Groundwater phenomena. Groundwater: characteristics and types

Underground water sources, for the most part, are considered strategic water resources.
Aquifers, moving under the influence of their own gravity, form free-flow and pressure-bearing horizons. The conditions of their occurrence are different, which makes it possible to classify them into types: soil, subsoil, interstratal, artesian, and mineral.

Differences in groundwater

They fill pores, cracks and all gaps between rock particles. They are considered to be a temporary accumulation of drip water in the surface layer and are not associated with the lower aquifer.

They form the first water-resistant horizon from the surface. This layer experiences some fluctuations in different seasons, that is, an increase in the level in the spring-autumn period and a decrease in the hot season.

Unlike groundwater, they have a more constant level in time and lie between two stubborn layers.

Filling the entire interstratal horizon, the source is considered to be pressure head and, significantly, clean, relative to groundwater.

They are considered pressure-bearing, enclosed in rock strata. When opened, they often gush, rising above the level of the earth's surface. They occur at a depth of 100-1000 meters.

They are waters with a content of dissolved salts and microelements, often of a medicinal nature.

Groundwater reserves

Soil water reserves directly depend on their replenishment with rain and melt runoff. The periods of their level change fall on the spring - summer and summer - autumn. In the first case, soil moisture evaporates by 2-4 mm / day, in the other case, by 0.5-2.0 mm / day. Their balance changes significantly based on weather conditions, as a result of which water resources increase or decrease. But, if there are no serious atmospheric influences, their reserves in the soil mass remain unchanged. The calculation of the same reserves is carried out empirically.

Groundwater reserves are replenished as a result of infiltration of the upper layers of soil moisture, especially during the precipitation season. Flowing over saturated horizons, they find exits to the surface in the form of springs, replenishing and forming streams, ponds, lakes, and other ground sources. Formed by infiltration of river, lake waters, due to atmospheric precipitation. They are also replenished with springs rising from deep horizons. Large reserves are concentrated in the bases of river valleys and foothill areas, cracks of shallow petrified limestones.

By the way, there is information that predicts a sharp reduction in fresh water reserves by 2 times in the next 25 years. Considering that their total reserves are 60 million km³, and 80 countries of the planet are already experiencing a moisture deficit, then bad predictions may come true.

To the great chagrin of earthlings, water supplies are not renewed.

Origin of groundwater

Underground waters, according to the conditions of occurrence, consist of atmospheric precipitation and condensation of air moisture. They are called soil or "hanging" and, not being the underlying impervious horizons, play an important role in the nutrition of plantings. Below this zone, layers of dry rocks appear, containing the so-called film water. During the period of heavy percolation of rains, melting of snows, accumulations of gravitational waters are formed above dry layers.

Groundwater, being the first from the surface of the earth, is also fed by atmospheric precipitation and ground sources. The depth of their occurrence depends on the geological laws.

Interstratal sources lie below groundwater sources and are located between water-resistant layers. Horizons with an open mirror are called free-flowing horizons. A water lens with a closed surface is considered a pressure lens and, more often, is called an artesian lens.

Thus, the origin of groundwater largely depends on the physical properties of the rocks. This can be porosity and duty cycle. It is these indicators that characterize the moisture content and water permeability of rocks.

So, two zones - the zone of aeration and saturation determine the occurrence of underground sources. The aeration zone represents the interval from the plane of the earth to the plane of groundwater, called soil. The saturation zone includes an earth vein up to the interstratal horizon.

Topic: The main varieties of groundwater. Formation conditions. Geological activity of groundwater

2. The main types of groundwater.

1. Classification of groundwater.

Groundwater is very diverse in chemical composition, temperature, origin, purpose, etc. According to the total content of dissolved salts, they are divided into four groups: fresh, brackish, salty and brines. Fresh water contains less than 1 g / l of dissolved salts; brackish waters - from 1 to 10 g / l; salty - from 10 to 50 g / l; brines - more than 50 g / l.

According to the chemical composition of dissolved salts, groundwater is divided into hydrocarbonate, sulfate, chloride and complex composition (sulfate hydrocarbonate, chloride hydrocarbonate, etc.).

