Hydrosphere

Hydrosphere - the totality of all the Earth's waters: continental (deep, soil, surface), oceanic and atmospheric. Sometimes the waters of the oceans and seas are combined into a kind of part of the hydrosphere - oceanosphere. This is logical, because the overwhelming part of the water is concentrated in the oceans and seas.

The appearance of water on Earth is usually associated with the condensation of water vapor from volcanic eruptions that have occurred since the beginning of the formation of the planet. Evidence for the presence of water in the geological past is sedimentary rocks with horizontal layering, which reflects the uneven deposition of mineral particles in the aquatic environment. Such rocks are known and their age dates back to 3.8-4.1 billion years. However, the appearance of droplet water could have been earlier - in the air, on the surface of the planet, in the voids of rocks. In order for water to concentrate in the depressions of the earth's surface and form pools, watering of the initially dehydrated rocks had to occur. The primary waters were highly mineralized, which is associated with the dissolution of various substances in them, which were released together with water vapor during volcanic manifestations. Fresh water appeared later. It is possible that an additional source of water on Earth was ice comets that invaded the atmosphere. Such a process is observed at the present time, as well as the formation of water during the condensation of vapors of volcanic eruptions.

Despite the diversity of natural waters and their different state of aggregation, the hydrosphere is one, because all its parts are connected by ocean and sea currents, channel, surface and underground runoff, as well as atmospheric transport. The structural parts of the hydrosphere are given in table. 5.3.

Physical and chemical properties of water. Water is the most amazing substance in the world. Despite the fact that A. Celsius used for the temperature scale the melting point of water as 0 ° and its boiling point as 100 °, this liquid can freeze at a temperature of 100 ° C and remain in a liquid state at -68 ° C, depending on the oxygen content and atmospheric pressure... It has many anomalous properties.

Fresh water is odorless, colorless and tasteless, while sea water is tasteful, colorless and can be odorless. Under natural conditions, only water is found in three states of aggregation: solid (ice), liquid (water) and gaseous (water vapor).

The presence of salts in water changes its phase transformations. Fresh water on the land surface at a pressure of one atmosphere has a freezing point of 0 ° C and a boiling point of 100 ° C. Seawater at a pressure of one atmosphere and a salinity of 35 ‰ has a freezing point of about -1.9 ° C and a boiling point of 100.55 ° C. The boiling point depends on atmospheric pressure: the higher the height above the ground, the lower it is. Water is a universal solvent: it dissolves more salts and other substances than any other substance. It is a chemically stable substance that is difficult to oxidize, burn, or decompose. Water oxidizes almost all metals and destroys even the most stubborn rocks.

Table 5.3 Water volume and water exchange activity different parts hydrospheres

Parts of the hydrosphere	Volume	Duration of conditional water exchange
thousand km 3	% of the total	% of the volume of fresh water
World Ocean		96,5	-	2500 years
The groundwater	23 700	1,72	30,9	1,400 to 10,000 years in the permafrost zone
Glaciers	26 064	1,74	68,7	9700 years
Lakes		0,013	0,26	17 years
Soil moisture	16,5	0,001	0,05	1 year
The waters of the atmosphere	12,9	0,001	0,037	8 days
Swamps	11,5	0,0008	0,033	5 years
Reservoirs	6,0	0,0004	0,016	0.5 years
The rivers	2,0	0,0002	0,006	16 days

When water freezes, it expands, increasing its volume by about 10%. The density of fresh water is 1.0 g / cm 3, sea water is 1.028 g / cm 3 (with a salinity of 35 ‰), fresh ice- 0.91 g / cm 3 (therefore ice floats in water). The density of other bodies (except for bismuth and gallium) increases during the transition from a liquid to a solid state. Water has a high specific heat capacity, i.e. the ability to absorb a large amount of heat and relatively little heat at the same time. This property is extremely important, since water stabilizes the planet's climate.

The abnormal properties of water are explained by the structure of its molecule: hydrogen atoms are attached to the oxygen atom not "classically", but at an angle of 105 °. Due to asymmetry, one side of the water molecule has positive charge and the other is negative. Therefore, a water molecule is an electric dipole.

The processes involving water are extremely multifaceted: photosynthesis of plants and respiration of organisms, the activity of bacteria and organisms that generate from water (mainly marine) for the construction of their skeletons or accumulate chemical elements (Ca, J, Co), nutrition processes and anthropogenic pollution and many others.

