The groundwater. Types of groundwater: description, characteristics and features

(up to a depth of 12-16 km) in liquid, solid and vapor 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. Permeable rocks include pebbles, sands, gravel. To waterproof (waterproof), practically impervious to water - clays, dense without cracks, frozen soils. The layer of rock that contains water is called an aquifer.

According to the conditions of occurrence, groundwater is divided into three types: located in the uppermost, soil layer; lying on the first permanent water-resistant layer from the surface; interstratal, located between two water-resistant layers. Groundwater is fed by infiltrated sediments, waters, lakes,. The groundwater level fluctuates with the seasons of the year and is different in different zones. So, in it practically coincides with the surface, 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. According to the chemical composition, 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 are distinguished. The natural outlets of groundwater to the earth's surface are called sources (springs, springs). They usually form in low places where aquifers cross the earth's surface. Springs are cold (with no higher than 20 ° C, warm (from 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 (,). The waters of the 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,; dissolve various substances in rocks and transfer them; cause landslides. They provide plants with moisture and population drinking water. Springs provide the purest 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.

A considerable part of the Earth's water reserves are underground basins that flow in the soil and rock layers. Huge accumulations of groundwater are lakes that wash out rock deposits and soil, forming pits.

The value of ground fluid is great not only for nature, but also for humans. Therefore, researchers conduct regular hydrological observations of its condition and quantity, and study deeper and deeper what underground water is. Definition, classification and other issues of the topic will be discussed in the article.

What is underground water?

Groundwater is water located in the interlayer spaces of rocks occurring in the upper layer of the earth's crust. Such water can be presented in any state of aggregation: liquid, solid and gaseous. Most often, groundwater is tons of flowing liquid. The second most common are blocks of glaciers that have been preserved since the permafrost period.

Classification

The division of groundwater into classes depends on the conditions of their occurrence:

• soil;
• ground;
• interstratal;
• mineral;
• artesian.

In addition to the listed types, groundwater is divided into classes depending on the level of the layer in which they are located:

• The upper horizon is fresh groundwater. As a rule, their depth is small: from 25 to 350 m.
• The middle horizon is the location of a mineral or saline liquid at a depth of 50 to 600 meters.
• The lower horizon is a depth of 400 to 3000 meters. Water with high mineral content.

Groundwater, located at great depths, may be young in age, that is, recently appeared, or relict. The latter could be laid in the underground layers together with the ground rocks in which it is "placed". Or, relic underground water was formed from permafrost: the glaciers melted - the liquid accumulated and persisted.

ground water

Soil water is a liquid that occurs in the upper layer of the earth's crust. It is mainly localized in spatial voids between soil particles.

If you understand what soil-type underground water is, it becomes obvious that this type of liquid is the most useful, since its surface location does not deprive it of all minerals and chemical elements. Such water is one of the main sources of "nutrition" for agricultural fields, forests and other crops.

This kind of liquid can not always lie horizontally, often its outlines are similar to the soil topography. In the upper layer of the earth's crust, moisture does not have a "solid support", so it is in a suspended state.

An excess amount of soil water is observed in the spring, when the snow melts.

ground water

The ground variety is the waters that are located at some depths of the upper earth layer. The depths of fluid flow can be large if it is an arid area or desert. In temperate climates with occasional regular rainfall, groundwater is not as deep. And with an excess of rain or snow, ground fluid can lead to flooding of the area. In some places, this kind of water comes to the surface of the soil and is called a spring, key or source.

Groundwater is replenished due to precipitation. Many confuse it with artesian, but the latter lies deeper.

Excess fluid can accumulate in one place. As a result of a standing position, swamps, lakes, etc. are formed from groundwater.

Interstratal

What is interlayer groundwater? These are, in fact, the same aquifers as ground and soil, but only the level of their flow is deeper than that of the previous two.

A positive feature of interstitial fluids is that they are much cleaner because they lie deeper. In addition, their composition and quantity always fluctuate within one constant limit, and if changes occur, then they are insignificant.

Artesian

Artesian waters are located at depths exceeding 100 meters and reaching 1 km. This variety is considered, and indeed is, the most suitable for human consumption. Therefore, on suburban areas drilling of underground wells is often practiced as a source of water supply for residential buildings.

When drilling a well, artesian water bursts to the surface as a fountain, since it is a pressure type of groundwater. It lies in the voids of rocks between water-resistant layers of the earth's crust.

A reference point for the extraction of artesian water are certain natural objects located on the surface: depressions, flexures, troughs.

mineral

Minerals are the deepest and most healing and valuable for human health. They have an increased content of various mineral elements, the concentration of which is constant.

Mineral waters also have their own classifications:

By appointment:

• canteen;
• medical;
• mixed.

According to the predominance of chemical elements:

• hydrogen sulfide;
• carbonic;
• glandular;
• iodine;
• bromine.

According to the degree of mineralization: from fresh to waters with the highest concentration.

Classification by purpose

Groundwater is used in human life. Their purpose is different:

• drinking water is water that is suitable for consumption either in its natural, untouched form, or after purification;
• technical is a liquid that is used in various technological, economic or industrial sectors.

Classification by chemical composition

The chemical composition of groundwater is influenced by those rocks that are adjacent to moisture in close proximity. The following categories are distinguished:

1. Fresh.
2. Weakly mineralized.
3. Mineralized.

As a rule, the waters lying in close proximity to the earth's surface are freshwater. And the deeper the moisture is located, the more mineralized its composition.

How was groundwater formed?

Several factors influence the formation of groundwater.

1. Precipitation. Precipitation in the form of rain or snow is absorbed by the soil in the amount of 20% of the total. They form soil or ground fluid. In addition, these two categories of moisture are involved in the water cycle in nature.
2. Melting permafrost glaciers. Underground waters form whole lakes.
3. There are also juvenile fluids that were formed in solidified magma. This is a kind of primary water.

Groundwater monitoring

Groundwater monitoring is an important necessity, which allows you to track not only its quality, but also its quantity, and in general, its presence.

If the quality of water is examined in the laboratory, surveying the seized sample, then the exploration of the presence implies the following methods, interconnected with each other:

1. The first is an assessment of the area for the presence of expected groundwater.
2. The second is the measurement of the temperature indicators of the detected liquid.
3. Next, the radon method is applied.
4. After that, basic wells are drilled, followed by core extraction.
5. The selected core is sent for research: its age, thickness and composition are determined.
6. A certain amount of groundwater is pumped out of the wells to determine their characteristics.
7. Based on the base wells, maps of the occurrence of the liquid are compiled, its quality and condition are assessed.

