Winter Low Water Research Articles

HYDROLOGICAL REGIME OF THE IKVA RIVER (SOUTHERN BUG BASIN)

This article reveals the issue of a detailed study of the hydrological regime of small plain rivers in the presence of data from regular observations. The Ikva River, the object of our study, belongs to the Southern Bug basin and is its small tributary, on which a hydrological indicators monitoring station has been operating since 1939. Since 1955, a continuous series of observations has been available, which allowed us to carry out a detailed analysis and description of the main hydrological characteristics – levels (H, cm) and water flows (Q, m3/s), to evaluate their fluctuations in time, cyclicity and the relationship Q= f(H). The construction of the corresponding graphs confirmed that the Ikva River is characterized by cyclic flow fluctuations, and since 1965 we have already observed two complete cycles of fluctuations in water level lasting about 30 years. At the moment (2022), the flow indicators record the minimum of the low-water phase of the second cycle, so we can expect an increase in the flow in the near future and the transition to a new cycle. We have also determined that the amplitude of water level fluctuations of the Ikva River at the post in the village of Stara Sinyava over many years is 60 cm, and varies from a minimum of 75 cm (1957) to 135 cm (1981), that is, a little more than 0.5 meters in total. This agrees quite well with the literature data and estimates of other authors, considering the plain nature and small size of this object. The long-term course of the water levels of the Ikva River is characterized by a slight increase, while the long-term fluctuations of the average water flow at this station also do not have a large amplitude: from 0.66 m3/s (2020) to 3.64 m3/s (1979) i.e. 2.98 m3/s. At the same time, the general trend line for multi-year cost fluctuations shows, on the contrary, a tendency to decrease them. Therefore, we can state that the graphs of multi-year costs and levels are not synchronous, which is evidence of the manifestation of vertical channel deformations in the area of the post. As the water level increases, the decrease in water consumption is a direct sign of siltation of the riverbed in this area and the raising of the bottom level due to accumulative processes over a long period. The largest amplitudes are characterized by the parameters of the maximum runoff, that is, the amplitudes of the maximum levels (∆Нmax = 168 cm) and maximum flows (∆Qmax = 92.9 m3/s), which is not surprising, because we are talking about the characteristics of the period of floods and inundations, which are always marked by significant fluctuations in time. An interesting fact, identified for us for the first time, is that the characteristics of the minimum flow of the closed period of the channel are characterized by higher amplitudes than the characteristics of the open period. Therefore, the summer low water is more pronounced than the winter low water, which means that in the warm period (summer), the lack of precipitation more clearly provokes a decrease in water levels and flows in the channel system than during the winter period. The reason can be both winter thaws and the specifics of the groundwater regime. Key words: hydrological regime; water level; water flows; hydrological cycle; low water phase; high water phase; relationship Q=f(H).

Оценка климатического и антропогенного вкладов в многолетние колебания сезонного стока рек бассейна р. Урал

The analysis of long-term fluctuations in seasonal runoff of the Ural basin rivers is performed, statistical relationships between runoff and the main meteorological factors (air temperature and precipitation) are estimated. Weather stations with the highest correlation between the main meteorological factors and seasonal runoff of the Ural, Sakmara, and Ilek rivers are selected. Empirical dependences of seasonal runoff on air temperature and total precipitation are substantiated for three hydrological stations located on these rivers during the period with minimum anthropogenic load on water resources (slightly disturbed runoff). Their statistical and graph-analytical analysis showed that they have a fairly high correlation for the period of spring flooding and the summer-autumn season, and the dependences for the period of winter low water are much less accurate. Based on the constructed dependencies for a period of significant anthropogenic load on the water resources of the region, a comparative analysis of the calculated (undisturbed) seasonal runoff of the Ural, Sakmara, and Ilek rivers with the observed one is performed.

