, determined from the V(t) plot and by the formula:

V(t) = , (n = 1, 2 ... 149)

is equal to 0.01 cm/year, which, in terms of mass, with the average area of ​​the Jurassic-Cretaceous Cenozoic marine basins close to modern ones, gives approximately 3.6 × 10 16 g/year, i.e. an order of magnitude less than in the Holocene. Consequently, during the period of spontaneous dehydration and oceanization of the Earth (60 million years), water was transferred to the surface:

3.6 10 16 g/year? 60 10 6 years = 2.2 10 24

This is 0.5 × 10 24 g more than the mass of the modern hydrosphere, which is 1.64 × 10 24 g. The question arises: where did this huge mass of water go? To answer it, we need to remember that over 60 million years of oceanization, a layer of sediments with an average thickness of 500 m was formed on the bottom of the oceans. Since their humidity, according to drilling data, is on average 30%, or (in terms of level) 3 10 4 cm, then it is possible to estimate the mass of water buried in the thickness of marine sediments:

300 10 16 cm 2? 3 10 4 cm? 1.03 g / cm 3 "0.1 10 24 g.

The value obtained is approximately 20% of the excess value - 0.52 × 10 24 g, i.e. annually, 1.7 × 10 15 g, or 5% of the average annual inflow of free water during the period of oceanization (3.6 × 10 16 g) goes to moisten the bottom sediments. Consequently, the rest of the water 0.42 · 10 24 g, which is absent in the modern volume of the hydrosphere, was lost to photolysis. From here it is possible to determine the mass of annual losses of water during the dissociation of its molecule in the upper layers of the atmosphere under the action of hard corpuscular solar radiation:

0.42 10 24 g / 60 10 6 years = 7 10 15 g,

those. losses due to photolysis are about 2.5% of the current free water inflows (3.6 10 17 g).

Determining the order of magnitude of these previously unknown scientific literature article of the balance of free water is of fundamental importance in assessing the general direction of the evolution of the Earth's hydrosphere, the ratio of land and sea areas, and with them the climate and natural environment in geological time scale and historical perspective.

In modern water balance schemes on Earth, the volume of water evaporated over the oceans and seas is considered by many researchers to be equal to the volume of water that returned to the World Ocean with precipitation, river and surface runoff, and melting glaciers. However, it should be recognized that this scheme of the water cycle is correct only in the first approximation and is realized under the condition of a constant total mass of water on the Earth's surface and a constant capacity of the depressions of the World Ocean. In other words, this scheme corresponds to a closed thermodynamic system with a closed cycle. But such a system, as you know, does not produce work, because it is in a stable equilibrium. Its entropy is maximum, which, as we showed above, is not observed under the conditions of the real Earth, because there is an inflow of intraplanetary water and dissipation of part of it into outer space. Based on the regularity V(t) we found, these balance items are now also defined in the existing schemes of the water cycle on Earth.

Let us explain the point “inflow of cosmogenic water”. The mass of cosmic matter falling annually to the Earth is estimated at 10 12 g. In terms of water (5% - based on data on meteorites), this is 5 10 10 g / year, i.e. about 0.00001% of the annual endogenous intake. Since the content of cosmogenic matter in sections of the earth's crust is known and does not exceed present-day inputs, it can be concluded from this that the earth's hydrosphere is of exclusively intraplanetary origin - it is the most important product of the evolution of protomatter.

The obtained planetary articles of the free water balance are of fundamental importance for reconstructing the picture of the evolution of the face of the Earth on the geological time scale. Small annualized masses of endogenous and dissipating water, being a permanent factor, essentially determine the dynamics of the evolution of the Earth's surface.

Given the nature of the dehydration and oceanization process that has been established over 60 million years, it would be unreasonable to expect its sudden decline, as well as an even greater increase in the next hundreds and thousands of years - a time scale that is negligible in comparison with the established total duration of this process. This makes it possible to predict future changes in the ocean level, and with it the climate and natural conditions. Without taking into account the deglaciation of polar glaciers, in 10 thousand years the ocean level will rise by 8 m, and in 100 thousand years - by 80 m.

Thus, the new water balance equation should look like this:

P + R + T - E - F = N (N>0),

where T - endogenous water intake, F - losses due to photolysis. However, in the course of transgression, which cannot be compensated in any way by the increase in the capacity of oceanic basins (in such a geologically short period of time), the general warming of the Earth's climate is inevitable. Consequently, the polar glaciers will continue to shrink and the endogenous transgression, as today, will be intensified by the eustatic one - by 63-65 m in the first 10 thousand years. Note that this estimate does not take into account the rates of coastal subsidence observed at 13% of the continental margins.

From the above it is clear that the modern balance of land and sea is a brief moment in geological history Earth. It continues to change, and the general direction of this variability is determined - the ocean, deepening, continues to expand its boundaries at the expense of land.

Thus, in all reconstructions of the continent-ocean system, from now on it is necessary to take into account the permanent factor of endogenous water inflow, which in the Cenozoic era of oceanization averaged 3.6 × 10 16 g/year, or 0.1 mm/year in terms of level, and in the Quaternary period reached its climax - 3.6 · 10 17 g/year, or 1 mm/year in terms of level. The modern balance of water on the Earth's surface can be represented in the form of a diagram and equations presented in Fig. V.3.