Groundwater exploration is divided into the following types:

1. Preliminary.
2. Detailed.
3. Operational.

Pollution problems

The problem of groundwater pollution is very relevant today. Scientists identify the following ways of pollution:

1. Chemical. This type of pollution is very common. Its globality depends on the fact that on Earth there is a huge number of agricultural and industrial enterprises, which dump their waste in liquid and solid (crystallized) form. These wastes penetrate very quickly into aquifers.
2. Biological. Polluted sewage from domestic use, faulty sewers - all these are the reasons for the contamination of groundwater with pathogens.

Classification by type of water-saturated soils

The following are distinguished:

• porous, that is, those that settled in the sands;
• cracked, those that fill the cavities of blocks of rocks and rocks;
• karst, those that are located in limestone rocks or other fragile rocks.

Depending on the location, the composition of the waters is also formed.

Stocks

Groundwater is regarded as a mineral that is renewable and participates in the water cycle in nature. The total reserves of this variety of minerals are 60 million km 3. But, despite the fact that the indicators are not small, groundwater is subject to pollution, and this significantly affects the quality of the consumed liquid.

Conclusion

Rivers, lakes, underground waters, glaciers, swamps, seas, oceans - all these are the water reserves of the Earth, which are somehow interconnected. Moisture located in the soil layers not only forms an underground pool, but also affects the formation surface water oem.

Groundwater is suitable for human drinking, therefore saving it from pollution is one of the main tasks of mankind.

In the history of the development of hydrogeology, the most various classifications groundwater. Here, a fundamentally important difference is the allocation of classification features. From this point of view, all classifications can be divided into general, chemical and private, General ones cover the global conditions of groundwater activity or combine many classification features. In other words, they are a combination of features that give some regular generality of groundwater life. Examples of such classifications are those of A.M. Ovchinnikov and F.P. Savarinsky on the conditions of occurrence and the regime of groundwater.

Particular classifications systematize groundwater according to one or more characteristics, that is, they represent special cases of groundwater activity. These include the classifications of B.L. Lichkova, O.K. Lange, A.M. Zhirmunsky, A.A. Kozyrev and many others. These include the classifications of N.I. Tolstikhina groundwater permafrost, A.N. Tokarev - radioactive groundwater, etc.

The most common in practice are the classifications of F.P. Savarinsky and A.M. Ovchinnikov, which have many common features and which form the basis for further consideration of groundwater.

15.1. The concept of groundwater regime

The groundwater regime is a regular change in time that occurs in the aquifer as episodic, daily, seasonal, annual, long-term and secular fluctuations due to meteorological and geological processes. The concept of the groundwater regime covers all aspects of their activity and properties: temperature, physical condition, nature of water exchange, level (pressure), flow rate, chemical and gas composition, etc. episodic climatic factors(upper groundwater horizons), permanent (lower groundwater horizons), very permanent (artesian waters).

15.2 Groundwater classification A.M. Ovchinnikova and her essence

According to the conditions of occurrence and the regime of A.M. Ovchinnikov identified types, subtypes and varieties of waters:

waters of the aeration zone - perched water (varieties: soil, marsh and suspended in the aeration zone);

groundwater with various subtypes;

artesian waters.

The waters of the permafrost regions and the waters of the regions of young volcanism are allocated to them as special types. On the basis of this classification, a further consideration of groundwater is built, and when characterizing them, the classifications of F.P. Savarinsky, N.I. Tolstikhina, G.V. Bogomolov and others.

15.2.1 Waters of the aeration zone - perched water (soil, marsh, suspended on lenses of water-resistant rocks in the aeration zone)

Rice. 23. Hydrogeological section of the aeration zone and the upper part of the saturation zone.

Legend:

C - aeration zone (perch water), D - saturation zone (ground water)

GWL - groundwater level.

These are the waters closest to the day surface. Their regime is extremely unstable and is entirely determined by hydrometeorological conditions. In dry times, they often disappear. Verkhovodka can form both in porous loose deposits and in the upper part of the weathering crust of fractured rocks. It is located where the processes of infiltration of atmospheric moisture through the aeration zone take place (Fig. 23). Most often, it is confined to the lenses of waterproof rocks, that is, as if “suspended”. It can gradually spread along the edges of the lens and feed groundwater. Part of the perch, or even all, can be used up for evaporation. Usually these are low-mineralized waters, in most cases they have a slightly acidic reaction. May contain organic matter, Fe, H 2 SiO 2 . Easily soiled. In the southern regions, with signs of an arid climate, perched water can be highly mineralized sodium chloride water, from which salts precipitate in drainless depressions. Usually rarely used for water supply due to intermittent regime and pollution. In rural areas, if the perch is deep, it is used for drinking and irrigation. In this case, the conservation of reserves is facilitated by planting forests, the creation of water-resistant barriers, etc. Varieties of perched water are soil water, swamp water, suspended (perched water itself) and dune water.

Soil waters.

lie in soils. The soil layer is an important, albeit very thin, layer of the earth's crust in which vital processes take place. The role of water in these processes is enormous. But it should not be confused with film and capillary water. This is gravitational water, which is involved in the nutrition of the root system of plants. Soil water seeps into the groundwater. The main source of soil water supply is atmospheric precipitation. They have a dual effect on soil fertility - improvement or deterioration (gleying, solonetzization, etc.). Hence, to assess the hydrogeological conditions great importance has the study of soil types and their condition. Change in soil moisture over time - hydroisopleths– lines of the same humidity (in mm or %). The soil layer consists of horizon A (eluvial) and B (illuvial) and subhorizons. There are 8 types of soils: 1) podzolic, 2) chernozem, 3) light chestnut and brown, 4) waterlogged, 5) solonetzes, 6) gray soils and solonchaks, 7) poorly developed soils, 8) laterites and red soils.

Swamp waters.

On the one hand, they are closely connected with surface waters, on the other hand, they are inextricably linked with perched water. A swamp is a wetted surface area covered with a layer of peat 20-30 cm, and if less or no peat, then wetlands.

The occurrence of swamps is associated with various reasons (groundwater outlets and poor drainage, flat surface and impermeable rocks in the upper part of the geological section).

Bogs can be:

1) low-lying, feeding on atmospheric and groundwater;

2) riding (sphagnum), feeding mainly on atmospheric precipitation;

3) mixed.

Hanging swamps are also distinguished, which are fed exclusively by groundwater on the gentle slopes of the valleys.