Долгосрочная оценка режима минимального зимнего стока рек бассейна озера Севан при изменении климата

Introduction. Analysis and assessment of the statistically significant consequences of climate change for the long-term minimum 30-day winter runoff of rivers in the Lake Sevan basin is of significant interest to consumers and water resource management, being an important hydrological issue. The relevance of consideration of the issue is due to the fact that for Armenia Lake Sevan is a strategic reservoir of fresh water, a large water management complex, a source of water for hydropower and agricultural irrigation, an object of tourism and recreation. Issues of formation and calculation of the minimum runoff of rivers in the lake basin. Sevan were discussed in works, the analysis of the spatial-temporal distribution of the winter minimum decade-day, monthly and 30-day runoff can be found, for example, in works.In contrast to the listed works, in this study a technique for assessing the statistically significant consequences of climate change for the hydrological regime in relation to small foothill watersheds of the rivers of the Lake Sevan basin (Republic of Armenia) is considered. The values of the minimum 30-day water runoff within the study area can be used when calculating standards for permissible discharges into rivers, to assess natural groundwater resources, as indicators of the extremeness of river flow and in other water management calculations. Research methods and materials. The methodology is based on a probabilistic model of the formation of long-term river runoff, which is approximated by a system of linear equations for the initial statistical moments. As the source material were used the data of actual hydrometeorological observations (minimum 30-day winter river runoff, air temperature and precipitation) of the “Center for Hydrometeorology and Monitoring” of the SNCO of the Ministry of Environment of the Republic of Armenia. Research results. The results of approbation of the methodology on retrospective material are presented, taking into account possible climate change both towards warming and towards cooling.The conditions for the applicability of the methodology to small foothill watersheds for assessing the minimum 30-water winter river runoff are identified. The obtained satisfactory results made it possible to assess the impact of climate change for the minimum runoff using the IPCC climate scenarios. Three climatic scenarios are considered, the model of the Max Planck Institute with a monthly time resolution. Conclusions. As a result, watersheds of rivers in the basin of Lake Sevan were identified, in which significant deviations of the predicted average annual values of the minimum 30-day winter runoff and the coefficients of its variation from the actual ones in the implementation of the considered scenarios can be expected. An analysis of the obtained results is given from the point of view of taking possible preventive measures, including strategic planning of the use of water resources in winter low water, in case of climate change.

Hydrochemical characteristics of left-bank tributaries of the Dniester within Ternopil Oblast


 
 
 The purpose of this article is to study the chemical composition of water and the hydrochemical regime of the left-bank tributaries of the Dniester within the Ternopil Oblast at 9 monitoring sites on the Zolota Lypa, Koropets, Strypa, Seret, Nichlava, and Zbruch Rivers. Water quality monitoring data from the State Agency of Water Resources of Ukraine for the period from 1993 to 2020 were used. The hydrographic assessment of the territory following the Water Code of Ukraine showed the presence of two medium-sized rivers (Seret and Zbruch) and four small rivers among the studied rivers. The chemical composition of the water was analyzed by the following groups of components: major ions and water salinity; physicochemical parameters; and biogenic components (nitrogen and phosphorus compounds). It was found that the water of most studied rivers is calcium bicarbonate by hydrochemical type. The water of the Nichlava River is calcium bicarbonate-sulfate. The average annual salinity of the water of the studied rivers varies from 476 mg∙dm-3 to 699 mg∙dm-3. It was determined that the water of most rivers is moderately fresh in terms of mineralization. The water of the Nichlava River is fresh with high mineralization. The hydrochemical regime of rivers is generally related to the hydrological regime. The minimum concentrations of the main ions and salinity values of the studied rivers are observed during the summer-autumn low water mark, which is explained by the significant amount of precipitation and the presence of floods during this period. In winter, the maximums of these indicators are observed. Among the biogenic compounds (ammonium, nitrite, nitrate, phosphate), the clearest manifestation of the hydrochemical regime was recorded for nitrate. The minimum NO3– concentrations are observed in the summer and autumn low-water periods when nitrates are consumed for the development of aquatic plants. In the autumn period, with the death of aquatic plants, nitrates accumulate, and during the winter low water, their maximum average content is observed. The analysis of the monitoring system of the State Agency of Water Resources of Ukraine for the content of the studied components in the water of the left-bank tributaries of the Dniester over a multi-year period for all samples showed that their concentrations were within the regulatory requirements, except for one case. Particularly, in the water of the Nichlava – Borshchiv River, an ammonium concentration of 15 mg∙dm-3 was recorded, which was 7.5 times higher than the standard (August 2, 2000).
 
