Groundwater population. Groundwater: characteristics and types. Conditions for the formation and occurrence of artesian waters
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 terms of 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 bicarbonate, sulfate, chloride and complex composition. (sulfate hydrocarbonate, chloride hydrocarbonate, etc.).
Waters with medicinal value are called mineral. Mineral waters come to the surface in the form of springs or are brought to the surface artificially with the help of boreholes. According to the chemical composition, gas content and temperature, mineral waters are divided into carbonic, hydrogen sulfide, radioactive and thermal.
Carbonic waters are widespread in the Caucasus, the Pamirs, Transbaikalia, and Kamchatka. Content carbon dioxide in carbonic waters it ranges from 500 to 3500 mg/l and more. The gas is present in water in dissolved form.
Hydrogen sulfide waters are also quite widespread and are associated mainly with sedimentary rocks. The total content of hydrogen sulfide in water is usually low, but the therapeutic effect hydrogen sulfide waters so significant that the content of H2 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 springs of Matsesta in the Caucasus).
Radioactive waters are divided into radon, containing radon, and radium, containing radium salts. The therapeutic 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, and Central Asia).
2. Main types of groundwater
According to the conditions of occurrence, they distinguish the following types groundwater:
soil;
· top water;
soil;
interstratal;
· karst;
Fissures.
ground water located at the surface and fill voids in the soil. The moisture contained in the soil layer is called soil water. They move under the influence of molecular, capillary and gravity forces.
In the aeration zone, 3 layers of soil water are distinguished:
1. soil horizon of variable moisture - root layer. It exchanges moisture between the atmosphere, soil and plants.
2. subsoil horizon, often “wetting” 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, wedged out aquiclude.
Verkhovodka - non-pressure groundwater, which occurs closest to the earth's surface and does not have a continuous distribution. Formed by infiltration of atmospheric and surface water, delayed by impermeable or slightly permeable pinch-out formations and lenses, as well as as a result of water vapor condensation in rocks. They are characterized by seasonality of existence: in dry times, they often disappear, and during periods of rain and intense snowmelt, they reappear. They are subject to sharp fluctuations depending on hydrometeorological conditions (the amount of precipitation, air humidity, temperature, etc.). Perched waters also include waters that temporarily appear in marsh formations due to excess feeding of marshes. Often, perched water occurs as a result of water leaks from the water supply system, sewerage, pools, and other water-bearing devices, which can result in swamping of the area, flooding of foundations and basements. In the area of distribution of permafrost rocks, permafrost waters are referred to as supra-permafrost waters. Verkhovodka waters are usually fresh, slightly mineralized, but often polluted. organic matter and contain high amounts of iron and silicic acid. Verkhovodka, as a rule, cannot serve as a good source of water supply. However, if necessary, measures are taken for artificial conservation: arrangement of ponds; diversions from rivers providing constant food operated wells; planting vegetation that delays snowmelt; creation of waterproof jumpers, etc. In desert regions, by arranging grooves in clayey areas - takyrs, atmospheric water is diverted to the adjacent area of sands, where a lens of perched water is created, which is a certain supply of fresh water.
ground water lie in the form of a permanent aquifer on the first from the surface, more or less sustained, impermeable layer. Groundwater has a free surface, which is called a mirror, or level, of groundwater.
Interstratal waters enclosed between water-resistant layers (layers). Interstratal waters under pressure are called pressure or artesian. When opening wells, artesian waters rise above the roof 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 conditional plane that determines the position of the pressure level in the aquifer (see Fig. 2) is called the piezometric level. The height of the rise of water above the water-resistant roof is called pressure.
artesian waters lie in permeable sediments enclosed between impervious ones, completely fill the voids in the reservoir and are under pressure. A hydrocarbon that has settled in a well is called piezometric, which is expressed in absolute terms. Self-flowing pressure waters have a local distribution and are better known to gardeners as "keys". The geological structures to which 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 - waterproof rocks; 2 - permeable rocks with pressure water; 4 - direction of groundwater flow; 5 - well.