Bog waters usually have low mineralization, contain organic matter such as humus and low molecular weight organic acids. The nature of the vegetation is a good indicator of the hydrogeological features of the swamp. Treeless bogs of lacustrine origin, characterized by black sticky alder shrubs, can serve as an indicator of the movement of swamp water. Pines develop on a dense peat base and on a powerful pure peat deposit (former raised bog). The filtration coefficient of a peat deposit depends on the degree of peat decomposition and ranges from 0.45 m/day in strongly decomposed ones to 0.85-4.5 m/day in weakly decomposed ones. Filtration through the lower, highly compacted peat layers is negligible. The flow increases significantly in the presence of rivers, drainage channels and channels.

Waters suspended on lenses of waterproof rocks in the aeration zone.

These waters are commonly referred to as "perch water proper". They are shown in fig. 23. Other characteristics are the same as those of other varieties.

15.2.2. Water saturation zone. ground water

ground water- these are free gravitational waters of the first permanently existing aquifers from the earth's surface, enclosed in loose sediments or in the upper part of bedrock. Groundwater can be both non-pressure and have pressure. Their feeding area, as a rule, coincides with the distribution area (Fig. 24). Groundwater is associated with atmospheric moisture, surface water and perched water. But since they occur already at greater depths - up to several tens of meters, their distribution does not always reflect geographic zoning and is subject to a special, hydrogeological zoning. At present, groundwater is understood not only as the first aquifer from the surface, but as a series or "aquifer complex" located in the zone of active water exchange, i.e. drained to varying degrees by a hydrogeographic network. The regime of these waters is directly influenced by hydrometeorological factors and is characterized by seasonal fluctuations in the level, flow rate and chemical composition. By age, groundwater is modern formations, formed on interfluve massifs, in alluvial deposits of river valleys, in foothill alluvial fans. More powerful groundwater basins are known and quite widespread, confined to ancient buried valleys, to sandy-pebble deposits of moraines and glacial rivers, to lava flows, etc.

According to A. M. Ovchinnikov, depending on the conditions of occurrence of groundwater, one should distinguish between ground flow and ground swimming pool , which can be in complex combinations with each other (Fig. 25).

Figure 25. Scheme of the structure of a ground flow (a) and a ground pool in combination with a ground flow (b): 1 - permeable sands; 2 - waterproof rocks; 3 - ground water level; 4 - direction of water movement; 5 - source of ground water.

The boundaries of the groundwater basin are determined by the distribution area and the degree of erosional dissection of sediments favorable for water accumulation. The depth of erosional dissection also determines the depth and shape of the groundwater surface. This surface for the first horizon is called the "mirror" of groundwater. On the map, it is depicted by hydroisohypses - lines of equal heights of the groundwater surface, above the conditional zero plane for each aquifer.

The impermeable rock underlying the groundwater is called the impervious bed or sole. In the case when the waters are blocked by a clay aquiclude, the latter is called the top of the aquifer.

Aquifer thickness is the vertical distance from an impervious bed to the groundwater surface or roof.

Although the surface of groundwater corresponds to some extent to the topography of the earth's surface, the watershed of groundwater does not always coincide with the surface.

The groundwater surface can change its slope under the influence of changes in the filtration properties of rocks. Let us consider this possibility based on the Darcy equation for a unit discharge of a ground flow:

where Q is the flow rate per 1 m of the flow, h is the power of the ground flow

that is, at a constant flow rate, the slope of the groundwater surface is inversely proportional to the filtration coefficient of the rocks and the power of the groundwater flow.

Nutrition conditions and groundwater regime.

Groundwater can have the following power sources:

Infiltration of atmospheric precipitation, which either directly penetrates through the aeration zone to groundwater, or moistens the soil layer until gravity water appears. The latter can fall on the surface of suspended capillary waters. At the same time, the groundwater level rises, especially in low-lying places, where infiltration occurs more intensively.

Infiltration of waters of rivers, lakes and other surface streams and reservoirs during flood periods. In low water, on the contrary, they feed groundwater. The relationship between surface and ground waters is diverse, which can be seen in Figure 26 (a, b, c, d, e).

Rice. 24. Groundwater supply area: 1 - sand; 2 - water-bearing sand; 3 - clay; four - depression curve; 5 - descending spring.

Groundwater recharge from deeper groundwater (Figure 32), which can be ascertained by careful analysis of the hydrogeological conditions. Hydrogeochemical data are especially helpful, since the microcomponent composition is a more sensitive indicator and more differentiated in different types of waters.

The groundwater regime depends on the location of the area in a particular geographical area. In the plain areas, the types of water regime associated with humid and arid climates and the presence of permafrost are well distinguished. In mountainous areas, there is a well-defined zonality of the water regime: with glacial feeding, summer maxima are observed associated with ice melting, and with snow - spring.

Figure 26. Various cases of the ratio of ground and river waters during flood periods: a- the river drains the groundwater horizon; b - the river always feeds groundwater; in- there is no hydraulic connection between ground and surface waters even during floods; G- there is no hydraulic connection between ground and surface waters only during the period of low level in the river; d- the river affects the groundwater level only in a narrow river strip; 1 - permeable rocks; 2 - waterproof rocks; 3 - ground water level.

G.N. Kamensky distinguishes two main types of groundwater regime:

1. Dividing type, characteristic of areas remote from rivers and other surface water bodies and groundwater, which do not have a hydraulic connection with the waters of surface watercourses and water bodies due to overlapping with impervious rocks.

2. Coastal type, characteristic of groundwater in coastal areas in the presence of hydraulic connection with the waters of rivers and other reservoirs. As they move away, their influence fades, and the regime passes into a watershed.

There are also mixed types of groundwater regime, among which three subtypes can be distinguished:

non-pressure groundwater of shallow occurrence with a very small aeration zone; 2) ground non-pressure deep waters with a powerful aeration zone; 3) pressure groundwater.

For the watershed type in the regime of the first subtype, sharp episodic fluctuations in the water level are important, in the second - seasonal. In general, the coastal regime reflects the type of river regime. Here you can see the rise in the level in the spring flood (flood) and the decrease in summer (summer low water), a slight rise in autumn and winter low water.

15.2.3. Groundwater zonation

The idea of ​​groundwater zoning belongs to V.V. Dokuchaev. His student P.V. Ototsky (1914) drew attention to the general pattern of occurrence of groundwater: "As you move south, groundwater deepens and mineralizes."

Let us consider the scheme of groundwater zoning by V.S. Ilyin, who made the first attempt to identify zonal and azonal groundwater in the European part of Russia and map them. He identified 7 groundwater zones and 6 types of azonal groundwater. The latter are not associated with certain zones and can move from one zone to another.

Zonal groundwater.

Tundra water zone

High water zone of the north

A zone of shallow ravines with waters occurring at a depth of 20-25 m.

A zone of deep ravines with waters of increased mineralization, occurring at a depth of 20-25 m.

The ravine-beam zone with hard or brackish waters.

Zone of the Black Sea gully with very deep waters.