Waters with medicinal value are called mineral waters. Mineral waters come to the surface in the form of sources or are artificially brought to the surface using boreholes. By chemical composition, gas content and temperature, mineral waters are divided into carbon dioxide, hydrogen sulfide, radioactive and thermal.

Carbonic waters are widespread in the Caucasus, Pamirs, Transbaikalia, Kamchatka. The content of carbon dioxide in carbon dioxide water ranges from 500 to 3500 mg / l and more. The gas is present in water in a dissolved form.

Hydrogen sulfide waters are also widespread and associated mainly with sedimentary rocks. The total content of hydrogen sulphide in water is usually low, however, the therapeutic effect of hydrogen sulphide waters is so significant that an H2 content of more than 10 mg / l already gives them medicinal properties. In some cases, the content of hydrogen sulfide reaches 140-150 mg / l (for example, the well-known sources of Matsesta in the Caucasus).

Radioactive waters are divided into radon, containing radon, and radium, containing radium salts. The healing effect of radioactive waters is very high.

By temperature, thermal waters are divided into cold (below 20 ° C), warm (20-30 ° C), hot (37-42 ° C) and very hot (over 42 ° C). They are common in areas of young volcanism (in the Caucasus, Kamchatka, Central Asia).

2. The main types of groundwater

According to the conditions of occurrence, the following types of groundwater are distinguished:

· Soil;

· Top water;

· Ground;

· Interstratal;

· Karst;

· Cracked.

Soil water are located near the surface and fill the voids in the soil. The moisture in the soil layer is called soil water. They move under the influence of molecular, capillary and gravity forces.

In the aeration belt, there are 3 layers of soil water:

1.soil horizon with variable moisture content - root layer. It exchanges moisture between the atmosphere, soil and plants.

2. subsoil horizon, often "wet" does not reach here and it remains "dry".

capillary moisture horizon - capillary border.

Verkhovodka - temporary accumulation of groundwater in the near-surface layer of aquifers within the aeration zone, lying on a lenticular, wedging out aquiclude.

Verkhovodka - free-flow underground waters, occurring most close to the earth's surface and not having continuous distribution. They are formed due to the infiltration of atmospheric and surface waters trapped by impermeable or poorly permeable wedging out layers and lenses, as well as as a result of condensation of water vapor in rocks. They are characterized by a seasonality of existence: in dry seasons they often disappear, and during periods of rains and intense snow melting they reappear. They are subject to sharp fluctuations depending on hydrometeorological conditions (amount of precipitation, air humidity, temperature, etc.). Waters that temporarily appear in bog formations due to over-feeding of bogs also belong to upper water. Quite often, waterlogging occurs as a result of water leaks from the water supply system, sewerage, swimming pools and other water-carrying devices, which may result in waterlogging of the area, flooding of foundations and basements. In the area of ​​distribution of permafrost rocks, the permafrost is classified as suprapermafrost waters. Verkhovka waters are usually fresh, slightly mineralized, but often contaminated with organic matter and contain increased amounts of iron and silicic acid. As a rule, Verkhovodka cannot serve as a good source of water supply. However, if necessary, measures are taken for artificial preservation: arrangement of ponds; branches from the rivers, providing constant power supply to the operated wells; planting of vegetation that retards snow melting; creation of waterproof lintels, etc. In desert areas, by means of grooves in clayey areas - takyrs, atmospheric waters are diverted to the adjacent sands area, where a lens is created for the verkhovodka, which is a certain reserve fresh water.

Ground water lie in the form of a permanent aquifer on the first, more or less sustained, waterproof layer from the surface. Groundwater has a free surface called the mirror, or level, of groundwater.

Interstratal waters enclosed between water-resistant layers (layers). Interstratal waters under pressure are called confined or artesian. When the wells are opened, artesian waters rise above the top of the aquifer, and if the pressure level mark (piezometric surface) exceeds the mark of the Earth's surface at this point, then the water will pour out (gush). The conventional plane that determines the position of the pressure head in the aquifer (see Fig. 2) is called the piezometric level. The height of the rise of water above the waterproof roof is called the head.

