Sources and causes of the appearance of groundwater. How to find groundwater: determining the level of rise

When purchasing land for construction, you must definitely pay attention to the level at which the groundwater is located here. Since the close location of such aquifers is fraught with a host of problems both for the future construction and for the owner himself.

Moreover, it is much easier to determine the location of all communications on the site than to find out the level of groundwater by eye. For this, it is necessary to do a geodetic examination. Therefore, do not hesitate to ask former owners lands a similar document. Otherwise, you will have to spend extra.

Important: high groundwater most often runs in soils located according to the principle of descent or in areas that are already in the lowland relative to the entire village. The close location of the reservoir to your land may also indicate the possible presence of a reservoir with life-giving moisture close to the surface.

Groundwater - aquifers with a thickness of 1 to 10 meters, located in the bowels of the soil. Most often, they serve as sources of moisture for equipping wells, wells on the site.

There are such ground waters:

• Artesian strata... The lowest layer of the aquifer. As a rule, it is located at a level of 25 meters and below the surface of the earth. Basically, such water is found between layers of limestone and free-flow veins. Artesian formations are used to equip wells on private property. Such veins do not have a detrimental effect on buildings and vegetation on the site.
• Unconfined groundwater... Such a layer is located at an elevation of 5 to 20 meters above ground level. Such veins are not subject to changes in water level as a result of seasonal precipitation. The dynamics of such a layer remains unchanged. Due to the free-flow vein, the reservoirs adjacent to your territory are filled. It is worth knowing that non-pressurized waters have a very detrimental influence on the foundation of the finished building and all communications laid underground.
• Verkhovodka. These groundwaters are the most difficult in terms of the arrangement of the territory. Such a layer with liquid is located, as a rule, at a level of up to 3 meters from the soil surface. High-water veins have a very detrimental effect on the orchard plantings on the site, and at the same time affect the foundation and communications. Although everything is purely individual for each piece of land.

Formation of "harmful" verkhovodka

Perhaps some are interested in the formation of the upper water layer. It should be said that such veins are formed under the influence of seasonal precipitation. The complex of formation of an aquifer also includes the level of soil freezing and its subsequent heaving. So, the formation of a reservoir of water looks like this:

• The soil tends to freeze and freeze as a result of temperature changes. Where the soil freezes and thaws, it becomes looser. Precipitation in the form of rain and snow seeps through it.
• Then the bottom layer of soil, not subject to freezing, is rammed for hundreds of years, turning into an impermeable layer. This is the bottom of the aquifer.
• Thus, water accumulates in a kind of chamber, forming the direction of its movement under the influence of its own power.
• Later, depending on the season, water will burn to flow through the veins towards the reservoir or seep up the soil towards the plants, thus evaporating through their nutrition. That is why in summer, in waterlogged areas, even in the heat, the greens are more juicy and rich.

The negative impact of water on the ground

A high level of groundwater is a problem that can and should be dealt with. Otherwise, the cost of maintaining the site will increase significantly.

What is the harm of nearby aquifers:

• On loamy, sandy and shale soils, such veins are capable of constantly eroding the soil, which will lead to subsidence of the foundation, and subsequently the walls of the house. The final collapse of the entire structure is possible.
• In addition, the aforementioned types of soil, under the influence of nearby layers with water, can eventually transform into quicksand. And this is a more complex problem that is almost impossible to cope with.
• All vegetation in the garden and vegetable garden in the purchased area will simply rot if the water table is too high. In this case, you will have to resort to special tricks like lifting the beds by adding soil. The trees will have to be rescued by planting them on special earthen embankments.

Important: you can determine the close water level to the surface of the earth using an existing building on the ground. In this case, the house will be distinguished by crumbling plaster in the corners, difficult to open / close windows and doors, and cracks in the glass.

All this is evidence that the foundation and the house itself are undergoing deformation as a result negative impact moisture to the foundation.

Determine the water level at the site

The initial assessment of the site for the level of groundwater can be carried out, as they say, by eye. To do this, first use the old-fashioned methods and note the vegetation:

• So, if you do not know how to determine the level of groundwater, then we pay attention to shrubs and grass on the purchased land. Where the groundwater is located very close to the surface, nettle, horsetail, coltsfoot, sedge, foxglove, etc. will prevail. That is, all moisture-loving plants. At the same time, at first glance, the territory may not seem waterlogged.
• It is worth taking a closer look at trees with shrubs. If the waters are located on the ground at a depth of up to 5 meters, then you will see reeds, poplar, reeds and other similar plants.
• If the water is at a level of up to 3 meters, then wormwood, licorice, etc. will be frequent plants here.
• It is also worth knowing that birch, willow, maple and alder always grow along the aquifers. Moreover, they always make a bias towards the vein.
• Oaks are always located at the intersection of a vein with water.
• And you can determine nearby groundwater and by observing insects. So, a large accumulation of mosquitoes and other flying "evil" is inherent in those places where it lived. That is, there is always a tangle of insects in the air above it.
• You can simply interview your neighbors and inquire about the water level in their wells and wells, as well as about the dynamics of the change in the water surface in connection with the seasons.
• It is possible to mechanically determine the level of groundwater at the site using the drilling method. To do this, with a simple garden auger, you need to remove the soil by an amount equal to the depth of the water. That is, you need to drill in several places and until you come across water. Based on the data obtained, we analyze the depth of occurrence of aquifers in the ground. In this case, drilling must be carried out exclusively in early spring when the reservoir rises to the highest level.