World ocean (oceanosphere)- a single continuous water shell of the Earth, which includes the oceans and seas. Currently, there are five oceans: Pacific, Atlantic, Indian, Arctic (Arctic according to foreign classifications) and South (Antarctic). According to the international classification, there are 54 seas, among which there are internal and marginal.

The volume of the waters of the World Ocean is 1340-1370 million km 3. The volume of land that rises above sea level is 1/18 of the volume of the ocean. If the Earth's surface were completely flat, the ocean would cover it with a layer of water of 2700 m.

The waters of the World Ocean make up 96.5% of the volume of the hydrosphere and cover 70.8% of the planet's surface (362 million km 2). Due to the huge water mass, the World Ocean has a great influence on the thermal regime of the earth's surface, performing the functions of a planetary thermostat.

The chemical composition of the waters of the World Ocean. Sea water is a special type of natural water. The formula for H 2 O water is also true for sea water. However, in addition to hydrogen and oxygen, seawater contains 81 out of 92 naturally occurring elements (theoretically, all elements of the periodic table that exist in nature can be found in seawater). Most of them are found in extremely low concentrations.

1 km 3 of sea water contains about 40 tons of dissolved solids, which determine its most important property - salinity. Salinity is expressed in ppm (0.1%) and its average value for ocean waters is 35 ‰ . Water temperature and salinity determine density sea ​​water.

The main ones that make up the sea water are given below.

1. Solids, constituting an average of 3.5% (by weight). Most of all, seawater contains chlorine (1.9%), i.e. more than 50% of all dissolved solids. This is followed by: sodium (1.06%), magnesium (0.13%), sulfur (0.088%), calcium (0.040%), potassium (0.038%), bromine (0.0065%), carbon (0.003%) ... The main elements dissolved in seawater form compounds, the main of which are: a) chlorides(NaCl, MgCl) - 88.7%, which give the sea water a bitter-salty taste; b) sulfates(MgSO 4, CaSO 4, K 2 SO 4) - 10.8%; v) carbonates(CaCO 3) - 0.3%. In fresh water, the opposite is true: most of all carbonates (60.1%) and least of all chlorides (5.2%).

2. Biogenic elements(nutrients) - phosphorus, silicon, nitrogen, etc.

3. Gases. Seawater contains all atmospheric gases, but in a different proportion than in air: nitrogen predominates (63%), which, due to its inertness, does not participate in biological processes. This is followed by oxygen (about 34%) and carbon dioxide (about 3%), argon and helium are present. In those sea areas where oxygen is absent (for example, in the Black Sea), hydrogen sulfide is formed, which in the atmosphere at normal conditions absent.

4. Trace elements present in low concentrations.

Geographic patterns of distribution of water temperature and salinity. The general regularities of the horizontal (latitudinal) distribution of temperature and salinity on the surface of the World Ocean are shown in Fig. 5.9 and 5.10. It is obvious that the water temperature decreases in the direction from the equator to the poles, and salinity is characterized by a pronounced minimum in the equatorial region, two maximums in tropical latitudes and decreased values ​​at the poles. The alternation of centers of low and high salinity at the equator and in the tropics is explained by the abundance atmospheric precipitation in the equatorial zone and the excess of evaporation over precipitation in the northern and southern tropics.

The water temperature decreases with depth, which can be seen in Fig. 5.11 for the northern part The Pacific... This pattern is typical for the World Ocean as a whole, however, changes in water temperature and salinity differ in its individual parts, which is explained by a number of reasons (for example, the season). The greatest changes occur in the upper layer to a depth of 50-100 m. With depth, the differences disappear.

Water masses is a large volume of water that forms in a certain area of ​​the World Ocean and has relatively constant physical, chemical and biological properties.

According to V.N. Stepanov (1982), the following water masses are distinguished vertically: superficial, intermediate, deep and bottom.

Among the superficial water masses allocate equatorial, tropical(north and south), subtropical(north and south), subpolar(subarctic and subantarctic) and polar(Arctic and Antarctic) water masses (Fig. 5.12).

Borders different types water masses are boundary layers: hydrological fronts, zones divergences(discrepancies) or convergence(convergence) waters.

