An aquifer or horizon is a series of rock layers with high water permeability. Their pores, cracks or other voids are filled with groundwater.
General concepts
Several aquifers can form an aquifer complex if they are hydraulically linked. Waters are used for water supply in forestry, for irrigation of forest nurseries, in human economic activity. When they come to the surface, they can become a source of waterlogging of the territory. This may contribute to the formation of lowland and transitional marshes.
Water permeability
The aquifer is characterized by the permeability of rocks. Water permeability depends on the size and number of interconnected cracks, pores, as well as on the sorting of rock granules. The depth of the aquifer can be different: from 2-4 m("perch water") and up to 30-50 m (artesian water).
Permeable rocks include:
- gravel;
- pebbles;
- coarse sands;
- fractured and intensely karst rocks.
Movement of water
There can be several reasons for the movement of water in the pores:
- gravity;
- hydraulic head;
- capillary forces;
- capillary-osmotic forces;
- adsorption force;
- temperature gradient.
Depending on the geological structure of the rocks of the aquifer, they can be isotropic in terms of filtration, i.e., the water permeability is the same in any direction. Rocks can also be anisotropic, in which case they are characterized by a uniform change in water permeability in all directions.
The depth of aquifers in the Moscow region
Throughout the entire territory of the Moscow Region, the depth of groundwater is not the same, therefore, for the convenience of studying it, it was divided into hydrological regions.
There are several aquifers:
- Southern region. The water level can be in the range of 10-70 m. The depth of wells in this area varies from 40 m to 120 m.
- Southwest region. The water horizon is not very abundant. The average depth of the wells is 50 m.
- Central District. This is the largestarea area. It, in turn, is divided into Large and Small. The average thickness of the horizons is 30 m. The waters here are carbonate, carbonate-sulphate.
- East region. The depth of the aquifer in this area is 20-50 meters. The waters are mostly highly mineralized and therefore unsuitable for water supply.
- Klinsko-Dmitrovsky district. It includes two horizons of the upper carbonate: Gzhel and Kasimov.
- Privolzhsky district. The average depth of the aquifer is 25 meters.
This is a general description of the districts. In a detailed study of aquifers, the composition of the waters of the layer, its thickness, specific flow rate, sediment density, etc. are considered.
It is worth noting that the hydrogeology of the Moscow region distinguishes one aquifer, which is divided into several horizons of the Paleozoic Carboniferous deposits:
- Podolsko-Myachkovsky layer of the Middle Carboniferous;
- Serpukhov aquifer and Oka suite of the Lower Carboniferous;
- Kashirsky aquifer of the Middle Carboniferous;
- Kasimov layer of Upper Carboniferous;
- Gzhel aquifer of the Upper Carboniferous.
Some aquifers have low water saturation and high salinity, making them unsuitable for human activities.
The aquifer of the Serpukhov and Oka formations of the Lower Carboniferous has a maximum thickness of 60-70 meters relative to other aquifers.
The Moscow-Podolsky aquifer can reach a maximum of 45 meters in depth, its average thickness is 25 meters.
How to determine the depth of an aquifer
Sandy aquifer - the name is conditional, because this horizon can consist of pebbles, a mixture of sand and pebbles. Sandy aquifers have different thicknesses, their depths also vary.
If we consider the hydrogeology of the Moscow region and adjacent areas, we can say with confidence that groundwater can be found already at a depth of 3-5 meters, depending on the relative height of the area under study. The depth of the aquifer also depends on the nearby hydrological features: river, lake, swamp.
The layer closest to the surface is called the "perch". It is not recommended to use its waters for food, because this layer is nourished by precipitation, snowmelt, etc., so harmful impurities can easily get here. However, often the water of the “perch water” is used on the farm, and it is also called “technical water”.
Good filtered water is at a depth of 8-10 meters. At a depth of 30 meters or more, the so-called "mineral waters" are located, for the extraction of which artesian wells are being built.
Determining the presence and depth of the upper aquifer is relatively easy. There are many folk ways: using a vine or a metal frame, using a clay pot, observing theplants growing on the territory.
