CHANGES IN THE PHYSICAL PROPERTIES OF SOILS UNDER THE INFLUENCE OF HYDROMORPHISM AROUND THE KATTAKURGAN RESERVOIR

SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 11 NOVEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 118 CHANGES IN THE PHYSICAL PROPERTIES OF SOILS UNDER THE INFLUENCE OF HYDROMORPHISM AROUND THE KATTAKURGAN RESERVOIR Z. Jabbarov1, J. Abdukarimov2, U. Imomov3, Sh. Abdullayev4 National university of Uzbekistan, Faculty of Biology and ecology department of Soil Science1,2,3,4 https://doi.org/10.5281/zenodo.17835773 Abstract. This study focuses on evaluating the impact of the Kattakurgan Reservoir’s activity on the physic -chemical properties of the surrounding soils. According to the results, active hydromorphism processes occur in the areas located near the reservoir due to the constant rise of groundwater levels. These processes have led to an increase in soil bulk density, a decrease in porosity, and a reduction in air exchange. In particular, in the northern–eastern parts (N-E -0.5 and N-E -1 profiles), the porosity was found to be moderate, while air exchange was weakened. In contrast, in areas farther from the reservoir (N-E-9, N-E -10, and background profiles), porosity was very good, and air exchange remained at an optimal level. Additionally, changes in the amount of micro aggregates in the soils were also investigated. The results showed that the proportion of micro aggregates smaller than 0.25 mm decreased in the areas close to the reservoir, which indicates degradation processes associated with hydromorphism and rapid fluctuations in soil moisture. Furthermore, the influence of the reservoir resulted in a decrease in the amount of organic matter, reduced microbial activity, and weakened aggregate stability. The findings demonstrate that changes in the water regime and physical structure of soils around the Kattakurgan Reservoir affect both soil fertility and ecological stability. Keywords: reservoir, soil, hydromorphism, porosity, bulk density. INTRODUCTION The granulometric composition of soils distributed around the KattakurganReservoir has undergone significant changes under the influence of constant moisture and hydromorphism. As a result, the content of physical clay has increased from 43.1% to 59.7% (Abdullaev et al., 2020). Several researchers (Rzetala et al., 2019; Zhou et al., 2018) have emphasized that the increase in physical clay content around reservoirs alters soil water permeability and aeration regimes. The main factor contributing to hydromorphism, the rise in physical clay content, and the deterioration of reclamation conditions in soils is the elevation of the groundwater table. In the study area, the groundwater level ranges between 85 and 155 cm. It was observed that in soil horizons where groundwater levels are higher, the physical clay content is greater. Similar findings were reported by Zhang et al. (2016), Arheimer and Pers (2017), and Foster et al. (2003), who noted that an increase in physical clay content around reservoirs negatively affects soil fertility. Furthermore, soils in reservoir-adjacent areas tend to experience increased salinization. The continuous presence of easily soluble salts leads to their accumulation within soil horizons, causing salinity development. Studies conducted in other regions have also confirmed the relationship between rising groundwater levels and variations in physical clay content (Ma et al., 2022), as well as the observed increase in soil salinity (Gebrekidan et al., 2021). The heavier granulometric composition contributes to enhanced salt accumulation (Li et al., 2024; Hossain et SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 11 NOVEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 