Karst waters lie in karst voids formed due to the dissolution and leaching of rocks.
fissure waters fill cracks in rocks and can be both pressure and 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 groundwater is used for water supply. GW 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 groundwater is highly mineralized, then at a height of 2.5 - 3.0 m it can cause secondary soil salinization. Finally, groundwater can make it difficult to excavate construction pits, set fire to built-up areas, aggressively affect the underground parts of structures, etc.
Groundwater is forming different ways. Some of them are formed as a result of infiltration of atmospheric precipitation and surface water through the pores and cracks of rocks. Such waters are called infiltration(the word "infiltration" means seepage).
However, the existence of groundwater cannot always be explained by precipitation infiltration. For example, in areas of deserts and semi-deserts, very little precipitation falls, and they quickly evaporate. However, 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, so 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 in hot weather is the only source of moisture for vegetation.
Groundwater can form due to the burial of the waters of ancient marine basins together with the sediments accumulating in them. The waters of these ancient seas and lakes may have been preserved in buried sediments and then seeped into surrounding rocks or out to the Earth's surface. Such underground waters are called sedimentary waters .
Part of the groundwater origin can be associated with cooling of molten magma. The release of water vapor from magma is confirmed by the formation of clouds and showers during volcanic eruptions. Groundwater of magmatic origin is called juvenile (from the Latin "juvenalis" - virgin). According to oceanologist X. Wright, the vast expanses of water that currently exist "grew drop by drop throughout the life of our planet due to water seeping from the bowels of the Earth."
The conditions for the occurrence, distribution and formation of HS depend on the climate, relief, geological structure, the influence of rivers, soil and vegetation cover, and economic factors.
a) Relationship of GW with 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 a map of plant moisture supply. Three zones (regions) have been identified in relation to precipitation to evaporation:
1. sufficient moisture
2. insufficient
3. Slight moisture
In the first zone, the main areas of waterlogged lands are concentrated, requiring drainage (in some periods, moisture is needed here). Areas of insufficient and insignificant moisture need artificial moisture.
In the three areas of HW supply by precipitation and their heat into the aeration zone, they are different.
In the area of sufficient moisture, infiltration feeding of groundwater at a depth of more than 0.5 - 0.7 m prevails over their thermal supply to the aeration zone. This regularity is observed during non-vegetation and vegetation periods, with the exception of severely dry years.
In the area of insufficient moisture, the ratio of precipitation infiltration to the evaporation of HW at their shallow occurrence is different in the forest-steppe and steppe zones.
In forest-steppes, in loamy rocks, in wet years, infiltration prevails over thermal HW into the aeration zone; in dry years, the ratio is reversed. In the steppe zone, in loamy rocks during the non-vegetation period, infiltration nutrition prevails over thermal HW, and during the growing season - less consumption. In general, over the year, infiltration nutrition begins to prevail over thermal groundwater.
In the area of insignificant moisture - in semi-deserts and deserts - infiltration in loamy rocks with a shallow GWL is incommensurably small compared to the flow into the aeration zone. In sandy rocks, infiltration begins to increase.
Thus, the supply of HW due to precipitation decreases, and the discharge to the aeration zone increases with the transition from the area of sufficient to the area of insignificant moisture.
b) Connection of groundwater with rivers.
Forms of connection between groundwater and rivers are determined by relief and geomorphological conditions.
Deeply incised river valleys serve as groundwater receivers, draining adjacent lands. On the contrary, with a small incision characteristic of the lower reaches of the rivers, the rivers feed the groundwater.
Various cases of the ratio of surface and ground waters are shown in the diagram.
Principal design scheme for the interaction of groundwater and surface water under conditions of surface runoff variability.
a - low water; b - ascending phase of the flood; c - descending phase of the flood.
in) The connection of groundwater with pressure.
If there is no absolutely impermeable layer between the groundwater and the underlying pressure horizon, then the following forms of hydraulic connection are possible between them:
1) GWL is higher than the level of pressure water, as a result of which GW may flow into pressure water.
2) The levels are almost the same. With a decrease in GWL, for example, by drains, GW will be fed by pressure ones.
3) GWL periodically exceed the level of pressure water (during irrigation, precipitation), the rest of the time GW is fed by precipitation.