This factor is ultimately decisive for the evaluation climate change past and future, degradation of polar glaciers, changes in the entire natural environment on the surface of our planet.

General balance equation

Continent: P 1 \u003d E 1 + R P + R + T - E - F \u003d N, N> 0 Ocean: P 2 \u003d E 2 - R

R 1 + R 2 \u003d E 1 + E 2

(108 = 62+46) ? 10 3 km 3 (517 = 517) ? 10 3 km 3 (409 \u003d 455 - 46)? 10 3 km 3

Rice. V.3. Diagram of the Earth's water balance

Thus, water on Earth is exclusively of intraplanetary origin, and its mass - 1.64 · 10 24 g - was accumulated gradually in the course of the geological evolution of protoplanetary matter. The progressive deepening and increase in the area of ​​the World Ocean, established by the Glomar Challenger drilling data, is compensated by the continuous inflow of endogenous water exceeding 0.78 mm/year, which is recorded in the endogenous component of the ocean level rise. This is explained by the relative stability of the capacity of oceanic depressions in the Holocene. Consequently, we can speak of a relatively calm tectonic regime of the Earth in the last 10 thousand years. During epochs of tectonic activity, the capacity of oceanic depressions will increase due to subsidence and deepening of the bottom, which will entail a partial decrease or suspension of level rise. However, taking into account the general reduction in the scale of tectonic activity in the area of ​​oceanic segments in the Pleistocene compared to the Cenozoic (it is localized by the ridge zone of rift ridges, island arc trenches, and the Pacific periphery), we should expect a continuation of the process of rising levels of the ocean and adjacent seas in the future. In the next 10 thousand years, if the current rate of deglaciation is maintained, it will be about 15 m, and if the glaciers of Greenland and Antarctica are completely degraded, it will be 70 m. The probability of the latter is predetermined by the expansion of the ocean area and, as a consequence, an increase in the moisture content of the Earth's surface and a general warming of the climate.

In particular, in the history of the Baltic Sea, the influence of eustatic and endogenous factors in the rise of the level begins to affect from the Litorinian time, when the connection between the sea and the ocean was restored (7200 years ago). In combination with tectonic subsidence, which is especially noticeable in the South Baltic, and the strength characteristics of the tops of the sedimentary cover, the progressive rise in sea level in the second half of the Holocene determines the rate of coastal destruction and abrasion. All coastal protection works in the South Baltic should be built taking into account the predicted sea level rise, which, taking into account the tectonic factor, is about 3.5 m per thousand years.

§ 3. Groundwater

The groundwater- these are waters located in the upper part of the earth's crust (up to a depth of 12-16 km) in liquid, solid and vaporous states. Most of them are formed due to seepage from the surface of rain, melt and river waters. Groundwater is constantly moving both vertically and horizontally. Their depth, direction and intensity of movement depend on the water permeability of the rocks. To permeable rocks include pebbles, sands, gravel. To waterproof(waterproof), practically impermeable to water - clays, dense rocks without cracks, frozen soils. The layer of rock that contains water is called aquifer.

According to the conditions of occurrence, groundwater is divided into three types: soil located in the uppermost, soil layer; ground lying on the first permanent water-resistant layer from the surface; interstratal located between two impermeable layers. Ground The waters are fed by infiltrated atmospheric precipitation, waters of rivers, lakes, and reservoirs. The groundwater level fluctuates with the seasons of the year and is different in different zones. So, in the tundra it practically coincides with the surface, in deserts it is located at a depth of 60-100 m. They are distributed almost everywhere, do not have pressure, move slowly (in coarse-grained sands, for example, at a speed of 1.5-2.0 m per day ). The chemical composition of groundwater varies and depends on the solubility of adjacent rocks. By chemical composition distinguish between fresh (up to 1 g of salts per 1 liter of water) and mineralized(up to 50 g of salts per 1 liter of water) groundwater. The natural outlets of groundwater to the earth's surface are called sources(springs, keys). They are usually formed in low places where the earth's surface is crossed by aquifers. Sources are cold(with water temperature not higher than 20 ° C, warm(20 to 37°C) and hot, or thermal (over 37 ° C). Periodically gushing hot springs are called geysers. They are located in areas of recent or modern volcanism (Iceland, Kamchatka, New Zealand, Japan). The waters of mineral springs contain a variety of chemical elements and can be carbonic, alkaline, hydrochloric, etc. Many of them have medicinal value.

Groundwater replenishes wells, rivers, lakes, swamps; dissolve various substances in rocks and carry them; cause landslides and waterlogging. They provide plants with moisture and population drinking water. Sources give the most clean water. water vapor and hot water Geysers are used to heat buildings, greenhouses and power plants.

Groundwater reserves are very large - 1.7%, but they are renewed extremely slowly, and this must be taken into account when spending them. Equally important is the protection of groundwater from pollution.

§ 4. Rivers

River- this is a natural water stream flowing in the same place constantly or intermittently during the dry season (drying rivers). The place where the river starts is called source. The source can be lakes, swamps, springs, glaciers. The place where a river flows into a sea, lake or other river is called mouth. A river that flows into another river is called tributary.