119 al., 2015). As the proportion of physical clay increases, the soil accumulates ions such as Cl⁻ and SO₄²⁻, thereby intensifying salinization processes. The soil pH also varies under these conditions. For instance, hydromorphism promotes the reduction of iron, resulting in decreased soil pH (Salmi et al., 2025). Conversely, an increase in organic matter due to hydromorphism can lead to a neutral pH environment (Adhikary & Pal, 2025). Consequently, it can be inferred that the hydromorphic processes occurring around reservoirs lead to an increase in the proportion of physical clay, which in turn facilitates salt accumulation and elevates the degree of soil salinization. The concept and causes of hydromorphism have been extensively analyzed in the scientific literature. Classical studies highlight the chemical changes occurring in water-saturated (submerged) soils, particularly focusing on the reduction processes of iron and manganese and their relationship with Eh (oxidation–reduction potential) dynamics. According to these sources, hydromorphism refers to the development of anaerobic conditions in soils due to prolonged or constant water saturation, where elements such as iron and manganese accumulate in reduced forms (Ponnamperuma, F.N., 1972). Several studies have also examined the transformation of organic matter in soils, including the composition of plant and microbial residues. In hydromorphic soils (especially in irrigated lands), reducing conditions caused by oxidation–reduction processes contribute to the specific accumulation of organic matter, which influences soil structure (Kögel-Knabner, 2002). Numerous scientific works have also addressed hydromorphism in the context of excessive moisture and irrigation agriculture, including issues of water balance and waterlogging. In regions with limited water resources, many studies discuss the challenges and opportunities in managing irrigation systems. Inefficient water use and poor drainage systems are among the key issues. Improper management of irrigation regimes leads to increased soil water content, rising groundwater levels, and intensified hydromorphic processes (Qadir et al., 2003). Research has also focused on providing economic and agrotechnical recommendations for sustainable water resource management in irrigated lands. Properly designed drainage systems and groundwater control have been identified as key factors in reducing hydromorphism risks (Oster & Wichelns, 2003). Furthermore, several fundamental studies have examined the protection of soils from salinization in irrigated areas. These works scientifically substantiate the interrelationship between water balance, waterlogging, and soil salinity. It has been emphasized that excessive water supply and inadequate drainage not only strengthen hydromorphic conditions but also accelerate soil salinization processes (Hillel, 2000). METHODS During the research, the main objective was to determine the physical properties of the soils — namely, bulk density, particle density, and porosity. All analyses were conducted in accordance with international and national standards (FAO, 2006; O‘z DSt 1053:2006). The amount of microaggregates in the soil was determined based on the Savvinov method. RESULTS Due to the continuous rise and persistence of groundwater levels around the KattakurganReservoir, hydromorphism processes actively occur. As a consequence, soil compaction increases, porosity decreases, and air exchange weakens. According to the results, such processes were not uniformly observed across the areas surrounding the reservoir (see Table – 1). Table 1. Changes in soil porosity, degree, and air exchange around the Kattakurgan Reservoir SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 11 NOVEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 120 Profile Depth (cm) Bulk density (g/cm³) Particle density (g/cm³) Porosity (%) Porosity level Air exchange North-Eastern Area N-E-0.5 0-12 1,46 2,65 44,91 Moderate Weak 12.