Researches of processes of flooding of built up territories in the zone of the irrigation

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The Tashkent institute ирригации and land improvements

RESEARCHES OF PROCESSES OF FLOODING OF BUILT UP TERRITORIES IN THE ZONE OF THE IRRIGATION

B.K. Saliev

M.B. Soliev

Uzbekistan

In the article the analysis about the water-economic reasons of flooding in a zone of irrigated agriculture, about necessities of studying of engineering ameliorative and hydro-geological conditions of city territories, a choice of protective drainage systems for the prevention from influence of subsoil waters is given. A necessary condition of a choice of a drainage is the estimation of conditions of formation of a mode and balance of subsoil waters as a result of which there was an occurrence of processes secondary salting and flooding of the city grounds.

Now more than 200 cities and settlements in the republic of Uzbekistan concern to ameliorative unsuccessful where immediate measures on improvement of their grounds are required on the basis of scientific recommendations. The reason of it is anthropogenous influence of an irrigation on the natural environment, which consequence scale rise of a level of subsoil waters (GWL) in a zone of irrigated agriculture, occurrence secondary salting and flooding of the grounds in regional and local scales - within the limits of the grounds of settlements and cities [1]. Vulnerability of the natural environment during economic activities of the person has come to light was evidently showed by the example of an irrigated zone of Uzbekistan. Therefore the major problem in present time is: The scientifically-grounded decision of a problem of city land improvement and drainage, carrying out of engineering researches for an estimation of the reasons and factors, installation of the correct diagnosis of process of flooding, detection of a zone of streams of «irrigational» subsoil waters, interception of these streams from the irrigated grounds, water basins, channels by their gathering, tap and a reuse [2]. In it the main preference is given drainage systems with which help it is possible to receive necessary decrease and to use underground water for maintenance of economy of region during the droughty periods with frequently repeating years of low water-security.

1. Materials and methods of researches

Rise of GWL and salting the grounds in a zone of an irrigation is connected to redistribution of water resources. There were significant losses of waters on a filtration, growth of water consumption has increased for the areas of the irrigated grounds [3,4] in the end of 1960 s. These negative processes are resulted in works of scientists: A.Kostyakov, S.Averyanov, P.Aydarov., A. Golovanov, N.Reshetkina, R.Alimov, N.Kenesarin, A.Rachinsky, S.Mirzaev, F.Rahimbaev, etc which in details give the reasons of process and ameliorative estimation of a condition of the irrigated grounds. By soil scientists of Republic it is marked, that the general area of the grounds subject salting, gypsum and to bogging, it is precisely unknown, as the authentic regular account of a ameliorative condition irrigated soil with the help of air photography and ground updating was not made [5]. For maintenance of prognosis-estimated filtration calculations with the initial information are applied special typification natural - the geological conditions determining an opportunity of formation of irrigational flooding. [6].

2. Problems of the forecast of flooding.

For conditions of the Central Asia the decision of problems of the forecast has ambiguous character as subsoil waters occurs not from an obvious source, and from a lot of superficial and underground components that demands deeper and versatile researches both in methodical, and in the theoretical plan, including:

for the forecast of change of mode GWL for skilled sites where there is their formation are applied classification of a mode of subsoil waters. With the help of classification its intensity and duration, an orientation of a mode of subsoil waters and speed of rise of their level [7, 8] are determined a kind infiltration a feed of subsoil waters.

At presence of various coverings of surfaces through which the filtration is carried out, infiltration of a moisture goes at incomplete saturation (i.e. in a slowed-up way) and thus there is constant rise GWL the account of an exchange of a moisture, air, heat and capillary dump.

Thus, two basic are established such as flooding: flooding of the irrigated grounds at superficial поливе and as a result them prop - flooding of the bases of buildings and constructions of cities and settlements. Therefore, the primary goals of the forecast are formulated as follows:

* An estimation of the maximal rise (decrease) GWL in view of its seasonal and long-term fluctuations in a zone intensive irrigation.

* The forecast of a mode of subsoil waters in mastered territory (during civil construction) at use of dependence of position GWL from intensity of a filtration has the big advantage in comparison with all known methods as does not demand long supervision. At presence of various coverings of surfaces through which the filtration is carried out, infiltration of a moisture goes at incomplete saturation (i.e. in a slowed-up way) and thus there is constant rise GWL of waters due to capillary dump.

3. The analysis of results of research.

The analysis of theoretical models of the equation of movement of subsoil waters and the received experimental data has shown, that intensity of infiltration (i) at any kind (irrigating) at an any course of intensity of absorbing waters in a ground is defined by expression

K =, (1)

where Km - infiltration ability of ground, the mm / ЯТФ, dependent on pressure of water, presence lateral prop or a pressure of underground waters:

?H = ,

where H - range of changes of water-heat-sink capacity of-grounds in a zone of aeration; б* - an elastic moisture capacity of a ground.

The equation (2) characterizes movement of an elastic liquid concerning an impenetrable first water-emphasis from a surface.

