MONITORING OF THE AYDAR–ARNASAY LAKE SYSTEM AND ASSESSMENT OF THE CHEMICAL COMPOSITION OF COLLECTOR WATER INFLOWS INTO THE LAKE ECOSYSTEM

ISSUE 11 Acceptance of papers November, 2025 Acceptance of papers Published monthly Topics economics, technology, social sciences INNOVATION SCIENCE AND TECHNOLOGY t.me/scupus_IST2100 2https://ist-journal.uz t.me/scupus_IST2100 Sharipov Kongiratbay Avezimbetovich, Doctor of Technical Sciences (DSc), Professor Ahmed Aziz Ismail Doctor of Technical Sciences (DSc), Professor (Egypt) Cham Tat Huei, Doctor of Philosophy (PhD), Professor (Malaysia) Asongu Simplice Doctor of Philosophy in Economics (PhD), Cameroon Abdurakhmanova Gulnora Kalandarovna, Doctor of Economic Sciences (DSc), Professor Lee Chin Doctor of Philosophy in Economics (PhD), (Malaysia) Muhammad Imran Sadiq Doctor of Philosophy in Economics (PhD), Professor, Malaysia Rui Dang Doctor of Chemistry (DSc), Professor, China Zahoor Ahmed Doctor of Philosophy in Economics (PhD), Turkey Shujaat Abbas Doctor of Philosophy in Economics (PhD), Russia Tina A Coffelt Doctor of Philosophy in Educational Sciences (PhD), USA Electronic publication, Issue 11. 63 pages. Approved for publication on November, 2025. EDITOR-IN-CHIEF: Mirzaliyev Sanjar Makhamatjon ugli DEPUTY EDITOR-IN-CHIEF: Makhmudov Nosir Makhmudovich DSc., Prof., Academican DEPUTY EDITOR-IN-CHIEF: Ochilov Bobur Bakhtiyor ugli – Senior lecturer at TSUI THE SCIENTIFIC-POPULAR ELECTRONIC JOURNAL "INNOVATION SCIENCE AND TECHNOLOGY" HAS BEEN REGISTERED UNDER THE NUMBER C-5669633 BY THE AGENCY FOR INFORMATION AND MASS COMMUNICATIONS (AOKA) OF THE REPUBLIC OF UZBEKISTAN, EFFECTIVE FROM OCTOBER 9, 2024. The scientific electronic journal “Innovation Science and Technology” has been included in the list of scientific publications recommended for the publication of main scientific results of dissertations for the award of PhD and DSc degrees in economics and technical sciences, in accordance with the Resolution No. 370 of the Presidium of the Higher Attestation Commission of the Republic of Uzbekistan, dated May 8, 2025. CONTACTS Phone: +998 50 737 87 88 Website: https://ist-journal.uz Email: [email protected] Editorial board: CONTENTS SOCIAL, ECONOMIC, SCIENTIFIC, AND TECHNICAL ACADEMIC JOURNAL11/2025 t.me/scupus_IST2100 3 https://ist-journal.uz CONTENTS POVERTY AND DEVELOPMENT ...............................................................................................................................................14 Kholmirzayev Abdulhamid Khapizovich WAYS TO ACHIEVE ECONOMIC STABILITY THROUGH THE IMPLEMENTATION OF INNOVATIVE TECHNOLOGIES IN INDUSTRIAL ENTERPRISES ..............................................................................................................23 Sadriddinov Bakhtiyor STRUCTURE–PROPERTY RELATIONSHIP OF ORGANOSILICON MATERIALS: EVALUATION BASED ON THERMOGRAVIMETRIC ANALYSIS ..................................................................................................................36 Tosheva Dilfuza Farxodovna, Siddikov Ikrom Iminjonovich, Rakhimov Firuz Fazlidinovich ''CREATING AN ALGORITHM AND SOFTWARE TOOL FOR PERSONAL IDENTIFICATION USING FACIAL SCANNING TO PROTECT THE OPERATING SYSTEM'' ...................................................................... 43 Usmonov Maxsud Tulqin o‘g‘li ENSURING INTERDISCIPLINARY INTEGRATION BASED ON MOBILE LEARNING TECHNOLOGIES .......... 51 Zaripov Olimjan Kuvandiq son MONITORING OF THE AYDAR–ARNASAY LAKE SYSTEM AND ASSESSMENT OF THE CHEMICAL COMPOSITION OF COLLECTOR WATER INFLOWS INTO THE LAKE ECOSYSTEM.............................................55 Erkabayev Furkat Ilyasovich, Madrimov Rajabboy Masharipovich, Aminov Khamza Khusanovich SOCIAL, ECONOMIC, SCIENTIFIC, AND TECHNICAL ACADEMIC JOURNAL INNOVATION SCIENCE AND TECHNOLOGY 11/2025 t.me/scupus_IST2100 55 https://ist-journal.uz MONITORING OF THE AYDAR–ARNASAY LAKE SYSTEM AND ASSESSMENT OF THE CHEMICAL COMPOSITION OF COLLECTOR WATER INFLOWS INTO THE LAKE ECOSYSTEM Erkabayev Furkat Ilyasovich Head of Laboratory, Doctor of Technical Sciences, Professor E-mail: [email protected] Madrimov Rajabboy Masharipovich Head of Laboratory, Doctor of Biological Sciences (PhD), Senior Research Fellow Aminov Khamza Khusanovich