Important: nevertheless, the best solution for private ownership would be a timely geodetic examination. Thus, it will be possible to protect the building from possible problems.

Fighting water

It is known that water in soil requires action to eliminate it. Otherwise, all the work on the territory will be in vain. You need to deal with groundwater only by means of its diversion. That is to equip good system drainage.

• The most common is considered to be open drainage. Used when groundwater interferes with plantings. To do this, you need to dig special ditches in the garden for drainage. Their depth should be at least 40 cm, while they should all look towards the slope of the site. In the garden between the crops, grooves are dug with a depth of no more than 10-15 cm. This system will perfectly cope with the drainage of water from the garden, but it is not perfect. The disadvantage of the system is that the maintenance of the garden and vegetable garden is complicated, and the design of the drainage system can be disturbed by winds, pets, etc.
• You can simply use the method of dewatering on the ground. To do this, you need to dig a pit, through the bottom of which water will leave. That is, the level of groundwater will decrease due to a decrease in the level of the bottom of the excavation. But this method is not suitable if soil particles are washed out with water. You can also find out through drilling or conducting geodetic soil analysis.
• Closed drainage system. It is used if the groundwater level interferes with the reliable and durable operation of the building. Such a water drainage system from the territory is hidden from prying eyes, but at the same time it has a significant disadvantage - rapid siltation. In such a system, the main components are trenches along the entire perimeter of the site, and corrugated pipes with perforations laid in them. Water will enter the sleeves and go through pipes to the intended place.
• You can use a more sophisticated installation to drain water from the ground. A needle-filter system and powerful pumps will be used here. The latter will pump out water and direct it to the drainage system.

• It is believed that there are no unsuitable land plots. Therefore, if you cannot fight water for a number of reasons, then it makes sense to change the design of the house so that it is more stable on waterlogged soil. Alternatively, a pile foundation or slab foundation can be used.
• If you do decide to conduct geodetic analysis, be prepared for high costs. The cost of such work will be within 500 USD. for an allotment of land. The amount can vary in both directions depending on the type of soil and the complexity of the terrain.
• If the decision is made to equip open system drainage, then all work must be carried out in the spring. At this time, the water is at the highest level, and its diversion will be more efficient. At the same time, it is worth knowing that you need to dig trenches from the lowest point of the territory towards the highest.
• For more convenience in installing the drainage system, you can find pipes on sale, one side of which is made in the form of a lattice. This will save you from additional work.

Important: all drainage systems, even on a seemingly perfectly flat piece of land, must be done taking into account the slope towards the water drainage. You can find out the direction of the slope by a simple assessment of the relief or using a geological assessment of the territory.

Determining the depth of groundwater is necessary if you want to find the right place for a well on the site. It is groundwater that is suitable for drinking and household needs. These waters are more accessible for extraction, as they are located in the initial aquifer from the top of the earth. The depth of water occurrence is very important, since the quantitative parameter of water inflow and the degree of moisture saturation of the soil layer depend on it. How to determine the depth of groundwater is the topic of the upcoming conversation. Let us point out direct and indirect evidence of a high rise in water, and describe the process of work. First, let's find out what kind of groundwater is and how it is characterized.

Classification

Before determining the depth of the water, it is a good idea to know which species all the water below the ground is divided into. That is, you need to know distinctive features each type of water.

All underground waters are divided into 3 main categories: groundwater, interstratal and upper water. The most superficial of these is the perch. Their formation is due to the filtration of sedimentary moisture (from snow and rain), melt water through the soil layer. Most often, their location is noted at a depth of 1–2 meters from the border of the earth. From the side of sanitary and epidemiological requirements, their suitability for drinking is extremely low. To use them, special water treatment is required. Therefore, they are not used. Their volume is small and more often equal to the amount of precipitation.

They have reliable protection against contamination. These waters owe their formation to filtration of water from the surface and, to some extent, of water from natural sources(rivers, ponds, lakes) above the ground. They lie without pressure. And permeable sandy loam and loam are impregnated with them. This type of water is safe and very reliable in terms of its organoleptic parameters.

