CC BY
5
https://doi.org/10.29013/AJT-23-1.2-24-28
Radkevich Mariya Viktorovna, Professor,
National Research University "Tashkent Institute of Irrigation and Agricultural Mechanization Engineers", Uzbekistan Aripov Islomjon Kakhramonovich, Basic doctoral student Gulistan State University, Uzbekistan Pochuzhevskyi Oleg Dmitrievich, Candidate of Technical Sciences, Associate Professor Krivoy Rog National University, Ukraina
ON THE POSSIBILITY OF ASSESSING ENVIRONMENTAL RISKS FROM SOIL SALINIZATION IN UZBEKISTAN
Abstract. The problem of salinization and secondary salinization of soils in Uzbekistan on the example of Syrdarya province is considered in the article. The task of ecological risks assessment from primary and secondary salinization is put.
Keywords: salinization, ecological risk, assessment, identification, analysis.
Introduction gime with intensity 20-30% of net irrigation norm
The problem of land salinization is widespread was adopted [2]. in Uzbekistan. One of the largest areas of irrigated However, this approach has led to serious side
agriculture in Uzbekistan is Golodnaya steppe - the effects: water withdrawal from rivers for irrigation
sum of areas suitable for irrigation here is more than has increased by 1.7-1.9 times. Drainage water dis-
800 thousand hectares. Natural salinity of Hungry charge into rivers by the end of the twentieth century
Steppe soils before active development of irrigation increased river water salinity, which also complicated
was well enough studied by the mid-20th century. the situation.
Hungry Steppe before irrigation was characterized At present, the area of saline, irrigated soils in
by predominance of automorphous soils, which were Hungry Steppe remains high and even increases.
referred to saline or potentially saline. In hydromor- This is confirmed by the data on salinization of ir-
phic soils, the main natural process before irrigation rigated lands of Syr-Darya province obtained in the
was the process of modern salinization [1; 2]. first half of the XXI century (Table 1).
Secondary salinization control was carried out It is possible to conclude from table data that
with alfalfa and other crops at the beginning of significant part of saline soils passes from category
XX century. However, the positive effect was not of slightly saline soils to category of medium and
achieved. strongly saline soils.
In 1964 a government decree on improvement of This state of affairs leads to a number of problems
meliorative condition of irrigated lands on the basis in different branches of national economy. Possible
of drainage construction and leaching irrigation re- negative consequences from salinization can be as-
sessed with the help of risk theory. Risks from soil sa- hensive consideration of risks from the problem of linization according to individual criteria have been salinization, especially secondary soil salinization, evaluated by some authors [4; 5; 6], but a compre- has not been carried out so far.
Table 1.- Dynamics of salinization of irrigated lands in Syr-Darya province [3]
Year Irrigated area, ha Non-saline area, ha Slightly saline, ha Medium saline, ha Strongly saline, ha
2012 286988 5050 232066 45790 4082
2013 286494 7675 224763 50011 4045
2014 286494 7059 223727 50222 5486
2015 287838 7073 230238 45955 4572
2016 287462 7305 222841 51765 5551
2020 286312 10333 202149 64091 9739
2021 287470 10058 204890 63542 8980
The aim of this article is an attempt to systematize the risks arising from secondary soil salinization, for the conditions of Syrdarya region of Uzbekistan.
Materials and methods
Syrdarya province of the Republic of Uzbekistan was chosen as the territory of the study, most of the territory ofwhich is occupied by the so-called Hungry Steppe, the condition ofwhich was considered above.
Elements of the risk theory were chosen as methods of research [7]. It is known that in carrying out any activity and making management decisions, risks inevitably arise. If there is no possibility to avoid risk completely, it is usually possible to reduce risk to acceptable values, including at water management impact on natural environment. At hydromeliorative impact economic and social risks can be considered as a consequence of environmental risk [8].
At present, there is no acceptable methodology for assessing the risk of reclamation activities. Works in the direction of creating such a methodology are carried out by a number of authors [7; 8].
The analysis of environmental risks is based on the following model [9]:
Block 1: Identification ofenvironmental risks: identification of environmental risks for a given process.
Block 2: Environmental risk assessment: a) Qualitative and quantitative analysis of risk factors, b) Assessment of environmental and human hazards
Block 3: Environmental risk monitoring: monitoring environmental risks for a given process
Block 4: Environmental risk management: a) Choosing the risk management methods for a given process; b) Implementing environmental risk management measures; c) Monitoring the effectiveness ofrisk management; d) Adjusting risk management measures.
