How does groundwater form? Types of groundwater and their geological activity

- Chemical composition of groundwater. - Mineral water. - Origin of groundwater. Formation of groundwater. - Extraction of groundwater. Groundwater license.

Groundwater – groundwater reserves, groundwater resources.

Groundwater is part of the planet's hydrosphere (2% of the volume) and participates in the general water cycle in nature. Groundwater reserves have not yet been fully explored. Now the official data shows a figure of 60 million cubic kilometers, but hydrogeologists are confident that in the bowels of the Earth there are colossal unexplored deposits of groundwater and the total amount of water in them can be 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.), it can be in a solid, liquid or gaseous state. According to V.I. Vernadsky, groundwater can exist to a depth of 60 km due to the fact that water molecules, even at a temperature of 2000 o 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 contained in the pores and cracks of water-bearing rocks. Natural resources – the amount of groundwater entering the aquifer under natural conditions through infiltration of atmospheric precipitation, filtration from rivers, overflow from higher and lower located aquifers.

2. Artificial stocks - this is the volume of groundwater in the reservoir, formed as a result of irrigation, filtration from reservoirs, and artificial replenishment 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 with increased recharge of groundwater caused by the operation of water intake structures.

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

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 the value of 36 g/l is accepted, corresponding to the average salinity of the waters of the World Ocean.

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

The above classification indicates significant changes in water mineralization - 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, the chemical properties of groundwater, classification by chemical composition, factors influencing the chemical composition of groundwater, and other aspects, read a separate article: Chemical composition of groundwater.

Groundwater - origin and formation of groundwater.

Depending on their origin, groundwater is:

• 1) infiltration,
• 2) condensation,
• 3) sedimentogenic,
• 4) “juvenile” (or magmogenic),
• 5) artificial,
• 6) metamorphogenic.

Groundwater - groundwater temperature.

Based on temperature, underground waters are divided into cold (up to +20 °C) and thermal (from +20 to +1000 °C). Thermal waters are usually characterized by a high content of various salts, acids, metals, radioactive and rare earth elements.

According to temperature, underground waters are:

Cold underground waters are divided into:

• supercooled (below 0°C),
• cold (from 0 to 20 °C)

Thermal underground waters are divided into:

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

The temperature of groundwater also depends on the depth of aquifers:

1. Groundwater and shallow interstratal water experience seasonal temperature fluctuations.
2. Groundwater lying at the level of the zone 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 zone 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, groundwater in the zone of constant temperatures, on the contrary, does not freeze even in winter.
  

3. Groundwater circulating below the constant temperature zone, 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 maximum values ​​in areas of modern volcanism (Kamchatka, Iceland, etc.), in the zones of mid-ocean ridges, reaching temperatures of 300-4000C. High-thermal groundwater in areas of modern volcanism (Iceland, Kamchatka) is used for heating homes, building geothermal power plants, greenhouse heating, etc.

Groundwater - methods for searching for groundwater.

• geomorphological assessment of the area,
• geothermal research,
• radonometry,
• drilling of exploratory wells,
• studying cores extracted from wells in laboratory conditions,
• experimental pumping from wells,
• ground exploration geophysics (seismic and electrical prospecting) 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 selection of water from the subsoil in a given quantity.

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

• Total groundwater reserves,
• The annual flow of water into aquifers,
• Filtration properties of water-bearing rocks,
• Level depth,
• Technical operating conditions.

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

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

• very small well flow rates;
• technical complexity of operation (sanding, salt deposition in wells, etc.);
• lack of necessary pumping equipment (for example, when operating aggressive industrial or thermal waters).

High-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 examined the topic Groundwater: general characteristics. Read further: History of groundwater studies.

Among land waters, the largest reserves are groundwater, the total reserves of which are 60 million km 3 . Groundwater can be in liquid, solid, or vapor state. They are located in the soil and rocks of the upper part of the earth's crust.

The ability of rocks to pass water depends on the size and number of pores, voids, and cracks.

In relation to water, all rocks are divided into three groups: water permeable(permeable to water well) waterproof(retain water) and soluble.

Soluble rocks - these are potassium and table salts, gypsum, limestone. When groundwater dissolves them, large voids, caves, sinkholes, and wells are formed at depth (this phenomenon is called karst).