4) GWL is constantly below UNV, so the latter feed 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 with pressure through tectonic faults.
The hydrodynamic zones of GW, determined by the relief and geological structure, are closely related to the geostructural conditions of the territory. Zones of high drainage are characteristic of mountainous and foothill areas. Zones of low drainage are characteristic of troughs and depressions of platform plains.
The zoning of HW feeding is most clearly manifested in the zone of low drainage in arid regions. It consists in a consistent increase in the mineralization of HW with the distance from the source of supply of the river, canal, etc. Therefore, in arid regions, wells for water supply are usually placed along canals, rivers.
4. Conditions for the formation and occurrence of artesian waters.
Artesian waters are formed with a certain geological structure - the alternation of permeable layers with impervious ones. They are confined mainly to synclinal or monoclinal 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 .
Power sources of pressure water - precipitation, seepage water of rivers, reservoirs, irrigation canals, etc. Pressure water under certain conditions is replenished with groundwater.
Their consumption is possible by unloading them into river valleys, coming to the surface in the form of springs, slowly seeping through the layers that contain the pressure layer, with overflowing into groundwater. The selection of AW for water supply and irrigation also constitutes the items of their expenditure.
In artesian basins, there are areas of nutrition, pressure and discharge.
Feeding area - the area where the artesian formation comes out to the surface of the earth, where it is fed. It is located at the highest elevations of the artesian basin in mountainous areas and watersheds, etc.
The pressure area is the main area of distribution of the artesian basin. Within its limits, groundwater has pressure.
Discharge area - area of pressure water outlet to the surface - open discharge (in the form of ascending springs or area of hidden discharge, for example in riverbeds, etc.)
The wells opening the AB are gushing, this is an example of artificial discharge of pressure waters.
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, usually characterized by a very large development area and the presence of several pressure aquifers (these are Moscow, Baltic, Dnieper-Donetsk, etc.)
2. artesian basins of folded areas confined to intensely deformed sedimentary, igneous and metamorphic rocks. Differ in the smaller area of development. Examples are the Fergana, Chui and other basins.
5. Geological activity of groundwater.
Underground waters carry out destructive and creative 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 water. Among the geological processes caused by the activity of the PW, karst phenomena should be mentioned first of all.
Karst.
Karst is the process of dissolution of rocks moving in them underground and infiltrating surface water. 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, Mammoth Cave (USA) has the longest total length moves which is about 200 km.
Salt-bearing rocks, gypsum, anhydrides and carbonate rocks are subject to karst. Accordingly, karst is distinguished: salt, gypsum, carbonate. The development of karst begins with the expansion (under the influence of leaching) of cracks. Karst causes 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 underground flows.
Areas subject to karst are characterized by rapid absorption of precipitation.
Within the massifs of karst rocks, zones of downward movement of water and horizontal movement towards river valleys, the sea, etc. are distinguished.
In karst caves, sinter 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 hydraulic structures. Significant leakage of water from reservoirs and canals is possible along karst voids. And at the same time, groundwater contained in karst rocks can be a valuable source for water supply and irrigation.
The destructive activity of groundwater includes suffusion (digging) - 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 groundwater is manifested in the deposition of various compounds that cement cracks in rocks.
1 Give the classification of groundwater.
2. Under what conditions is groundwater formed?
3. Under what conditions are artesian groundwater formed?
4. What is the geological activity of groundwater?
5. Name the main types of groundwater.
6. How does perched water affect construction?
Through layers of sand, gravel, pebbles, cracked limestone. The layers composed of these rocks are called permeable.
But rainwater reaches a layer of clay and stops: after all, clay almost does not let water through. Layers of rocks that do not pass or very weakly pass water through themselves are called waterproof (waterproof). Granite, sandstone, shale can be attributed to water-resistant layers, but only if they do not have cracks.
Above the waterproof layer, groundwater accumulates, forming aquifer (horizon) - a layer of permeable rock that lies above the water-resistant layer and contains groundwater.
Types of underground sources
Springs (keys)
If the water-resistant layer has an inclination in one direction or another, then the water begins to flow along this layer in the direction of its inclination and usually comes to the surface somewhere in a river valley or in a ravine. The place of natural outlet of underground water to the surface is called source, key or spring(Fig. 84). The spring water is usually clean and cold.