 

АНАЛІЗ ВНУТРІШНЬОРІЧНОГО РОЗПОДІЛУ СТОКУ ВОДИ ЛІВОБЕРЕЖНИХ ПРИТОК ДНІСТРА В МЕЖАХ ТЕРНОПІЛЬСЬКОЇ ОБЛАСТІ

The Dniester basin is characterized by heterogeneity and diversity of water runoff formation conditions. Therefore, the issue of studying the basin of this river and its tributary basins has always received attention from scientists. Despite a fairly large number of publications, especially those analyzing the hydrological regime of the rivers of Ternopil, there are still no comprehensive studies of river-basin systems in the region. The Dniester River basin within Ternopil Oblast includes 1174 rivers and streams with a total length of 5195 km. The main feature of the Dniester basin’s hydrographic network is the absence of significant tributaries: there are only 6 medium rivers in Ukraine (two of which are within Ternopil Oblast – the Seret and the Zbruch rivers). Small rivers with a length of up to 10 km prevail, and their total length is 94% of the total length of all rivers in the Ukrainian part of the basin. This research focuses on small and medium rivers such as the Zolota Lypa, the Koropets, the Strypa, the Seret, the Nichlava, and the Zbruch. To assess the trends of long-term fluctuations in runoff characteristics and distribution of runoff within months and seasons, we used data from observations of the average annual water flow at 11 hydrological stations on the left bank of the Dniester. The period used for the research is from the beginning of the observation to 2020 inclusive. Using the difference integral curves, the long-term fluctuations of the average annual runoff of the left-bank tributaries of the Dniester for the selected observation period were estimated. It was found that the fluctuations in the runoff characteristics of the studied rivers are generally in-phase, and for some hydrological stations – synchronous. It has been established that the modern period is characterized by a downward trend in the values of runoff characteristics, which is associated with the impact of modern climate change and economic activity in river basins. Based on the analysis of the difference integral curves constructed for the studied rivers of the basin, a common water cycle was identified, which began in the mid-1960s and ended in the second half of the 1990s. Summarizing the above results of the study, we can conclude that, with the exception of some tributaries, fluctuations in the average annual runoff of the rivers on the left bank of the Dniester are natural. The current intra-annual distribution of runoff in the left-bank tributaries of the Dniester basin is characterized by a decrease in the volume of spring flood runoff, which is associated with an increase in air temperature during the period of snow accumulation and a decrease in precipitation in winter and an increase in the flow of the summer-autumn and winter low water marks as a percentage of the annual runoff between the studied periods..

Modern changes in climatic characteristics and minimum flow of the rivers in the basin of lake Sevan

Formulation of the problem. Studies and data on modern changes in the winter minimum average monthly flow of the rivers of the Lake Sevan basin and their climatic characteristics have acquired great practical importance and considerable interest due to the increased use of water resources for the purposes of various types of economic activities, in particular, in connection with the development of the economy, hydropower, irrigation, population growth and rising living standards. Especially relevant are the calculations of the minimum flow in relation to solving the problems of water supply for settlements, industrial enterprises. The aim of the work. Assessment of modern changes in the winter minimum average monthly runoff of rivers in the Lake Sevan basin and their climatic characteristics. Methods. The following methods were used in the work: mathematical-statistical, extrapolation, interpolation, spatial analysis, analogy, correlation and cartography. Results. A physical map has been compiled with a network of meteorological stations and hydrological posts in the Lake Sevan basin. Close correlations were obtained between the values of the winter minimum average monthly runoff and the average runoff of the winter period for a hydrological year. These dependences can be used for preliminary estimates of the minimum runoff of the winter low-water period of unstudied rivers in the territory under consideration. In the course of the research, the winter minimum average monthly discharges were calculated by months and for the entire observation period, the average value of the minimum runoff for the winter low water, and the linear trend of the climatic characteristic. Based on the obtained results, a map of the distribution of the modul of the average minimum runoff of the winter low-water period and the coefficients of the linear trend of the winter air temperature were constructed. Examples of curves of long-term changes in precipitation amounts for the autumn and winter periods, the sum of positive temperatures and the number of days with a positive average daily air temperature in the winter period for a series of meteorological stations in the study area are presented. The rivers of the Lake Sevan basin are characterized by an uneven spatio-temporal distribution of winter minimum runoff and climatic characteristics, changes in the winter average monthly minimum runoff, precipitation amounts for the autumn and winter periods are multidirectional, and air temperature changes are only an upward trend. In the area under consideration, there is mainly (by 8 out of 12 stations under study) a tendency to decrease in the values of the minimum average monthly river flow. The conducted studies lead us to the conclusion that the main factor causing changes in the low-water runoff of the rivers in the Lake Sevan basin in winter is the air temperature, or rather, its increase. It follows from this that when calculating and forecasting winter runoff, it is necessary to relate the values of runoff and air temperature.