The zone of the Caspian ravines, where, unlike the previous zone, there are areas with shallow waters; waters are often highly mineralized.

Subsequently, a number of schemes of the regional plan appeared. For Western Siberia Yu.K. Smolenkov compiled such a scheme. It will be discussed in the course "Regional Hydrogeology".

Azonal groundwater.

1. Waters of terminal moraines.

2. Fractured waters massive rocks and products of their destruction on the Kola Peninsula, the Urals and the South Russian crystalline ridge.

3. Karst waters

4. Swamp waters, i.e. waters of those areas in which the groundwater level is directly dependent on the water level in swamps and is almost not subject to fluctuations.

5. Waters of alluvial and fluvio-glacial deposits.

6. Salt waters.

When assessing the hydrogeological conditions of the entire territory of the Russian Federation from the point of view of the distribution of waters, O.K. Lange in V.S. Ilyin and distinguishes three sharply isolated provinces of zonal groundwater:

the province of permafrost, which is characterized by negative average annual temperatures;

a province with high air humidity, positive average annual temperatures;

a province with high air dryness and a large amplitude of temperature fluctuations.

The map of hydrochemical groundwater zones for the European part of the Russian Federation was compiled by I.V. Harmonov. He singled out (from north to south): a zone of hydrocarbonate-silica waters; zone of bicarbonate calcium waters; zone of predominance of sulfate and chloride waters; subzone of continental salinity; the zone of bicarbonate calcium waters of the mountainous regions of the Crimea and the Caucasus.

The most common is the scheme of groundwater zoning proposed by G.N. Kamensky for the entire territory of the Russian Federation. He singled out two provinces in which two genetic types of waters are developed, respectively:

The waters of the leaching province

The waters of the province of continental salinity

In addition, he singled out separate areas of continental salinity waters among leaching waters, as well as mountainous areas with the development of predominantly leaching waters.

Formation of leaching waters occurs in conditions of excessive moisture, i.e. the predominance of runoff over evaporation in conditions of good drainage. The chemical composition is formed under the influence of the process of leaching of soils and rocks during soil formation and weathering.

Formation of waters of continental salinity occurs with a small amount of precipitation, intense evaporation and the absence of natural drainage. Evaporation predominates in the discharge part of the groundwater balance, which contributes to the formation of ascending capillary currents. The chemical composition of waters of continental salinity is formed in the processes of runoff, when rain and melt waters wash away the salts accumulated on the surface of saline soils (salt efflorescence). Salinization of water occurs when temporary reservoirs dry out, when water evaporates from the soil surface and transpiration by plants, and when groundwater evaporates by capillary rise. In the groundwater zone of continental salinity, the influence of geomorphological factors and the composition of water-bearing rocks strongly affects. Salt waters are distributed mainly in lowland areas, and fresh waters are developed on the watersheds, which are areas of nutrition. As one approaches the foot of the slopes and into wide ravines, the salinity of the waters increases; in the ravines and valleys there are highly mineralized saline groundwaters, accompanied by solonchaks.

15.2.4. The main varieties of groundwater

In accordance with the classification of A.M. Ovchinnikov, the most characteristic varieties of groundwater for the territory of the Russian Federation are waters:

alluvial deposits

glacial deposits

southern non-glacial regions

mountainous areas.

Groundwater of alluvial deposits.

Distributed in ancient and modern deposits of river valleys (Fig. 27). They are of great national economic importance, tk. are widely used for water supply of settlements. Alluvial waters play a significant role in river runoff.

The difference in the velocities of water flow in the channel during high water and low water conditions determines the layered distribution of sedimentary material according to the grain size. The areas of accumulation of floodplain sediments differ from the accumulation of channel sediments (in the first - silty, in the second - sandy).

The diversity of the composition of alluvial deposits is due to the mode of alluvium sedimentation, which largely depends on fluctuations in the erosion basis. Fluctuations in the erosion base of the river often lead to the formation of overdeep areas of the bedrock of the valley, filled with alluvial deposits (Fig. 28). The reason may be soft, easily destroyed rocks (limestone, gypsum, salts, etc.) or the presence of tectonic faults and crushing zones in the bedrock. Such areas require special attention, because. are of considerable interest in the search and exploration of groundwater.

Ancient buried valleys are usually associated with powerful groundwater flows with a large flow rate (tens of thousands of m 3 /day), which allows them to be widely used for water supply. The regime of alluvial waters is closely related to the regime of surface streams. Therefore, in hydrogeological studies, it is important to establish this relationship. Hydroisohypses of groundwater flows often have a complex shape, depending on, for example, the draining river and the outlines of the valley's bedrock banks.

Rice. 27. Cross section of the river length with groundwater horizons in permeable sediments of river terraces.

Legend:

1 - sand; 2 - gravel; 3 – root bed of the valley (igneous rocks); 4- clay; 5- loam.

Rice. 28. Overdeepened areas of the bedrock of a river valley with "pockets" of ancient runoff hollows filled with groundwater.

Legend:

1 – covering loams and clays; 2 - sand; 3 - clay; 4 - "pocket" with groundwater; 5 – root bed of the river valley; 6 - river terraces.

Infiltration of atmospheric precipitation in the most permeable areas or in individual depressions creates a "dome-shaped" surface of ground flows, expressed on the map by closed isohypses. Alluvial waters have pressure. The areas of their nutrition and distribution sometimes often do not coincide. They can even be used for the water supply of large centers. "Under-channel underground rivers" are less polluted than surface waters, but their pollution is not excluded, and self-purification of waters depends on the lithological composition of rocks and the degree of technogenic load.

Ground waters of glacial deposits.

The humid climate (moisture!), good reservoir properties of glacial deposits create favorable conditions for the formation of significant groundwater reserves. For example, Germany is located in the area of ​​Quaternary glacial deposits and widely uses these waters for the water supply of large cities.

There are 2 groups of deposits characterized by certain hydrogeological conditions:

Deposits of eskers - heaps of sandy-boulder material oriented along the movement of the glacier. In the northwestern part of the Russian Federation, the eskers are elongated like dams in the middle of a flat swampy area. In Sweden, the city of Uppsala (near Stockholm) is supplied with water from lake waters.

Fluvio-glacial deposits - sands, pebbles; are widespread in Germany and Poland, where there are several ridges of terminal moraines, elongated in the latitudinal direction, and between them there are ancient valleys containing powerful groundwater flows. The width of the valleys is from 3 to 25 km. Some of them flow such rivers as the Vistula, Oder, Elbe and others.

Before the construction of the Moscow Canal, the groundwater basin in the Mytishchi region was the only source of water supply for the capital (the so-called "Mytishchensky water pipeline"), which was equipped at the end of the 18th century.