There are especially many springs in ravines, along the banks of rivers, in cliffs, since water-resistant layers come to the surface there.
Mineral springs
In some regions of the globe, water comes to the surface of the earth, in which salts and gases are dissolved in a fairly large amount. This water is called mineral water. The water of mineral springs is used for the treatment of various diseases. Hospitals and resorts spring up around these springs. Resorts in the Caucasus (Borjomi, Kislovodsk, etc.) enjoy world-famous fame.
Water is the most common substance on our planet, thanks to which life is supported on it. It is found both in the lithosphere and in the hydrosphere. The Earth's biosphere consists of ¾ of water. An important role in the circulation of this substance is played by its underground species. Here it can be formed from mantle gases, during runoff, etc. In this article, we will consider the types of groundwater.
concept
Groundwater is understood as the latter located in the earth's crust, located in rocks below the surface of the earth in various aggregate states. They form part of the hydrosphere. According to V. I. Vernadsky, these waters can be located at a depth of up to 60 km. The estimated volume of groundwater located at a depth of up to 16 km is 400 million cubic km, that is, one third of the waters of the oceans. They are located on two floors. In the lower of them there are metamorphic and igneous rocks, so the amount of water here is limited. The bulk of the water is located in the upper floor, in which sedimentary rocks are located.
Classification according to the nature of exchange with surface waters
There are 3 zones in it: the upper one is free; middle and lower - slow water exchange. Types of groundwater composition in different zones are different. So, in the upper of them there are fresh waters used for technical, drinking and economic purposes. In the middle zone there are ancient waters of various mineral composition. In the lower part there are highly mineralized brines from which various elements are extracted.
Mineralization classification
The following types of groundwater are distinguished by mineralization: ultra-fresh, having a relatively high mineralization - only the last group can reach a mineralization level of 1.0 g / cu. dm; brackish, saline, high salinity, brines. In the latter, mineralization exceeds 35 mg / cu. dm.
Occurrence classification
The following types of groundwater are distinguished according to the conditions of occurrence: perched water, groundwater, artesian and soil water.
Verkhovodka is mainly formed on lenses and wedged out layers of poorly permeable or water-resistant rocks in the aeration zone during infiltration of surface and atmospheric waters. Sometimes it is formed due to the illuvial horizon under the soil layer. The formation of these waters is associated with the processes of condensation of water vapor in addition to those listed above. In some climatic zones, they form sufficiently large reserves of high-quality water, but mainly thin aquifers are formed that disappear during drought and form during periods of intense moisture. Basically, this type of groundwater is typical for loams. Its thickness reaches 0.4-5 m. Relief has a significant influence on the formation of perched water. On steep slopes, it exists for a short time or is completely absent. On flat steppes with saucer-shaped depressions and flat watersheds, on the surface of river routes, a more stable perched water is formed. It does not have a hydraulic connection with river waters, while it is easily polluted by other waters. At the same time, it can feed groundwater, and can be spent on evaporation. Verkhovodka can be fresh or slightly mineralized.
Groundwater is part of groundwater. They are located on the first aquifer from the surface, lie on the first aquifer sustained over the area. Basically, they are non-pressure waters, they can have a small pressure in areas with a local impervious overlap. The depth of occurrence, their chemical and physical properties are subject to periodic fluctuations. Distributed everywhere. They feed by infiltration of precipitation from the atmosphere, filtration from surface sources, condensation of water vapor and intra-ground evaporation, additional nutrition coming from lower aquifers.
Artesian water is part of groundwater with pressure, occurring in aquifers between relatively water-resistant and water-resistant layers. They lie deeper than the ground. In most cases, their areas of nutrition and pressure do not match. Water appears in the well below the established level. The properties of these waters are less subject to fluctuations and pollution compared to groundwater.