Deputy Director, Doctor of Technical Sciences, Professor E-mail: [email protected] Abstract: The Aydar–Arnasay lake system is located in a natural depression in the southern part of the Kyzylkum Desert, southwest of the Shardara Reservoir. It is a system of endorheic (closed) lakes that receive water from the collector– drainage network and the Shardara Reservoir. Over the past 50 years, the lake system has accumulated 2.5 times more water than all 53 regional reservoirs combined. Studies conducted on the concentrations of major pollutants in the Aydar– Arnasay lake system revealed significant exceedances of almost all parameters. The most pronounced factor is the total mineralization of water, which exceeds established standards by more than 25 times, thereby affecting the system’s biodiversity and overall ecological stability. Key words: Aydar–Arnasay lake system, water quality, monitoring, collector–drainage water, mineralization, pollution, ecological condition, biodiversity, hydrochemistry, water resources. Annotatsiya: Aydar–Arnasoy ko‘llar tizimi Qizilqum cho‘lining janubiy qismida, Shardara suv omborining janubi-g‘arbida joylashgan tabiiy pasttekislikda joylashgan. Bu tizim kollektоr–drenaj tarmoqlari va Shardara suv omboridan suv oluvchi oqmas ko‘llar majmuasidir. So‘nggi 50 yil davomida ko‘llar tizimida mintaqadagi 53 ta suv ombori umumiy hajmidan 2,5 baravar ko‘p suv to‘plangan. Aydar–Arnasoy ko‘llar tizimidagi suvning asosiy ifloslantiruvchi moddalar konsentratsiyasini o‘rganish bo‘yicha olib borilgan tadqiqotlar deyarli barcha ko‘rsatkichlar bo‘yicha sezilarli ortiqcha miqdorlar aniqlanganini ko‘rsatdi. Eng e’tiborga molik holat — bu suvning umumiy mineralizatsiyasi bo‘lib, u belgilangan me’yorlardan 25 baravardan ortiqni tashkil etadi va tizimdagi biologik xilma-xillikka hamda ekologik barqarorlikka salmoqli ta’sir ko‘rsatadi. Kalit so‘zlar: Aydar–Arnasoy ko‘llar tizimi, suv sifati, monitoring, kollektоr–drenaj suvlari, mineralizatsiya, ifloslanish, ekologik holat, biologik xilma-xillik, gidrokimyo, suv resurslari. Аннотация: Айдар-Арнасайская озёрная система расположена в природной впадине на юге пустыни Кызылкум, к юго-западу от Шардаринского водохранилища. Это система бессточных озёр, питаемая водой из коллекторнодренажной сети и Шардаринского водохранилища. За последние 50 лет в озёрной системе накопилось воды в 2,5 раза больше, чем во всех 53 водохранилищах региона, вместе взятых. Проведённые исследования по изучению концентраций основных загрязняющих веществ в воде Айдар-Арнасайской озёрной системы выявили значительные превышения практически всех показателей. Наиболее выраженным является общий показатель минерализации воды, превышающий нормативы более чем в 25 раз и оказывающий существенное влияние на биологическое разнообразие системы и её общее экологическое состояние. Ключевые слова: Айдар-Арнасайская система озёр, качество воды, мониторинг, коллекторно-дренажные воды, минерализация, загрязнение, экологическое состояние, биологическое разнообразие, гидрохимия, водные ресурсы. SOCIAL, ECONOMIC, SCIENTIFIC, AND TECHNICAL ACADEMIC JOURNAL INNOVATION SCIENCE AND TECHNOLOGY 11/2025 t.me/scupus_IST2100 56 https://ist-journal.uz INTRODUCTION The Aydar–Arnasay Lake System (AALS) is a complex of endorheic lakes, including Aydarkul, Tuzkan, and the Eastern Arnasay lakes, located in the Republic of Uzbekistan with a total area of about 4,000 km². The AALS lies approximately 260 kilometers from Tashkent, in the middle reaches of the Syrdarya River, south of the Shardara Reservoir (Republic of Kazakhstan), within the territories of the Jizzakh and Navoi regions of Uzbekistan. It occupies a natural depression in the southern part of the Kyzylkum Desert. Historically, the bottom of the vast AALS consisted of dry salt flats and solonchaks. Until the development of the Mirzachul (Hunger Steppe) region, only the Tuzkan depression was periodically filled with water, mainly supplied by the Kly River. In 1969, during the regulation of the Syrdarya River flood peak, more than 21 km³ of water was discharged from the Shardara Reservoir into the Arnasay lakes. As a result, a significant restructuring of the hydrological network occurred within the Eastern Arnasay lakes, and the