Permeable rocks can be divided into two categories: permeable throughout their entire mass (uniformly permeable) and relatively permeable (semi-permeable). Examples of highly permeable rocks are pebbles, gravel, and sand. Semi-permeable materials include fine-grained sand, peat, etc.

In addition, permeable rocks can be moisture-intensive or non-moisture-intensive.

Non-moisture-intensive rocks - These are rocks that freely allow water to pass through without becoming saturated with it. These are, for example, sand, pebbles, etc.

Moisture-intensive - these are rocks that hold a certain amount of water (for example, one cubic meter of peat holds over 500 liters of water).

TO waterproof mountain rocks include clays, massive crystalline and sedimentary rocks. However, these rocks can be fractured and become permeable under natural conditions.

Layers of waterproof rocks over which aquifers lie are called waterproof.

On waterproof rocks, water seeping down is retained and fills the gaps between the particles of the overlying permeable rock, forming aquifer.

Layers of permeable rock that contain water are called aquiferous.

On plains composed of sedimentary rocks, permeable and impervious layers usually alternate.

Groundwater occurs in layers (Fig. 1). They can be divided into three horizons:

• Upper horizon- These are fresh waters located at a depth of 25 to 350 m.
• Middle horizon - waters lying at a depth of 50 to 600 m. They are usually mineral or salty.
• Lower horizon- water, often buried, highly mineralized, represented by brines. It lies at a depth of 400 to 3000 m.

Deep water horizons can be juvenile (of igneous origin) or relict. In most cases, the water of the lower horizons was formed during the formation of the sedimentary rocks enclosing them.

According to the conditions of occurrence, groundwater is divided into soil, perched water and saturation water - groundwater and interlayer (Fig. 2).

Soil waters and perched water

Soil water fill part of the gaps between soil particles. They are necessary for normal plant life.

Verkhovodka It lies shallow, exists temporarily, and is not abundant. In our climatic conditions, it appears in the spring after the snow melts, sometimes in the fall.

Rice. 1. Layers of groundwater

Rice. 2. Types of water according to conditions

Groundwater

Groundwater form an aquifer on the first aquifer layer from the surface. The groundwater surface is called groundwater mirror. The distance from the groundwater table to the aquifer layer is called thickness of the waterproof layer.

Groundwater is fed by infiltrated precipitation, water from rivers, lakes, and reservoirs.

Due to its shallow location from the surface, the groundwater level experiences significant fluctuations according to the seasons of the year: it either rises after precipitation or snow melts, or falls during dry times. During severe winters, groundwater can freeze.

Since the depth of groundwater is determined primarily by climatic conditions, it varies in different natural zones. Thus, in the tundra the groundwater level practically coincides with the surface, and in semi-deserts it is at a depth of 60-100 m, and not everywhere, and these waters do not have sufficient pressure.

The degree of dissection of the territory's topography has a great influence on the depth of groundwater. The stronger it is, the deeper the groundwater is.

Groundwater is significantly susceptible to pollution.

Interformational waters

Interformational waters- underlying aquifers enclosed between two impermeable layers. Unlike groundwater, the level of interstratal water is more constant and changes less over time. Interstratal waters are cleaner than groundwater.

A special group of groundwaters consists of pressure interstratal waters. They completely fill the aquifer and are under pressure. All waters contained in layers located in concave tectonic structures have pressure.

Opened by wells and rising upward, they pour out to the surface or gush out. That's how they work artesian wells(Fig. 3).

Rice. 3. Artesian well

The chemical composition of groundwater varies and depends on the solubility of adjacent rocks. Based on their chemical composition, there are fresh (up to 1 g of salts per 1 liter of water), slightly mineralized (up to 35 g of salts per 1 liter of water) and mineralized (up to 50 g of salts per 1 liter of water) groundwater. In this case, the upper horizons of groundwater are usually fresh or slightly mineralized, and the lower horizons can be highly mineralized. Mineral waters can be carbonated, alkaline, ferrous, etc. in composition. Many of them have medicinal value.

Groundwater temperature

Based on temperature, underground waters are divided into cold (up to +20 °C) and thermal (from +20 to +1000 °C). Thermal waters are usually characterized by a high content of various salts, acids, metals, radioactive and rare earth elements.