The deepest layer (third) is an interstratal pressure (sometimes non-pressure) water layer. Such types of waters also have another name - artesian. They are the cleanest and safest from the point of view of epidemiology and radiation. That is why they are so highly valued. In those places where, under pressure, it breaks through earth surface key sources are located. Such waters are surrounded by impermeable strata on each side.

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Determination of location

For economic purposes, groundwater is considered the most in demand. In one place in natural conditions it has existed for quite a long time. Where it seeps out, springs appear. The volume and level of its rise is quite simple to understand.

But let's make a reservation right away that both the first and the second depend on several factors (for example, on atmospheric changes and seasonality).

For example, their temperature and level of rise are not constant values, but change over time. It is known that they rise higher in rain, and sink lower in dry weather. The level changes very often and in different seasons.

The greatest rise is observed in the spring, in winter the level decreases. The depth of soil freezing is also taken into account. These features are relevant in construction and gardening.

For example, for gardeners, the fact that the waters are close to the surface will be important, since fruit shrubs and trees are not planted on such a site. For such a case, checking the level groundwater it is done like this: they dig a hole one and a half meters deep and wait. If water collects in the recess, then vegetation cannot be planted in this place. Otherwise, their root system will be destroyed and the trees will die. The construction of a house also provides for a deeper finding of groundwater.

The aeration zone is the gap between the surface and the water surface below the ground. This distance depends on the relief of the territory, climate conditions, type rocks.

Lecture number 7

Groundwater is formed by the percolation of water falling out in the form of precipitation (infiltration), sometimes groundwater is formed from water contained in magma (juvenile), sedimentary, groundwater captured from the surface by formed rocks and revived (formed during the metamorphism of minerals and rocks. Groundwater is classified according to the hydraulic principle - gravity and pressure, and according to the conditions of occurrence - upper water, groundwater and interstratal.

Verkhovodka is called temporary accumulations of water in the very upper layers of the earth's crust over local aquicludes or semi-aquicludes (lenses of clays and loams in the sand, interlayers of denser rocks). During the period of snow melting and heavy rains during infiltration, water is temporarily retained and forms an aquifer. Verkhovodka is a significant danger for urban areas. Lying within the underground parts of buildings and structures (basements, boiler rooms, etc.), it can cause flooding. V recent times As a result of significant leaks of water (water supply), the emergence of upstream horizons in the territories of industrial facilities and residential areas was noted.

Groundwater is called groundwater that occurs on the first aquiclude from the surface. Groundwater has a free surface called a mirror. Groundwater is nourished by atmospheric precipitation and water inflow from surface water bodies and rivers. Ground water is open for the penetration of surface water into it, which leads to a change in its composition and pollution with harmful impurities. Groundwater is in motion and forms streams, which often leads to suffusion.

Interstratal waters are groundwaters occurring between two aquicludes. According to the conditions of occurrence, these waters can be free-flow and pressure-bearing, that is, artesian.

Over time, there are changes in the position of the level and nature of the surface of groundwater, their temperature and chemical composition... The combination of these changes is called the groundwater regime. Its study is the most important task, since the quantitative and qualitative change in groundwater significantly affects the conditions for the construction and operation of structures and should affect the design. The reasons for fluctuations in the level of groundwater are:

1 meteorological factors (precipitation);

2 hydrological conditions (influence of rivers and reservoirs);

3 vibration of the earth's crust;

4 human construction activities (leaks from water supply and sewerage systems, reduction of water evaporation due to buildings, various pumping out of wells and boreholes).

To monitor the level of groundwater, boreholes are used, made in the required places singly or located in a certain order.

In each well, the depth of the appearance of water relative to the earth's surface is determined, which is then recalculated at an absolute elevation. To determine the depth of the level, use:

1 measuring rod (at shallow depths);

2 measuring ropes, at the ends of which floats, crackers, whistles are suspended);

3 level meters with electrical circuits;

4 float meters.

- these are gravitational groundwaters of the first permanent aquifer from the Earth's surface, located on a regional aquiclude.

They are formed mainly due to infiltration (seepage) of atmospheric precipitation and waters of rivers, lakes, reservoirs, irrigation canals. In areas of river valleys, groundwater reserves are replenished by rising waters from deeper horizons (for example, waters artesian basins), as well as due to condensation of water vapor.

Characteristics of groundwater

The surface of the groundwater is free, because groundwater is usually free-flowing. In some areas, where there is still a local watertight overlap, groundwater acquires a local pressure. The areas of recharge and distribution of groundwater coincide. As a result, the conditions of formation and the regime of groundwater differ from deeper artesian waters: groundwater is sensitive to all atmospheric changes... Depending on the amount of atmospheric precipitation and the depth of groundwater, their surface experiences seasonal and long-term fluctuations. The values ​​of seasonal and long-term amplitudes of fluctuations in groundwater levels can reach 20 meters or more, which must be taken into account when building various types of facilities. Near rivers and water bodies, changes in the level, discharge and chemical composition of groundwater are determined by the nature of their hydraulic connection with surface waters and the regime of the latter. The amount of groundwater runoff over a long-term period is approximately equal to the amount of water supplied by infiltration.