Aydarkul basin was filled. Following the breach of the natural embankment, Aydarkul merged with Tuzkan, forming a unified lake system now known as the Aydar–Arnasay Lake System. Over the years, this newly formed hydroecosystem has developed favorable conditions for the rapid growth of flora and fauna. At present, the AALS contains more water than all the reservoirs of the Central Asian region combined. The inflow components of the AALS water balance include water from the Shardara Reservoir, collector–drainage inflows discharged into the lake depressions, atmospheric precipitation over the lake surface, and groundwater directly entering the system [1]. Since the formation of the AALS, its surface area, water volume, the amount of inflow from the Shardara Reservoir and collector–drainage network, as well as water salinity and natural evaporation, have undergone significant changes. Essentially, the system functions as a natural receiver of collector–drainage and discharge waters from the irrigation networks of the Syrdarya and Jizzakh regions. Its location in an arid zone, the reduction of freshwater inflow from the Shardara Reservoir, and the increased discharge of collector–drainage water have led to a rise in lake water mineralization and pollution. The mineralization level of the lake system has been increasing annually, and the decrease—or even complete absence—of water discharge from the Shardara Reservoir during 2000–2022 has adversely affected the ecological condition of the AALS [2–4]. Over the past fifty years, the Aydar–Arnasay Lake System has served not only as an important fishery water body but also as a vital habitat for numerous bird species, including rare and endangered ones listed in the International Red Book and the Red Book of Uzbekistan. The area supports the natural reproduction of dozens of fish species and provides nesting and resting sites for a wide variety of birds such as mallards, ruddy shelducks, red-headed and red-crested pochards, gray geese, pelicans, sandpipers, herons, swans, cormorants, and many others. In the reed and tugai thickets live pheasants, wild boars, jackals, badgers, reed and steppe cats, among other animals. The vegetation spectrum of the lakes is diverse — from hydrophilic plants growing near the water’s edge to desert halophytic associations. In 2008, the AALS was included in the Ramsar List of Wetlands of International Importance. According to environmental specialists, this inclusion has drawn the attention of the global community to the necessity of preserving and improving the ecological stability of this unique biosystem [5–7]. The hydrological, hydrochemical, and hydrobiological regimes of the system are unstable; many parameters change rapidly, making it extremely difficult to trace their dynamics even with available cartographic and analytical materials. Consequently, many modern publications contain incomplete or outdated information. Under such conditions, there is an urgent need for an advanced system of environmental monitoring for water bodies — incorporating a stationary observation network, comprehensive field expeditions equipped with modern instruments, and the application of remote sensing and satellite data. The present study highlights part of the conducted research aimed at investigating, analyzing, and assessing the dynamics of water resource changes within the Aydar–Arnasay Lake System. LITERATURE REVIEW The Aydar–Arnasay Lake System (AALS) has been extensively studied for its hydroecological dynamics, water balance, and anthropogenic impacts. Early surveys (2011) documented the system’s artificial formation due to collector–drainage discharges from the Syrdarya Basin and the Shardara Reservoir, emphasizing its mixed natural–anthropogenic origin and ecological significance. Recent studies highlight the growing ecological stress in the system. Taylakov and Khasanova (2022) found a steady rise in mineralization and pollution levels caused by reduced freshwater inflows and dominant collector–drainage inputs. Kiriyigitov (2022) predicted long-term ecological degradation linked to increased salinity, while Ergasheva (2022) identified the Kly and Akbulak collectors as key sources affecting water composition through