River mouths can be deltas and estuaries. Delta arise in shallow areas of the sea or lake as a result of the accumulation of river sediments, have a triangular shape in plan. The riverbed here branches into many branches and channels, which are usually fan-shaped. Estuaries- single-arm, funnel-shaped mouths of rivers, expanding towards the sea (the mouths of the Thames, Seine, Congo, Ob). Usually, the part of the sea adjacent to the estuary has great depths, and river sediments are removed sea ​​currents. Shallow desert rivers sometimes end blind mouths, i.e. do not reach the reservoir (Murghab, Tejent, Coopers Creek).

The main river with all tributaries forms river system . The area from which a river collects surface and groundwater is called swimming pool. Each river has its own basin. The largest pools have the Amazon river (more than 7 million km 2), the Congo (about 4 million km 2), in Russia - the Ob (about 3 million km 2) - see table. V.1. The boundary between river basins is called watershed.

The flowing water of the river over a long time produces long and complex river valleys. river valley- a concave winding form of relief that stretches from the source to the mouth and has a slope towards the mouth. It consists of a channel, floodplain, terraces.

Table V.1
The main rivers of the world

Name	Length, km	Basin area, thousand km 2
Elba (Laba)
Oder (Odra)
Amur (with Argun)
Yenisei (with Biy-Khem)
Neil (with Kagera)
Congo (Zaire)
Mississippi (with Missouri and Red Rock)
St. Lawrence
Colorado
Colombia
Amazon (with Marañon)
	Australia
Murray (with Darling)

channel- a deepening in a river valley, through which the waters of the river constantly flow. floodplain- part of the river valley, which is filled with water during the flood period. Above the floodplain, the slopes of the valley usually rise, often in a stepped form. These steps are called terraces. They arise as a result of the eroding activity (erosion) of the river. The river channel in plan view usually has a sinuous shape and is characterized by the alternation of deeper sections ( stretches) with smaller ones ( rifts). The meanders of the river are called meanders, or meanders, lines of greatest depths - fairway.

All the given characteristics of the river are its natural characteristics. In addition to them - and no less important - is a set of design characteristics that are closely related, and sometimes interspersed with natural ones.

Important characteristics of a river are its fall, slope, flow rate, discharge and runoff. The fall river - the excess of its source above the mouth (height difference of two points). slope channels - the ratio of the fall to the length of the river. For example, the height of the source of the Volga is 226 m, the mouth
-28 m, length 3530 km. Then its slope will be equal to: 226 - (-28) / 3530 = = 7.2 cm / km. The falls and slopes of individual sections of the river are also calculated if their height and length are known. The fall and slopes, as a rule, decrease from the sources to the mouth, the flow velocity depends on their magnitude, they characterize the energy of the flow.

Every river has upper, average and bottom currents. The upper course is distinguished by significant slopes and large scouring activity, the lower one - the largest mass water and slower speed.

Current speed Water flow is measured in meters per second (m/s) and is not the same in different parts of it. It consistently increases from the bottom and walls of the channel to the middle part of the stream. Speed ​​is measured in various ways, for example, hydrological floats or hydrometric turntables.

The water regime of the river is characterized by water flow and runoff. Consumption is the amount of water passing through the riverbed in one second, or the volume of water flowing through the cross section of the stream per unit time. The cost is usually expressed in terms of cubic meters per second (m 3 / s). He equal to area cross section of the flow multiplied by average speed currents. Water consumption over a long period of time - month, season, year - is called runoff. The amount of water that rivers carry in an average year is called water content.

The most abundant river the globe- Amazon. Its average consumption is 20 thousand m 3 /s, the annual flow is about 7 thousand km 3. In the lower reaches, the width of the Amazon in some places reaches 80 km. The second place in terms of water content is occupied by the Congo River (flow rate - 46 thousand m 3 / s), then the Ganges, the Yangtze. In Russia, the most abundant rivers are the Yenisei (discharge 19.8 thousand m 3 /s) and the Lena (17 thousand m 3 /s). The longest river in the world is the Nile (with Kagera) - 6671 km, in Russia - the Amur (with Argun) - 4440 km.

Rivers, depending on the relief, are divided into two large groups: flat and mountainous. Many rivers in the upper reaches are mountainous, while those in the middle and lower reaches are flat. Mountain rivers have significant falls and slopes (up to 2.4 and even up to 10 m/km), fast flow (3-6 m/s), usually flow in narrow valleys. Sections of rivers with a rapid course, confined to places where hard-to-wash rocks come to the surface, are called thresholds. The fall of water from a steep ledge in a river bed is called waterfall. The highest waterfall on Earth is Angel (1054 m) on the Caroni River (a tributary of the Orinoco, South America); Victoria Falls on the Zambezi River (Africa) has a height of 120 m and a width of 1800 m. plain rivers are characterized by slight falls and slopes (10-110 cm/km), slow flow (0.3-0.5 m/s), usually flow in wide valleys.