Results and discussion
Let's make an assessment of geo-ecological risks at various hydromeliorative works processes in the Hungry Steppe (by the example of Syr-Darya region). Consideration of risks will be made for existing method of irrigation with creation of hydromor-phous regime
1. Identification of ecological risks
In this case the reason of ecologically unfavorable region is secondary salinization.
2. Qualitative and quantitative analysis of risk factors.
Let us consider the consequences caused by secondary salinization of soils (Fig. 1)
a) Qualitative analysis
b) quantitative analysis
1) Increased irrigation water consumption:
• In Kazakhstan and Central Asia, 50-60 million hectares of land suitable for irrigation. There are enough water resources for irrigation of 8-10 million hectares;
Figure 1. Risks of secondary salinization
• lWatering norms of about 20 thousand m3/ha
• 80% of irrigation water is spent on evaporation, and salts remain in the soil [10].
2) Yield reducing:
• with low salinity at 0...33%
• with an average salinity of 50%
• with strong salinity at 67.83%
• with very strong salinity at 100% [10].
3) Decommissioning of part of the land
• The number of highly saline soils in the Syrdarya region;
2020-9739 ha
2021-980 ha [3, 11];
• The area under raw cotton crops decreased from 2013 to 2016 in the Syrdarya region from 235185 ha to 191188 ha [3].
4) Mineralization of rivers:
• At the exit from the mountainous territory, the mineralization of river water does not exceed 0.3.0.4% and has a bicarbonate character. As it mixes with return waters from irrigated territories and groundwater drained by rivers, the mineralization of river water reaches 1.2 g/l, gradually acquiring a sulfate-chloride character due to the discharge of drainage effluents from the overlying irri-
gated territories. The mineralization of river waters has increased 3.8 times over the past 50 years [10];
• Huge norms of fertilizers (up to 600 kg/ha) and pesticides after washing the soils strongly mineralize the waters and saturate them with toxic substances. These waters are discharged in large quantities into the Syr Darya and Amu Darya and are reused downstream for irrigation;
5) Mineralization of groundwater:
• Irrigation channels create sources of concentrated water loss in groundwater, thereby forming their local pressure;
• lGroundwater (with an unexplored degree of mineralization) can be used as an additional source of irrigation water [3].
In 11 key areas of the Syrdarya and Jizzakh regions [12], the groundwater level at a depth of 0.8.2.5 m, i.e. much higher than the "critical" level of the GW. Mineralization is weak (3.86 g/l), average 8-10 g/l, strong 10-25 g/l
3. Assessment of environmental hazards to the environment and humans
• Irrigation water consumption - reduction of fresh water reserves - water crisis;
• Secondary anthropogenic salinization of irrigated lands is a process leading to disruption of the global biosphere mechanism [10].
• For humans (ecological and social risks):
• Decrease in yield - shortage of agricultural products [13];
• Decommissioning of part of the land is a social danger of unemployment of the population;
• Additional expenses incurred to minimize salinization, as well as to repair buildings and infrastructure elements affected by salinization.
4. Monitoring of environmental risks in this process
• Measurements of soil salinity;
• Measurement of the level of GW (measurement of the level of GW during the growing season, determination of the mineralization of GW);
• Control of GW effluents.
5. Environmental risk management
• The creation and maintenance of an optimal water-salt regime of the soil of the Hungry Steppe is achieved only with the implementation of a complex of reclamation measures, the most important of which are:
• Drainage;
• Layout;
• Flushing;
• Differentiated regime and technique of irrigation of agricultural crops [14];
• For difficult-to-reclaim gypsum-bearing soils, special complex agro-reclamation systems are required for large water consumption for washing >20 thousand m3/ha for a period of improvement of 6-8 years.
Conclusion. The preliminary analysis shows that there are significant risks associated with soil salinization in the Syrdarya region.
The measures used require a long time and large capital investments. In addition, all these activities can also be sources of environmental and geoeco-logical risks to be assessed.
Therefore, the tasks of further research are:
1. carrying out an updated assessment of the probability of occurrence of environmental and socio-economic risks from salinization;
2. determination of the extent of possible damage from secondary salinization to the environment and various spheres of human activity;
3. identification of risks and damage during the implementation of measures to reduce salinization
(including the use of drip irrigation).
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