Spatial-Temporal Regularities of Hydrooptical Characteristics of the Ob River

Field studies conducted in spring (March 26 — April 9, 2022) and summer (June 5-16, 2022) in the Ob River mouth region at the three hydromorphological stations „Kazym-Mys“, „Azovy“, and „Salemal“ (YaNAO) to obtain new data on the hydrooptical characteristics of water in the Lower Ob river. Also, the trophic status and ecological state of the Lower Ob river region were assessed. The greatly varying light attenuation coefficient ε(λ) was calculated at the four characteristic wavelengths of 430, 450, 550, and 670 nm, respectively. It ranges from 9.3 m-1 to 22.1 m-1 during the winter low water (freeze-up) period and from 7.3 m-1 to 33.0 m-1 during the open water (high water) period. The calculated relative spectral contributions of major optically active components of water (pure water, suspension, yellow substance, chlorophyll) to ε(λ) suggest that suspension and yellow substance make up the maximal contribution at different horizons. Additionally, the calculated coefficient of light absorption by yellow substance кys(λ) varies within the ranges from 5.5 m-1 to 9.9 m-1 (spring) and from 3.1 m-1 to 17.0 m-1 (summer), respectively. The relative transparency was measured using the Secchi disc. The concentrations of yellow substance and major photosynthetic pigments — chlorophylls a, b, c, and carotenoids — were estimated alongside. The obtained results could be useful for environmental monitoring and predicting the dynamics of aquatic ecosystems in the region under climate change and increased anthropogenic pressure caused by the use of natural resources.

Nutrient Flux under the Influence of Melt Water Runoff from Volcanic Territories and Ecosystem Response of Vilyuchinskaya and Avachinskaya Bays in Southeastern Kamchatka

Nutrient fluxes with river runoff can largely determine the state of coastal water ecosystems. The Vilyuchinskaya and Avachinskaya Bays of Kamchatka Peninsula were surveyed on 4–5 July 2022, just after the peak of the spring–summer flood of the Vilyucha and Avacha Rivers associated with the snow melting in volcanic areas. Additionally, water sampling was performed in river water in December 2022, in the period of winter low water. A general undersaturation of CO2 of surface waters was observed in the Vilyuchinskaya and Avachinskaya Bays. Strong supersaturation of CO2 of the near-bottom waters was observed, due to microbial destruction of organic matter, especially in Avachinskaya Bay. This organic matter was formed as a result of photosynthesis in the water column, which subsequently gravitated to the bottom and concentrated in specific bottom depressions in the studied bays. In these depressions, black sediments were found, in which sulfate reduction occurred. The porewater of sediments had a very high concentration of organic carbon, dissolved and organic nitrogen, and phosphates, as well as CO2 partial pressure. The source of nutrients for the studied bays is tephra (volcanic suspended particles), which covers all the watersheds, including the soil and snow, as a result of volcanic activity in the study region. Based on the calculated nutrient fluxes in river runoff for the summer and winter seasons and the DIN/DIP ratios in river, sea, and pore waters, the causes of phytoplankton blooms, including the occurrence of red tides, are discussed. The maximum flux of nutrients and, accordingly, phytoplankton blooms should be expected in the years with the highest volcanic activity and high summer air temperatures, since the melting of nutrient-rich snow and ice will be maximum. This will determine the flux of nutrients in the river runoff of the Kamchatka Peninsula and contribute to phytoplankton blooms.