Natural outlets of groundwater (usually groundwater) to the surface of the earth are called sources(springs, springs). They are usually formed in low places where aquifers cross the earth's surface.

The springs are cold (with a water temperature 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 volcanism (Iceland, Kamchatka, New Zealand, Japan).

Significance and protection of groundwater

Groundwater is of great importance in nature: it is the most important source of nutrition, swamps; dissolve various substances in rocks and transport them; with their participation, karst and landslide landforms are formed; when lying close to the surface, they can cause waterlogging processes; supply plants with moisture and nutrients dissolved in them, etc. They are widely used by humans: they are sources of clean drinking water; used to treat a number of human diseases; provide the production process with water resources; used to irrigate fields; a large number of different chemicals are obtained from thermal waters (iodine, Gauberian salt, boric acid, various metals); The thermal energy of groundwater can be used to heat buildings, greenhouses, generate electricity, etc.

Today, in many regions, the condition of groundwater is assessed as critical and has a dangerous tendency to further deteriorate. Despite the fact that groundwater reserves are large, they are renewed extremely slowly, and this must be taken into account when using them. No less important is the protection of groundwater from pollution.

Groundwater (and not only surface water, but also deep water), like other elements of the environment, is subject to the polluting influence of human economic activity: from mining enterprises, chemical waste and fertilizer storage facilities, landfills, livestock farms, populated areas, etc. The predominant substances that pollute groundwater are: petroleum products, phenols, heavy metals (copper, zinc, lead, cadmium, nickel, mercury), sulfates, chlorides, nitrogen compounds. The area of ​​groundwater pollution centers reaches hundreds of square kilometers. The quality of drinking water is deteriorating.

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

Groundwater forms part of the hydrosphere - the watery shell of the globe. They are found in boreholes at depths of up to several kilometers. According to V.I. Vernandsky, groundwater can exist to a depth of 60 km due to the fact that water molecules, even at a temperature of 2000 o 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 World Ocean.

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

In the first millennium BC, the first ideas about the properties and origin of natural waters, the conditions of 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, etc.).

The study of groundwater was facilitated by the expansion of work related to water supply, the construction of capture structures (for example, kariz among the peoples of the Caucasus, Central Asia), the extraction of salt water for evaporation of salt 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-pouring. The latter received the name artesian - from the province of Artois (ancient name "Artesia") in France.

During the Renaissance and later, groundwater and its role in natural processes were devoted to the work of many scientists - Agricolla, Palissy, Steno, etc.

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

Until the mid-19th century, the study of groundwater developed as an integral part of geology. Then it is separated 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 study of underground waters of past geological eras).

Dynamics of groundwater studies the movement of groundwater under the influence of natural and artificial factors, develops methods for quantitative assessment of 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) that occur under the influence of various natural factors (precipitation, and the conditions of their infiltration, evaporation, temperature and humidity, and soil layer, influence of regimes of surface reservoirs, rivers, technogenic human activities).

In the second half of the 20th century, methods for predicting the regime of groundwater began to be developed, which is of great practical importance in the exploitation of groundwater, hydraulic engineering construction, irrigated agriculture and solving 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%) million square meters. km is occupied by land. In the northern hemisphere, land accounts for 39.3% of the hemisphere's area, in the southern hemisphere - 19.1%. The specific gravity of the elements of moisture circulation and their influence on the overall circulation of water in nature can be judged from the data given below:

Table 1

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 is transported in the form of steam by air currents to the continents.

Under certain conditions, water vapor condenses and falls in the form of rain, snow, hail, etc. Atmospheric precipitation that falls on land flows down the slopes of the area, forming streams and rivers that carry their waters back into the World Ocean.

Some of the precipitation evaporates, some seeps into the ground, forming groundwater, which flows into streams and rivers through underground runoff and thus also returns to the ocean. This closed exchange process 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 atmospheric precipitation waters falling onto the earth's surface and seeping waters(infiltrating) into the ground to a certain depth, and from waters from swamps, rivers, lakes and reservoirs, also seeping into the ground. The amount of moisture driven into the soil in this way is 15-20% of the total amount of precipitation.