Groundwater of non-glacial areas

Non-glacial areas include landscape zones of steppes, semi-deserts and deserts. The northern strip of steppes is a transition from humid to arid climate. The conditions for the formation of groundwater are unfavorable here - a highly developed drainage system ravines, there are no forests and swamps.

In semi-deserts, there are areas of exposed soils, which, like soils, are usually saline, there are many salt lakes, among which there are also self-planting ones. Condensation processes are beginning to take on importance in groundwater recharge.

As you move south, the proportion of infiltration decreases. The large deserts of the CIS are Kara-Kum, Kyzyl-Kum and Muyun-Kum. As a rule, groundwater in continental deposits has a single mirror.

The groundwater supply of the Kara-Kum desert is composed as follows: filtration from rivers - 74%, runoff from Kopet-Dag - about 11%, local infiltration through bare sands - 15%.

The main mass of water is spent on evaporation, which leads to salinization of groundwater. Fresh water in the form of lenses can be found in dunes.

Ground waters of mountain regions and foothills.

A high percentage of runoff in the expenditure part of the balance sheet is characteristic. At the foot of the ridges, as well as in intermontane depressions and basins, thick strata of pebbles are deposited, containing groundwater. From above they are covered with loams.

Replenishment of water reserves occurs at the expense of surface water, which is lost in boulders (“disappearing rivers” in “kurums” - boulder deluvium).

The same picture is observed in the intermountain depressions, which are drainless basins rich in pressure groundwater.

Rice. 29. Groundwater foothills.

15.2.5 Artesian waters

These are waters lying between water-resistant layers within fairly large geological structures, and having pressure. When opening such aquifers, water rises above the roof of the aquifer (horizon) and often pours out to the surface or gushing.

A correct understanding of the formation of artesian waters is possible only with a thorough study of the geological structure of the region and the history of its development.

In each artesian aquifer, three main elements can be distinguished: the feeding area; pressure area; unloading area (Fig.11,30,31).

Hydrogeological conditions within one horizon are different within these 3 areas.

In the recharge area, the aquifer is usually elevated and drained, so the waters here have a free surface and do not fundamentally differ from groundwater.

In the pressure area, the level to which water can rise is located above the top of the aquifer. The vertical distance from the top of the aquifer to this level is called the head. In the case of an imaginary level located above the surface of the earth, water pours out (spouts) (Fig. 11). The pressure level is also called piezometric, and the isolines of the absolute marks of the pressure level are called hydroisopieses .

In the discharge area, artesian water comes to the earth's surface in the form of subaerial, subaquatic or submarine sources.

If there are several aquifers, each of them can have its own piezometric surface, which is determined by the conditions of supply and runoff of groundwater (Fig. 30.31).

Rice. 30. Artesian basin with inverted relief.

Rice. 31. Artesian basin with direct relief (syncline).

If the well opens two artesian waters bearing horizons and they communicate, then in the case of an inverted relief (Fig. 30), the water in the well will go from the upper to the lower horizon, i.e. the well will be absorbing. This is very important when solving the issues of burial of various industrial effluents.

The relationship between artesian and groundwater.

With monoclinally occurring or wedging out aquifers, so-called asymmetric artesian basins or artesian slopes are formed on the framing of mountainous countries.

Artesian structures are usually represented by a system of alternating water-permeable and relatively water-resistant rocks. The more stable the aquifer, the larger the area of ​​the discharge area, the more watery the artesian horizon.

If the feeding area is large, then the largest volume is occupied by fresh waters, because. a significant area of ​​aquifers is located in the zone of intensive water exchange. In large depressions, the recharge area is small compared to the total area of ​​distribution of aquifers.

Rice. 32. The relationship between artesian and groundwater ( by A.M. Ovchinnikov) :

a- supply of artesian waters with groundwater; b - transition of artesian waters to groundwater; in - groundwater supply by artesian. 1 - aquifer loose Quaternary deposits; 2 - aquifers in bedrock; 3 - waterproof rocks; four - water level; 5 - direction of water movement

All the waters of the earth's crust, located below the surface of the Earth in rocks in gaseous, liquid and solid states, are called groundwater.

Groundwater is part of the hydrosphere - the water shell the globe. They are found in boreholes at depths up to several kilometers. According to V.I. Vernandsky, groundwater can exist up to a depth of 60 km due to the fact that water molecules, even at a temperature of 2000 ° C, are dissociated by only 2%.

Approximate calculations of fresh water reserves in the bowels of the Earth to a depth of 16 kilometers give a value of 400 million cubic kilometers, i.e. about 1/3 of the waters of the oceans.

The accumulation of knowledge about groundwater, which began in ancient times, accelerated with the advent of cities and irrigated agriculture. The art of building dug wells up to several tens of meters was known for 2000-3000 thousand years BC. in Egypt, Central Asia, India, China. In the same period, mineral water treatment appeared.

In the first millennium BC, the first ideas about the properties and origin of natural waters, the conditions for their accumulation and the water cycle on Earth appeared (in the works of Thales and Aristotle - in Ancient Greece; Titus Lucretia Cara and Vitruvius - in Ancient Rome, etc.).

The study of groundwater was facilitated by the expansion of work related to water supply, the construction of capping facilities (for example, karez among the peoples of the Caucasus, Central Asia), the extraction of salt water for salt evaporation by digging wells, and then drilling (territory of Russia, 12-17 centuries) . Later, the concept of waters arose non-pressure, pressure(rising from bottom to top) and self-flowing. The latter received the name artesian - from the province of Artois (the ancient name "Artesia") in France.

In the Renaissance and later, the works of many scientists - Agricolla, Palissy, Steno and others - were devoted to groundwater and their role in natural processes.

In Russia, the first scientific ideas about groundwater as natural solutions, their formation by infiltration of atmospheric precipitation and the geological activity of groundwater were expressed by M.V. Lomonosov in the essay "On the Layers of the Earth" (1763).

Until the middle of the 19th century, the doctrine of groundwater developed as an integral part of geology. Then it separates into a separate discipline - hydrology.

General hydrogeology studies the origin of groundwater, their physical and Chemical properties, interaction with host rocks.

The study of groundwater in connection with history tectonic movements, the processes of sedimentation and dianogenesis made it possible to approach the history of their formation and contributed to the emergence in the 20th century of a new branch of hydrogeology - paleohydrogeology(the doctrine of groundwater of past geological eras).

Groundwater dynamics studies the movement of groundwater under the influence of natural and artificial factors, develops methods for quantifying productivity production wells and groundwater resources.