-38 1,47 2,65 44,53 Moderate Weak 38-92 1,47 2,65 44,53 Moderate Weak 92-120 1,48 2,65 44,15 Moderate Weak N-E-1 0-21 1,48 2,65 44,15 Moderate Weak 21-57 1,47 2,65 44,53 Moderate Weak 57-112 1,48 2,65 44,15 Moderate Weak 112-165 1,46 2,65 44,91 Moderate Weak N-E -2 0-36 1,39 2,65 47,55 Good Adequate 36-69 1,39 2,65 47,55 Good Adequate 69-108 1,42 2,65 46,42 Good Adequate 108-170 1,41 2,65 46,79 Good Adequate N-E -3 0-28 1,36 2,65 48,68 Good Adequate 28-74 1,37 2,65 48,30 Good Adequate 74-106 1,37 2,65 48,30 Good Adequate 106-180 1,39 2,65 47,55 Good Adequate N-E -4 0-30 1,37 2,65 48,30 Good Adequate 30-67 1,37 2,65 48,30 Good Adequate 67-158 1,38 2,65 47,92 Good Adequate N-E -5 0-42 1,35 2,65 49,06 Good Adequate 42-74 1,36 2,65 48,68 Good Adequate 74-165 1,37 2,65 48,30 Good Adequate N-E -6 0-38 1,35 2,65 49,06 Good Adequate 38-69 1,35 2,65 49,06 Good Adequate 69-120 1,36 2,65 48,68 Good Adequate 120-156 1,37 2,65 48,30 Good Adequate N-E -7 0-25 1,34 2,65 49,43 Good Adequate 25-66 1,35 2,65 49,06 Good Adequate 66-101 1,36 2,65 48,68 Good Adequate 101-160 1,36 2,65 48,68 Good Adequate N-E -8 0-40 1,32 2,65 50,19 Good Optimal 40-87 1,33 2,65 49,81 Good Adequate 87-124 1,33 2,65 49,81 Good Adequate 124-165 1,34 2,65 49,43 Good Adequate N-E -9 0-38 1,31 2,65 50,57 Very good Optimal 38-84 1,31 2,65 50,57 Very good Optimal 84-95 1,32 2,65 50,19 Very good Optimal 95-145 1,33 2,65 49,81 Good Adequate SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 11 NOVEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 121 145-170 1,37 2,65 48,30 Good Adequate N-E -10 0-42 1,32 2,65 50,19 Very good Optimal 42-69 1,32 2,65 50,19 Very good Optimal 69-88 1,33 2,65 49,81 Good Adequate 88-135 1,34 2,65 49,43 Good Adequate 135-168 1,37 2,65 48,30 Good Adequate Backgro und site FON 0-42 1,31 2,65 50,57 Very good Optimal 42-75 1,31 2,65 50,57 Very good Optimal 75-141 1,33 2,65 49,81 Good Adequate 141-176 1,35 2,65 49,06 Good Adequate North West region N-W-0,5 0-15 1,49 2,65 43,77 Moderate Weak 15-35 1,46 2,65 44,91 Moderate Weak 35-52 1,46 2,65 44,91 Moderate Weak 52-63 1,46 2,65 44,91 Moderate Weak N-W-1 0-20 1,48 2,65 44,15 Moderate Weak 20-32 1,48 2,65 44,15 Moderate Weak 32-50 1,49 2,65 43,77 Moderate Weak 50-62 1,45 2,65 45,28 Good Adequate 62-78 1,45 2,65 45,28 Good Adequate N-W-2 0-7 1,47 2,65 44,53 Moderate Weak 7.-27 1,46 2,65 44,91 Moderate Weak 27-44 1,46 2,65 44,17 Moderate Weak 44-54 1,46 2,65 44,17 Moderate Weak 54-80 1,46 2,65 44,91 Good Weak N-W-3 0-30 1,38 2,65 47,92 Good Adequate 30-53 1,38 2,65 47,92 Good Adequate 53-75 1,39 2,65 47,55 Good Adequate 75-145 1,39 2,65 47,55 Good Adequate N-W-4 0-30 1,36 2,65 48,68 Good Adequate 30-58 1,36 2,65 48,68 Good Adequate 58-90 1,37 2,65 48,30 Good Adequate 90-154 1,37 2,65 48,30 Good Adequate N-W-5 0-32 1,33 2,65 49,81 Good Adequate 32-46 1,33 2,65 49,81 Good Adequate 46-70 1,34 2,65 49,43 Good Adequate 70-110 1,35 2,65 49,06 Good Adequate 110-175 1,35 2,65 49,06 Good Adequate N-W-6 0-30 1,32 2,65 50,19 Very good Optimal 30-48 1,34 2,65 49,43 Good Adequate 48-125 1,34 2,65 49,43 Good Adequate 125-165 1,34 2,65 49,43 Good Adequate N-W-7 0-25 1,35 2,65 49,06 Good Adequate SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 11 NOVEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 122 25-45 1,35 2,65 49,06 Good Adequate 45-87 1,35 2,65 49,06 Good Adequate N-W-8 0-26 1,33 2,65 49,81 Good Adequate 26-44 1,33 2,65 49,81 Good Adequate 44-70 1,34 2,65 49,43 Good