irrigation return flows. SOCIAL, ECONOMIC, SCIENTIFIC, AND TECHNICAL ACADEMIC JOURNAL INNOVATION SCIENCE AND TECHNOLOGY 11/2025 t.me/scupus_IST2100 57 https://ist-journal.uz The biological impacts are equally pronounced. Mustafaeva et al. (2022) noted shifts in hydrobiont species composition due to salinization, and Khudoyberdieva and Esanova (2022) reported a decline in traditional fish species, replaced by more salt-tolerant forms. Tuynazarova and Kalonov (2022) emphasized sustainable fishery management and regular ecological monitoring as essential for maintaining biodiversity. From a geophysical perspective, Vereshchagina et al. (2013) showed that dust and salt transfer from drying lake surfaces contributes to soil salinization in adjacent lands, while Chub (2007) linked climate change and increasing aridity to hydrological instability in the region. Overall, the literature demonstrates that although the AALS remains an important ecological and economic water body, it faces increasing challenges from salinization and human-induced water regulation. These findings provide a scientific basis for adaptive management measures, including hydrological stabilization, continuous monitoring, and transboundary cooperation with Kazakhstan. RESEARCH METHODOLOGY The research was conducted in June 2023. The Aydar–Arnasay Lake System (AALS) (40°56′13″ N, 66°03′18″ E) was selected as the primary object of study (Fig. 1). Water samples were collected from eight monitoring points located at the main inflow sites of the AALS: the Kly, Okbulak, Central Mirzachul Collector (Zolotoy Most), and Pogranichny collectors. Additional sampling sites included the Tuzkan Lake near the settlements of Navruz, Chimkurgan, and Uchkulach, as well as the Aydarkul Lake near the settlement of Kyzylkum (Fig 1). Figure 1. The Aydar–Arnasay Lake System Research Areas and Study Objects The Aydar–Arnasay Lake System (AALS) is an endorheic complex of lakes in Uzbekistan that includes Aydarkul, Tuzkan, and the Eastern Arnasay lakes. It lies within a saline depression in the easternmost part of the Kyzylkum Desert, southwest of the Shardara Reservoir. The total area of the lakes is approximately 4,000 km². As a result of the discharge of collector–drainage runoff from the Mirzachul (Hunger Steppe) irrigation system and partial release of floodwaters from the Shardara Reservoir, water flooded the Prituzkan Lowland, raised the level of Lake Tuzkan, and filled the saline basin of Aydar. In 1969, during an extreme flood in the Syrdarya River basin, the Arnasay Depression was used as a natural water accumulator. The total discharge from the Shardara Reservoir reached 21.8 km³, leading to the formation of the Arnasay Lake System. The level of Lake Tuzkan rose by approximately 10 meters, while in the Upper Arnasay lakes, it decreased by 2–3 meters due to water transfer into the Aydar depression. SOCIAL, ECONOMIC, SCIENTIFIC, AND TECHNICAL ACADEMIC JOURNAL INNOVATION SCIENCE AND TECHNOLOGY 11/2025 t.me/scupus_IST2100 58 https://ist-journal.uz According to N.E. Gorelkin and A.M. Nikitin, a continuous lake system was formed with a total length of 155 km, a maximum width of 33 km, a volume of up to 20 km³, and a water surface area of 2,300 km². The Aydar–Arnasay Lake System exhibits an intra-annual hydrological cycle characterized by winter–spring filling, summer drawdown, and autumn–winter equilibrium phases. Lake Aydarkul is the largest endorheic lake in northeastern Uzbekistan and functions as an artificial reservoir within the Arnasay system. In 2005, its volume reached 44.3 km³, and today the lake covers around 3,000 km², extending almost 250 km in length and up to 15 km in width. The water mineralization level in Aydarkul is relatively low, averaging 2 g/L (0.2%). Numerous fish species—such as carp, pike perch, bream, catfish, asp, sabrefish, and snakehead—have been introduced and now form the basis of the region’s fisheries. Lake Tuzkan, the second largest water body of the system after Aydarkul, is a brackish, endorheic lake of partly natural origin. Unlike the other Arnasay lakes, which were entirely formed from discharge waters, Tuzkan has a prehistoric natural origin later modified by human activity. The lake is situated in