The penetration of water into the soils (water permeability) that make up the earth's crust depends on the physical properties of these soils. With regard to water permeability, soils are divided into three main groups: water-permeable, semi-permeable And waterproof or waterproof.

TO permeable rocks include coarse rocks, pebbles, gravel, sands, fractured rocks, etc. Waterproof rocks include massively crystalline rocks (granite, marble), which have minimal absorption of moisture, and clay. The latter, having been saturated with water, do not allow it to pass through in the future. To the breeds semi-permeable include 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 are used for drinking, household and technical water supply. In the middle zone there are mineral waters of various compositions. These are ancient waters. The lower zone contains highly mineralized brines. Bromine, iodine and other substances are extracted from them.

Groundwater is formed in various ways. One of the main ways of underground water formation is infiltration, or infiltration, of precipitation and surface water (lakes, rivers, seas, etc.). According to this theory, seeping water reaches the impermeable layer and accumulates on it, saturating porous and porous-fissured rocks. In this way, aquifers, or groundwater horizons, arise. The groundwater surface is called groundwater table. The distance from the groundwater table to the aquitard is called the thickness of the aquitard.

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 heavy rain, since the The more intense the precipitation, the faster the falling water flows over the soil surface.

Steep slopes increase surface runoff and reduce the infiltration of precipitation into the ground; flat ones, on the contrary, increase their seepage. Vegetation cover (forest) increases the evaporation of fallen moisture and at the same time increases precipitation. By retaining surface runoff, it promotes moisture seepage 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 drops 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 increasing temperature in the depths of the Earth. As a result, a counter flow of water vapor arises from the depths of the Earth upward to a layer of constant temperatures. And in a zone of constant temperatures, as a result of the collision of two streams of water vapor, they condense 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 - through infiltration and through condensation of atmospheric water vapor in rocks - are the main ways of groundwater accumulation. Infiltration And condensation waters 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, as Suess believed, 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, formed 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, clarification of the regime and their quality.

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

Groundwater can be formed due to artificial hydraulic structures, such as irrigation canals. Thus, during the construction of the Karakum irrigation system, due to the transfer of part of the flow of Siberian rivers, a significant amount of water in the desert part 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 drop in water levels due to filtration of water into the soil was large. All this, in addition to reducing the river flow, 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 became salinized and polluted with silt.

Classification of groundwater
conditions of their occurrence

There are several classifications of groundwater.

According to the conditions of movement in aquifers, underground waters circulating in loose (sand, gravel and pebble) layers and in fractured rocks are distinguished.

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

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

pore - in sands, pebbles and other clastic rocks;

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

karst (fissure-karst) - in soluble rocks (limestones, dolomites, gypsum, etc.).

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

Verkhovodka are called underground waters that occur near the surface of the earth and are characterized by variable distribution. Typically, perched water is confined to lenses of waterproof or weakly permeable rocks, overlain by water-permeable strata.

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

Perched water often includes soil water, or water in the soil layer. Soil water is represented by almost bound water. Droplet-liquid water is present in soils only during periods of excess moisture.

Groundwater. Groundwater is the water that lies on the first impermeable horizon below the perched water. They usually refer to impermeable formations and are characterized by a more or less constant influx of water. Groundwater can accumulate both in loose porous rocks and in hard fractured reservoirs. The groundwater level is an uneven surface, which, as a rule, repeats the unevenness of the relief in a smoothed form: at higher elevations it is lower, in low places it is higher.

Groundwater moves towards lower 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, human economic activity and much more.

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

Pressure, or artesian waters. Pressure waters are those that are located in an aquifer, enclosed between aquifer layers, and experience hydrostatic pressure due to the difference in levels at the point of recharge and release of water to the surface. The recharge area of ​​artesian waters usually lies above the area of ​​water flow and above the outlet of pressure waters to the surface of the Earth. If an artesian well is placed 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 dimensions of artesian basins can be very significant - up to hundreds and even thousands of kilometers. The feeding areas of such basins are often significantly removed from the places where water is extracted. Thus, water that falls 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 falls in the form of precipitation over Europe.

Artesian waters are characterized by constant water and good quality, which is important for its practical use.

Based on their origin, there are several types of groundwater.

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

Condensation groundwater are 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 modified buried waters of marine origin - sodium chloride, calcium-sodium chloride, etc. These also include buried brines of salt basins, as well as ultra-fresh waters of sand lenses in moraine deposits.