The doctrine of the regime and balance of groundwater considers changes in groundwater (their level, temperature, chemical composition, conditions of nutrition and movement), which occur under the influence of various natural factors (precipitation, and the conditions of their infiltration, evaporation, temperature and humidity of the air and soil layer, the influence of the regimes of surface water bodies, rivers, man-made human activities).

In the second half of the 20th century, methods for predicting the groundwater regime began to be developed, which is of great importance. practical value in the exploitation of groundwater, hydraulic engineering construction, irrigated agriculture and other issues.

Now, out of 510 million square kilometers of the globe, 361 million square kilometers. km (70.7%) are occupied by seas and oceans, forming a single World Ocean, the remaining 149 (29.3%) mln. km is covered by land. In the northern hemisphere, land accounts for 39.3% of the area of ​​the hemisphere, in the southern - 19.1%. About specific gravity elements of moisture circulation and their influence on the total circulation of water in nature can be judged from the data given below:

Table 1

Under the influence solar energy about 450.0 thousand km 3 of water evaporate on average from the surface of the World Ocean. Some of this moisture in the form of steam is carried by air currents to the continents.

Under certain conditions, water vapor condenses and falls out in the form of rain, snow, hail, etc. Precipitation that falls on land flows down the slopes of the area, forming streams and rivers that carry their waters back to the oceans.

Part of the precipitation evaporates, part seeps into the ground, forming groundwater, which flows into streams and rivers as underground runoff and, thus, also returns to the ocean. This closed process of exchange between the atmosphere and the earth's surface is called the water cycle in nature.

Thus, the water content of rivers used in the national economy as water sources is related to the Earth's moisture cycle and depends on the distribution of water between the individual elements of the water cycle in nature.

origin of groundwater

Groundwater is formed mainly from precipitation water falling on the earth's surface and percolating waters(infiltrating) into the ground to some depth, and from waters from swamps, rivers, lakes and reservoirs, also seeping into the ground. The amount of moisture driven in this way into the soil is 15-20% of the total amount of precipitation.

Penetration of waters into soils (water permeability), constituting the earth's crust depends on the physical properties of these soils. With regard to water permeability, soils are divided into three main groups: permeable, semipermeable and waterproof or waterproof.

To permeable rocks include coarse-grained rocks, pebbles, gravel, sands, fractured rocks, etc. To waterproof rocks - massively crystalline rocks (granite, marble), which have a minimum absorb moisture, and clays. The latter, having been saturated with water, do not let it through in the future. To breeds semipermeable clayey sands, loose sandstones, loose marls, etc.

Groundwater in the earth's crust is distributed in two floors. The lower floor, composed of dense igneous and metamorphic rocks, contains a limited amount of water. The bulk of the water is in the upper layer of sedimentary rocks. In it, according to the nature of water exchange with surface waters, three zones are distinguished: a zone of free water exchange (upper), a zone of slow water exchange (middle) and a zone of very slow water exchange (lower). The waters of the upper zone are usually fresh and serve for drinking, household and technical water supply. In the middle zone are mineral water different composition. These are ancient waters. The lower zone contains highly mineralized brines. Bromine, iodine and other substances are extracted from them.

Groundwater is formed in various ways. One of the main ways of underground water formation is seepage or infiltration of atmospheric precipitation and surface waters (lakes, rivers, seas, etc.). According to this theory, infiltrating water reaches the water-resistant layer and accumulates on it, saturating rocks of a porous and porous-fractured nature. Thus, aquifers, or groundwater horizons, arise. The groundwater surface is called groundwater mirror. The distance from the groundwater table to the aquiclude is called the thickness of the impervious layer.

The amount of water seeping into the soil depends not only on its physical properties, but also on the amount of precipitation, the slope of the terrain to the horizon, vegetation cover, etc. At the same time, prolonged drizzling rain creates Better conditions for seepage than a heavy downpour, since the more intense the precipitation, the faster the fallen water flows down the soil surface.

The steep slopes of the terrain increase surface runoff and reduce the infiltration of precipitation into the ground; gently sloping, on the contrary, increase their seepage. Vegetation cover (forest) increases the evaporation of the precipitated moisture and at the same time increases precipitation. Detaining surface runoff, it contributes to the infiltration of moisture into the soil.

For many areas of the globe, infiltration is the main method of groundwater formation. However, there is another way of their formation - due to water vapor condensation in rocks. In the warm season, the elasticity of water vapor in the air is greater than in the soil layer and underlying rocks. Therefore, atmospheric water vapor continuously enters the soil and descends to a layer of constant temperatures located at different depths - from one to several tens of meters from the earth's surface. In this layer, the movement of air vapor stops due to an increase in the elasticity of water vapor with an increase in temperature in the depths of the Earth. As a result, there is a counter flow of water vapor from the depths of the Earth upwards - to a layer of constant temperatures. And in the zone of constant temperatures, as a result of the collision of two streams of water vapor, their condensation occurs with the formation of underground water. Such condensation water is of great importance in deserts, semi-deserts and dry steppes. During hot periods of the year, it is the only source of moisture for vegetation. In the same way, the main reserves of underground water arose in the mountainous regions of Western Siberia.

Both methods of groundwater formation - by infiltration and by condensation of atmospheric water vapor in rocks - are the main ways of groundwater accumulation. Infiltration and condensation water sometimes called vandose waters (from the Latin "vadare" - to go, to move). These waters are formed from atmospheric moisture and participate in the general water cycle in nature.

Some researchers note another way of groundwater formation - juvenile. Many outlets of these waters in areas of modern or recent volcanic activity are characterized by elevated temperatures and significant concentrations of salts and volatile components. To explain the genesis of such waters, the Austrian geologist E. Suess in 1902 put forward the theory of juvenile (from the Latin "juvenilis" - virgin). Such waters, according to Suess, were formed from gaseous products released in abundance during volcanic activity and differentiation of magmatic lava.

Later studies showed that pure juvenile waters, as E. Suess understood them, do not exist in the surface parts of the Earth. AT natural conditions groundwater, which arose in different ways, mixes with each other, acquiring certain properties. However, determining the genesis of groundwater is of great importance: it facilitates the calculation of reserves, the clarification of the regime and their quality.

The groundwater level is subject to constant fluctuations. So, during the spring floods and floods, the water level in the river, rising above the level of the river flow directed to the river, causes an outflow of water from it and a rise in the groundwater level. This reduces the height of the spring floods. At the recession, groundwater begins to feed the river, and the level of groundwater drops.