A significant part of the water flow is made up of dissolved salts and solids. All solid material carried by a river is called solid runoff. It is expressed by the mass or volume of material that the river carries over a certain time (season, year). This is an extremely large work of rivers. The average annual solid runoff, for example, of the Amu Darya is about 100 million tons of solid material. River sediments clog irrigation systems, fill reservoirs, and impede the operation of hydro turbines. The volume of solid runoff depends on the turbidity of the water, which is measured in grams of the substance contained in 1 m 3 of water. On the plains, the turbidity of river waters is the lowest in the forest zone (in the taiga - up to 20 g / m 3), and the highest - in the steppe (500 - 1000 g / m 3).

The most important characteristic of rivers is their food. There are four power sources: snowy, rainy, glacial, underground. The role of each of them in different seasons of the year and in different places is not the same. Most rivers have mixed food. Rain is typical for the rivers of the equatorial, tropical and monsoon regions. Snow feeding is noted near rivers of temperate latitudes with cold, snowy winters. Glacier-fed rivers originate in high, glacier-covered mountains. Almost all rivers are fed by groundwater to some extent. Thanks to them, the rivers do not dry up in the summer and do not dry out under the ice.

The regime of rivers largely depends on nutrition. Mode rivers is a change in the amount of water discharge by seasons of the year, level fluctuations, changes in water temperature. In the annual water regime of rivers, periods with typically repeating levels are distinguished, which are called low water, high water, flood.

low water- the lowest water level in the river. In low water, the flow and flow of rivers are insignificant, the main source of nutrition is groundwater. In temperate and high latitudes, there is summer and winter low water. Summer low water occurs as a result of the absorption of precipitation by the soil and strong evaporation, winter low water - as a result of the lack of surface nutrition.

high water- a high and prolonged rise in the water level in the river, accompanied by flooding of the floodplain. Occurs annually in the same season. During the flood, the rivers have the highest water content, this period accounts for most of the annual flow (up to 60-80%). Floods are caused by the spring melting of snow on the plains or the summer melting of snow and ice in the mountains and in the polar regions. Often floods cause long and heavy rains in the warm season.

high water- a rapid but short-term rise in the water level in the river. Unlike floods, floods occur irregularly. It is usually formed from rains, sometimes from rapid melting of snow or discharges of water from reservoirs. Down the river, the flood spreads in a wave that gradually fades.

floods- the highest rises of water, flooding areas located in the river valley, and adjacent lowland areas. Floods are formed as a result of an abundant influx of water during the period of snowmelt or heavy rains, as well as due to blockage of the channel by ice during the period of ice drift. AT Kaliningrad region(R. Pregolya) and St. Petersburg (R. Neva), they are also associated with wind surge of water from the sea and backwater of the river flow. Floods are common on rivers Far East(monsoon rains), on the Mississippi, Ohio, Danube, Ganges, etc. They cause great harm.

The rivers of cold and temperate latitudes freeze and become covered with ice during the cold season. The thickness of the ice cover can reach 2 m or more. However, some sections of the rivers do not freeze, for example, in a shallow section with a fast current, or when rivers emerge from a deep lake, or at the site of a large number of sources. These areas are called polynyas.

The opening of the river in spring, in which the movement of broken ice floes downstream of the river is observed, is called ice drift. Ice drift is often accompanied by traffic jams and jams. congestion- accumulation of floating ice caused by any obstacles. Zazhory- Accumulation of intra-water ice. Both cause a sharp rise in the water level, and in case of a breakthrough, its rapid movement along with the ice.

§ 5. Use of rivers. Channels. reservoirs

From surface water highest value in life and economic activity rivers have man. Rivers contribute economic development states. Since ancient times, people have created their settlements along the banks of the rivers, from time immemorial and still the rivers serve as communication routes. The waters of the rivers are used to supply the population with drinking and technical water, for fishing and human hygiene, and in last years more and more active - for rest and treatment. Rivers are widely used for irrigation and irrigation of fields, contain a huge supply of cheap energy and, thanks to the creation of power plants, are the most important source of electricity. With full right, one can recall the ancient saying: “Water is life!”

The experience of man's constant habitation on the banks of rivers suggested the shortest way from one river to another. This, as it were, connected different rivers and significantly expanded the possibilities of using them for swimming. In arid regions, the waters of rivers have also been actively used for irrigation since ancient times by diverting part of the water to fields (ditches).

Later, in the interests of human economic activity, permanent and more grandiose hydraulic structures began to be created. Began to be built channels designed for irrigation, water transport, providing the population with drinking and technical water. The Karakum Canal carries part of the waters of the Amu Darya to Ashgabat, the Saratov Canal - the waters of the Volga to the trans-Volga steppes, and the North Crimean Canal - to the steppes of the Crimea. Navigation channels connect natural sea and river routes. They provide the shortest waterway between the seas. The main navigable canals of Russia: Volga-Don (connects the Volga and Don), White Sea-Baltic (White Sea and Lake Onega), Volga-Baltic waterway (Volga - Rybinsk reservoir - Lake Onega), Volga - Moscow canal. The system of these canals forms a through waterway between the White and Baltic Seas in the northwest and the Caspian, Azov and Black Seas in the south.