Soil waters are those that are confined to the soil water layer, take part in the supply of plants with this substance, are associated with the atmosphere, perched water and groundwater. They have a significant impact on the chemical composition of groundwater at their deep occurrence. If the latter are located shallow, then the soil becomes waterlogged and waterlogging begins. Gravitational water does not form a separate horizon, the movement is carried out from top to bottom under the action of capillary forces or gravity in different directions.
Formation classification
The main types of groundwater are infiltration, which are formed due to infiltration of atmospheric precipitation. In addition, they can be formed as a result of the condensation of water vapor, which enters the fractured and porous rocks along with air. In addition, relict (buried) waters are distinguished, which were in ancient basins, but were buried by thick layers of sedimentary rocks. Also, thermal waters, which were formed at the last stages of magmatic processes, are a separate species. These waters form igneous or juvenile species.
Classification of the movement of the objects under consideration
The following types of groundwater movement are distinguished (see figure).
Seepage and precipitation from the atmosphere occurs in the aeration zone. At the same time, this process is divided into freely carried out and normal infiltration. The first involves the movement from top to bottom under the influence of gravity and capillary forces through certain tubules and capillary pores, while the porous space is not saturated with water, which contributes to the preservation of air movement. During normal infiltration, hydrostatic pressure gradients join the forces listed above, which leads to the fact that the pores are completely filled with water.
In the saturation zone, hydrostatic pressure and gravity act, which contributes to the movement of free water along cracks and pores to the sides, a decrease in pressure or slope of the horizon surface that carries water. This movement is called filtration. The highest speed of water movement is observed in underground karst caves and channels. Pebbles are in second place. A much slower movement is observed in the sands - the speed is 0.5-5 m / day.
Types of groundwater in the permafrost zone
These groundwaters are classified into supra-permafrost, inter-permafrost and sub-permafrost. The former are located in the thickness of permafrost on an aquiclude, mainly at the foot of slopes or at the bottom of river valleys. They, in turn, are divided into seasonally freezing, perched, located in the active layer; into seasonally partially frozen ones, with the upper part in the active layer, into seasonally non-freezing ones, the occurrence of which is noted below the seasonally freezing layer. In some cases, there may be a break in the active layer of various soils, which leads to the release of some part of the supra-permafrost water to the surface, where it takes the form of ice.
Interpermafrost waters may be present in the liquid phase, but are most common in the solid phase; as a rule, are not subject to seasonal thawing/freezing processes. These waters in the liquid phase provide water exchange with above- and subpermafrost waters. They can come to the surface as springs. Subpermafrost waters are artesian. They can be from fresh to brines.
The types of groundwater in Russia are the same as those discussed above.
Pollution of the considered objects
The following types of groundwater pollution are distinguished: chemical, which, in turn, is divided into organic and inorganic, thermal, radioactive and biological.
The main chemical pollutants are liquid and solid waste from industrial enterprises, as well as pesticides and fertilizers from agricultural producers. Heavy metals and other toxic elements most affect groundwater. They spread over aquifers over considerable distances. Radionuclide contamination behaves in a similar way.
Biological contamination is caused by pathogenic microflora. The sources of pollution are usually barnyards, faulty sewers, cesspools, etc. The spread of microflora is determined by the rate of filtration and the survival of these organisms.
It is an increase in the temperature of groundwater that occurs during the operation of the water intake. It can occur at wastewater disposal sites or when a water intake is located near a reservoir with warmer surface waters.
Subsoil use
The extraction of groundwater as a type of subsoil use is regulated by the Federal Law "On Subsoil". A license is required for the extraction of these objects. It is issued in relation to groundwater for a period of up to 25 years. The period of use begins to be calculated from the moment of state registration of the license.
Mining operations must be registered with Rosreestr. Then they draw up a draft and submit it for state expertise. Then they prepare a project for organizing an underground water intake sanitary zone, assess the reserves of these waters and transfer the calculations to the state expertise, the geoinformation fund and Rosgeolfond. Further, certificates of ownership of the land are attached to the received documents, after which an application for a license is submitted.
Finally
What types of groundwater are there in Russia? The same as in the world. The area of our country is quite large, so it has permafrost, and artesian, and groundwater, and soil water. The classification of the objects under consideration is quite complicated, and in this article it is reflected incompletely, its most basic points are shown here.