Adequate 70-170 1,34 2,65 49,43 Good Adequate N-W-9 0-28 1,32 2,65 50,19 Very good Optimal 25-74 1,32 2,65 50,19 Very good Optimal 70-112 1,33 2,65 49,81 Good Adequate 105-165 1,33 2,65 49,81 Good Adequate N-W-10 0-25 1,32 2,65 50,19 Very good Optimal 25-70 1,32 2,65 50,19 Very good Optimal 70-105 1,32 2,65 50,19 Very good Optimal 105-160 1,32 2,65 50,19 Very good Optimal Backgro und site FON 0-27 1,31 2,65 50,57 Very good Optimal 27-72 1,31 2,65 50,57 Very good Optimal 72-110 1,32 2,65 50,19 Very good Optimal 110-165 1,32 2,65 50,19 Very good Optimal Northerly region N-1 0-35 1,47 2,65 44,53 Moderate Weak 35-60 1,48 2,65 44,15 Moderate Weak 60-70 1,48 2,65 44,15 Moderate Weak 70-120 1,48 2,65 44,15 Moderate Weak N-2 0-38 1,46 2,65 44,91 Moderate Weak 38-58 1,47 2,65 44,53 Moderate Weak 58-96 1,47 2,65 44,53 Moderate Weak 96-125 1,48 2,65 44,15 Moderate Weak N-3 0-25 1,36 2,65 48,68 Good Adequate 25-39 136 2,65 50,08 Very good Optimal 39-77 1,37 2,65 48,30 Good Adequate N-4 0-25 1,35 2,65 49,06 Good Adequate 25-39 1,35 2,65 49,06 Good Adequate 1,36 2,65 48,68 Good Adequate 1,37 2,65 48,30 Good Adequate N-5 0-27 1,34 2,65 49,43 Good Adequate 27-49 1,34 2,65 49,43 Good Adequate 49-66 1,35 2,65 49,06 Good Adequate 66-166 1,36 2,65 48,68 Good Adequate N-6 0-28 1,35 2,65 49,06 Good Adequate 28-51 1,36 2,65 48,68 Good Adequate 51-65 1,36 2,65 48,68 Good Adequate 65-125 1,37 2,65 48,30 Good Adequate 125-158 1,37 2,65 48,30 Good Adequate SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 11 NOVEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 123 N -7 0-26 1,36 2,65 48,68 Good Adequate 26-61 1,36 2,65 48,68 Good Adequate 61-84 1,37 2,65 48,30 Good Adequate 84-105 1,37 2,65 48,30 Good Adequate 105-161 1,37 2,65 48,30 Good Adequate N -8 0-32 1,34 2,65 49,43 Good Adequate 32-68 1,34 2,65 49,43 Good Adequate 68-92 1,35 2,65 49,06 Good Adequate 92-123 1,36 2,65 48,68 Good Adequate 123-163 1,37 2,65 48,30 Good Adequate N -9 0-30 1,32 2,65 50,19 Very good Adequate 30-61 1,32 2,65 50,19 Very good Adequate 61-96 1,33 2,65 49,81 Good Adequate 96-142 1,34 2,65 49,43 Good Adequate 142-168 1,34 2,65 49,43 Good Adequate N -10 0-33 1,31 2,65 50,57 Very good Optimal 33-64 1,32 2,65 50,19 Very good Optimal 64-91 1,33 2,65 49,81 Good Adequate 91-135 1,33 2,65 49,81 Good Adequate 135-161 1,34 2,65 49,43 Good Adequate Backgro und site FON 0-31 1,32 2,65 50,19 Very good Optimal 31-64 1,32 2,65 50,19 Very good Optimal 64-92 1,33 2,65 49,81 Good Adequate 92-140 1,34 2,65 49,43 Good Adequate 140-168 1,34 2,65 49,43 Good Adequate 168-195 1,34 2,65 49,43 Good Adequate According to the data presented in the table, a reduction in soil porosity and weakening of air exchange were clearly observed in the soils of profiles N-E-0.5 and N-E -1, located in the northeastern part of the KattakurganReservoir. In the subsequent profiles — N-E -2, N-E -3, N-E -4, NE-5, N-E -6, N-E -7, and N-E -8 — the soils exhibited good porosity and adequate air exchange. In contrast, in the soils of N-E -9, N-E -10, and the background area, which are situated farther from the reservoir, porosity levels were good to very good, and air exchange was at an adequate to optimal level. In the north-western sector of the reservoir, this trend was even more pronounced. According to the results, soils from profiles N-W-0.5, N-W -1, and N-W-2 demonstrated moderate porosity and weak air exchange. In the subsequent profiles — N-W-3, N-W-4, N-W-5, N-W-6, NW-7, and N-W-8 - the soils showed good porosity with adequate air exchange. However, in profiles N-W -9, N-W -10, and those from the background area, located farther from the reservoir, the influence of the water body was negligible. These soils exhibited very good porosity and optimal air