Canals redistribute the flow of rivers, sharply increase the flow of water, which can lead to negative consequences: an increase in water flow in the Amu Darya reduced the flow of its waters into the Aral Sea. As a result, the sea dries up, its salinity has increased, and the coastline has receded by 20, in some places by 150 km.

The construction of canals, numerous hydroelectric power stations required the redistribution of the river flow of these rivers in time, the creation of water reserves for the normal functioning of the entire system. To this end, they began to create artificial reservoirs. The largest reservoirs in our country are: Bratsk on the Angara, Kuibyshev, Rybinsk, Volgograd on the Volga, Kiev, Kremenchug and Kakhovskoe on the Dnieper, Votkinskoe and Kama on the Kama, as well as Tsimlyanskoe, Vileika and others. Reservoirs have similarities with a lake and a river: with the first - in slow water exchange, with the second - in the progressive nature of the movement of water.

How large reservoir structures violate the natural balance of the area: flooding of fertile lands, swamping of adjacent territories, deforestation, genetic migration routes of fish are interrupted in rivers, the weather often changes unpredictably.

§ 6. Lakes

Lake- this is a closed depression of land filled with water and not having a direct connection with the ocean. Unlike rivers, lakes are reservoirs of slow water exchange. The total area of ​​the Earth's lakes is about 2.7 million km 2, or about 1.8% of the land surface. Lakes are ubiquitous, but uneven. The geographic location of lakes is greatly influenced by the climate, which determines their nutrition and evaporation, as well as factors that contribute to the formation of lake basins. In areas with a humid climate, there are many lakes, they are full-flowing, fresh and mostly flowing. In regions with a dry climate, ceteris paribus, there are fewer lakes, they are often shallow in water, more often drainless, and therefore often saline. Thus, the distribution of lakes and their hydrochemical features are determined by geographic zonality.

Most large lake- Caspian (area 368 thousand km 2). The largest are also lakes Superior, Huron and Michigan (North America), Victoria (Africa), Aral (Eurasia). The deepest are Baikal (Eurasia) - 1620 m and Tanganyika (Africa) - 1470 m.

Lakes are usually classified according to four criteria:

• origin of lake basins;
• origin of the water mass;
• water regime;
• salinity (amount of dissolved substances).

By origin of lake basins lakes are divided into five groups.

1. Tectonic lake basins are formed as a result of the formation of cracks, faults and subsidence of the earth's crust. They are distinguished by great depth and steep slopes (Baikal, the Great North American and African lakes, Winnipeg, the Great Slave, the Dead Sea, Chad, Air, Titicaca, Poopo, etc.).
2. Volcanic, which are formed in the craters of volcanoes or in depressions of lava fields (Kuril and Kronotskoe in Kamchatka, many lakes of Java and New Zealand).
3. Glacial lake basins are formed in connection with the plowing activity of glaciers (erosion) and the accumulation of water in front of glacial landforms, when a glacier melted and deposited transported material, forming hills, ridges, uplands and depressions. These lakes are usually narrow and long, oriented along the lines of glacier melting (lakes in Finland, Karelia, the Alps, the Urals, the Caucasus, etc.).
4. Karst lakes, the basins of which arose as a result of failures, soil subsidence and erosion rocks(limestone, gypsum, dolomite). The dissolution of these rocks with water leads to the formation of deep, but insignificant lake basins.
5. Zaprudnye(dammed, or dammed) lakes arise as a result of blocking the channel (valley) of the river with blocks of rocks during landslides in the mountains (Sevan, Tana, many lakes of the Alps, the Himalayas and other mountainous countries). From a large mountain collapse in the Pamirs in 1911, Sarez Lake was formed with a depth of 505 m.

A number of lakes are formed by other reasons:

• firth lakes are common on the shores of the seas - these are coastal areas of the sea, separated from it by means of coastal spits;
• oxbow lakes- lakes that arose in the old riverbeds.

Origin water mass lakes are of two types.

1. atmospheric. These are lakes that have never been part of the oceans. Such lakes predominate on Earth.
2. relic, or residual, lakes that appeared on the site of the retreating seas (Caspian, Aral, Ladoga, Onega, Ilmen, etc.). In the recent past, the Caspian Sea was connected with the Azov Strait, which existed on the site of the current valley of the Manych River.

By water regime also distinguish two types of lakes - waste and closed.

1. sewage lakes are lakes into which rivers flow and flow out (lakes have a drain). These lakes are most often located in the zone of excessive moisture.
2. Drainless- into which rivers flow, but none flows out (lakes do not have a drain). Such lakes are located mainly in the zone of insufficient moisture.

According to the amount of dissolved substances, four types of lakes are distinguished: fresh, salty, brackish and mineral.

1. Fresh lakes - the salinity of which does not exceed 1 ‰ (one ppm).
2. brackish- the salinity of such lakes is up to 24 ‰.
3. Salty- with the content of dissolved substances in the range of 24.7-47 ‰.
4. mineral(47‰). These lakes are soda, sulfate, chloride. In mineral lakes, salts can precipitate. For example, self-sustaining lakes Elton and Baskunchak, where salt is mined.

Usually sewage lakes are fresh, as the water in them is constantly updated. Endorheic lakes are more often saline, because evaporation prevails in their water flow, and all mineral substances remain in the reservoir.