All waters that are in the thickness of rocks in a solid, liquid or gaseous state are 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 structures are associated with the need to take into account the movement of groundwater, their composition and condition. Physical and mechanical properties and the state of many rocks depend on groundwater. They often flood construction pits, ditches, trenches and tunnels, and, when they come to the surface, they contribute to the swamping of the territory. Groundwater can be an aggressive environment in relation to rocks. They are the main cause of many physical and geological processes that occur 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, that 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 mineral natural table water, which includes groundwater with a total mineralization of not more than 1 g / dm 3 that does not require water treatment or does not change its 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, technical specifications or consumers.
Groundwater is also divided into:
Groundwater is mainly formed as a result of infiltration (infiltration) of precipitation and surface water into the earth's crust. Water passes through permeable rocks to an impermeable layer and accumulates on it, forming an underground pool 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 rocks of the upper stratum, their structure and texture, as well as the tectonic structure of the area. Infiltration groundwater is the most common.
Underground water can also be formed by condensation of vaporous water constantly circulating in the pores of rocks. Condensation underground water is formed only in summer and partially in spring and autumn, and in winter it is not formed at all. A.F. 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 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 thickness of the earth's crust. The water contained in the sedimentary strata of these basins is called relic.
Groundwater generation is a complex process that begins with the accumulation of sediments and is closely related to the geological history of the area. Very often, groundwater of various origins mix with each other, forming mixed on the origin of 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 all pores of rocks are always filled with water. All waters of the aeration zone are fed by atmospheric precipitation, intensively evaporate and are absorbed by plants. The amount of water in this zone is determined by climatic conditions. In the saturation zone, regardless of climatic conditions, all the pores of rocks are always filled with water. Above the saturation zone there is a subzone of capillary moistening. In this subzone, thin pores are filled with water, while large pores are filled with air.
In the aeration zone, soil water and perched water are formed. soil water lies directly at the surface of the earth. This is the only water that does not have an aquiclude under it and is represented mainly by bound and capillary water. Soil water is in a complex relationship with animals and plants. It is characterized by sharp fluctuations in temperature, the presence of microorganisms and humus. Builders encounter soil water only in wetlands.
Verkhovodka formed in the aeration zone on waterproof lenses. Verkhovodka is also called any temporary accumulation of water in the aeration zone. Atmospheric precipitation penetrating this zone can temporarily linger on poorly permeable or compacted layers. Most often this happens in the spring during the period of snowmelt or during the period of heavy rains. During dry periods, the perch may disappear. The characteristic features of perched water are the inconstancy of existence, limited distribution, low power and non-pressure. Verkhovodka often creates difficulties for builders, since the presence or possibility of its formation is not always established during engineering geological surveys. The resulting perched water can cause flooding of engineering structures, swamping of territories.
Ground called water, lying on the first permanent water-resistant layer from the surface of the earth. Groundwater is always present. They have a free water surface called groundwater mirror, and waterproof bed. The projection of the groundwater table onto a vertical plane is called groundwater level (U G V). The distance from the aquiclude to the groundwater level is called the thickness of the aquifer. The level of groundwater, and, consequently, the thickness of the aquifer, is not constant and can change throughout the year depending on climatic conditions. Groundwater is fed mainly by atmospheric and surface waters, but they can also be mixed, infiltration-condensation. The area of the earth's surface from which surface and atmospheric water flows into an aquifer is called food area ground water. The area of groundwater recharge always coincides with the area of their distribution. Groundwater, due to the presence of a free water surface, is free-flowing, i.e., the water level in the well is set at the same level at which water was encountered.
Depending on the conditions of occurrence of groundwater, groundwater flows and pools are distinguished. Ground flows have an inclined mirror and are in continuous motion towards the slope of the aquiclude. Ground pools have a horizontal mirror and are much less common.
Groundwater, being in constant motion, has a close relationship with surface watercourses and reservoirs. In areas where precipitation outweighs evaporation, groundwater usually feeds rivers. In arid regions, very often water from rivers enters the groundwater, replenishing underground streams. There may also be a mixed type of connection, when groundwater feeds the river from one bank, and water from the river enters the ground stream from the other. The nature of the relationship may vary depending on climatic and some other conditions.