As criterion of potential floodness it is possible to choose the attitude of a layer of saturation by a moisture of a zone of aeration to depth of GWL at the end of recession

,

where h1a - depth of GWL at the end of annual recession; Having marked

A = Hmax - Hmin,

At Hmin - we have a layer of saturation of a zone of aeration Н up to flooding:

.where: And - amplitude of fluctuation GWL for a year, m; hk - height of capillary rise of the moisture, dependent from granularmetric structure of a ground which will consist of two zones

H = hash,

where he - a zone of the sated moisture up to a limiting moisture capacity; ha - a layer of transit of a moisture from a zone he up to a surface of the ground where the zone of aeration still contains air pairs (fig. 1).

Fig. 1. A schematization of quantity indicators seasonal mode of subsoil waters.A modeling problem

At flooding there is a saturation of all zone Н, that is

H = A + hk,

If we shall put down value in the period of GWL (fig. 2), we shall receive

Кп - the grounds.

With approach of GWL a day time surface parameters, also process evaporation increases, taking a place of a moisture - air pairs. At watering there is a return process. flooding irrigated agriculture groundwater

Kп

H = A + ha + hk;

H - a layer of saturation of a zone of aeration up to the beginning flooding; A - amplitude of fluctuation GWL for a year, m; hk - a zone sated with a moisture up to limiting влагаёмкости; ha - a layer of transit of a moisture from a zone hk up to a surface of the ground where air pairs still contain; h1a - depth GWL at the end of recession, m.

4. The received results and their discussions

The tendency of flooding in a zone of an irrigation was kept and to this day. Our long-term researches gave the following parameters of efficiency of irrigating systems: in the interfarm channels which are not having coverings, irrigating losses make 5…15 %, in channels with concrete clothes - 0,5…1,5 %, in local allocators: before reconstruction of 7…24 %, and after reconstruction of 5…25 %.

Insufficient water-security and complex natural conditions in a cotton-growing facilities of a site of «Beech» at bad work of a collector and-drainage network from year to year increases the areas of flooding of the grounds and salinities of ground. In result of watering in top parts Коkaral district of a file started to raise GWL, in comparison with the first year the total maintenance of salts from 0,04 % has reached up to 0,24 % from dry weight of ground. Initial in the bottom horizon (on depth 7,5 м) GWL as a result of regional prop from Коkaral district a file started to raise and has reached on the second year up to 5,6 m. Change of many years GWL (Н) and heights capillari rise (hk) and to humidity of grounds on a skilled site is submitted to fig.2.

Fig. 2. Change of factor of flooding in dependence of rise GWL

It means, that at superficial watering simultaneously with rise GWL there is a process secondary засоления due to increase in intensive processes infiltration and evaporations. Thus, depth of saturation of ground - грунтов with approach GWL grows and at closing capillary edge reaches a full field moisture capacity. Hence, characteristic parameters of flooding are position GWL, height of capillary rise, mid-annual irrigation norm, and also the maintenance of total quantity of salts in earth water. On quantity indicators, depending on a range of values Кn the degree of floodness the grounds, describing is established: at Кn > 1-it is weak flooded zones (sites); Кn ? 1 - flooding, or subject seasonal flooding; Кn < 1 - flooded it is constant. Saturation by a moisture geological and litological a cut in area of flooding proceeds at an incidental and periodic feed of subsoil waters and seldom non-stationary character has: There is a fast occurrence mound subsoil waters to the subsequent by its spreading over.

References

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2. Badov V.V., Kiselyov A.A. joint movement of subsoil waters and a moisture of a zone of aeration. //Water resources. - M., 1982. № 1. W. 16-26.

3. Baron V.A. model of a mode of subsoil waters in reclaimed areas //Water resources. - M., 1985. № 2. p. 172-174.

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2. Gafurova L., Kuziev R., Ahmeds А., Yaminova I., Turapov I., Ramazonov О., Bairov A. Meliorativnaja an estimation of a modern condition irrigated sojl Hungry steppe // the Bulletin of agrarian science Uzbekistan. - Tashkent, 2006. № 4 (26). p. 39-43.

3. Denisov J.M., Gringof I.G. bas of mathematical modelling of processes of carry of a moisture, heat and salts in grounds for an estimation of pollution. //Всесторонный the analysis of the environmental natural environment. Works of III Soviet-American symposium. - L., 1978. p. 200-211.

4. Saliev B.K., Abduraupov R. R., Soliev M.B. Estimabion of Drainable Urban Area Groundnaber Resources Recovery. //Tashkent Institute of Irrigation and Agricultural Mechanization Engineers. - Tashkent, 2001.

5. Saliev B.K., Alikulov P.U., Soliev M.B. Ekologicheskie aspects of influence of water-economic construction on process of flooding. //Мат. Центрально-азиатской межд. научно-практ. конф., посв. 15-летию МКВК. - Алматы, 2007. С. 186-189.

6. Saliev B.K. “Calculation of groundwater resources in urban areas” Joint scientific journal. - M., 2008.

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