Аккумуляция ртути в двустворчатых моллюсках в гидроэкосистеме устьевой области реки Красная (Вьетнам)

The article presents analysis of mercury content in different tissues such as gills, mantle, hepatopancreas and body (leg) in 4 species of bivalve molluscs in the estuary of the Red River in Vietnam. The studies were carried out in 2016–2021 during the main hydrological seasons (during the summer flood and winter low water) at 37 stations in the delta and estuarine coast of the Red River. There are shown the dependences of mercury content in mollusc tissues on the age parameters (length and mass of tissues) and on the content of pollutant in dissolved, suspended forms of near-bottom water layers and in bottom sediments. The mercury content in the tissues of molluscs varies whithin 0,023 ± 0,001 to 0,459 ± 0,007 mg/kg wet weight. The highest content of mercury was found in the hepatopancreas 
 of Austriella corrugata, and the lowest - in the leg of Lutraria rhynchaena. Significant close positive correlations were registered between the mercury concentrations in the mollusc tissues and the mercury content in the near-bottom water layer and in bottom sediments (r from 0.68 to 0.92, p < 0.05). All studied species of molluscs are classified as macroconcentrators of mercury in water; Austriella corrugata can actively accumulate mercury not only from the water, but also from the bottom sediments. Bivalve molluscs can be used as an object of biomonitoring when studying the distribution of mercury in the estuary of the Red River.

FEATURES OF THE CONTENT OF MICROELEMENTS MO, MN, ZN IN THE GLACIER WATER OF THE CENTRAL CAUCASUS FOR THE PERIOD 2019-2021

The results of a study of the content of the main microelements (Mo, Mn, Zn) in the waters of three glacial rivers of the Central Caucasus with glacial feeding during winter low water periods and summer rain floods are presented. It is shown that in the dynamics of their concentrations there is a downward trend from the zone of the upper reaches to the zone of entry into the low-mountain zone and the features of the level of pollution inherent in each river in the upper reaches. The studies were carried out over a three-year period — from 2019 to 2021. The main water pollutants in the rivers Malka, Baksan, Terek have been identified. The concentrations of trace elements in the water of mountain rivers during the main phases of the hydrological regime are presented. A comparative interannual analysis was carried out.

Investigation of the conditions for the development of waves at the interface of water masses of different densities

The influence of differences in the hydrochemical characteristics of the waters of merging rivers on the formation of density currents and the behavior of the density jump layer is studied numerically. The problem is solved for the velocity regimes of the confluent Chusovaya and Sylva rivers (Russian Federation), which are characterized by significantly different salinity values. To study the specific features of layered structures, numerical simulation is performed in the framework of a two-dimensional approach. The calculations are carried out for a section of the Chusovaya River with a length of 300 m, located downstream from confluence of the Chusovaya and Sylva rivers. The Chusovskoy water intake of the city of Perm is located on this site. In the winter-spring season, in this area a regime is established in which a stable layer of density and velocity jumps is observed. With the confluence parameters typical of the winter low water season in the area of the Chusovskoy water intake, 8 km below the confluence point, field measurements detected fluctuations in the concentration and flow velocity in the density jump layer. The two-dimensional numerical simulations performed in the present work also showed the presence of velocity and concentration fluctuations in the jump layer. We found that vortex structures are formed in the jump layer, leading to fluctuations in the concentration in time at a given point and to the formation of a wave structure of the concentration field at different times.

ПРОСТРАНСТВЕННЫЕ И СЕЗОННЫЕ ИЗМЕНЕНИЯ ОБЩЕГО СОДЕРЖАНИЯ НЕФТЕПРОДУКТОВ В ПОВЕРХНОСТНЫХ ВОДАХ РЕКИ ТОБОЛ (В ПРЕДЕЛАХ КУРГАНСКОЙ ОБЛАСТИ)

The Tobol River is the main water artery of the Kurgan region, providing the region’s population with drinking and household water, which necessitates environmental and analytical studies of the river. The main water pollutants of the Tobol River are compounds of manganese, copper, iron, easily oxidized organic substances and those resistant to oxidation, and also oil products. The article presents the results of a study of the Tobol River water within the territory of the Kurgan region conducted to find the content of oil products. Water samples were taken from the river at five observation site during the main hydrological phases: May – spring flood, September – summer-spring low water, and February – winter low water. Based on the chemical analysis, the shares of the maximum allowable concentrations of oil products in the water of the Tobol River were calculated, the territorial location of observation sites with the excess of the maximum allowable concentrations of oil products was studied, and the mass of oil products in the studied sections was determined. The alleged sources of oil products entering surface waters of the Tobol River are indicated.

