Types of groundwater and their geological activity. Underground springs

THE GROUNDWATER

All water in the pores and cracks of rocks below the surface

Lands are classified as groundwater. Some of these waters move freely in the upper

part of the earth's crust under the influence of gravitational forces, and the other part is in a very

thin pores, held by surface tension forces. Groundwater cannot

exist without exchange with surface water and are actively involved in the water cycle

in nature.

The structure and properties of water are determined by the structure of its molecule - H2O in the form

a tetrahedron with an oxygen atom in the center. At the ends of one of the ribs

tetrahedron are two positive charges of the nuclei of hydrogen atoms, which is

hydrol or an elementary additional structural unit of water.

Types of groundwater

1. Crystallization water is included in the crystal lattice of some

minerals, for example, in gypsum - CaSO4 2H2O (.21% water by mass), mirabilite

Na2SO4.10H2O (.56% water by mass

2. Water in solid form is found in permafrost in the form of crystals and

streaks of ice. Also, ice is formed during seasonal freezing of water contained

3. Water in the form of steam is contained in the air, which is in the pores of the soil.

4. Strongly bound water is located in the form of a molecular discontinuous film on

surfaces of the smallest particles of rocks such as clays and loams. This film

held by the forces of molecular cohesion and cannot drain from the surface of the particle

5. Loosely bound water is a thicker film of several layers

water molecules on rock particles. This water has the ability to move from

thicker film to a thinner one.

6. Drip-liquid (gravitational) water already has the ability to freely

move in soils along cracks and pores under the influence of gravity,

starting from the top soil layer.

7. Capillary water, as the name suggests, is located in the thinnest capillary tubes or pores, in which it is held by the forces of surface tension to form menisci. Capillary water is usually located above the groundwater level and at the same time it can rise upward from this level by 1.5 - 3 m. The capillary border, being connected with the groundwater level, fluctuates with it.

Above the groundwater level, there may be another narrow border of capillary-suspended water retained in the fine pores of the soil and subsoil

horizons of loams and clays.

Groundwater is distributed in the upper part of the earth's crust quite naturally. The uppermost part of the earth's crust, near the surface, is called the aeration zone, because it is associated with the atmosphere and the soil cover. Below it lies a zone of complete saturation, where water is distributed mainly in liquid form, while in the aeration zone it can also be vaporous. If the temperatures are negative, then the water in these two zones can

present in the form of ice.

Thus, the aeration zone is like a transitional buffer layer

between the atmosphere and the hydrosphere.

Groundwater can be classified according to different criteria - according to conditions

occurrence, by origin, by chemical composition.

Types of groundwater according to the conditions of occurrence. Free-flow waters are allocated,

subdivided into top water, ground and interstratal, as well as pressure or

artesian.

Verkhovodka is a temporary accumulation of water in the near-surface layer within

aeration zones located in aquifers lying on a lenticular,

wedging out waterproofing. As a rule, the vermicompost appears in the spring, when the snow melts or in a rainy season, but then it can disappear. Therefore, the wells dug before the top water dry up in the summer.

Any pinch-out lenticular formations can be temporary seals.

clays and heavy loams, located in the stratum of aquifers alluvial or

fluvioglacial deposits.

Groundwater is the first permanent aquifer from above.

horizon, located on the very first extended water-resistant layer. Feed on

groundwater from a catchment area within an aquifer. Ground water

can be associated with any rock, both loose and hard, but

fractured.

The surface of the groundwater is called the mirror, and the thickness of the water-containing

the layer is estimated by the vertical from the mirror to the top of the water-resistant horizon and it is not

remains constant, but changes due to uneven terrain, the position of the unloading level,

the amount of precipitation, bending of the roof of the waterproof layer. Above the mirror

groundwater is formed by a border of capillary drawn water.

Groundwater movement and regime.

The groundwater mirror behaves depending on the relief, rising by

watersheds and descending to rivers, ravines and other drainage sites. Naturally, the water in the aquifer under the influence of gravity is in continuous motion and tends to reach the lowest place in the relief, for example, the water edge in a river, thalweg of the bottom of a ravine. It is there, in the area of \u200b\u200bgroundwater discharge, that springs are formed. Water in the aquifer moves depending on the porosity of the rocks, the nature of particle contact, the shape and size of the pores, and the slope of the aquifer. Usually in sands the speed of water movement at small slopes is from 0.5 to 2-3 m / day. But if the slope is large and the pores are large, then the speed can reach the first tens of meters per day.