Lakes, like rivers, are the most important natural resources; used by man for navigation, water supply, fishing, irrigation, obtaining mineral salts and chemical elements. In some places, small lakes are often artificially created by man. Then they are also called reservoirs.

§ 7. Swamps

As a result of sediment accumulation and overgrowing, the lakes gradually become shallow, and then turn into swamps and become dry land.

swamps- excessively moistened land areas with a peculiar marsh vegetation and a layer of peat of at least 0.3 m. With a lower thickness of peat or its absence, excessively moistened territories are called wetlands. Bogs are formed when water bodies become overgrown or water stagnates in forests, meadows, clearings, burnt areas, etc. They can occur both in low reliefs and on watersheds. The development of swamps is facilitated by flat and slightly dissected relief, excessive moisture, water resistance of soils, close location of groundwater, and permafrost. Bogs develop in different climatic conditions, but are especially characteristic of the forest zone of the temperate zone and tundra. Their share in Polissya accounts for 28%, in Karelia - about 30%, and in Western Siberia(Vsyuganye) - over 50% of the territory. Swampiness sharply decreases in the steppe and forest-steppe zones, where there is less precipitation, and evaporation increases. The total area occupied by swamps is about 2% of the land area.

According to the nature of the water supply and vegetation, the swamps are divided into three types: lowland, upland and transitional.

Lowland bolts are formed on the site of former lakes, in river valleys and in depressions that are permanently or temporarily flooded with water. They feed mainly on groundwater rich in mineral salts. The vegetation cover is dominated by green mosses, various sedges and grasses. Birch, alder, and willow appear on older swamps. These swamps are characterized by low peat content - the thickness of peat does not exceed 1-1.5 m.

riding swamps form on flat watersheds, feed mainly on atmospheric precipitation, the vegetation is characterized by a limited species composition - sphagnum mosses, cotton grass, rosemary, cranberries, heather, and woody - pine, birch, less often cedar and larch. The trees are very depressed and stunted. Sphagnum moss grows better in the middle of the marsh massif, on the outskirts it is oppressed by mineralized waters. Therefore, raised bogs are somewhat convex, their middle rises by 3-4 m. The peat layer reaches a thickness of 6-10 m or more.

transitional swamps occupy an intermediate position; in terms of nutrition and vegetation, they are mixed. They are ground and atmospheric. There are sedges and reeds, a lot of peat mosses, thickets of birches, etc. here.

The swamps don't stay the same. The most characteristic process is the change of low-lying bogs as a result of the accumulation of plant mass and peat by transitional, and then by riding ones. Raised bogs are overgrown with meadow or forest vegetation.

Marshes have great importance. They extract peat, which is used as an environmentally friendly fuel and fertilizer, as well as for the production of a number of chemicals. After draining, the swamps turn into high-yielding fields and meadows. But at the same time, swamps affect the climate of adjacent places, they are natural reservoirs of water, which often feed rivers.

§ 8. Glaciers

Glacier- moving masses of ice that have arisen on land as a result of the accumulation and gradual transformation of solid atmospheric precipitation. Their formation is possible where more solid precipitation falls during the year than it has time to melt or evaporate. The limit above which snow accumulation is possible (the predominance of negative temperatures during the year) is called snow line. Below the snow line, positive temperatures prevail and all the snow that has fallen has time to melt. The height of the snow line depends on climatic conditions, at the equator it is located at an altitude of 5 km, in the tropics - 6 km, and in the polar regions it drops to ocean level.

Regions are distinguished in the glacier nutrition and runoff. In the feeding area, snow accumulates to form ice. In the runoff area, the glacier melts and is mechanically unloaded (separations, landslides, sliding into the sea). The position of the lower edge of the glacier can change, it advances or recedes. Glaciers move slowly, from 20 to 80 cm per day, or 100-300 m per year in mountainous countries. Polar glaciers (Greenland, Antarctica) move even more slowly - from 3 to 30 cm per day (10-130 m per year).

Glaciers are divided into continental (cover) and mountain. Mainland(Greenland, Antarctica, etc.) occupy 98.5% of the area of ​​modern glaciation, cover the land surface, regardless of its relief. They have a flat-convex shape in the form of domes or shields, which is why they are called ice sheets. The movement of ice is directed along the slope of the glacier surface - from the center to the periphery. The ice of continental glaciers is consumed mainly by breaking off its ends, descending into the sea. As a result, floating ice mountains are formed - icebergs, which are extremely dangerous for navigation. An example of continental (cover) glaciation is the ice sheet of Antarctica. Its thickness reaches 4 km with an average thickness of 1.5 km. Mountain glaciers are much smaller and have a variety of shapes. They are located on the tops of mountains, occupy valleys and depressions on the slopes of mountains. Mountain glaciers are located at all latitudes: from the equator to the polar islands. Forms of the glacier are predetermined by the relief, but valley mountain glaciers are the most widespread. The largest mountain glaciers are located in Alaska and the Himalayas, the Hindu Kush, the Pamirs and the Tien Shan.

The total area of ​​glaciers on Earth is about 16.1 million km 2, or 11% of the land (mainly in polar latitudes). Glaciers are huge natural storehouses of fresh water. They contain many times more fresh water than in rivers and lakes combined.