Сезонная изменчивость концентрации хлоридных ионов в воде Куйбышевского водохранилища

According to long-term observations in the period 2001–2019. regularities of seasonal variability of the content of chlorides in the water of the Kuibyshev reservoir were studied. Stationary hydrochemical observation point is located in the outlet section of the reservoir. To study the causes of seasonal variability in chloride concentrations, hydrological data were used at the inlet (Cheboksary and Nizhnikamsk waterworks) and outgoing (Zhigulevsk waterworks) sections of the Kuibyshev reservoir. It was found that over the 19-year observation period, the range of seasonal fluctuations in average monthly chloride concentrations was 14–42 <math xmlns="http://www.w3.org/1998/Math/MathML"><mfrac><mrow><mi>m</mi><mi>g</mi></mrow><mrow><mi>d</mi><msup><mi>m</mi><mn>3</mn></msup></mrow></mfrac></math>. Seasonal variability of chloride content is pronounced and is characterized by alternating maxima and minima of chloride concentration. The winter maximum is observed in April before the beginning of the spring flood, and the summer maximum is observed in July before the beginning of the autumn low water. The spring minimum is observed in May at the peak of the spring flood, and the autumn minimum is observed in December before the freeze-up begins. The seasonal variability of chlorides includes four periods (I, II, III, IV), which are formed as a result of the interaction of genetically heterogeneous water masses in the reservoir. Period I is characterized by a gradual increase in the concentration of chlorides due to the inflow of groundwater during the winter low water. The short-term period II is characterized by a sharp decrease in the concentration of chlorides due to the entry of soil-surface waters into the reservoir during the spring flood. Period III is characterized by an increase in the concentration of chlorides due to an increase in the role of soil and groundwater during the summer low water period. Period IV is the longest and is characterized by a gradual decrease in the concentration of chlorides during the autumn low water period. The revealed patterns of seasonal variability of chlorides are unchanged and were observed annually during 2001–2019. However, the values of chloride concentrations significantly depended on the hydrometeorological conditions of a particular year. In dry years, the concentration of chlorides increased, and in high-water years, they decreased in all hydrological seasons of the year.

Features of the dynamics of ice formation in Western Yakutia

Ice formation may cause quite serious and even catastrophic complications during the construction and operation of various types of engineering facilities. Forming on the surface of the earth, ice affects the surrounding landscape, changes the morphology of river valleys, amount of solar radiation, temperature, evaporation, condensation. Accumulating underground runoff in winter, ice redistributes it and regulates the surface runoff giving water reserves in spring and summer that were abandoned during long winter. The paper considers the dynamics of ice formation located in the basin of an unnamed watercourse, the left tributary of the Taryng-Yuryakh River. The main purpose of the study is to identify ice, observe annual changes in its shape, volume, area and power. The research area is located in the south-west of Yakutia. The length of the stream is 5 km, the watershed area is 7.62 km2. The water regime is characterized by spring floods, summer floods, long and low-water summer and winter low water, stable ice supply. According to the results of the study, the correlation between the maximum ice area, the value of atmospheric precipitation of the previous year and the sum of negative average monthly air temperatures was not established.

Changes in River Runoff during Winter Low Water Periods in the Basin of the Ural River

Changes in River Runoff during Winter Low Water Periods in the Basin of the Ural River

Assessment of the low-water flow of the Ile river

The study examined the low-water flow of the Ili River in the Kapshagai Gorge. Data on low-water water consumption for the period 1940-2015 were collected. Hydrographs of the low-water flow for typical years are constructed. As a result of the analysis of hydrographs, the dates of the onset and end of the low-water periods of the Ile River were clarified. As a result of the analysis of hydrographs built on the hydrological post located 37 km below the HPP, the months October-November for the winter period and December-March for the winter period were taken. The characteristics of the low-water flow for the autumn and winter low-water periods are calculated. It was revealed that after the construction of the Kapshagai reservoir along the Ili River, there was a change in the low-water flow. Therefore, the hydrological calculations of the characteristics of the low-water water flow were carried out separately for the period 1940-1971, when the conditional natural water regime of the Ile River was still observed, and for the period from 1971 to 2015, when there was an increase in the anthropogenic load on the flow of the river basin. For these periods, the statistical parameters of the low-water flow of autumn and winter low water were calculated. It is shown that during the period of increased anthropogenic load on the Ili River, the coefficient of variation of the low-water flow series of the autumn low – water period increased more than twice, and for the winter period – significantly. The values of 75-97% of the low-water consumption security were determined for each period separately. It is shown that the low-water flow of the Ili River has significantly decreased over the last period.