Surface water most actively interact with the atmosphere. In the surface layer, intensive mixing of waters takes place; it is rich in oxygen, carbon dioxide and living organisms. They can be called the waters of the "oceanic troposphere".

Along with surface currents (see Fig. 7.11) in the World Ocean there are countercurrents, subsurface and deep water movements, as well as vertical mixing, tidal currents, level fluctuations.

Rice. 5.9. Average annual temperature (° С) of the World Ocean surface (according to V. N. Stepanov 1982): 1 - isotherms; 2 - areas of maximum water temperature; 3 - areas of water temperature below average (average water temperature 18.56 ° C)

Rice. 5.10. Average annual salinity (‰) of the World Ocean surface (according to V.N. Stepanov, 1982): 1 - isohaline; 2 - areas of maximum salinity; 3 - salinity areas below average; 4 - areas of minimum salinity (average salinity 34.7 8 ‰)

Rice. 5.11. Graphs of the vertical distribution of temperature, typical for the arctic (1), subarctic (2), subtropical (3), tropical (4) and equatorial (5) water types

The relief of the bottom of the World Ocean. The following structures are distinguished in the relief of the bottom of the World Ocean: shelf(continental shelf), usually limited by the 200 m isobath, continental(continental) slope to a depth of 2000-3000 m and ocean bed. According to another classification, there are: littoral(and sublittoral), bathyal, abyssal(fig.5.13). Plots with depths over 6000 m make up no more than 2% of the ocean floor area with a depth of less than 200 m - about 7%.

Rice. 5.12. Oceanic fronts and surface water masses of the World Ocean (according to V.N. Stepanov, 1982): types of water masses: Ar- arctic; SbAr- subarctic; SbTS - subtropical Northern Hemisphere; Tc- tropical Northern Hemisphere; NS- equatorial; Ty - tropical Southern Hemisphere; SatTu- subtropical southern hemisphere; Sat - subantarctic; An - antarctic; Tar- the Arabian Sea; 715 - Bay of Bengal. The names of the oceanic fronts are shown in the figure.

Rice. 5.13. Schematic subdivision of the ocean floor

The role of the oceanosphere. Various (thermal, mechanical, physical, chemical, etc.) processes occurring on the vast (more than 70% of the Earth's surface) water area of ​​the World Ocean have a significant impact on the processes occurring on land and in the atmosphere. Chemical elements, which are part of the sea water, participate in the processes of gas, mass and moisture exchange at the boundaries of the hydrosphere - lithosphere - atmosphere. Hydrochemical processes affect the animal and vegetable world not only the ocean, but the planet as a whole. Constant gas exchange with the atmosphere regulates the gas balance of the Earth: the content of carbon dioxide in seawater is 60 times greater than in the atmosphere.

Sushi waters, despite the relatively small volume, play a huge role in the functioning of geographic envelope and the vital activity of organisms. It should be noted that not all land waters are fresh; there are salt lakes and springs. The ionic composition of fresh and sea water is given in table. 5.4.

The rivers- the most active representative of fresh land waters. Rivers include permanent and relatively large streams. Smaller streams are called streams. The relief, geological structure, climate, soils, vegetation affect the regime of rivers and form their natural appearance. The river has source - the place where it starts, and mouth- the place where the river flows directly into the receiving reservoir (lake, sea, river). The estuary can branch out, forming delta rivers. The land area along which the river flows is called riverbed. The main river and its tributaries put the river system. Rivers flowing into the World Ocean form estuaries- vast areas of mixing of river and sea water. Estuaries are largely influenced by ocean waters.

Table 5.4. Ionic composition of river and sea water (according to P. Weil, 1977)

Jonah	River water	Sea water (salinity 35 ‰ )
Cations
Na +	0,27	468,0
K +	0,06	10.0
Mg 2+	0,34	107,0
Ca 2+	0,75	20,0
Sum	1,42	605,0
Anions
Сl -	0,22	546,5
HCO 3 -	0,96	2,3
SO 4 2-	0,24	56,2
Sum	1,42	605,0

The nature of the river flow is associated with their nutrition, which is rain, snow, glacial and underground, and is determined by the climatic conditions in the river basin. Rivers of predominantly snow supply have a pronounced spring flood and summer low water (Volga, Dnieper, Danube, Northern Dvina, Amur, etc.). Underground power smoothes out annual flow... Rain-fed rivers often have their maximum runoff during different seasons of the year. Areas of the earth's surface and strata of soils and soils, from where the river receives food, are called catchment area.