Artesian waters lie in permeable sediments enclosed between watertight ones, completely fill the voids in the formation and are under pressure. The hydrocarbon established in the well is called piezometric, which is expressed in absolute marks. Self-flowing pressurized water has a local distribution and is better known among gardeners as "keys". The geological structures to which the artesian aquifers are confined are called artesian basins.

Rice. 1. Types of groundwater: 1 - soil; 2 - top water; 3 - ground; 4 ~ interstratal; 5 - waterproof horizon; 6 - permeable horizon

Rice. 2. Scheme of the structure of the artesian basin:

1 - impermeable rocks; 2 - permeable rocks with pressurized water; 4 - direction of groundwater flow; 5 - well.

Karst waters occur in karst cavities formed by dissolution and leaching of rocks.

Fissured water fill cracks in rocks and can be either pressure or non-pressure.

3. Conditions for the formation of groundwater

Groundwater is the first permanent aquifer from the earth's surface... About 80% of rural settlements use groundwater for water supply. Hot water has long been used for irrigation.

If the waters are fresh, then at a depth of 1–3 m they serve as a source of soil moisture. At a height of 1-1.2 m, they can cause waterlogging. If the groundwater is highly mineralized, then at a height of 2.5 - 3.0 m, they can cause secondary soil salinization. Finally, groundwater can make it difficult to dig construction pits, scorch built-up areas, aggressively affect the underground parts of structures, etc.

Groundwater forms different ways. Some of them are formed as a result of the seepage of atmospheric precipitation and surface water through the pores and cracks of rocks... Such waters are called infiltrative(the word "infiltration" means seepage).

However, the existence of groundwater cannot always be explained by the infiltration of atmospheric precipitation. For example, in areas of deserts and semi-deserts, very little precipitation falls, and they evaporate quickly. At the same time, even in desert areas, groundwater is present at some depth. The formation of such waters can only be explained condensation of water vapor in the soil... The elasticity of water vapor in the warm season in the atmosphere is greater than in soil and rocks; therefore, water vapor continuously flows from the atmosphere into the soil and forms groundwater there. In deserts, semi-deserts and dry steppes, water of condensation origin during hot times is the only source of moisture for vegetation.

Groundwater can form due to the disposal of the waters of ancient sea basins together with the accumulated sediments... The waters of these ancient seas and lakes could have survived in buried sediments and then seep into the surrounding rocks or emerge to the surface of the Earth. Such underground waters are called sedimentation waters .

Some of the groundwater origin may be associated with cooling molten magma... The release of water vapor from magma is confirmed by the formation of clouds and showers during volcanic eruptions. Underground waters of magmatic origin are called juvenile (from Latin "juvenalis" - virgin). According to oceanologist H. Wright, the vast expanses of water that exist at the present time, "grew drop by drop throughout the life of our planet due to water seeping from the bowels of the Earth."

The conditions of occurrence, distribution and formation of HS depend on the climate, relief, geological structure, the influence of rivers, soil and vegetation cover, and on economic factors.

a) The relationship between hot water and climate.

Precipitation and evaporation play an important role in the formation of mountain waters.

To analyze the change in this ratio, it is advisable to use the map of plant moisture supply. In relation to precipitation to evaporation, 3 zones (areas) are identified:

1.sufficient moisture

2.insufficient

3.slight moisturizing

In the first zone, the main areas of waterlogged lands are concentrated, requiring drainage (in some periods, moisture is required here). Areas of insufficient and insignificant moisture need artificial moisture.

In the three regions, the supply of HW by precipitation and their heat to the aeration zone are different.

In the area of ​​sufficient humidification, the infiltration supply of groundwater at a depth of more than 0.5 - 0.7 m prevails over their thermal supply to the aeration zone. This pattern is observed in non-growing and growing seasons, with the exception of very dry years.

In the area of ​​insufficient moisture, the ratio of precipitation infiltration with evaporation of HS at their shallow occurrence is different in the forest-steppe and steppe zones.