1. Galai I.P., Meleshko E.N., Sidor S.I. A geography manual for university applicants. Minsk: Highest. school, 1988. 448 p.
2. Geography: Reference materials: A book for students of middle and older age / A.M. Berlyant, V.P. Dronov, I.V. Dushin and others; Ed. V.P. Maksakovskiy. M.: Prosveshchenie, 1989. 400 p.
3. Davydov L.K., Dmitrieva A.A., Konkina N.G. General hydrology. Tutorial/ Ed. HELL. Dobrovolsky and M.I. Lvovich. Leningrad: Gidrometizdat, 1973. 462 p.
4. Methodology for teaching geography in high school: Teacher's Manual / Ed. I.S. Matrusova. Moscow: Education, 1985. 256 p.
5. A geography manual for applicants to universities / Ed. V.G. Zavriev. Minsk: Highest. school, 1978. 304 p.
6. Khromov S.P., Mamontova L.I. Meteorological dictionary. Leningrad: Gidrometizdat, 1974. 568 p.
7. Eaglet V.V. The history of water on Earth and other planets // Geography at school. 1990. No. 5. S. 9-15.

In quantitative terms, undoubtedly, the world ocean is the leader, which accounts for 1,338,000 thousand km 3 or 96.4% of all water on Earth.

On land there is 49675 km 3 or about 3.6% of the planet's water in the form of snow and glaciers, rivers, lakes, reservoirs, swamps, groundwater. Almost all atmospheric water (90%) is concentrated in the lower part of the troposphere at a height of 0-5 km. In total, there is 13 thousand km 3 of water or 0.001% here. In organisms, it is even less - about 0.0001% of the Earth's water (about 1 thousand km 3).

There are several hypotheses for the origin of water. Recently, it is generally accepted that the main masses of water came as a result of magma degassing. During the formation of the primary basalt crust, 92% of basalts and 8% of water were formed from the mantle. Modern lavas also contain water vapor from 4 to 8%. At present, up to 1 km3 of water is formed annually by degassing. These waters are called juvenile (young). Water also comes from space.

One of the most important processes in the geographical shell is the water cycle (moisture cycle). Moisture circulation is the transfer of matter and energy in the geographic shell through water. There are small and large cycles. Small cycles include regional moisture cycles: continental-atmospheric; ocean-atmospheric; oceanic-atmospheric-continental.

In a large cycle, all small cycles are its links. In a large cycle, the following main links can be distinguished: Mainland; atmospheric; Oceanic. The cycle carries out the transfer of moisture and heat, it connects the earth's shells and plays an extremely important role in the formation of the complex natural shell of the Earth.

The water cycle on earth

The water cycle, or moisture cycle, on Earth is one of the most important processes in the geographical envelope. It is understood as a continuous closed process of water movement, covering the hydrosphere, atmosphere, lithosphere and biosphere. The fastest water cycle occurs on the Earth's surface. It is performed under the influence of solar energy and gravity. Moisture circulation consists of the processes of evaporation, the transfer of water vapor by air currents, its condensation and sublimation in the atmosphere, precipitation over the Ocean or land and their subsequent runoff into the Ocean. The main source of moisture in the atmosphere is the World Ocean, land is of less importance. A special role in the circulation is occupied by biological processes - transpiration and photosynthesis. Living organisms contain more than 1000 km 3 of water. Although the volume biological waters small, they play an important role in the development of life on Earth and the enhancement of moisture circulation: almost 12% of the evaporating moisture into the atmosphere comes from the land surface due to its transpiration by plants. In the process of photosynthesis carried out by plants, 120 km 3 of water decomposes annually into hydrogen and oxygen.

In the surface water cycle on Earth, the small, large and intracontinental cycles are conventionally distinguished. Only the Ocean and the atmosphere participate in the small circulation. Most of the moisture evaporating from the surface of the Ocean falls back onto the sea surface, making a small cycle.

A minor part of the moisture is involved in a large surface cycle, carried by air currents from the ocean to the land, where a number of local moisture cycles occur. From the peripheral parts of the continents (their area is about 117 million km 2), water again enters the Ocean through surface (river and glacial) and underground runoff, completing a large cycle.

Territories that do not have a runoff into the World Ocean are called areas of internal runoff (non-drainage in relation to the Ocean). Their area is more than 32 million km2. Water, evaporated from the closed territories of the land and again falling on it, forms an intracontinental circulation. The largest areas of internal flow are the Aral-Caspian, Sahara, Arabia, Central Australian. The waters of these areas exchange moisture with the peripheral areas and the ocean, mainly through its transfer by air currents.

The mechanism of moisture exchange ocean - atmosphere - land - ocean is actually much more complicated. It is connected with the general global exchange of matter and energy, both between all the geospheres of the Earth, and between the entire planet and the Cosmos. The global moisture cycle of the Earth is an open process, since in the volume in which water is released from the bowels of the earth, it no longer returns back: when exchanging matter with outer space, the process of irretrievable loss of hydrogen during the dissipation of water molecules prevails over its arrival. However, the amount of water in the hydrosphere does not decrease due to the inflow of water from the bowels.