the Farish District of the Jizzakh Region, about 56 km northeast of the city of Jizzakh, in the southeasternmost part of the Kyzylkum Desert. Within the AALS, Tuzkan occupies the southernmost position, connecting to Aydarkul in the northwest. The lake stretches from northwest to southeast in an approximately triangular shape, with a current length of 35 km and an average width of 25 km, reaching 35 km in the eastern bays. The Upper Arnasay Reservoir has a surface area of 140 km² and a relatively low mineralization level of up to 1.5 g/dm³. The shape and boundaries of Lake Tuzkan are not constant. About 15–20% of its surface is covered by aquatic vegetation. The northeastern shoreline is highly indented, forming numerous narrow and elongated shallow bays, some of which have become isolated into smaller lagoons. The surrounding areas often consist of saline flats (solonchaks), interspersed with small islands. The adjacent landscape comprises desert plains with saxaul shrubs and reed thickets in wetter zones. The southern shoreline is more even, while in the southern extremity, the Kly River (known as the Sanzar in its lower course), together with the Akbulak and Central Mirzachul Collectors, flows into Tuzkan. Near this large water body lie smaller saline lakes such as Togay and Tuzchikudukkul, and the surrounding terrain is partially marshy. The southwestern shore merges with the low Pistalitau Ridge, a spur of the Nuratau Range, while the western margin transitions into sandy dunes and isolated hills [8]. Soil and Climatic Characteristics of the Study Area To the east of the Aydar–Arnasay Lake System (AALS), the dominant soils are gray-brown oasis soils, significantly modified by irrigated agriculture. These include newly irrigated meadow–gray soils of medium loamy texture, exhibiting moderate to strong salinization. In the immediate vicinity of Lake Tuzkan, light gray loamy and sandy loam soils prevail, interspersed with solonchaks and saline patches. To the south and southeast of the Upper Arnasay Reservoir, light gray loamy and sandy loam soils are also common, often displaying moderate to severe salinization [8]. In the shallow depressions and lagoons that become exposed during seasonal drops in the Tuzkan water level, saline and solonchak soils develop. From these areas, salt deflation and subsequent aeolian transport contribute to the salinization of adjacent lands. The soils in the desiccated zones of these water bodies— typical for arid regions—are composed primarily of sedimentary materials, such as weakly vegetated loess and sandy soils, bottom silts, and evaporitic solonchaks (often locally called shors). Frequently, these surfaces are covered by a powdery salt crust, within which the salt content in the upper 1.5 cm layer reaches 45–60% [8]. The climate of the study area is sharply continental, characterized by cold, low-snow winters and hot, arid summers. The AALS is situated at the boundary of two distinct climatic subregions—the irrigated zone of the Mirzachul (Hunger Steppe) and the Kyzylkum Desert—each possessing unique hydrometeorological characteristics. Within the study area, the degree of climatic continentality increases progressively from east to west. The mean long-term air temperatures vary from approximately 0 °C in winter to +29 °C in summer. Along the depressions of Aydarkul and Tuzkan Lakes, which stretch for about 180 km in a west–northwest direction, the temperature gradient reaches 3–4 °C, while humidity differences range between 4–5%. This pattern reflects a gradual intensification of continental climatic features toward the west. The thermal regime of the lakes is typical of southern shallow-water ecosystems, marked by rapid warming during the spring season, high summer maxima—reaching up to +30 °C according to field observations—and an extended ice-free period. In recent years, ice phenomena have been occasionally observed, lasting from 10 to 30 days; however, based on climatic records, the average duration of ice cover rarely exceeds 5–10 days. On average, stable ice formation events occur approximately once every 10–11 years [9]. The research tasks included water sampling and laboratory–analytical investigations. In field conditions, the