When designing and constructing engineering structures, it is necessary to take into account groundwater regime, i.e., the change in 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 diverse and often directly related to the construction activities of man. Climatic factors cause both seasonal and long-term changes in groundwater levels. 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 on the maps is depicted using hydroisohypses and hydroisobats. Hydroisohypses- lines connecting points with the same absolute groundwater levels. These lines are similar to the contour lines of the relief and, like them, reflect the relief of the groundwater table. The hydroisohypse map is used to determine the direction of groundwater movement and to determine the value of the hydraulic gradient. The direction of groundwater movement is always perpendicular to the hydroisohypses from higher to lower elevations. The directions in which groundwater moves during a steady motion that does not change in time are called current lines. If the streamlines are parallel to each other, then such a stream is called flat. The flow can also be convergent and divergent. The smaller the distance between hydroisohypses, the greater the hydraulic gradient of the soil flow. Hydroisobats- lines connecting points with the same depth of groundwater.
Interstratal Groundwater refers to aquifers that lie between two aquicludes. They can be non-pressure and pressure. 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 the most common is synclinal. Artesian water always fills the entire aquifer from the bottom to the roof and does not have a free water surface. The area of distribution of one or more levels of artesian aquifers is called artesian basin. The areas of artesian basins are huge and are measured in tens, hundreds, and sometimes thousands of square kilometers. In each artesian basin, there are areas of nutrition, distribution and discharge. The feeding area of artesian basins is usually located at greater distances from the center of the basin and at higher elevations. It never coincides with the area of their distribution, which is sometimes called the pressure area. Artesian waters experience hydrostatic pressure due to the difference in the elevations 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 unloading area. If the piezometric line passes above the surface of the earth, then when the aquifer is opened by wells, flowing will occur, and the pressure is called positive. When the piezometric level is located below the surface of the earth, then the pressure is called negative, and water does not pour out of the well. Artesian waters tend to be more mineralized and less connected to surface streams and water bodies than groundwater.
Fractured waters called groundwater confined to fractured igneous, metamorphic and sedimentary rocks. The nature of their movement is determined by the size and shape of cracks. Fissure waters can be non-pressure and pressure. They are unstable and can change the nature of the movement. The erosion and dissolution of rocks lead to the expansion of cracks, and the crystallization of salts and the accumulation of sediments - to their narrowing. Fissure water flow can reach 500 m 3 /h. Fissure waters create significant difficulties in the construction of underground structures.
Groundwater in the city
In cities, the demand for water is high, 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 underground water resources, but also for the level of their pollution.
AT last years the study of groundwater in urban spaces is part of the hydrogeology section.
Problems arising from the interaction of groundwater with the urban environment include groundwater pollution through sewage pipes, lowering the groundwater level by pumping systems, and the threat of groundwater flooding underground spaces of the urban environment (for example, metro).
Now the issue of preserving and protecting groundwater from pollution is particularly acute. After all, it is on them that the stability of the development of most cities largely depends, which brings the problem to the level of a global scale.
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 and 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 highly influenced by external factors. It is very important to monitor the level of groundwater and the degree of contamination. This delicate balance is extremely important for the sustainable development of urban space. Negligent attitude to water resources leads to very deplorable consequences. For example, in Mexico City, the constant decline in the water table led to subsidence, and then to environmental problems.
Groundwater indicators in Russian FederationThe resource potential of groundwater in Russia is 869.1 million m 3 /day and is unevenly distributed over the territory, which is determined by the variety of geological and hydrogeological conditions and climatic features.
On 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 District; in the Asian territory of Russia - 522.7 million m 3 / day and ranges from 159.2 million m 3 / day in the Far East to 250.9 million m 3 / day in the Siberian Federal District.
The current role of groundwater in the domestic and 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 underground water 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 water supply sources.
In rural areas, groundwater in domestic and drinking water supply accounts for 80–85% of 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 for 37 cities there are no explored groundwater reserves at all.
The degree of use of groundwater in the domestic 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 pursued for many years to provide the population with drinking water through the priority use of surface water.