In forest-steppe, in loamy rocks in wet years, infiltration prevails over thermal HS into the aeration zone; in dry years, the ratio is reversed. In the steppe zone, in loamy rocks, during the non-growing season, infiltration nutrition prevails over the heat GW, and during the growing season, less consumption. In general, over the course of a year, infiltration recharge begins to prevail over the thermal recharge of groundwater.

In the area of ​​insignificant moisture - in semi-deserts and deserts - infiltration in loamy rocks with a shallow GWL bed is incommensurably small compared to the flow rate into the aeration zone. In sandy rocks, infiltration begins to increase.

Thus, the supply of HS due to precipitation decreases, and the flow rate to the aeration zone increases with the transition from the region of sufficient to the region of insignificant moisture.

b) Connection of ground waters with rivers.

The forms of connection between groundwater and rivers are determined by the relief and geomorphological conditions.

The deeply incised river valleys serve as a sink for groundwater, draining the adjacent lands. On the contrary, with a small incision, typical of the lower reaches of rivers, the rivers feed groundwater.

Various cases of the ratio of surface water and groundwater are shown in the diagram.

Principal design scheme for the interaction of groundwater and surface waters under conditions of variability of surface runoff.

a - low water; b - the ascending phase of the flood; c - the descending phase of the flood.

v) Relationship between groundwater and pressure water.

If there is no absolutely watertight layer between the groundwater and the underlying confined horizon, then the following forms of hydraulic connection are possible between them:

1) GWL is higher than the pressure water level, as a result of which the overflow of hot water into the pressure water is possible.

2) The levels are almost the same. With a decrease in the GWL, for example, by drains, the GW will be replenished by pressurized ones.

3) GWL periodically exceed the level of confined waters (during irrigation, precipitation), the rest of the time GW is fed by precipitation.

4) The groundwater level is constantly lower than the UNV, so the latter feed the groundwater.

Groundwater can be fed from artesian waters and through the so-called hydrogeological windows - areas where the continuity of the water-resistant layer is disturbed.

It is possible to feed hydrocarbons by pressure head through tectonic faults.

Hydrodynamic zones of GW, determined by the relief and geological structure, are closely related to the geostructural conditions of the territory. Areas of high drainage are characteristic of mountainous and foothill areas. Areas of low drainage are characteristic of troughs and depressions of platform plains.

The zoning of HS feeding is most clearly manifested in the zone of low drainage of the arid regions. It consists in a sequential increase in the mineralization of HS with distance from the source of the river, canal, etc. Therefore, in arid regions, water supply wells are usually placed along canals and rivers.

4. Conditions of formation and occurrence of artesian waters.

Artesian waters are formed at a certain geological structure- alternation of water-permeable reservoirs with water-resistant ones. They are confined mainly to synclinal or monoclinal bed formations.

The area of ​​development of one or more artesian layers is called an artesian basin. AB can occupy from several tens to hundreds of thousands of km 2.

The sources of pressure water supply are sediments, seepage waters of rivers, reservoirs, irrigation canals, etc. Pressure waters under certain conditions are replenished with groundwater.

Their consumption is possible by unloading them into river valleys, coming out to the surface in the form of springs, slowly seeping through the strata enclosing the pressure layer, with overflowing into groundwater. The selection of water supplies for water supply and irrigation also constitutes their expenditure items.

In artesian basins, areas of nutrition, pressure and discharge are distinguished.

Recharge area - the area where the artesian layer emerges on the surface of the earth, where it is fed. It is located at the highest elevations of the artesian basin relief in mountainous areas and watersheds, etc.

The pressure area is the main area of ​​distribution of the artesian basin. Within its limits, groundwater has a pressure.

Discharge area - area of ​​outlet of pressure water to the surface - open discharge (in the form of ascending springs or area of ​​hidden discharge, for example, in river beds, etc.)

Wells that penetrate AB gush out, this is an example of artificial discharge of pressure water.

In formations containing gypsum, anhydrides, salts, artesian waters have increased mineralization.

Types and zoning of artesian waters

Artesian basins are usually typified by the geostructure of water-bearing and water-resistant rocks.