exchange, indicating stable physical conditions. Similarly, soil samples collected from the northern part of the reservoir displayed a comparable pattern. The soils in N-1 and N-2 profiles showed moderate porosity and weak air exchange, while those from N-3 to N-9 exhibited good porosity and adequate air exchange. In the Sh-9 profile and the background soils, porosity was found to be good to very good, and air exchange remained at adequate to optimal levels. Long-term observations also SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 11 NOVEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 124 examined changes in soil micro aggregate composition around the Kattakurgan Reservoir. The distribution of aggregates of 10 mm, 7 mm, 5 mm, 3 mm, 2 mm, 1 mm, 0.5 mm, 0.25 mm, and <0.25 mm fractions was analyzed. Results revealed that in the areas closer to the reservoir, the content of micro aggregates smaller than 0.25 mm had decreased significantly (see Table -1). Table 1. Changes in the content of soil micro aggregates around the Kattakurgan Reservoir Samples Microaggregates, mm 10 7 5 3 2 1 0,5 0,25 <0,25 N-E-1 33,40 8,67 9,87 16,95 17,15 11,86 1,40 0,20 0,50 N-E -2 15,63 5,81 8,04 21,34 24,58 19,78 1,69 2,79 0,89 N-E -3 24,52 10,97 9,18 15,57 15,45 16,06 4,25 3,92 0,34 N-E -4 18,15 6,66 7,52 43,07 3,76 10,81 1,72 7,41 1,83 N-E -5 20,10 7,94 8,93 14,02 17,37 19,35 4,35 4,22 4,09 N-W-1 29,71 6,12 9,82 19,01 19,01 12,42 2,94 1,13 0,33 N-W -2 21,97 5,54 9,41 20,29 20,71 16,00 2,36 3,45 0,52 N-W -3 22,15 8,25 7,21 32,03 17,72 10,97 0,84 1,46 0,05 N-W -4 19,26 4,99 5,86 12,72 28,34 27,79 0,35 0,59 0,39 N-W -5 20,00 7,64 6,97 10,45 12,02 24,28 1,91 12,1 2 5,27 N-1 17,46 5,57 8,15 19,29 24,94 22,78 1,00 1,16 0,42 N-2 26,59 6,95 7,68 11,46 15,61 20,07 3,05 8,17 0,98 N-3 27,49 8,68 13,97 12,97 13,88 11,77 9,86 1,00 1,00 N-4 24,40 6,45 10,87 20,35 18,23 18,35 1,38 0,83 0,06 N-5 16,45 10,19 11,78 16,24 17,52 19,43 2,34 3,29 2,76 Western 15,73 9,60 6,32 10,33 11,26 19,67 3,29 13,4 0 11,02 Souther n 27,71 6,46 4,93 7,79 7,34 13,25 3,94 18,2 9 10,84 DISCUSSION Under the influence of the Kattakurgan Reservoir’s activity, moisture remains within the soil layers, and at certain times its rapid loss is observed. As a result of this process, soil aggregates smaller than 0.25 mm are more prone to degradation processes. When moisture is present, the “hydrating” forces within aggregates become active, making disaggregation (the breaking apart of aggregates) easier. The periodic fluctuations of water levels near the reservoir — frequent rising and lowering of the water table — create cyclic wetting and drying conditions in the soil. These cycles can weaken the internal bonding strength of aggregates, since organic matter and microbial activity are highly moisture-dependent. During these fluctuations, microbial activity declines, decomposition of organic matter accelerates, and aggregates begin to detach from one another. In hydromorphic soils, organic matter content decreases, leading to a loss of aggregate stability. As a result, macro aggregates (>0.25 mm) become dominant, while micro aggregates break down and decrease in quantity. In areas near the reservoir, due to the constant fluctuation of water levels, strong erosion, dust formation, and leaching of fine soil particles into drainage channels are observed. These processes cause micro aggregates to fragment into smaller particles, ultimately leading to their loss. SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 11 NOVEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 125 The hydrological stresses induced by the reservoir — such as cyclic changes in water level, alternating wet and dry conditions, and variations in moisture regime — have