Currently, there is a low level of use of explored groundwater deposits and their reserves. The average level of use of total explored reserves is 18-20%, and within the exploited fields with explored reserves - 30-32%.
Over the past 5 years, the increase in estimated operational reserves amounted to 6.8 million m 3 /day.
28.2 million m 3 /day of water was taken from underground sources to meet the drinking needs of the population and water supply for industrial facilities. The total value of extraction and extraction of groundwater amounted to 33.1 million m 3 /day, 5.9 million m 3 /day was discharged without use (17.8% of the total extraction and extraction of groundwater).
27.2 million m 3 /day were used for household needs, including: 20.6 million m 3 /day for household and drinking water supply (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 production of groundwater in some areas, large regional depression funnels have formed, the areas of which reach significant sizes (up to 50 thousand km 2), and the decrease in the level in the center is up to 65–130 m (the cities of Bryansk, Petersburg).
In the city of Bryansk, a regional depression funnel formed in the Upper Devonian aquifer complex has a radius of more than 150 km and a level drop of more than 80 m. Extensive depression funnels formed near the cities of Kursk and Zheleznogorsk and at the Mikhailovsky iron ore quarry. The “Kursk” depression funnel in the Batkellovian aquifer has a radius of 90–115 km, the level decrease in the center is 64.5 m.
In the Moscow region, intensive exploitation of groundwater of the Lower Carboniferous aquifer for 100 years led to the formation of an extensive deep funnel, the area of which exceeds 20 thousand km 2, and the maximum decrease in the level is 110 m. formation of a regional depression funnel with a total area of up to 20 thousand km 2 with a level decrease 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, 4002 sites of pollution have been identified, of which more than 80% are located in groundwater aquifers, which are usually not sources of drinking water supply for the population.
By expert opinion, in the Russian Federation, the share of contaminated groundwater does not exceed 5–6% of the volume of their use for drinking water supply of the population.
The largest number of groundwater pollution sites is located on the territory of the following federal districts: Privolzhsky (30%), Siberian (23%); Central (16%) and Southern (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 pulling up substandard natural waters in case of violation of the mode of operation of water intakes;
§ 10% groundwater pollution is “mixed” and is caused by the activities of industrial, municipal and agricultural facilities;
§ For 17% of the plots, the source of groundwater pollution has not been identified.
The most tense environmental situation has developed in areas of groundwater pollution by substances of hazard class I. These sites were identified in the areas of individual large industrial enterprises in following cities and settlements: 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, mercury), Sayansk (mercury), Svobodny (mercury), Usolye-Sibirskoye (mercury), Khabarovsk (beryllium, mercury), Cherepovets (beryllium), etc.
The greatest environmental hazard is the pollution of groundwater, identified in individual wells at water intakes for drinking water supply.
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 of 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 Lucretius Cara and Vitruvius - in Ancient Rome, and 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, its physical and chemical properties, and interaction with host rocks.
The study of groundwater in connection with the history of tectonic movements, 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 the productivity of production wells and groundwater reserves.
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 practical importance in the exploitation of groundwater, hydraulic engineering, 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
Name of indicator
Volume
Evaporation from the ocean
Evaporation from land
total evaporation
precipitation on the surface of the ocean
Precipitation on land
Total precipitation
Runoff of rivers and groundwater
447.9 thousand km 3
70.7 thousand km 3
518.6 thousand km 3
411.6 thousand km 3
107.0 thousand km 3
518.6 thousand km 3
36.3 thousand km 3
Under the influence of solar energy, an average of about 450.0 thousand km 3 of water evaporates 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.
The penetration of water into soils (permeability) that make up the earth's crust depends on physical properties 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 there are mineral waters of various composition. These are ancient waters. The lower zone contains highly mineralized brines. Bromine, iodine and other substances are extracted from them.
Groundwater is formed different 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. Under natural conditions, groundwater, which has arisen 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. So, 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-filtration 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.
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 operate all year round and feed the rivers during the winter and summer low water periods (or at low levels of the 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 groundflow modulus 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 groundflow modules 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. Under certain conditions, aquifers can penetrate 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 of the 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.
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