RU2288329C2 - Method for operating lens of fresh water floating on zonal salty waters - Google Patents

Abstract

FIELD: water-supply engineering, primarily for agricultural needs in arid zones.

SUBSTANCE: in accordance to method for operating lens of freshwater floating on zonal salty waters and formed below open sands, across its area at level of zonal salty waters draining network is constructed in form of tubular drain lines with locking devices on outlet. In lower point of draining network water collector in form of tank without bottom is provided. Water of precipitations being filtered is intercepted by drain lines and dropped into water collector. From water collector water is taken for agricultural needs in volume of 50-60% from value of annual precipitations. Appearance of flora is not allowed at section of freshwater lens. In case of influx of salty waters drain lines are temporarily closed.

EFFECT: increased operation debit of water received from fresh lenses, substantial practically unlimited increase of lifetime of water-intake system.

1 cl, 2 dwg

Description

The invention relates to methods of water supply mainly for agricultural needs in arid zones.

In arid, low-water areas, in particular in the Caspian lowland, the local population receives fresh water from wells (hoods). The latter are located among open, devoid of vegetation, sand dunes. The appearance of fresh water here is due to the infiltration of precipitation and the formation of “fresh lenses” (V.N. Kunin, 1959, N.F. Kulik, 1979). The same lenses are formed under depressions (estuaries) on the clay plains of the arid zone, where surface runoff accumulates (M.K.Sapanov, 2004). Fresh lenses are formed on the sandy beaches of the seas.

Soils in combination with a water-resistant horizon are a capacity for the accumulation and storage of liquid moisture in sediments. In the arid zone on the sands, the process of water accumulation occurs when there is no vegetation on the site and no surface runoff. In this case, part of the precipitation is filtered through the aeration zone and accumulates in groundwater in the form of a fresh lens. The rest of the annual precipitation is spent on physical evaporation. In the event that vegetation appears on the site, it consumes the accumulated moisture for transpiration and the infiltration of water to groundwater is reduced or stopped entirely.

The role of water confinement can be played by zonal, inherent in a given area (O.K. Lange, 1958), saline groundwater. Filtered fresh water as having a lower density falls on salt water in the form of a lens and does not mix with it. In most cases, the mineralization of water in a fresh lens is 1–2 g / l, and in zonal groundwater it reaches 30–50 g / l. The upper surface of the lens rises above the level of zonal salt water by 0.5-1 m. The area of the lens depends on the area of open, devoid of vegetation, sands under which they are formed, or depressions where surface water flows. The power of fresh lenses varies from a few centimeters to tens of meters. In Russia, fresh lenses are most often found in the Caspian lowland at a depth of 2-4 m.

The annual volume of water that goes into the formation of the lens on the sand depends on the amount of annual rainfall. On the sands of the Northern Caspian, 100-150 mm of precipitation is filtered per year, on the Tersko-Kumsky sands 150-200 mm, which is 50-60% of the annual precipitation. According to the results of many years of research, the amount of submerged precipitation in the Volgograd region is 70% of the annual precipitation (N.F. Kulik et al., 1996).

The operation of fresh lenses is carried out using wells or wells, they open only a fresh layer of ground water. However, the service life of these water intake facilities is small and is 2-3 years. When taking water in a well or well from below, salt water is suitable and the quality of drinking water is deteriorating. Usually this well is abandoned and a new one is dug nearby. To increase the life of the wells they are made two side by side. Fresh water is pumped out one by one, and salt water by another, thereby preventing the rise of salt water (N.G. Shevchenko et al., 1963). To increase the drainage flow of operating fresh lenses, mine wells with horizontal beam filters are also used. The upper tier of the filters is placed in a fresh lens, the lower - in salt water. Fresh and salt water are pumped out simultaneously (I.G.Shevchenko et al., 1963).

Paired wells and horizontal beam filters are quite complicated in construction and roads in operation. The described methods of water intake are used on powerful fresh lenses, where a layer of fresh water reaches ten meters or more. Low-power lenses, where the layer of fresh water is 1-2 m and which prevail in the Caspian lowland, operate with the help of shallow wells. But they, as noted above, are short-lived in operation and have a low flow rate.

The problem to which the claimed invention is directed is to increase the operational flow rate of water obtained from fresh lenses, and a significant almost unlimited increase in the life of the water intake system.

The specified result is achieved in the following way.

On the area of the fresh lens or in parts of it create a drainage network in the form of tubular drains with a locking device at their exit. The network is located at the level of zonal saline groundwater located around the lens. At the bottom of the network there is a catchment in the form of a tank without a bottom. Filtered fresh water of sediments is collected in drains and discharged into the catchment, from where they are used for household needs. The volume of withdrawn water should not exceed 50-60% of the annual precipitation. This ensures the sustainable use of fresh water. In the case of salt water coming from any drain, it is temporarily closed until the water is desalinated. On open sands, where the lens is located, vegetation is not allowed.

The invention is illustrated by drawings.

Figure 1 shows a vertical section of a sandy steppe and a fresh lens formed under open, devoid of vegetation sand dunes. A lens floats on zoned saltwater. Shown are tubular drains located in a freshwater lens at the level of zonal saline groundwater located around the lens.

Figure 2 shows the layout of the drainage network on the area of the fresh lens and the freshwater catchment, where the drains come with locking devices.

In the drawing, the following notation:

1. Sandy steppe covered with vegetation.

2. Open, devoid of vegetation, sand dunes.

3. A fresh lens floating on zoned salty groundwater.

4. Tubular drains.

5. Zone salt water.

6. The level of zoned salt groundwater.

7. Locking devices on tubular drains.

8. The catchment.

We give an example of determining the area of the drainage system, which can provide the Shepherd’s brigade with fresh water. In the Northern Caspian, the average annual rainfall is 250 mm. A lens on an area of two hectares with a drainage network can collect 2500 m ^{3 of} water (precipitation accumulation efficiency is 50%). This water is enough to drink 1000-1500 heads of sheep, 50 heads of cattle and to provide water for the domestic needs of the shepherd brigade.

Literature

1. N.F. Kulik. The water regime of the sands of the arid zone. M .: Gidrometeoizdat, 1979. S.90-93.

2. N.F. Kulik, I.S. Zyuz, V.P. Rogachev. On the possibility of condensation of atmospheric moisture by sand deposits at the level of groundwater // Soil Science, 1996, No. 5, p. 635-639.

3. V.N. Kunin. Local waters of the desert and issues of their use. M .: Publishing. USSR Academy of Sciences, 1959, pp. 131-139.

4. O.K. Lange. The basics of hydrology. Ed. Moscow State University, 1958, p. 99.

5. M.K. Sapanov. Ecological features of the functioning of artificial forest biogeocenoses in the Northern Caspian. Abstract of dissertation for the degree of Doctor of Biological Sciences. M., 2004, S.9-10.

6. N. G. Shevchenko, I. S. Glazunov and others. Lenses of fresh water in the desert. Ed. USSR Academy of Sciences. 1963, p. 106-161.

Claims (1)

A method of operating a fresh water lens floating on zoned salt water, characterized in that for a fresh water lens formed under open sands, a drainage network in the form of tubular drains with shut-off devices at the exit at the lower point is created at the level of zoned salt water the drainage network has a water collector in the form of a tank without a bottom, intercepts filtered sediment water with drains and discharges it into the water collector, from where fresh water is taken for household needs in the amount of 50-60% of the annual precipitation, etc. and this does not allow the appearance of vegetation in the fresh lens area, and in the case of salt water, the drains are temporarily closed.

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