Groundwater zoning

Differences in the conditions for the formation of groundwater determine the zoning of their geographical distribution, which is closely related to the zonation of climate, soil and vegetation cover. In forest, forest-steppe and steppe regions, fresh (or low-mineralized) groundwater is widespread; within dry steppes, semi-deserts and deserts, salty groundwater predominates on the plains, among which fresh waters are found only in certain areas. The most significant reserves of groundwater are concentrated in alluvial sediments of river valleys, in fans of foothill areas, as well as in shallow massifs of fractured and karst limestones (less often in fractured igneous rocks).

Groundwater application

Groundwater, due to its relatively weak protection against pollution, is of limited use as a source of water supply. industrial enterprises and cities. However, for the water supply of villages and settlements in rural areas, their role is quite large. According to the magnitude of the anthropogenic impact on groundwater, natural, slightly disturbed, disturbed, severely disturbed and artificial groundwater regimes are distinguished. The artificial regime is formed mainly under the influence of technogenic factors (intensive exploitation of groundwater, irrigation of lands in the arid zone). Natural long-term changes in the groundwater regime in many cases can be the reason for the intensification of landslide activity, karst-suffusion processes, regional flooding of the territory, suppression of terrestrial ecosystems, etc.

To study the patterns and mechanisms of the formation and forecasting of the groundwater regime in Russia, state and departmental services for its study and forecast (hydrogeological monitoring) have been organized. A regulatory and methodological framework for monitoring and methods of seasonal and long-term forecasts have been developed.

Sources: General hydrogeology. P.P. Klimentov -M., 1980; Study, forecast and mapping of the groundwater regime. Semenov S. -M., 1980; Hydrogeology. Savarensky F.P. -M., 1935.

Classification of groundwater by origin

1) Infiltration - formed due to the percolation of atmospheric precipitation (usually fresh and cold)

2) Condensation - formed due to the condensation of atmospheric moisture on loose coarse deposits, this process is possible near large water bodies (usually ultra-fresh and cold)

3) Sedimentation - formed as a result of diagenesis of marine sediments (usually cold and brines)

4) Juvenile or magmatic - they enter the earth's crust from magma (usually hot and thermal)

Physical condition of groundwater

1. Vaporous (moves in cavities of rocks from places with a higher vapor pressure to places with a lower vapor pressure).

2. Solid (ice) - occurs in places where permafrost is spread

3.1. Tightly bound

a) Crystallization - is a part of the crystal lattice in the form of H 2 O molecules. Example (CaSO 4 2H 2 O). When heated above 107 0 С, it is released.

b) Constitutional - the ions H + and OH - which are part of the minerals. The release of water is possible with the complete destruction of minerals.

c) Hygroscopic - a single molecular film on the surface of particles, adsorbed from air (density 1.5 g / cm 3, freezing point (-78 0 С))

All strongly bound water is inaccessible to plants and is immobile ...

3.2. Loosely tied

a) The film is held by molecular forces, forms a film over hygroscopic. Movement occurs from places with a thick film to places with a thin film. This moisture is inactive and difficult for plants to access.

b) Capillary - moderately available moisture for plants, held by capillary forces

3.3. Gravitational - moves under the action of gravity in large-porous rocks.

a) Soil waters

b) Verkhovodka - temporary aquifers, formed in the aeration zone on the lenses of waterproof rocks. They are used for rural water supply, are unreliable and often contaminated

c) Groundwater - the first regional aquifer on the first water-resistant horizon with a free upper open surface. Groundwater level (GWL) is the level at which water is established in wells and wells. The groundwater level changes over the years and seasons and depends on the amount of atmospheric precipitation. The distance from the surface to the groundwater level is called the aeration zone. Groundwater is fed by infiltration of atmospheric precipitation, unloading into rivers. Groundwater is a source of rural water supply.

d) Interstratal non-confined waters - lie between two impervious horizons, while not completely filling the entire thickness of the horizon.

e) Artesian confined waters - underground waters with a hydrostatic head - when the aquifer is opened, the water rises above the top of the aquifer. The line connecting the marks of the steady-state pressure level is called the piezometric level. Fresh water used for central water supply and irrigation.

Temperature classification of groundwater

1) Cold (up to 20 0 С)

2) Warm (20-42 0 С)

3) Hot or thermal (more than 42 0 С)

Classification of groundwater by mineralization

1) fresh (up to 1g / l)

2) brackish (1-10g / l)

3) salty (10-50g / l)

4) brines (more than 50g / l)