TO THE QUESTION OF COMPREHENSIVE ASSESSMENT OF SURFACE WATER IN THE CENTRAL CAUCASUS DURING WINTER BETWEEN AND SUMMER FLOOD

Based on long-term observations, the assessment of the pollution of the rivers of the Central Caucasus was carried out by comparing the calculated coefficients of the complexity of pollution and the specific combinatorial index of pollution of surface waters, and the quality classes were determined. The results of chemical analysis of the concentration levels of trace impurities (Mo, Pb, Zn, V, Ni, Cr, Mn, Ag) and inorganic nitrogen compounds (NO2 -, NO3 — and NH4 +) in the waters of 13 rivers in two permanent sections of each watercourse were used. The results of calculating the indicators of pollution in the waters of rivers of winter low water and summer high water are presented. The most polluted watercourses and the frequency of pollution in each river are identified, estimated by the values of the specific combinatorial index of water pollution, the coefficient of complexity of pollution, and the class of water quality is presented. The assessment of the most polluted water bodies during the winter low-water period and summer flood is given according to the classification of water quality. According to long-term observations, the features of watercourses and their differences in terms of pollution are presented.

Calculation of winter average ten-day minimum flows of rivers of the Lake Sevan Basin and analysis of its time variability

Studying decadal minimum costs, especially in the context of expected climate change, is relevant and urgent. Both on the rivers of the study area and the whole republic, minimum water discharge is observed during periods of summer- autumn and winter low water. In both cases, the power of the rivers is mostly underground. However, summer-autumn rains can often disrupt the river’s feeding patterns and cause flooding. The paper calculated the winter average ten-day minimum costs for posts that have a long series of observations on rivers flowing into Lake Sevan. In a number of longterm observations, the dynamics of changes in the winter average ten-day minimum costs of rivers flowing into the basin and the patterns of their spatial distribution have been estimated. As a source material daily data from actual observations at 12 hydrological posts in the study area of the Service of the Hydrometeorology and Active Influence on Atmospheric Phenomena, Ministry of Emergency Situations of the Republic of Armenia, are used. All observed hydrological posts have a number of observations 40 years or more. The methods used in the work are: mathematical-statistical, extrapolation, interpolation, analysis, analogue and correlation. It turned out that most rivers in the Lake Sevan Basin have a tendency to increase in winter average ten-day minimum costs.

Trace elements in the spring waters of Moscow

Data on the content of major ions (Na+, K+, Mg2+, Ca2+, Cl–, SO42–, HCO3–) and dissolved trace elements (Rb, Cs, Be, Sr, Ba, B, Si, Pmin, V, Cr, Ge, As, Mo, W, Sb, Te, Mn, Fe, Co, Ni, Cu, Zn, Cd, Ag, Sn, Pb, Al, Ga, Ti, Zr, U) in the waters of 30 springs in Moscow during the winter low water period are presented. The geometric mean values and ranges of concentration of the studied components, as well as correlations between them, were established. The presence of hydrochemical anomalies of dissolved iron and manganese in the north-east of Moscow with an excess of maximum allowable concentration (MAC) for these elements was revealed, whereas in the rest of the city their concentration almost everywhere correspond to the natural background.

The Amur River Water During the Winter Low-water Period: The Many-year dynamics of the Sulfates Content and Runoff

Sulfates are the dominant ions among the major ones in the Amur region’s sewage. Therefore, the purpose of the research is to study the long-term dynamics of the content and runoff of sulfates in the Amur River in the winter low-water, based on the materials of Roshydromet for 1943-1976 and the author’s data for 1999-2019.Significant variations in the main areas were found due to both the diversity of natural conditions and anthropogenic influence in the areas of large cities and localities. The impact of the construction of hydroelectric power plants, significant economic changes in the Chinese part of the Amur basin, as well as the closure of pulp and paper and microbiological industries in the Russian part of the Amur basin on the long-term dynamics of the content and flow of sulfates is estimated. The maximum content of sulfates in the Amur River was observed after the accident at the Jilin chemical plant in China in December 2005. The influence of major floods on the increase in the flow of sulphates in the winter low-water was established.