Groundwater can be formed by artificial hydraulic structures such as irrigation canals. Thus, during the construction of the Karakum irrigation system, due to the transfer of part of the flow of Siberian rivers, in the desert part, a significant amount of water was spent not so much for irrigation needs, but for evaporation and into the ground. This happened due to the fact that most of the irrigation system passed through sandy soils, where the filtration coefficient is quite high, and despite anti-seepage measures, the drops in water levels due to water seepage into the soil were large. All this, in addition to reducing the flow of rivers, led to the fact that the salts contained in the soil were dissolved by groundwater, and when underwater flows moved back into the canal, it was salinized and polluted with silt.

Groundwater classification
conditions of their occurrence

There are several classifications of groundwater.

According to the conditions of movement in aquifers, groundwater is distinguished, circulating in loose (sand, gravel and pebble) layers and in fractured rocks Oh.

Groundwater moving under the influence of gravity is called gravitational, or free, in contrast to waters bound, held by molecular forces - hygroscopic, film, capillary and crystallization.

Depending on the nature of the voids of water-bearing rocks, groundwater is divided into:

porous - in sands, pebbles and other clastic rocks;

fissure (vein) - in rocks (granites, sandstones);

karst (fissure-karst) - in soluble rocks (limestone, dolomite, gypsum, etc.).

According to the conditions of occurrence, three types of groundwater are distinguished: top water, ground e and pressure, or artesian.

Verkhovodka called groundwater, lying near the surface of the earth and characterized by the inconsistency of distribution. Usually, perched water is associated with lenses of impervious or poorly permeable rocks overlain by permeable strata.

Verkhovodka occupies limited territories, this phenomenon is temporary, and it occurs during a period of sufficient moisture; in dry times, the naked perch disappears. Verkhovodka refers to the first water-resistant layer from the surface of the earth. In cases where the water-resistant layer lies near the surface or comes to the surface, waterlogging develops during the rainy seasons.

Soil waters, or waters of the soil layer, are often referred to as perched water. Soil waters are represented by almost bound water. Drop-liquid water in soils is present only during the period of excessive moisture.

ground water. Ground waters are waters that lie on the first water-resistant horizon below the perch. They usually belong to an impervious formation and are characterized by a more or less constant flow of water. Groundwater can accumulate both in loose porous rocks and in solid fractured reservoirs. The groundwater level is an uneven surface, which, as a rule, repeats the unevenness of the relief in a smoothed form: on hills it is lower, in lower places it is higher.

Groundwater moves in the direction of lowering the relief. The groundwater level is subject to constant fluctuations - it is influenced by various factors: the amount and quality of precipitation, climate, topography, the presence of vegetation cover, economic activity person and much more.

Groundwater accumulating in alluvial deposits is one of the sources of water supply. They are used as drinking water, for irrigation. Groundwater outlets to the surface are called springs, or springs.

Pressure, or artesian waters. Pressure waters are waters that are located in an aquifer enclosed between water-resistant layers and experience hydrostatic pressure due to the difference in levels at the place of supply and water outlet to the surface. The area of ​​supply near artesian waters usually lies above the area of ​​water runoff and above the outlet of pressure waters to the Earth's surface. If an artesian well is laid in the center of such a bowl, then water will flow out of it in the form of a fountain according to the law of communicating vessels.

The sizes of artesian basins are quite significant - up to hundreds and even thousands of kilometers. The feeding areas of such pools are often far from the places of water extraction. Thus, water that has fallen in the form of precipitation on the territory of Germany and Poland is obtained from artesian wells drilled in Moscow; in some oases of the Sahara they receive water that has fallen in the form of precipitation over Europe.

Artesian waters are characterized by the constancy of water and good quality which is important for its practical use.

By origin, several types of groundwater are distinguished.

Infiltration water are formed due to seepage from the Earth's surface of rain, snowmelt and river waters. In composition, they are predominantly bicarbonate-calcium and magnesium. When gypsum-bearing rocks are leached, sulfate-calcium is formed, and when salt-bearing rocks are dissolved, chloride-sodium waters are formed.

Condensation groundwater formed as a result of condensation of water vapor in the pores or cracks of rocks.

sedimentation waters are formed in the process of geological sedimentation and usually represent altered buried waters of marine origin - sodium chloride, calcium chloride-sodium, etc. They also include buried brines of saline basins, as well as ultra-fresh waters of sandy lenses in moraine deposits.

The waters formed from magma during its crystallization and volcanic metamorphism of rocks are called igneous, or juvenile(according to the terminology of E. Suess).

feeding of rivers with groundwater and calculation of groundwater runoff

Groundwater serves as a reliable source of food for rivers. They act all year round and provide food for rivers in winter and summer low water (or during low levels standing water horizon) when there is no surface runoff.

At very slow rates of movement of groundwater, compared with surface water, groundwater in the river runoff acts as a regulatory factor.

Also, at very slow or low speeds of groundwater movement, on the rivers of the Far North at low air temperatures, freezing (complete or partial) of the river is observed, and then the water enters from the retaining part of the reservoir into which the river flows (this may be the main river , sea, lake, etc.). Such phenomena are observed, for example, in the settlement of Nizhneyansk, which is located 25 km from the mouth of the Yana River, where during the period of low temperatures and complete freezing of the river on the riffles, salt water enters the riverbed upstream from the place of freezing from backwater from the Arctic Ocean.

The quantitative measure of nutrition is the value of underground runoff, which, in turn, is characterized by the so-called groundwater module:

M subtitle = K M 0 /100 ,

where M subtitle– underground runoff module, l/s from 1 km 2 catchment area;

M 0 is the average long-term module of the total runoff, l/s from 1 km 2 surface drainage basin;

To- modular coefficient showing the percentage of underground runoff in the total runoff and determined by the formula

K=M min /M 0 ,

where M min- minimum drain module, l/s from 1 km 2 surface drainage basin, determined by the winter flow of the river and equal to the groundwater runoff module, since rivers are fed mainly by groundwater in winter.

The groundwater flow module is a reliable indicator for assessing the water content of rocks distributed in the catchment area of ​​a river, since it represents the amount of groundwater (in l / s) entering the river from 1 sq. km. km of one or another aquifer drained by the river.

In addition to these formulas, the amount of underground runoff can be determined by the hydrochemical method (according to A.T. Ivanov):

where Q subtitle– annual volume of underground runoff;

Q 0 is the annual volume of river runoff;

With- concentration of any component (for example, chlorine) in river water during the observation period;

c 1 is the concentration of the same component in groundwater in the same period;

c 2 - concentration of the same component in surface waters in the same period.

According to B.I. Kudelin, for a more accurate calculation of the underground runoff of small and medium-sized rivers, it is proposed to distinguish four types of river feeding by groundwater:

Feeding by groundwater not hydraulically connected to the river;

Feeding by groundwater hydraulically connected to the river;

Mixed ground nutrition ( a+ b);

Mixed ground and artesian nutrition ( a+ b+ c).

