Water is the most common substance on our planet, thanks to which life is sustained 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, in the process of precipitation runoff, etc. In this article, we will consider the types of groundwater.
Concept
Under groundwater understand the latter, located in the earth's crust, located in rocks below the surface of the Earth in various states of aggregation. 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 the exchange withsurface 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.
Classification by mineralization
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.
Classification by occurrence
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 low-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 are formed inperiods 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 the 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 are fed by infiltration of precipitation from the atmosphere, filtration from surface sources, condensation of water vapor and intra-ground evaporation, additional nutrition coming from underlying 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, movement is carried out from top to bottom under the action of capillary forces or gravity in different directions.
Classification by formation
The main types of groundwater are infiltration, which are formed due to infiltration of 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 objects under consideration
The following types of groundwater movement are distinguished (see figure).
Infiltration of surface water and precipitation from the atmosphere occurs in the aeration zone. AtThis 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 helps to maintain air movement. During normal infiltration, hydrostatic pressure gradients are added to 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, reducing the pressure or slope of the surface of the horizon carrying 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. 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 suprapermafrost, interpermafrost and subpermafrost. 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 it may happenrupture of the active layer of various soils, which leads to the release of some of the supra-permafrost waters to the surface, where it takes the form of ice.
Inter-permafrost 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 range from bland to brine.
Types of groundwater in Russia are the same as discussed above.
Contamination of the objects in question
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. Pollution with radionuclides behaves in a similar way.
Biological contamination is caused by pathogenic microflora. The sources of pollution are usually barnyards, filtration fields, faulty sewers, cesspools, etc. The spread of microflora is determined by the rate of filtration and the survival of these organisms.
Thermal pollution is an increase in groundwater temperature that occurs during the operation of a water intake. It can occur at wastewater disposal sites or when the water intake is located near a body of water with warmer surface water.
Use of subsurface resources
Groundwater extraction 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 work must be registered with Rosreestr. Next, they draw up a project of geological exploration and transfer it to the 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.
In closing
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.