Rivers do significant work, eroding the channel, transporting and depositing erosion products - alluvium. They not only mechanically destroy, but also dissolve rocks. River deposits sometimes form vast alluvial plains with an area of ​​millions of kilometers (Amazonian, West Siberian lowlands, etc.). It is estimated that the rivers simultaneously contain 2,100 km 3 of water, while 47,000 km 3 flows into the ocean annually. This means that the volume of water in the rivers is renewed approximately every 16 days. For comparison, let us point out that the waters of the World Ocean carry out a large cycle in about 2500 years.

Lakes- a natural body of water with a slowed down water exchange, which has no direct connection with the ocean. For its formation, it is necessary to have a closed lowering of the earth's surface (basin). The lakes cover a total area of ​​approximately 2 million km 2, and the total volume of their waters exceeds 176 thousand km 3. According to the conditions for the formation of the basin, size, chemical composition waters, thermal regime of the lake are very diverse. Many artificial lakes have also been created - reservoirs(about 30 thousand), the volume of water in which is more than 5 thousand km 3. About half of the lake waters are saline, and most of them are concentrated in the largest closed lake - the Caspian Sea (76 thousand km 3). The largest freshwater lakes are Baikal (23 thousand km 3), Tanganyika (18.9 thousand km 3), Verkhnee (16.6 thousand km 3). The regime of the lakes is characterized by heat influx, fluctuations in water level, currents, water exchange conditions, ice coverage, etc. Large lakes largely determine the climatic conditions of adjacent territories (for example, Lake Ladoga).

Swamps- these are land areas characterized by excessive moisture, stagnant or weakly flowing water regime and hydrophytic vegetation. They occupy an area of ​​2.7 × 10 6 km 2, or about 2% of the land surface. The volume of swamp waters in the world is about 11.5 km 3, which is 5 times higher than the one-time volume of water in rivers. The emergence of swamps is associated with both climatic conditions (excess moisture) and geological structure territories (close to an aquatic horizon) that contribute to land swamping or overgrowing of water bodies. In some areas of temperate and subpolar latitudes, permafrost plays the role of an aquiclude. The specific formation of swamps is peat.

The groundwater- these are waters that are in rocks in a liquid, solid or gaseous state. According to recent studies, the water content in rocks within the lithosphere exceeds the data indicated in Table. 5.3, and is about 0.73 - 0.84 billion km 3. This is only half of what it contains in the seas, oceans and surface water bodies, including the world's ice reserves. Water accumulates in all kinds of voids - channels, cracks, pores. Found to be below level groundwater to a depth of 4 - 5 km and more, almost all cavities in rocks are filled with water. According to deep drilling, the water in the cavities of rocks is located at a depth of more than 9.5 km, i.e., below the average level of the bottom of the World Ocean.

The totality of watercourses (rivers, streams, canals), reservoirs (lakes, reservoirs) and other water bodies (swamps, glaciers) is hydrographic network.

Land waters have been greatly transformed by humans due to irrigation, land reclamation, plowing of land and other urban processes, in connection with which the problem of drinking water has become acute.

The complexity of its solution lies in the fact that the needs for clean water grow, but its reserves remain the same. Used v everyday life, in industrial and agricultural cycles, fresh water most often returns to river network as Wastewater, variously peeled or unrefined at all.

I cannot imagine summer without a vacation by the sea or at least an ordinary trip to the lake. The greatness of the Russian rivers simply amazes me, and the beauty of some lakes, for example, Baikal, is something incredible. Such a variety of reservoirs is part of the hydrosphere - the water shell of our planet. Without water, there would be no life on Earth, so it must be protected.

What parts does the hydrosphere consist of?

Water is found everywhere on our planet and in different states. Most of all it is in liquid form. These include:

• oceans;
• seas;
• lakes and reservoirs;
• rivers;
• The groundwater.

Here you need to understand that salt water is about 95% and only 5% is fresh (the one that most living organisms consume).

The planet has huge reserves of groundwater. Scientists estimate them at about 5% of the entire hydrosphere of the planet, but there is a theory about a huge underground ocean deep in the bowels. True, I can hardly believe it.