On this basis, two types of artesian basins are distinguished (according to N.I. Tolstikhin):

1.artesian platform basins, which are usually characterized by a very large area of ​​development and the presence of several confined aquifers (these are the Moscow, Baltic, Dnieper-Donetsk, etc.)

2. artesian basins of folded areas confined to intensively dislocated sedimentary, igneous and metamorphic rocks. They differ in a smaller development area. Examples are the Fergana, Chui and other basins.

5. Geological activity of groundwater.

Groundwater carries out destructive and constructive work. The destructive activity of groundwater is manifested mainly in the dissolution of water-soluble rocks, which is facilitated by the content of dissolved salts and gases in the water. Among the geological processes caused by the WR activity, first of all, karst phenomena should be named.

Karst.

Karst is the process of dissolution of rocks moving underground and percolating through them. surface waters... As a result of karst, caves and voids of various shapes and sizes are formed in the rocks. Their length can reach many kilometers.

Of the karst systems, the Mammoth Cave (USA) has the greatest length, the total length of the passages of which is about 200 km.

Saline rocks, gypsum, anhydrides and carbonate rocks are subject to karst. Accordingly, karst is distinguished: salt, gypsum, carbonate. Karst development begins with expansion (under the influence of leaching) cracks. Karst determines specific landforms. Its main feature is the presence of karst funnels with a diameter of several to hundreds of meters and a depth of up to 20-30 m. Karst develops the more intensively, the more precipitation falls and the greater the speed of movement of underground streams.

Areas prone to karst are characterized by rapid absorption of precipitation.

Within the massifs of karst rocks, zones of downward movement of water and horizontal movement are distinguished in the direction of river valleys, the sea, etc.

In karst caves, drip formations of a predominant carbonate composition are observed - stalactites (growing down) and stalagmites (growing from below). Karst weakens rocks, reduces their quantity as a basis for GTS. Through karst voids, significant water leakage from reservoirs and canals is possible. And at the same time, groundwater trapped in karst rocks can be a valuable source for water supply and irrigation.

The destructive activity of groundwater includes suffusion (undermining) - this is the mechanical removal of small particles from loose rocks, which leads to the formation of voids. Such processes can be observed in loess and loess-like rocks. In addition to mechanical, chemical suffusion is distinguished, an example of which is karst.

The creative work of underground waters is manifested in the deposition of various compounds, cementing cracks in rocks.

Control questions:

1 Give the classification of groundwater.

2. Under what conditions is groundwater generated?

3. Under what conditions artesian groundwater is formed?

4. What is manifested in geological activity groundwater?

5. Name the main types of groundwater.

6. How does the vermicompost influence the construction?

(to a depth of 12-16 km) in liquid, solid and vapor states. Most of them are formed as a result of seepage from the surface of rain, melt and river waters. Groundwater is constantly moving both vertically and horizontally. The depth of their occurrence, direction and intensity of movement depend on the water permeability of the rocks. Permeable rocks include pebbles, sands, gravel. To waterproof (waterproof), practically impermeable 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 waterproof layer from the surface; interstratal, located between two water-resistant layers. Groundwater is fed by leaked sediments, waters, lakes,. The groundwater level varies with the seasons of the year and is different in different zones. So, in it practically coincides with the surface, it is located at a depth of 60-100 m. They are distributed almost everywhere, do not have pressure, move slowly (in coarse-grained sand, for example, at a speed of 1.5-2.0 m per day). The chemical composition of groundwater is not the same and depends on the solubility of the adjacent rocks. By chemical composition, fresh (up to 1 g of salt per 1 l of water) and mineralized (up to 50 g of salts per 1 l of water) underground waters are distinguished. Natural discharges of groundwater to the earth's surface are called sources (springs, springs). They form usually in low places where the earth's surface is crossed by aquifers. 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 carbon dioxide, alkaline, saline, etc. Many of them have medicinal value.

Underground waters replenish wells, rivers, lakes,; dissolve various substances in rocks and transfer them; cause landslides,. They provide plants with moisture and population drinking water... The 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 using them. Protection of groundwater from pollution is no less important.