Depending on the amount of precipitation, the volume of groundwater can

change and in summer the flow rate of the sources decreases, and in severe droughts the springs even dry up. The groundwater table can be especially low in connection with the intake of water for industrial needs. Around the wells that pump out water, the groundwater level gradually decreases and a depression funnel is formed

Interstratal free-flow underground waters are confined to aquifers,

located between two waterproof layers. Sometimes such aquifers

there may be several. If the aquifer has a large capacity or more

its mirror is a lake, pond or river, then the direction of the flow of water in the aquifer

the horizon will follow curved lines tending to the river.

Pressurized or artesian interstratal waters are formed if

an aquifer sandwiched between two impermeable ones, confined either to a gentle

syncline or trough, or to monocline, or to some other structures in which the formation of a pressure gradient is possible. Pressurized water has the ability to pour out and gush itself, because are under hydrostatic pressure.

For the first time, such fountains of water were obtained in France in the province of Artesia, therefore

they began to be called artesian. Each artesian pool includes

areas: nutrition, pressure and unloading. The first area represents the exit to

the surface of the aquifer, on which all precipitation falls, feeding

this aquifer. The head area is enclosed between two aquicludes -

a waterproof roof and a waterproof bed, and where the aquifer appears on

surface, or penetrated by wells, but below the recharge area, is called

unloading area. Often, in artesian basins, several

aquifers confined horizons, which is especially typical for artesian basins in

intermontane depressions, where the depths of the aquifers can exceed 1000-1500 m.

In platform areas where artesian basins are large, the upper

aquifers to depths of 200-5 m contain mainly fresh water, and

below the water they already have high mineralization.

In the center of the European part of Russia is the Moscow artesian basin,

located in a shallow bowl-shaped depression - the Moscow syneclise. Aquifers

horizons are associated with fractured Carboniferous and Devonian limestones, and

clay interlayers serve as seals. Feeding areas are located on the wings

syneclises. In Devonian carbonate deposits at depths from 400 to 600 m

mineral waters with a salinity of 2.4-4.5 g / l. This is the well-known Moscow

mineral water. Large reserves are concentrated in the Moscow artesian basin

fresh and industrial waters. Maps have been compiled for the entire territory of Russia

distribution of artesian basins and calculated the reserves of water in them, as fresh,

both industrial and thermal.

Types of sources. Everyone is well aware of the outcrops of groundwater to the surface in

in the form of springs and springs with cold, tasty water. Springs appear where

unloading of aquifers occurs.

Descending springs are most often located near the water's edge in the valley

rivers, in the lower part of the slopes of ravines, where waterproof ones approach the surface

horizons. Sources of this type are associated with both verkhvodka and groundwater, as well as

interstratal waters. All of them are characterized by a variable flow rate, up to

drying out in hot summer. In springs of a descending type, water pours out calmly, into

view of the small angle of inclination of the layers. You can often see along the river bank

a solid line of oozing groundwater. Downstream sources usually

are water abundant, so in places they give rise to streams and small rivers, like

occurs with karst springs flowing from the caves.

Ascending sources are exits to the surface at points of discharge of pressure head

waters, while the aquifer itself is much lower. Water can

climb up cracks or a tectonic fault.

Around mineral springs, especially carbonic waters, on the surface

an accumulation of the so-called. calcareous tuff or travertine, sometimes reaching

several meters of power. Such travertines of white, yellowish or pink colors

are known in the city of Mashuk in Pyatigorsk, in the region of the Caucasian mineral waters. Tuff

formed from bicarbonate-calcium waters, when bicarbonate Ca (HCO3) 2

turns into CaCO3 when CO2 - carbon dioxide escapes into the air. In travertines often

find prints of plant leaves, bones of ancient animals, which gradually

enveloped with limestone tuff.

Groundwater - water located in the rock mass of the upper part of the earth's crust in a liquid, solid and gaseous state.

Classification

According to the conditions of occurrence, groundwater is divided into several types: soil, groundwater, interstratal, artesian, and mineral.

Soil water fill part of the gaps between soil particles; they can be free (gravitational), moving under the influence of gravity, or bound, held by molecular forces.

Ground water form an aquifer on the first water-resistant layer from the surface. Due to the shallow bedding from the surface, the groundwater level experiences significant fluctuations according to the seasons of the year: it either rises after precipitation or snow melts, then decreases during dry times. In severe winters, groundwater can freeze through. These waters are more susceptible to pollution.

Interstratal waters - underlying aquifers, enclosed between two water-resistant layers. Unlike groundwater, the interstratal water level is more constant and changes less over time. Interstratal waters are cleaner than groundwater. Pressurized interstratal waters completely fill the aquifer and are under pressure. All waters enclosed in layers lying in concave tectonic structures have a head.

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

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

• porous - occur and circulate in Quaternary sediments: in sands, pebbles, and other clastic rocks;
• fissure (vein) - in rocks (granites, sandstones);
• karst (fissure-karst) - in soluble rocks (limestone, dolomite, gypsum, etc.).

Groundwater reserves

Groundwater is part of the Earth's water resources; total groundwater reserves are over 60 million km³. Groundwater is regarded as a mineral. Unlike other types of minerals, groundwater reserves are renewable during operation.

Groundwater exploration

To determine the presence of underground water, exploration is carried out:

• geomorphological assessment of the area,
• temperature studies,
• radon method,
• support wells are drilled with coring,
• the core is studied and the relative geological age of the rocks, their thickness (thickness),
• experimental pumping is carried out, the characteristics of the aquifer are determined, an engineering-geological report is drawn up;
• for several reference wells, maps, sections are drawn up, a preliminary assessment of mineral reserves (in this case, water) is carried out;

Origin of groundwater

Groundwaters have different origins: some of them were formed as a result of the penetration of melt and rainwater to the first impervious horizon (that is, to a depth of 1.5-2.0 m, which form groundwater, that is, the so-called top water); others occupy deeper cavities in the ground.

A large part of the Earth's water reserves are underground basins that flow in the soil and layers of rocks. 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 they are studying deeper and deeper what underground water is. Definition, classification and other issues of the topic will be discussed in the article.

What is groundwater?

Groundwater is water that is located in the interlayer spaces of rocks that occur 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, which have been preserved since the permafrost period.

Classification

The subdivision 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 a place where a mineral or saline fluid is deposited at a depth of 50 to 600 meters.
• Lower horizon - depth from 400 to 3000 meters. Water with a high mineral content.

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

Soil water

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

If you understand what is groundwater of a soil type, 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 agricultural crops.

This type of liquid can not always lie horizontally, often its outlines are similar to the relief of the soil. In the upper layer of the earth's crust, moisture has no "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 water that is located at some depths in the upper earth layer. The depths of fluid flow can be large if it is an arid area or desert. In a temperate climate with periodic constancy of precipitation, the groundwater does not lie so deep. And with an excess of rain or snow, ground liquid can lead to flooding of the area. In some places, this type of water comes to the surface of the soil and is called a spring, spring or source.

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

Excessive amounts of liquid can accumulate in one place. As a result of the standing position, swamps, lakes, etc., are formed from underground waters.

Interstratal

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

A positive feature of interstratal fluids is that they are much cleaner, as they occur deeper. In addition, their composition and quantity always fluctuate in 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, in suburban areas drilling of underground wells is often practiced as a source of water supply for residential buildings.

When drilling a well, artesian water fountains out to the surface, since it is a pressure type of groundwater. It occurs in rock voids between water-resistant layers of the earth's crust.

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

Mineral

Mineral minerals are the deepest and most curative 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.

By the predominance of chemical elements:

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

By 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.

Chemical classification

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

1. Fresh.
2. Low mineralized.
3. Mineralized.

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

How was groundwater formed?

Several factors influence the formation of groundwater.

1. Precipitation. Fallout 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 of glaciers of permafrost. Underground waters form whole lakes.
3. There are also juvenile fluids that formed in frozen magma. This is a type of primary water.

Groundwater monitoring

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

If the quality of water is examined in a laboratory, observing the seized sample, then the exploration of availability implies the following methods, interrelated with each other:

1. The first is an assessment of the area for the presence of the expected groundwater.
2. Second, the temperature indicators of the detected liquid are measured.
3. Then the radon method is applied.
4. After that, base wells are drilled, accompanied by core sampling.
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. For base wells, maps of fluid occurrence are drawn up, its quality and condition are assessed.

Groundwater exploration is subdivided into the following types:

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

Pollution problems

The problem of groundwater pollution is very urgent today. Scientists identify the following pollution methods:

1. Chemical. This type of pollution is very common. Its globality depends on the fact that there are a huge number of agricultural and industrial enterprises on Earth that dump their waste in liquid and solid (crystallized) form. This waste penetrates very quickly into water-bearing horizons.
2. Biological. Contaminated sewage from household use, faulty sewerage systems - all these are the causes of contamination of groundwater by pathogens.

Classification by type of water-saturated soils

The following are distinguished:

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

The composition of the waters is also formed depending on the location.

Stocks

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

Conclusion

Rivers, lakes, groundwater, glaciers, swamps, seas, oceans - all these are the water reserves of the Earth, which are somehow interconnected. The moisture located in the soil layers not only forms an underground basin, but also affects the formation of surface water bodies.

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

All water in the mass of rocks in a solid, liquid or gaseous state is called underground

On the continents, they form a continuous shell, which is not interrupted even in areas of dry steppes and deserts. Like surface waters, they are in constant motion and participate in the general water cycle in nature. The construction and operation of most surface structures and all underground ones are associated with the need to account for the movement of groundwater, their composition and condition. The physical and mechanical properties and state of many rocks depend on groundwater. They often flood construction pits, ditches, trenches and tunnels, and, coming to the surface, contribute to waterlogging of the territory. Groundwater can be an aggressive environment for rocks. They are the main reason for many physical and geological processes occurring in natural conditions, during the construction and operation of engineering structures.

Distinguish:

Drinking water - water, in terms of its quality in its natural state or after processing, meets regulatory requirements and is intended for drinking and domestic needs of a person, or for the production of food products. This type of water also includes natural mineral table waters, which include underground waters with a total salinity of no more than 1 g / dm 3, which do not require water treatment or do not change their natural composition after water treatment.

Technical groundwater -waters of various chemical composition (from fresh to brines), intended for use in production, technical and technological purposes, the quality requirements of which are established by state or industry standards, specifications or consumers.

Groundwater is also subdivided:

Groundwater is mainly formed as a result of seepage (infiltration) of atmospheric precipitation and surface water into the earth's crust. Water flows through permeable rocks to the water-resistant layer and accumulates on it, forming an underground basin or stream. This underground water is called infiltration... The amount of infiltration water depends on the climatic conditions of the area, relief, vegetation, the composition of the upper strata rocks, their structure and texture, as well as the tectonic structure of the area. Infiltration groundwater is the most common.

Groundwater can also be formed by condensation of vaporous water that is constantly circulating in the pores of rocks. Condensing groundwater is formed only in summer and partly in spring and autumn, and in winter it is not formed at all. AF Lebedev explained the formation of significant reserves of underground water in the zones of deserts and semi-deserts, where the amount of precipitation is negligible by the condensation of water vapor. Not only atmospheric water vapor can condense, but also water vapor released from magma chambers and other high-temperature zones of the earth's crust. Such groundwater is called juvenile .Juvenile groundwater is usually highly mineralized. In the course of geological development, buried water basins can be preserved in the earth's crust. The water contained in the sedimentary strata of these basins is called relict.

The formation of groundwater is a complex process that begins with the accumulation of sediments and is closely related to the geological history of the region. Very often, groundwater of various origins mixes with each other, forming mixed by the origin of the water.

The upper part of the earth's crust, from the point of view of the distribution of groundwater, is usually divided into two zones: the aeration zone and the saturation zone. In the aeration zone, not always all pores of rocks are filled with water. All waters of the aeration zone are fed by atmospheric precipitation, are intensively evaporated and absorbed by plants. The amount of water in this zone is determined by climatic conditions. In the saturation zone, regardless of climatic conditions, all pores of rocks are always filled with water. Above the saturation zone is the capillary humidification subzone. In this subzone, fine pores are filled with water, and large ones with air.

In the aeration zone, soil water and upper water are formed. Soil water lies directly at the surface of the earth. This is the only water that does not have a water seal under it and is represented mainly by bound and capillary water. Soil water is in a complex relationship with animals and plants. It is distinguished by sharp temperature fluctuations, the presence of microorganisms and humus. Builders are faced with soil water only in wetlands.

Verhovodka formed in the aeration zone on waterproof lenses. Any temporary accumulation of water in the aeration zone is also called high water. Atmospheric precipitation that penetrates this zone can temporarily linger on low-permeability or compacted layers. Most often this occurs in the spring during the period of snow melting or during the period of heavy rains. During dry periods, the perch may disappear. The characteristic features of the upstream are the inconstancy of existence, limited distribution, low power and pressurelessness. Verkhovodka often creates difficulties for builders, since the presence or possibility of its formation is not always established during engineering geological surveys. Formed upstream water can cause flooding of engineering structures, waterlogging of territories.

Ground is called water that occurs on the first permanent waterproof layer from the earth's surface. Groundwater exists constantly. They have a free water surface called a mirror of groundwater,and a waterproof bed. The projection of the groundwater mirror onto a vertical plane is called groundwater level (UGV).The distance from the aquiclude to the groundwater level is called the thickness of the aquifer.The groundwater level, and, consequently, the thickness of the aquifer are variable values \u200b\u200band can vary throughout the year depending on climatic conditions. Groundwater is fed mainly from atmospheric and surface waters, but they can also be mixed, infiltration-condensation. The area of \u200b\u200bthe earth's surface from which surface and atmospheric water enters the aquifer is called nutritional areagroundwater. The area of \u200b\u200bgroundwater recharge always coincides with the area of \u200b\u200btheir distribution. Ground waters, due to the presence of a free water surface, are free-flowing, that is, the water level in the well is set at the same mark at which the water is encountered.

Depending on the conditions of groundwater occurrence, ground streams and basins are distinguished. Ground streams have an inclined mirror and are in continuous motion towards the slope of the aquiclude. Ground basins have a horizontal mirror and are much less common.

Groundwater, being in constant motion, has a close connection with surface watercourses and water bodies. In areas where precipitation predominates over evaporation, groundwater usually feeds rivers. In arid regions, very often water from rivers flows into groundwater, replenishing underground streams. There can also be a mixed type of communication, when from one side the groundwater feeds the river, and from the other, the water from the river enters the ground flow. The nature of the connection may vary depending on climatic and some other conditions.

When designing and building engineering structures, it is necessary to take into account groundwater regime, that is, the change over time of indicators such as fluctuations in the level of groundwater, temperature and chemical composition. The level and temperature of groundwater are subject to the greatest changes. The reasons for these changes are very varied and are often directly related to human construction activities. Climatic factors cause both seasonal and long-term changes in the level of groundwater. Floods on rivers, as well as reservoirs, ponds, irrigation systems, canals, drainage structures, lead to a change in the groundwater regime.

The position of the groundwater table is depicted on maps using hydroisohypsum and hydroisobaths. Hydroisogypsum - lines connecting points with the same absolute marks of the groundwater level. These lines are similar to the contours of the relief and, like them, reflect the relief of the groundwater table. The hydroisohypsum map is used to determine the direction of groundwater movement and to determine the value of the hydraulic gradient. The direction of movement of groundwater is always perpendicular to the hydroisohypsum from higher to lower elevations. The directions along which groundwater moves with a steady motion that does not change in time are called streamlines.If the streamlines are parallel to each other, then such a flow is called flat. The stream can also be converging and diverging. The smaller the distance between the hydroisohypsum, the greater the hydraulic gradient of the soil flow. Hydroisobates - lines connecting points with the same groundwater depth.

Interstratalground waters are aquifers that lie between two aquicludes. They can be non-pressure and pressure-bearing. Interstratal non-confined waters are rare. By the nature of the movement, they are similar to groundwater. Interstratal pressure waters are called artesian.The occurrence of artesian waters is very diverse, but synclinal is the most common. Artesian water always fills the entire aquifer from the bottom to the top and has no free water surface. The area of \u200b\u200bdistribution of one or more levels of artesian aquifers is called artesian basin.The areas of artesian basins are enormous and are measured in tens, hundreds, and sometimes thousands of square kilometers. In each artesian basin, areas of feeding, distribution and discharge are distinguished. The recharge area of \u200b\u200bartesian basins is usually located at large distances from the center of the basin and at higher elevations. It never coincides with the area of \u200b\u200btheir distribution, which is sometimes called the area of \u200b\u200bpressure. Artesian waters experience hydrostatic pressure due to the difference in the marks of the supply area and the discharge area, according to the law of communicating vessels. The level at which artesian water is established in the well is called piezometric.Its position is determined piezometric line, or a pressure line, a conditional straight line that connects the supply area with the discharge area. If the piezometric line passes above the surface of the earth, then when the aquifer is opened with wells, gushing will occur, and the head is called positive. When the piezometric level is located below the surface of the earth, then the head is called negative, and water does not pour out of the well. Artesian waters are generally more saline and less associated with surface streams and bodies of water than groundwater.