According to these data, B.I. Kudelin proposed formulas for determining the layer h subtitle and groundwater runoff coefficient α subtitle. The groundwater flow rate is expressed in millimeters per year (or any other unit of time) per square kilometer of groundwater basin area and is calculated as:

where h subtitle- a layer of underground runoff, mm/year;

Q subtitle is the volume of underground runoff from the basin area, m 3 /year;

F- the area of ​​the pool, m 2 .

Ground flow coefficient α subtitle is the ratio of underground runoff to precipitation falling on the area of ​​a given river drainage basin, and shows the part of the precipitation that goes to feed the underground zones of very intensive water exchange in the basin:

where x- a layer of precipitation, mm/year.

Groundwater calculations are usually summarized in the form of groundwater recharge maps, coefficients and modules of groundwater flow, reflecting the natural resources of various types of groundwater developed within small and medium-sized river basins and their individual regions and sections.

Main problems of groundwater use and protection

Due to its location, groundwater is better protected from external influences than surface water, however, there are serious symptoms of an adverse change in the groundwater regime on large areas and over a wide range of depths. These include: depletion and lowering of groundwater levels due to over-extraction; the introduction of sea salt water on the coast; formation of depression funnels and others.

Groundwater pollution is a major threat. There are two types of pollution - bacterial and chemical. AT certain conditions can penetrate aquifers sewage and technogenic industrial waters, polluted surface waters and precipitation.

When creating reservoirs, as a result of backwater, an increase in the level of groundwater occurs. A positive consequence of such a regime change is an increase in their resources in the coastal zone of the reservoir; negative - flooding coastal zone, which causes swamping of the territory, as well as salinization of soils and groundwater due to their increased evaporation at shallow occurrence.

Due to small flood events (or their absence at all) on regulated rivers, the flood supply of groundwater is significantly reduced. The flow rates on such rivers are reduced, which contributes to the silting of the channel; therefore, the relationship between river and groundwater is difficult.

Under certain conditions, groundwater abstraction can have a significant impact on the quality of surface water. First of all, this applies to industrial operation and the discharge of mineralized water, the discharge of mine and associated oil water. Therefore, the integrated use and regulation of surface and groundwater resources should be envisaged. Examples of such an approach are the use of groundwater for irrigation in dry years, as well as the artificial replenishment of groundwater reserves and the construction of underground reservoirs.

Ph.D. O.V. Mosin

list literature

1. Novikov Yu.V., Sayfutdinov M.M. Water and life on earth. – M.: Nauka, 1981. – 184 p.

2. Kissin I.G. Water underground. – M.: Nauka, 1976. – 224 p.

3. Bondarev V.P. Geology. Lecture course: Tutorial for students of institutions of secondary vocational education. - M.: Forum: Infra M., 2002. - 224 p.

4. Goroshkov I.F. hydrological calculations. - L.: Gidrometeoizdat, 1979. - 432 p.

5. Cherdantsev V.A., Pivon Yu.I. Guidelines for the discipline: "Hydrology". - Novosibirsk: NGAEiU, 2004, 112 p.

6. Reference manual of a hydrogeologist. In 2 volumes. Ed. V.P. Yakutseni. - L .: Nedra, 1967. - T.1. - 592s.

The water shell of the Earth - the hydrosphere - is formed by groundwater, atmospheric moisture, glaciers and surface water bodies, including oceans, seas, lakes, rivers, swamps. All waters of the hydrosphere are interconnected and are in continuous circulation.

The main composition of the hydrosphere is salt water. Fresh water accounts for less than 3% of the total volume. The figures are arbitrary, since only explored reserves are taken into account in the calculations. Meanwhile, according to the assumptions of hydrogeologists, in the deep layers of the Earth there are colossal groundwater storages, the deposits of which have yet to be discovered.

Groundwater as part of the planet's water resources

Groundwater - water contained in water-bearing sedimentary rocks that make up the upper layer of the earth's crust. Depending on environmental conditions such as temperature, pressure, types of rocks, water is in a solid, liquid or vapor state. The classification of groundwater directly depends on the soils that make up the earth's crust, their moisture capacity and depth. Layers of water-saturated rocks are called "aquifers".

Freshwater aquifers are considered one of the most important strategic resources.

Characteristics and properties of groundwater

There are non-pressure aquifers, limited by a layer of waterproof rocks from below and called groundwater, and pressure ones, located between two water-resistant layers. Classification of groundwater by type of water-saturated soil:

• porous, occurring in the sands;
• fissures filling the voids of solid rock;
• karst, found in limestone, gypsum and similar water-soluble rocks.

Water, a universal solvent, actively absorbs the substances that make up the rocks, and is saturated with salts and minerals. Depending on the concentration of substances dissolved in water, fresh, brackish, salt water and brines are distinguished.

Types of water in the underground hydrosphere

Water underground is in a free or bound state. Free groundwater includes pressure and non-pressure water that can move under the action of gravitational forces. Related waters include:

• water of crystallization, which is chemically included in the crystal structure of minerals;
• hygroscopic and film water physically bound to the surface of mineral particles;
• water in a solid state.

Groundwater reserves

Groundwater accounts for about 2% of the total hydrosphere of the planet. The term "groundwater reserves" means:

• The amount of water contained in a water-saturated layer of soil is natural reserves. Replenishment of aquifers occurs due to rivers, precipitation, water flow from other water-saturated layers. When assessing groundwater reserves, the average annual volume of groundwater flow is taken into account.
• The volume of water that can be used when opening the aquifer is elastic reserves.

Another term - "resources" - refers to the operational reserves of groundwater or the volume of water of a given quality that can be extracted from an aquifer per unit of time.

Groundwater pollution

Experts classify the composition and type of groundwater pollution as follows:

Chemical pollution

Untreated liquid effluents and solid waste from industrial and agricultural enterprises contain various organic and inorganic substances, including heavy metals, petroleum products, toxic pesticides, soil fertilizers, and road chemicals. Chemical substances penetrate into aquifers through groundwater and are improperly isolated from adjacent water-saturated reservoirs. Chemical pollution of groundwater is widespread.

Biological pollution

Untreated domestic wastewater, faulty sewer lines and filtration fields located near water wells can become sources of pathogen contamination of aquifers. The higher the filtration capacity of soils, the slower the spread of biological pollution of groundwater.

Solving the problem of groundwater pollution

Given that the causes of groundwater pollution are anthropogenic, measures to protect groundwater resources from pollution should include monitoring domestic and industrial wastewater, modernizing wastewater treatment and disposal systems, limiting wastewater discharges into surface water bodies, creating water protection zones, and improving production technologies.