Page 1 of 6

- these are waters below the earth's surface and contained in water-bearing sedimentary rocks of the upper layer of the earth's crust and in the soil.

Groundwater - groundwater reserves, groundwater resources.

They are part of the hydrosphere of the planet (2% of the volume) and participate in the general water cycle in nature. Groundwater reserves have not yet been fully explored. Now in the official data there is a figure of 60 million cubic kilometers, but hydrogeologists are confident that there are colossal unexplored underground water deposits in the bowels of the Earth, and the total amount of water in them can amount to hundreds of millions of cubic meters.

Groundwater is found in boreholes at depths of up to several kilometers. Depending on the conditions in which groundwater occurs (such as temperature, pressure, types of rocks, etc.), they can be in a solid, liquid and gaseous state. According to V.I. Vernadsky, 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%.

• Read about underground water reserves: Oceans of water underground. How much water is there on Earth?

When assessing groundwater, in addition to the concept of "groundwater reserves", the term "groundwater resources" is used, which characterizes the recharge of the aquifer.

Classification of groundwater reserves and resources:

1. Natural reserves - the volume of gravitational water trapped in the pores and cracks of water-bearing rocks. Natural resources - the amount of groundwater entering the aquifer in natural conditions by infiltration of atmospheric precipitation, filtration from rivers, overflow from higher and lower aquifers.

2. Artificial stocks Is the volume of groundwater in the reservoir, formed as a result of irrigation, filtration from reservoirs, artificial recharge of groundwater. Artificial resources Is the flow rate of water entering the aquifer during filtration from canals and reservoirs in irrigated areas.

3. Attracted resources - this is the flow rate of water entering the aquifer when increasing the supply of groundwater caused by the operation of water intake facilities.

4. Concepts operational reserves and operational resources are, in essence, synonyms. They are understood as the amount of groundwater that can be obtained by technically and economically rational water intake structures under a given operating mode and with a water quality that meets the requirements during the entire estimated period of water consumption.

www.whymap.org - full version maps of groundwater reserves.

• Blue areas on the map - areas rich in groundwater,
• Brown - areas where there is a shortage of groundwater freshwater.

As you can see from the map, Russia is one of the countries with significant reserves of groundwater. Brazil and the countries of Central and South Africa, where torrential tropical downpours contribute to the year-round replenishment of groundwater reserves, also do not experience a shortage of groundwater. But not everywhere in the world groundwater reserves are renewable. For example, in North Africa and the Arabian Peninsula, groundwater reservoirs were filled 10,000 years ago when the area was more humid.

All over the world, groundwater resources are actively used, but in some countries, groundwater is practically the only source of water consumption.

• In the European Union, already 70% of all water used by water consumers is taken from underground aquifers.
• In arid countries, water is almost entirely taken from underground sources (Morocco - 75%, Tunisia - 95%, Saudi Arabia and Malta - 100%)

Groundwater - the chemical composition of groundwater.

The chemical composition of groundwater is not the same and depends on the solubility of the adjacent rocks. Groundwater is a natural solution containing over 60 chemical elements and microorganisms. The amount of substances dissolved in water, excluding gases, determines its mineralization (expressed in g / l or mg / l).

By chemical composition, the following types of groundwater are distinguished:

• - fresh (up to 1 g of salt per 1 liter of water),
• — slightly mineralized(up to 35 g of salts per 1 liter of water),
• — mineralized(up to 50 g of salts per 1 liter of water).

In this case, the upper horizons of groundwater are usually fresh or slightly mineralized, and the lower horizons can be highly mineralized.

Ground waters, which, due to their physicochemical properties, have a beneficial physiological effect on the human body and are used for medicinal purposes, are called mineral. The chemical composition of mineral waters is very diverse: there is carbonic water (Kislovodsk and other resorts in the region of the Caucasian Mineral waters, Borjomi, Karlovi-Vari, etc.), nitrogen (Tskhal-tubo), hydrogen sulfide (Matsesta), ferrous, radon, etc.