Quantitatively, the water cycle on Earth is characterized by water balance. The water balance of the Earth is the equality between the amount of water entering the surface of the globe in the form of precipitation and the amount of water evaporating from the surface of the oceans and land for the same period of time. On average, the annual amount of precipitation, as well as evaporation, is 1132 mm, which in volume units is 5,77,060 km 3 of water.

Scheme of moisture circulation of water in nature (according to L.K. Davydov):

1 - evaporation from the ocean surface; 2 - precipitation on the ocean surface; 3 - precipitation on the land surface; 4 - evaporation from the land surface; 5 – surface, non-conditional runoff into the ocean; 6 - river runoff into the ocean; 7 - underground runoff into the ocean or into an endorheic area.

In the history of the Earth, major changes in water balance characteristics have been repeatedly noted, which is associated with climate fluctuations. During periods of cooling, the world water balance changes towards greater moisture content of the continents due to the conservation of water in glaciers. The water balance of the Ocean becomes negative, and its level goes down. During periods of warming, on the contrary, a negative water balance is established on the continents: evaporation increases, transpiration increases, glaciers melt, the volume of lakes decreases, the flow into the Ocean increases, the water balance of which becomes positive.

The average annual water balance of the Earth (according to R. K. Klige and others)

Elements of balance	Water volume km 3 / year	Water layer, mm	% of consumption
The globe as a whole
Evaporation
Precipitation
World Ocean
Evaporation
Precipitation
river runoff
glacial runoff
underground runoff
Balance discrepancy
land area
Precipitation
Evaporation
river runoff
glacial runoff
underground runoff
Balance discrepancy

An increase in air temperature by almost 1°C in the 20th century caused a violation of the global water balance: it became positive for the oceans, and negative for the land. Warming has led to an increase in evaporation from the ocean surface and an increase in cloudiness both over the oceans and over the continents. Atmospheric precipitation over the Ocean and in the coastal regions of the land increased, but decreased in the inland regions. The melting of glaciers has increased significantly. Such changes in the global water balance lead to an increase in the level of the World Ocean by an average of 1.5 mm/year, and in recent years up to 2 mm/year.

Since evaporation consumes heat, which is released during the condensation of water vapor, the water balance is associated with the heat balance, and the moisture cycle is accompanied by a redistribution of heat between the spheres and regions of the Earth, which is very important for the geographic envelope. Along with the energy exchange in the process of moisture circulation, there is an exchange of substances (salts, gases).

The increase in the reserves of the water mass of the main links of the surface hydrosphere (but R. K. Klige and others)

Elements of the hydrosphere	Change in water volume, km 3 / year
World Ocean
The groundwater
reservoirs

Different parts of the hydrosphere on the Earth's surface have different periods of water exchange. It can be seen from the table that the shortest periods of water exchange are with atmospheric moisture (8 days), the longest - with terrestrial and underground glaciers (10 thousand years).

The period of water exchange of individual parts of the hydrosphere on the surface of the Earth (according to the monograph "World Water Balance and Water Resources of the Earth", with additions)

Types of natural waters	Volume, thousand km 3	Average period of conditional renewal of water reserves
Water on the surface of the lithosphere
World Ocean
Glaciers and permanent snow cover
reservoirs
Water in the rivers
Water in swamps
Water at the top of the lithosphere
The groundwater
underground ice
Water in the atmosphere and living organisms
Water in the atmosphere
Water in organisms		Few hours

Some elements of the water cycle are amenable to human control, but only in the boundary layers of the hydrosphere, lithosphere and atmosphere: water accumulation in reservoirs, snow accumulation and snow retention, artificial rains, etc. But such measures should be very careful and thoughtful, since in nature everything is interconnected and changes in one place can have undesirable consequences in another region.

The importance of water in nature, life and economic activity is extremely high. It is water that makes the Earth the Earth, it participates in all physical-geographical, biological, geochemical and geophysical processes occurring on the planet. A. de Saint-Exupery wrote about water: “You cannot say that you are necessary for life: you are life itself”: and Indira Gandhi owns the saying: “Civilization is a dialogue between man and water.”

Fresh water is used for industrial and domestic water supply, for irrigation and irrigation. Water is used in obtaining electricity, in navigation, the importance of water lines in military operations and in many other things.

Until recently, the prevailing belief was that humanity would have enough water forever. The rapid growth of the world's population, development industrial production and agriculture are causing increasing rates of water consumption, which already reach about 5 thousand km3/year. 80% of the water used is associated with agriculture, and first of all with the irrigation of 240 million hectares of land.

Since fresh water reserves are sharply reduced in quantity and quality due to the rapid pace of its consumption, it is necessary to organize the rational use of water and their protection. This is one of the most important environmental issues on the ground.

Literature.

1. Lyubushkina S.G. General geography: Proc. allowance 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.

The change of the entire volume of atmospheric moisture occurs every 10 days or 36 times a year. The deepest underground waters are renewed the slowest - about 5000 years. About 453 thousand km 3 of water annually evaporates from the surface of the World Ocean. The process of water evaporation and condensation of atmospheric moisture provide fresh water on Earth. The continuous movement of water under the influence of solar energy is called the global water cycle.

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