Fissured waters called groundwater confined to fractured igneous, metamorphic and sedimentary rocks. The nature of their movement is determined by the size and shape of the cracks. Fractured waters can be non-confined and confined. They are fickle and can change the nature of their movement. Erosion and dissolution of rocks lead to the expansion of cracks, and the crystallization of salts and the accumulation of sediments - to their narrowing. Fracture water consumption can reach 500 m 3 / h. Fractured waters pose significant difficulties in the construction of underground structures.

Underground water in the city

In cities, the demand for water is great, but groundwater resources are limited. In many ways, the process of restoring water resources depends on the state of the urban environment itself, its ecology. This important factor is responsible not only for the volume of groundwater resources, but also for the level of their pollution.

In recent years, the study of groundwater in urban areas has been included in the section of hydrogeology.

Problems arising from the interaction of groundwater with the urban environment are groundwater pollution through sewage pipes, and lowering of the groundwater level by pumping systems, and the threat of groundwater flooding of underground spaces of the urban environment (for example, the subway).

Now the issue of preserving and protecting groundwater from pollution is especially acute. After all, the stability of the development of most cities largely depends on them, which brings the problem to a global level.

Based on the tasks set and based on the latest achievements in the field of hydrogeology, scientists are developing new schemes for monitoring and monitoring the level of groundwater pollution, their activity within the underground space of the urban environment.

And yet, no matter how important its connection with groundwater plays in the development of urban space, it is quite obvious that in this type of interaction the urban environment is assigned the lot of an external limiter, rather than an equal participant.

Many cities use underground water as drinking water. Everyone knows that water is a renewable resource, but at the same time it is strongly influenced by external factors. It is very important to monitor the level of groundwater and the degree of their pollution. This delicate balance is extremely important for the sustainable development of urban space. A negligent attitude towards water resources leads to very disastrous consequences. For example, in Mexico City, the constant decline in the water table has led to subsidence, and then to environmental problems.

The resource potential of groundwater in Russia is 869.1 million m 3 / day and is unevenly distributed throughout the territory, which is determined by the variety of geological and hydrogeological conditions and climatic features.

In the European territory of Russia, its value is 346.4 million m 3 / day and varies from 74.1 million m 3 / day in the Central to 117.7 million m 3 / day in the Northwestern Federal Districts; in the Asian territory of Russia - 522.7 million m3 / day and ranges from 159.2 million m3 / day in the Far East to 250.9 million m3 / day in the Siberian federal districts.

The current role of groundwater in the drinking water supply of the population of the Russian Federation is characterized by the following indicators. The share of groundwater in the balance of household and drinking water supply (from surface and groundwater sources) is 45%.

More than 60% of cities and urban-type settlements satisfy their drinking water needs using groundwater, and about 20% of them have mixed sources of water supply.

In rural areas, groundwater in the drinking water supply accounts for 80–85% of the total water consumption.

The most difficult problem is the provision of drinking water to the population of large cities. About 35% of large cities have practically no underground sources of centralized water supply, and 37 cities have no proven reserves of groundwater at all.

The degree of use of groundwater in the household drinking water supply of the population is determined both by the patterns of distribution of groundwater resources across the territory of Russia, and by the policy of providing the population with drinking water through the priority use of surface waters for many years.

Currently, there is a low level of use of explored underground water deposits and their reserves. The average level of utilization of the total explored reserves is 18–20%, and within the exploited fields with proven reserves - 30–32%.

Over the past 5 years, the increase in the estimated operational reserves amounted to 6.8 million m 3 / day.

From underground sources to meet the drinking needs of the population and water supply to industrial facilities, 28.2 million m3 / day of water was taken. The total amount of extraction and extraction of groundwater amounted to 33.1 million m3 / day, without use, 5.9 million m3 / day was discharged (17.8% of the total amount of extraction and extraction of groundwater).