According to the degree of general mineralization, waters are distinguished (according to V.I. Vernadsky):

• fresh (up to 1 g / l),
• brackish (1-10 g / l),
• salted (10-50 g / l),
• brines (more than 50 g / l) - in a number of classifications, a value of 36 g / l is adopted, corresponding to the average salinity of the waters of the World Ocean.

In the basins of the East European Platform, the thickness of the fresh groundwater zone varies from 25 to 350 m, salt water - from 50 to 600 m, brines - from 400 to 3000 m.

The above classification indicates significant changes in water salinity - from tens of milligrams to hundreds of grams per 1 liter of water. The maximum value of mineralization, reaching 500 - 600 g / l, has recently been found in the Irkutsk basin.

For more information about the chemical composition of groundwater, chemical properties of groundwater, classification by chemical composition, factors affecting the chemical composition of groundwater, and other aspects, read a separate article: Chemical composition of groundwater.

Groundwater - the origin and formation of groundwater.

Depending on the origin, groundwater is:

• 1) infiltration,
• 2) condensing,
• 3) sedimentogenic,
• 4) "juvenile" (or magmogenic),
• 5) artificial,
• 6) metamorphogenic.

Groundwater is the temperature of groundwater.

By temperature, groundwater is divided into cold (up to +20 ° С) and thermal (from +20 to +1000 ° С). Thermal waters are usually high in various salts, acids, metals, radioactive and rare earth elements.

In terms of temperature, underground waters are:

Cold groundwater is subdivided into:

• hypothermic (below 0 ° С),
• cold (from 0 to 20 ° С)

Thermal underground waters are subdivided into:

• warm (20 - 37 ° С),
• hot (37 - 50 ° С),
• very hot (50 - 100 ° С),
• overheated (over 100 ° C).

Groundwater temperature also depends on the depth of the aquifers:

1. Groundwater and shallow interstratal waters experience seasonal temperature fluctuations.
2. Groundwater at the level of the belt of constant temperatures, maintain a constant temperature throughout the year, equal to the average annual temperature of the area.

• There, where the average annual temperatures are negative, groundwater in the belt of constant temperatures is in the form of ice all year round. This is how permafrost ("permafrost") is formed.
• In areas where the average annual temperature is positive, on the contrary, underground waters of the belt of constant temperatures do not freeze even in winter.

3. Groundwater circulating below the constant temperature belt, heated above the average annual temperature of the area and due to endogenous heat. The water temperature in this case is determined by the magnitude of the geothermal gradient and reaches its maximum values ​​in areas of modern volcanism (Kamchatka, Iceland, etc.), in the zones of mid-ocean ridges, reaching temperatures of 300-4000C. Highly thermal groundwater in areas of modern volcanism (Iceland, Kamchatka) is used for heating homes, building geothermal power plants, greenhouse heating, etc.

Groundwater - methods for finding groundwater.

• geomorphological assessment of the area,
• geothermal research,
• radonometry,
• drilling of exploration wells,
• study of core extracted from wells in laboratory conditions,
• experienced pumping out of wells,
• ground exploration geophysics (seismic and electrical exploration) and well logging

Groundwater - extraction of groundwater.

An important feature of groundwater as a mineral is the continuous nature of water consumption, which necessitates the constant withdrawal of water from the subsoil in a given amount.

When determining the feasibility and rationality of groundwater extraction, the following factors are taken into account:

• General reserves of groundwater,
• Annual water input into aquifers,
• Filtration properties of water-bearing rocks,
• The depth of the level,
• Technical operating conditions.

Thus, even if there are large reserves of groundwater and its significant annual flow into aquifers, the extraction of groundwater is not always rational from an economic point of view.

For example, groundwater extraction will be irrational in the following cases:

• very low well production rates;
• the complexity of operation in technical terms (sanding, scaling in wells, etc.);
• lack of the necessary pumping equipment (for example, when operating aggressive industrial or thermal waters).

Highly thermal groundwater in areas of modern volcanism (Iceland, Kamchatka) is used for heating homes, building geothermal power plants, greenhouse heating, etc.

In this article, we looked at the topic Groundwater: a general characteristic. Read on: