What is groundwater: definition, characterization and types

A large part of the water resources of the Earth are underground basins that flow in the soil and layers of rocks. Huge accumulations of groundwater - lakes, which wash away deposits of rocks and soil, forming pits.

The value of groundwater is great not only for nature, but also for humans. Therefore, researchers conduct regular hydrological observations of its condition and quantity, and they study deeper and deeper what groundwater is. Definition, classification and other issues of the topic will be discussed in the article.

what is underground water

What is groundwater?

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

groundwater classes


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

  • soil;
  • ground;
  • interlayer;
  • mineral;
  • artesian.

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

  • The upper horizon is freshwater groundwater. As a rule, their deep finding is small: from 25 to 350 m.
  • The middle horizon is the place of occurrence of a mineral or saline liquid at a depth of 50 to 600 meters.
  • Bottom horizon - depth from 400 to 3000 meters. Water with increased mineral content.

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

groundwater lake

Soil water

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

If you understandwhat is groundwater of soil type, it becomes obvious that this kind of fluid is the most useful, because its surface location does not deprive it of all minerals and chemical elements. Such water is one of the main sources of "food" for agricultural fields, forests and other agricultural crops.

This kind of liquid can not always lie horizontally, often its outlines are similar to the relief of the soil. In the upper layer of the earth's crust, the moisture does not have a "solid support", so it is in limbo.

Excessive amount of soil water is observed in the spring, when the snow melts.


The soil variety is waters that are located at some depths of the upper earth layer. The depth of flow of a fluid can be great if it is arid or desert. In a temperate climate with a periodic constancy of precipitation, the groundwater does not lie so deep. And with an excess of rain or snow, groundwater can flood the area. In some places, this kind of water comes to the surface of the soil and is called a spring, key or source.

groundwater swamps

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

Excess fluid may accumulate in one place. As a result of the standing position, bogs, lakes, etc., are formed from the groundwater.


What is groundwater inter-layer category? These are essentially the same aquifers as groundwater and soil, but only the level of their flow is deeper than that of the previous two.

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


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, underground drilling is often practiced as a source of water supply for residential buildings.

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

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


Mineral - the deepest and most healing and valuable for human health. They contain a high content of various mineral elements whose concentration is constant.

Mineral waters also have their own classifications:

To destination:

  • canteen;
  • therapeutic;
  • mixed

According to the predominance of chemical elements:

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

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

Classification by purpose

Groundwater is used in human life. Their purpose is different:

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

Chemical Classification

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

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

As a rule, the waters close to the earth’s surface are freshwater. And the deeper the moisture is located, the more mineralized its composition.

groundwater swamp glaciers

How did groundwater form?

Several factors affect 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. They form a soil or groundwater fluid. In addition, these two categories of moisture are involved in the water cycle in nature.
  2. Melting glaciers of permafrost. Groundwater forms whole lakes.
  3. There are also juvenile fluids that have formed in solidified magma. This is a type of primary water.

Groundwater monitoring

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

If the quality of water is examined laboratory, surveying the withdrawn sample, then the presence intelligence implies the following methods, which are interrelated with each other:

  1. The first is the assessment of the location for the presence of the estimated groundwater.
  2. The second is that the temperature indicators of the detected fluid are measured.
  3. Next, the radon method is applied.
  4. After the base wells are drilled, followed by core recovery.
  5. The selected core is sent to the study: determine its age, thickness and composition.
  6. A certain amount of groundwater is pumped out of the wells to determine their characteristics.
  7. The base wells make maps of the occurrence of fluid, assess its quality and condition.

Groundwater exploration is divided into the following types:

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

groundwater permafrost

Pollution problems

The problem of pollution of groundwater 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, which dump their waste in liquid and solid (crystallized) form. This waste very quickly penetrates into the water bearing horizons.
  2. Biological. Contaminated wastewater from domestic use, faulty sewers - all these are causes of groundwater contamination by pathogens.

lakes underground waters glaciers

Classification by type of water-saturated soils

There are the following:

  • pore, that is, those who settled in the sands;
  • cracked, those that fill the cavities of rocks and rocks;
  • karstic, those that are located in limestone rocks or other fragile rocks.

Depending on the location, the composition of the waters is also formed.


Groundwater is regarded as a mineral that is renewable and participates in the water cycle in nature. The total reserves of this variety of minerals are 60 million km3. But, despite the fact that the indicators are not small, groundwater is subject to pollution, and this significantly affects the quality of the consumed fluid.


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

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

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