For household needs, 27.2 million m 3 / day were used, including: for domestic and drinking water supply 20.6 million m 3 / day (76%); industrial and technical water supply - 6.0 million m 3 / day (22%); irrigation of lands and watering of pastures - 0.5 million m 3 / day (2%).

As a result of the extraction and extraction of groundwater in some areas, large regional depression craters have formed, the areas of which reach significant sizes (up to 50 thousand km 2), and the level decrease in the center - up to 65-130 m (the cities of Bryansk, Kursk, Moscow, St. Petersburg).

In the city of Bryansk, the regional depression funnel, formed in the Upper Devonian aquifer, has a radius of more than 150 km and a decrease in the level of more than 80 m. Extensive depression funnels formed in the area of \u200b\u200bthe cities of Kursk and Zheleznogorsk and at the Mikhailovsky iron ore quarry. The “Kursk” depression funnel in the Batkellovy aquifer has a radius of 90–115 km, the level decrease in the center is 64.5 m. At the Mikhailovsky open pit, the funnel has reached 60–90 km in radius, and the level has decreased by 77.4 m since the beginning of open pit drainage.

In the Moscow region, the intensive exploitation of groundwater in the Lower Carboniferous aquifer complex for 100 years has led to the formation of an extensive deep funnel, the area of \u200b\u200bwhich exceeds 20 thousand km 2, and the maximum decrease in the level is 110 m. The long-term exploitation of groundwater in the Gdov aquifer in St. the formation of a regional depression funnel with a total area of \u200b\u200bup to 20 thousand km 2 with a decrease in the level to 35 m.

On the territory of Russia, according to the state monitoring of the state of the subsoil of the Ministry of Natural Resources of Russia, 4,002 pollution sites have been identified, of which more than 80% are located in ground aquifers, which are usually not sources of drinking water supply for the population.

According to expert estimates, in the Russian Federation the share of polluted groundwater does not exceed 5–6% of the volume of their use for drinking water supply to the population.

The largest number of groundwater contamination sites are located in the following federal districts: Privolzhsky (30%), Siberian (23%); Central (16%) and South (15%). Of the total number of groundwater pollution sites:

§ 40% of pollution is associated with industrial enterprises;

§ 20% - with agricultural production;

§ by 9% - with housing and communal services,

§ 4% pollution occurs as a result of retraction of substandard natural waters in violation of the operating regime of water intakes;

§ 10% of groundwater pollution is “mixed” and is caused by the activity of industrial, municipal and agricultural facilities;

§ for 17% of sites the source of groundwater pollution has not been identified.

The most tense ecological situation has developed in the areas of groundwater pollution with substances of I hazard class. These areas were identified in the areas of individual large industrial enterprises in the following cities and towns: Amursk (mercury), Achinsk (phosphorus), Baikalsk (mercury), Georgievsk (mercury), Essentuki (mercury), Yekaterinburg (phosphorus), Iskitim (beryllium), Novokuznetsk (phosphorus), Kazan (beryllium, mercury), Kislovodsk (phosphorus), Mineralnye Vody (mercury), Lermontov (mercury), Komsomolsk-on-Amur (beryllium), Magnitogorsk (tetraethyl lead), Novosibirsk (beryllium), Saya r (mercury), Svobodny (mercury), Usolye-Sibirskoye (mercury), Khabarovsk (beryllium, mercury), Cherepovets (beryllium), etc.

The greatest environmental hazard is posed by groundwater pollution detected in individual wells at drinking water intakes.

The groundwater - water in the rock mass of the upper part of the earth's crust in a liquid, solid and gaseous state. Groundwater is one of the main existing and promising sources of water supply. In comparison with surface waters, they are of a higher quality, do not require expensive cleaning, are better protected from surface pollution and are ubiquitous. Groundwater accounts for about 40% of the total water volume. However, groundwater is a factor complicating construction work. They worsen the mechanical properties of loose and clayey waters, can be an aggressive medium for metal and concrete structures, and contribute to the formation of unfavorable engineering-geological processes.

Origin of groundwater (theory)

There are two main theories of the origin of groundwater: infiltration and condensation.