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

feeding rivers with groundwater and calculating groundwater flow

Groundwater serves as a reliable source of river nutrition. They operate all year round and provide food to rivers during winter and summer low water (or at low levels of the water horizon), when there is no surface flow.

At very slow speeds of groundwater movement, compared to surface water, groundwater in river flow acts as a regulating 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 village 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 rifts, salt water enters from the backwater into the river bed upstream from the place of freezing from the Arctic Ocean.

A quantitative measure of nutrition is the value of underground flow, which, in turn, is characterized by the so-called underground flow module:

M Subtitle = K M 0 /100 ,

Where M Subtitle– underground drainage module, l/sec from 1 km 2 drainage area;

M 0 – average long-term module of total flow, l/sec 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/sec from 1 km 2 surface drainage basin, determined by the winter river flow and equal to the module of underground flow, because In winter, rivers are fed primarily by groundwater.

The groundwater flow module is a reliable indicator for assessing the water content of rocks distributed in the drainage basin of a river, because it represents the amount of underground water (in l/sec) entering the river from 1 sq. km of one or another aquifer drained by a river.

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

Where Q subsection– annual volume of underground flow;

Q 0 – annual volume of river flow;

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

c 1 – concentration of the same component in groundwater during the same period;

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

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

Recharge by groundwater not hydraulically connected to the river;

Recharge by groundwater hydraulically connected to the river;

Mixed soil nutrition ( a+ b);

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

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

Where h subsection– layer of underground drainage, mm/year;

Q subsection– volume of underground runoff from the pool area, m 3 /year;

F– pool area, m 2 .

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

Where x– layer of sediments, mm/year.

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

Main problems of use and protection of groundwater

Due to its location, groundwater is better protected from external influences than surface water, but there are serious symptoms of unfavorable changes in the groundwater regime over large areas and over a wide range of depths. These include: depletion and decline of groundwater levels due to over-extraction; introduction of sea salt waters to the coast; formation of depression craters and others.

Groundwater pollution poses a great danger. Two types of pollution can be distinguished: bacterial And chemical. Under certain conditions, they can penetrate into aquifers. sewage And man-made industrial waters, contaminated surface waters and precipitation.

When reservoirs are created, the groundwater level rises as a result of backwater. A positive consequence of this change in regime 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 increased evaporation when they are shallow.

Due to minor flood events (or their absence at all) on regulated rivers, the flood recharge of groundwater is significantly reduced. Flow speeds on such rivers are reduced, which contributes to siltation of the riverbed; therefore, the relationship between river and groundwater is difficult.

Under certain conditions, groundwater withdrawals can have a significant impact on surface water quality. First of all, this applies to industrial operation and discharge of mineralized water, discharge of mine and associated oil water. Therefore, integrated use and regulation of surface and groundwater resources must be provided. Examples of this approach include the use of groundwater for irrigation in dry years, as well as 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. Course of lectures: Textbook for students of secondary vocational education institutions. – 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. Hydrogeologist's Reference Guide. In 2 volumes. Ed. V.P. Yakutseni. – L.: Nedra, 1967. – T.1. – 592s.

A significant part of the Earth's water reserves are underground pools that flow through the soil and rock layers. Huge accumulations of underground water - lakes, which wash away rock deposits and soil, forming pits.

The importance of soil fluid is great not only for nature, but also for humans. Therefore, researchers carry out regular hydrological observations of its condition and quantity, and are studying more and more deeply what groundwater is. Definition, classification and other issues of the topic will be discussed in the article.

What is underground water?

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

Classification

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

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

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

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

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

Soil water

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

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

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

Excessive amounts of soil water are observed in the spring when the snow melts.

Groundwater

The ground variety is water that is located at some depths of the upper layer of the earth. The depth of liquid flow can be greater if it is an arid area or desert. In a temperate climate with periodic, constant precipitation, groundwater does not lie so deep. And with excess rain or snow, ground liquid can lead to flooding of the area. In some places, this type of water comes to the surface of the soil and is called a spring, spring or spring.

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

Excessive fluid may accumulate in one area. As a result of the standing position, swamps, lakes, etc. are formed from groundwater.