contributed to the disintegration of micro aggregates. A lack of organic matter has reduced the soil’s ability to reform and stabilize these micro aggregates. Additionally, leaching of mineral binding agents (Ca²⁺, Mg²⁺, and others) and changes in pH have intensified dispersion and aggregate breakdown. Samples collected near the reservoir (Sh-shq-1, Sh-shq-2, etc.) show lower contents of micro aggregates (0.25 mm and <0.25 mm), while those collected farther away (South, Western) contain significantly higher proportions of small aggregates (10% or more). These findings confirm the above analysis: micro aggregate content decreases near the reservoir as a result of moisture fluctuations, organic matter deficiency, and physicochemical dispersion. The changes in soil micro aggregate composition under the influence of the Kattakurgan Reservoir can therefore be explained by the following key factors (see Table-3 ). Table-3 Factor Impact Water level changes Soils near a reservoir are exposed to cycles of moisture and drought, resulting in the breakdown of aggregates. Low organic matter In areas close to reservoirs, plant biomass and the rate of their conversion into humus are low, resulting in unstable microaggregates. Mineral component washing As water is absorbed, binding ions such as Ca²⁺ and Mg²⁺ are washed away → the amount of micro aggregates decreases. Mechanical erosion In areas close to reservoirs, soils are subject to waterlogging, resulting in the loss of fine fractions. Sedimentation In areas far from the reservoir, microaggregates are protected, which increases the accumulation process of microaggregates. Based on the above findings, it can be concluded that the amount of micro aggregates in soils located near the reservoir has decreased, which has led to the disruption of soil structure, an increased risk of erosion, and a decline in agronomic quality. To preserve soil micro aggregates, agro technical measures such as the application of organic matter and regulation of water level fluctuations are recommended. CONCLUSION The analysis results demonstrate that the morphological and ecological conditions of soils and vegetation communities surrounding the Kattakurgan Reservoir vary significantly. With increasing distance from the reservoir, soil moisture decreases, mineralization levels rise, and sandy layers become dominant in the soil’s mechanical composition. These changes directly affect vegetation cover — as the physical and chemical properties of the soil deteriorate, the density and diversity of plant species decline. Furthermore, the results reveal that the ecosystem relationships between soil and vegetation are highly complex and interdependent. A deeper study of the geochemical processes occurring in this area is crucial for establishing a solid scientific foundation for effective soil restoration and the preservation of biological diversity. The findings of this research can serve as a basis for developing practical recommendations aimed at preventing soil degradation, selecting appropriate plant species, and organizing effective eco-restoration measures SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 11 NOVEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 126 in the areas surrounding the Kattakurgan Reservoir. Ultimately, these efforts will contribute to ensuring regional ecological stability and promoting the sustainable use of natural resources. Acknowledgments. The authors express their gratitude to the Agency for Innovative Development of the Republic of Uzbekistan and the leadership of the Faculty of Biology and ecology, who funded this research under the IL-9224094166 project. REFERENCES 1. 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