The hydrosphere also contains ice. There are a huge number of glaciers on the planet, which are concentrated at the poles of our planet. But if you look at the absolute amount, then in the hydrosphere they make up only 2%. Upon learning this, I was very surprised.

Water vapor is also part of the hydrosphere, but very, very small. Although thanks to him, precipitation falls.

The water cycle in nature

On the planet, water is in motion. It passes from one state to another, but its quantity remains constantly unchanged.

The cycle is as follows. Water evaporates from various bodies of water and rises upward, forming clouds. Thanks to the wind, they are transported to another place. Water droplets form in the clouds and then fall to the planet's surface.

Without this process, the vegetation simply would not receive the moisture it needs.

How did water appear on the planet

There is one common theory. Previously, there was almost no atmosphere on the planet, and our Earth was bombarded by various asteroids and meteorites. Many of them were composed of ice. Thus, this substance, important for life, was brought in.

Each of the spheres of the planet has its own characteristic features... None of them has yet been fully studied, despite the fact that research is ongoing. Hydrosphere - the watery shell of the planet, represents great interest both for scientists and for simply curious people who want to study more deeply the processes taking place on Earth.

Water is the basis of all life, it is a powerful vehicle, an excellent solvent and a truly endless storehouse of food and mineral resources.

What does the hydrosphere consist of?

The hydrosphere includes all water that is not chemically bound and no matter in what state of aggregation(liquid, vaporous, frozen) it abides. General form the classification of parts of the hydrosphere looks like this:

World Ocean

This is the main, most significant part of the hydrosphere. The totality of the oceans is a non-continuous water envelope. It is divided by islands and continents. The waters of the World Ocean are characterized by a general salt composition. Includes four main oceans - Pacific, Atlantic, Arctic and Indian oceans... Some sources also distinguish the fifth, the Southern Ocean.

The study of the oceans began many centuries ago. The first explorers are considered navigators - James Cook and Ferdinand Magellan. It was thanks to these travelers that European scientists received invaluable information about the scale of the water space and the outlines and dimensions of the continents.

The oceanosphere makes up approximately 96% of the world's oceans and has a fairly homogeneous salt composition. The oceans receive and fresh water, but their share is small - only about half a million cubic kilometers. These waters enter the oceans with precipitation and river flows. The small amount of incoming fresh water determines the constancy of the salt composition in ocean waters.

Continental waters

Continental waters (also called surface waters) are those that are temporarily or permanently in water bodies located on the surface the globe... These include all water flowing and collecting on the surface of the earth:

• swamps;
• rivers;
• seas;
• other drains and reservoirs (for example, reservoirs).

Surface waters are classified as fresh and saline, and are the opposite of groundwater.

The groundwater

All waters in the earth's crust (in rocks) are named. They can be in a gaseous, solid or liquid state. Groundwater makes up a significant part of the planet's water reserves. Their total is 60 million cubic kilometers. Groundwater is classified by depth. They are:

• mineral
• artesian
• unpaved
• interstratal
• soil

Mineral waters are those that contain trace elements, dissolved salt.

Artesian is a pressurized groundwater located between water-resistant layers in rocks. They are classified as minerals, and usually occur at a depth of 100 meters to one kilometer.

Ground waters are gravitational waters located in the upper, closest to the surface, water-resistant layer. This type of groundwater has a free surface and usually does not have a solid rock roof.

Interstratal waters are low-lying waters between layers.

Soil waters are those that move under the influence of molecular forces or gravity and fill some of the gaps between the soil cover particles.

General properties of the constituent parts of the hydrosphere

Despite the variety of states, compositions and locations, the hydrosphere of our planet is one. All the waters of the globe are united by a common source of origin (the earth's mantle) and the interconnection of all waters included in the water cycle on the planet.

The water cycle is an uninterrupted process, which consists in constant movement under the influence of gravity and solar energy... The water cycle is a connecting link for the entire shell of the Earth, but it also unites other shells - the atmosphere, biosphere and lithosphere.

During this process, it can be in three basic states. Throughout the existence of the hydrosphere, it is renewed, and each of its parts is renewed for a different period of time. Thus, the period of renewal of the waters of the World Ocean is about three thousand years, water vapor in the atmosphere is completely renewed in eight days, and the cover glaciers of Antarctica may take up to ten million years to renew. Interesting fact: all waters that are in a solid state (in permafrost, glaciers, snow covers) are united by the name cryosphere.