Interlayer

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

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

Artesian

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

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

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

Mineral

Mineral ones are the deepest and most healing and valuable for human health. They contain a high content of various mineral elements, the concentration of which is constant.

Mineral waters also have their own classifications:

By purpose:

• dining room;
• medicinal;
• mixed.

According to the predominance of chemical elements:

• hydrogen sulfide;
• carbon dioxide;
• glandular;
• iodine;
• bromine

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

Classification by purpose

Groundwater is used in human life. Their purpose varies:

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

Classification by chemical composition

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

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

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

How was groundwater formed?

Several factors influence the formation of groundwater.

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

Groundwater monitoring

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

If the quality of water is examined in a laboratory by examining a sample taken, then exploration of the presence involves the following methods, interconnected with each other:

1. First, the area is assessed for the presence of suspected groundwater.
2. Secondly, the temperature indicators of the detected liquid are measured.
3. Next, the radon method is used.
4. Afterwards, base wells are drilled, followed by core removal.
5. The selected core is sent for research: its age, thickness and composition are determined.
6. A certain amount of groundwater is pumped from wells to determine its characteristics.
7. Based on the base wells, liquid occurrence maps are drawn up and its quality and condition are assessed.

Groundwater exploration is divided into the following types:

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

Pollution problems

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

1. Chemical. This type of pollution is very common. Its global nature depends on the fact that there are a huge number of agricultural and industrial enterprises on Earth that dump their waste in liquid and solid (crystallized) form. This waste very quickly penetrates into water-bearing horizons.
2. Biological. Contaminated wastewater from domestic use, faulty sewers - all these are causes of contamination of groundwater with pathogenic microorganisms.

Classification by type of water-saturated soils

The following are distinguished:

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

Depending on the location, the composition of the water is formed.

Reserves

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

Conclusion

Rivers, lakes, groundwater, glaciers, swamps, seas, oceans - all these are the Earth's water reserves, which are interconnected in one way or another. Moisture located in the soil layers not only forms an underground pool, but also affects the formation of surface reservoirs.

Groundwater is suitable for people to drink, therefore saving it from pollution is one of the main tasks of humanity.

Classification

According to the conditions of occurrence, groundwater is divided into:

• soil;
• interstratal;

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

Groundwater form an aquifer on the first aquifer layer from the surface. Due to its shallow location from the surface, the groundwater level experiences significant fluctuations according to the seasons of the year: it either rises after precipitation or snow melts, or falls during dry times. During severe winters, groundwater can freeze. These waters are more susceptible to pollution.

Interformational waters- underlying aquifers enclosed between two impermeable layers. Unlike groundwater, the level of interstratal water is more constant and changes less over time. Interstratal waters are cleaner than groundwater. Pressure interstratal waters completely fill the aquifer and are under pressure. All waters contained in layers located in concave tectonic structures have pressure.

According to the conditions of movement in aquifers, underground waters circulating in loose (sand, gravel and pebble) layers and in fractured rocks are distinguished.

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

• pore- lie and circulate in Quaternary sediments: in sands, pebbles and other clastic rocks;
• cracked(vein) - in rocks (granites, sandstones);
• karst(fissure-karst) - in soluble rocks (limestones, dolomites, gypsum, etc.).

Groundwater reserves

Groundwater is part of the Earth's water resources; total groundwater reserves amount to over 60 million km³. Groundwater is considered a mineral resource. Unlike other types of minerals, groundwater reserves are renewable during exploitation.

Groundwater research

Groundwater exploration

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

• reference wells are drilled with core sampling,
• the core is studied and the relative geological age of the rocks, their thickness (thickness) is determined,
• Experimental pumping is carried out, the characteristics of the aquifer are determined, and a geotechnical report is drawn up;
• Maps and sections are drawn up for several reference wells, and a preliminary assessment of mineral reserves (in this case, water) is carried out;

Origin of groundwater

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

see also

Links

• Taking into account the influence of groundwater when designing foundations

Literature

• // Encyclopedic Dictionary of Brockhaus and Efron: In 86 volumes (82 volumes and 4 additional ones). - St. Petersburg. , 1890-1907.
• Lange O.K. Underground waters of the USSR, parts 1-2, M., 1959-1963.

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