The infiltration theory explains the formation of groundwater by the percolation of atmospheric precipitation and surface water into the interior of the Earth. Seeping through large cracks and pores, water is retained on waterproof layers and gives rise to groundwater. The process is changeable in time and is determined by the natural conditions of the area: relief, water permeability of rocks, vegetation cover, human activity. With a decrease in the groundwater level, surface evaporation decreases, and at a certain depth it becomes equal to zero. Under these conditions, the amount of infiltration supply of groundwater increases.

The condensation theory assumes the formation of groundwater due to the condensation of water vapor, which penetrates into pores and cracks from the atmosphere. These theories complement each other. The infiltration path of groundwater formation is the main one for groundwater occurring in the zone of active water exchange, in areas with a sufficiently high amount of atmospheric precipitation. In areas with a small number of them (deserts, dry steppes), the role of condensation of water vapor in the formation and nutrition of groundwater increases significantly. In addition, the waters of the earth's crust are replenished with juvenile waters, which arise from the oxygen and hydrogen released by magma. Juvenile waters have a direct outlet to the Earth's surface in the form of vapors and hot springs during volcanic activity.

22. Physical and chemical properties of groundwater, their hardness, aggressiveness.

1. Physical properties of groundwater

When evaluating groundwater for water supply, taste, smell, color, clarity, temperature and other physical properties that characterize the organoleptic properties of water are examined. They are usually transparent, colorless, and odorless. The taste depends on the type and amount of dissolved salts and gases. The temperature of groundwater varies widely depending on the depth of the aquifer. There are cold waters (0 ... 20 ° C), warm or subthermal (20 ... 37 ° C), thermal (37 ... 100 ° C), overheated (over 100 ° C). Very cold groundwater circulates in the permafrost zone, in high mountain areas; superheated waters are typical for areas of young volcanic activity (Kamchatka). In the areas of existing water intakes, cold waters with a temperature of 5 ... 20 ° C are mainly common. With an increase in the depth of occurrence, the water temperature increases according to the law of the geothermal step, reaching 100 ° C or more at a depth of several kilometers. The density of water changes depending on the temperature and the amount of substances dissolved in it. Fluctuations from 0.8 (250 ° C) to 1.4 g / cm (due to salts). The compressibility of groundwater is characterized by the compressibility coefficient, which shows how much of the initial volume of liquid the volume decreases with an increase in pressure of 105 Pa. The compressibility factor is (2.5 ... 5.0) 10-5Pa, i.e. to some extent, water has elastic properties, which is important in the study of pressurized groundwater. The viscosity of water characterizes the internal resistance of particles to its movement. With increasing temperature, the viscosity decreases. The electrical conductivity depends on the amount of salts in the water (0.02 to 1.00 Ohm m). The radioactivity of groundwater is caused by the presence of radioactive elements (uranium, strontium, cesium, radium, radon, etc.) in it. Even negligible concentrations (hundredths and thousandths of mg / l) of some radioactive elements can be harmful to humans.

2 Groundwater is a complex aqueous solution containing dissolved salts, gases, organic matter and colloids. The quantitative relationships between the individual components determine the physical properties and chemical composition of groundwater. Ionic-salt composition. Groundwater is not found in a chemically pure form. More than 60 elements of the periodic table were found in it. The main components (ions) that determine the chemical type of water are Cl, SO4, HCO3, Na, Mg, Ca, K. The total content of minerals dissolved in water is called total mineralization. Its value is judged by the dry or dense residue, which is obtained after evaporation of a certain volume of water at a temperature of 105 ... 110 ° C.

3. The property of water, due to the content of calcium and magnesium ions in it, is called hardness. Distinguish: general hardness (all ions Ca and Mg); carbonate hardness (content of carbonate and bicarbonate ions); removable (temporary) stiffness, determined experimentally after boiling the sample; non-carbonate hardness, determined by subtracting carbonate hardness from the total hardness; irreparable (constant) rigidity, determined by subtracting the removable rigidity from the total rigidity. Hard waters give scale in steam boilers, do not lather well and cause other undesirable phenomena.

4. Groundwater aggressiveness. The aggressive effect of water on concrete is manifested in the dissolution of its calcium carbonate, as well as in the formation of salts CaSO42H2O, MgSO42H2O and calcium hydrosulfoaluminate, which causes swelling and crumbling of concrete. Aggressive action on metal (corrosion). It manifests itself mainly due to the oxidation of iron with the formation of rust. Soft water is even more aggressive because of its high solubility.