following parameters were measured on-site: water temperature and pH. In laboratory conditions, the following physicochemical indicators were analyzed: Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), suspended solids, water hardness, total mineralization, SOCIAL, ECONOMIC, SCIENTIFIC, AND TECHNICAL ACADEMIC JOURNAL INNOVATION SCIENCE AND TECHNOLOGY 11/2025 t.me/scupus_IST2100 59 https://ist-journal.uz chlorides, sulfates, ammonium nitrogen, nitrite nitrogen, phosphates, petroleum hydrocarbons, and the concentrations of copper (Cu²⁺), hexavalent chromium (Cr⁶⁺), and ferric iron (Fe³⁺) ions. All laboratory and analytical studies were carried out in the laboratories of the State Specialized Inspection for Analytical Control under the Ministry of Ecology, Environmental Protection, and Climate Change of the Republic of Uzbekistan, as well as in the laboratories of the Center for State Sanitary and Epidemiological Supervision of the Republic of Uzbekistan. Field investigations, including sample collection and sample preparation, were conducted in accordance with nationally approved methodologies adopted in Uzbekistan and in compliance with the “List of Certified and Provisionally Approved Methods for Determining the Concentration of Pollutants in Natural and Waste Waters.” ANALYSIS AND RESULTS The conducted studies demonstrate that the surface water temperature at the investigated sampling points did not exceed 11 °C, which is typical for the spring season. The pH values fully correspond to the maximum permissible concentrations (MPC) standards and do not exceed 8.2, indicating a stable chemical environment. The Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD₅) are among the most important indicators used in water quality assessment. COD represents the amount of oxygen required for the chemical oxidation of pollutants, while BOD₅ reflects the amount of oxygen needed for the biological decomposition of organic contaminants by microorganisms. In the Aydar–Arnasay Lake System, COD values range from 17.0 to 80.0 mg/L, exceeding the MPC by approximately 2.6 times, while BOD₅ values vary between 21.4 and 43.0 mg/L, surpassing the standard limits by 3.5–7.2 times. These results indicate active oxidation processes and elevated levels of organic matter in the lake water. The suspended solids present in natural water typically consist of clay particles, sand, silt, and suspended organic and inorganic matter, as well as plankton and other microorganisms. In the studied samples, the concentration of suspended solids exceeds the permissible levels by 1–18.2 times. This variation is primarily influenced by seasonal factors (particularly in spring), the pattern of surface runoff and wastewater inflow, and anthropogenic activities such as agricultural operations in nearby territories. Suspended particles significantly affect water transparency, light penetration, and thermal conditions, which in turn influence the absorption of toxic impurities, sediment composition, and deposition rates within the aquatic ecosystem. Increased turbidity also promotes the redistribution of fine particles and facilitates the accumulation of contaminants in bottom sediments, thereby affecting the self-purification capacity of the water body. As a result of the continuous discharge of collector–drainage waters into the lake depressions, the Aydar– Arnasay Lake System has experienced a noticeable increase in pollution levels and a significant rise in overall mineralization. This trend indicates the influence of external inflows on the hydrochemical balance of the ecosystem, emphasizing the importance of regular environmental monitoring and mitigation measures (Table 1). Table 1. Results of Water Sample Analyses from the Aydar–Arnasay Lake System Parameters MPC (mg/L or specified unit) Collector Kly Collector Okbulak Central Mirzachul Collector Collector Pogranichny Lake Tuzkan (Navruz Village) Lake Tuzkan (Chimkurgan Village) Lake Tuzkan (Uchkulach Village) Lake Aydarkul (Kyzylkum Village) Exceedance of MPC 1 3 4 5 6 2 7 8 9 12 рН 6,5-8,5 7,17 8,24 7,73 8,0 8,13 7,36 8,01 8,25 Within limits COD 30,0 32,3 47,2 18,8 25,4 31,0 80,0 17,0 24,0 2.6 × higher BOD₅6,0 40,0 30,9 34,1 34,1 43,6 21,4 26,5 37,8 3.5 – 7.2 × higher