The hydrosphere of the earth is the watery shell of the earth.

Introduction

The earth is surrounded by an atmosphere and hydrosphere, which are noticeably different, but at the same time complementary from each other.

The hydrosphere arose in the early stages of the formation of the Earth, like the atmosphere, influencing all life processes, the functioning of ecological systems, determining the emergence of many animal species.

What is the hydrosphere

Hydrosphere in translation from Greek means a sphere of water or water shell of the earth's surface. This shell is continuous.

Where is the hydrosphere

The hydrosphere is located between two atmospheres - the gaseous shell of the planet Earth, and the lithosphere - a hard shell, which means land.

What does the hydrosphere consist of?

The hydrosphere consists of water, which differs in chemical composition and is presented in three various conditions- solid (ice), liquid, gaseous (vapor).

The structure of the Earth's water envelope includes oceans, seas, reservoirs that can be salty or fresh (lakes, ponds, rivers), glaciers, fjords, ice caps, snow, rain, atmospheric water, and liquid flowing in living organisms.

The share of seas and oceans in the hydrosphere is 96%, another 2% are groundwater, 2% are glaciers, and 0.02 percent (a very small share) are rivers, swamps and lakes. The mass or volume of the hydrosphere is constantly changing, which is associated with the melting of glaciers and the departure of significant areas of land under water.

The volume of the water envelope is equal to 1.5 billion cubic kilometers. The mass will constantly increase, given the number of volcanic eruptions and earthquakes. Most of the hydrosphere is made up of the oceans that form the World Ocean. This is the largest and most saline body of water on Earth, in which the salinity percentage reaches 35%.

According to the chemical composition, the waters of the oceans contain all the known elements that are located in the periodic table. The total part of sodium, chlorine, oxygen and hydrogen reaches almost 96%. The ocean crust includes basalt and sedimentary layers.

The hydrosphere also includes groundwater, which also differ in chemical composition. Sometimes the salt concentration reaches 600%, and gases and derivatives are present in them. The most important of these are oxygen and carbon dioxide, which are consumed by plants in the ocean during the process of photosynthesis. It is necessary for the formation of limestone rocks, corals, shells.

Fresh water is of great importance for the hydrosphere, part of which in the total volume of the shell is almost 3%, of which 2.15% is stored in glaciers. All components of the hydrosphere are interconnected, being in high or low revolutions, which allows the water to undergo a complete renewal process.

Hydrosphere boundaries

The waters of the World Ocean cover an area of ​​71% of the Earth, where the average depth is 3800 meters, and the maximum is 11022 meters. The so-called continental waters, which provide all the life of the biosphere, water supply, water supply and irrigation.

The hydrosphere has lower and upper boundaries. The lower one runs along the so-called Mohorovichich surface - crust at the bottom of the ocean. The upper border is located in the most upper layers atmosphere.

Functions of the hydrosphere

Water on Earth has essential for people and nature. This manifests itself in the following signs:

• First, water is important source minerals and raw materials, because people use water more often than coal and oil;
• Secondly, it provides relationships between ecological systems;
• Thirdly, it acts as a mechanism that transfers bioenergetic ecological cycles of global importance;
• Fourthly, it is a part of all living beings that live on Earth.

For many organisms, water becomes a medium of origin, and then further development and formation. Development of land, landscapes, karst and slope rocks is impossible without water. In addition, the hydrosphere facilitates the transport of chemicals.

• Water vapor acts as a filter against the penetration of radiation rays from the Sun to the Earth;
• Water vapor on land helps regulate temperature regime and climate;
• The constant dynamics of the movement of ocean waters is maintained;
• A stable and normal circulation is ensured throughout the planet.

• Each part of the hydrosphere participates in the processes that take place in the Earth's geosphere, which include water in the atmosphere, on land and underground. In the atmosphere itself, in the form of steam, there are more than 12 trillion tons of water. Steam is restored and renewed due to condensation and sublimation, turning into clouds, fog. In this case, a significant amount of energy is released.
• The waters located underground and on land are divided into mineral and thermal waters, which are used in balneology. In addition, these properties have a recreational effect on both humans and nature.

All parts of the hydrosphere are interconnected by the already known process of the water cycle in nature.

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Natural science grade 5

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