Suspended solids (mg/L) 30,0 23,0 13,0 35,0 16,0 21,0 547,0 12,0 20,0 1.1 – 18.2 × higher Hardness (mg-eq/L) 7,0 44,0 86, 40,0 94,0 83,0 92,0 89,0 94,0 5.6 – 13.1 × higher SOCIAL, ECONOMIC, SCIENTIFIC, AND TECHNICAL ACADEMIC JOURNAL INNOVATION SCIENCE AND TECHNOLOGY 11/2025 t.me/scupus_IST2100 60 https://ist-journal.uz Total mineralization (mg/L) 1000,0 5406,0 10184,0 6090,0 6306,0 18758,0 15200,0 15152,0 26534,0 5.4 – 26.5 × higher Chlorides (mg/L) 350,0 491,3 1965,4 912,5 772,1 2035,5 2386,5 4141,2 2105,7 1.4 – 11.8 × higher Sulfates (mg/L) 500,0 1473,2 2259,4 1164,6 1138,7 2251,2 2248,7 2296,0 2179,9 1.2 – 4.6 × higher Ammonium nitrogen (mg/L) 2,0 1,8 1,8 1,8 0,98 8,35 1,87 1,80 4,63 2.3 – 4.1 × higher Nitrite nitrogen (mg/L) 0,5 0,02 0,02 0,02 0,02 0,01 0,02 0,01 0,01 Within limits Phosphates (mg/L) 1,0 0,003 0,005 0,092 0,005 0,004 0,004 0,003 0,004 Within limits Petroleum hydrocarbons (mg/L) 0,3 0,26 0,27 0,20 2,54 19,36 19,36 0,62 5,23 2.0 – 64.5 × higher Copper (Cu²⁺)1,0 1,0 0,0034 0,0028 1,0 1,0 0,0046 0,003 1,0 Within limits Chromium (VI) 0,1 0,1 0,11 0,07 0,1 0,1 0,11 0,11 0,1 1.1 × higher Iron (III) 0,5 0,11 0,3 0,11 0,21 0,19 0,21 0,14 0,19 Within limits Discussion of Hydrochemical and Ecological Findings Water hardness represents the combined concentration of all dissolved substances (excluding gases) that dissociate into charged particles—ions. In the analyzed samples, the total hardness exceeded the maximum permissible concentrations (MPC) by 5.6–13.1 times. According to national environmental regulations, the allowable total mineralization for non-potable surface waters is 1,000 mg/L, including up to 350 mg/L of chlorides and 100–500 mg/L of sulfates. In the studied samples, total mineralization exceeded these limits by 5.4–26.5 times. The chloride concentrations ranged from 491.3 to 4,141.2 mg/L, and sulfates from 1,138.7 to 2,296.0 mg/L, rendering the water unsuitable for any practical use. Long-term monitoring data from the Western Arnasay Hydrometeorological Station indicate a progressive increase in the average annual mineralization of inflowing waters—from 8.25 g/L in 2006 to 10.53 g/L in 2020, and 11.6 g/L in 2022. For comparison, the average salinity of the world’s oceans is 30–35 g/L; in the central Caspian Sea, mineralization varies between 1.4 and 13 g/L, in the northern Caspian (Volga Delta) from 0.2 to 11 g/L, while the Aral Sea historically reached 110–210 g/L. Nitrogen analysis revealed that ammonium nitrogen concentrations ranged from 0.98 to 8.35 mg/L, exceeding the standard by up to 4.1 times. Nitrite nitrogen values (0.01–0.02 mg/L) complied with MPC norms, and phosphate concentrations were within acceptable limits, not exceeding 0.092 mg/L . Petroleum hydrocarbons surpassed the MPC of 0.3 mg/L by 2.0–64.5 times, with the highest concentrations—19.3 mg/L—recorded near the settlements of Navruz and Chimkurgan. Concentrations of copper and iron (III) remained below their respective MPC values of 1.0 mg/L and 0.5 mg/L, while chromium (VI) slightly exceeded the norm by 1.1 times . The gradual increase in total mineralization, sulfates, and chlorides in the Aydar–Arnasay Lake System (AALS) over an extended period has affected the fish population and reduced its commercial significance. For instance, in 1991, common carp (Cyprinus carpio) accounted for 45.1 % of the total catch, whereas by 2010 its share had declined to 18.2 %. Although the overall fish catch volume decreased only 1.2 times, the catch of carp dropped more than threefold compared with 1991. Since 2005, catfish (Silurus glanis) have been absent from recorded catches. The harvesting of asp (Aspius aspius), bream (Abramis brama), and other herbivorous species has become irregular, with occasional multi-year absences from catches. The principal factors contributing to the decline in fish stocks include: • a steady increase in water mineralization, which impedes natural fish reproduction; • insufficient regulation and monitoring of fishing and aquaculture enterprises; • lack of fish stock restoration programs and measures to preserve and enhance aquatic biodiversity; • non-scientific fishing practices, where lessees lack accurate data on fish species composition and population structure;