High-water Years Research Articles

Some solutions to improve the efficiency and environmental safety of reservoir use

Abstract Flood and landslide control and unhindered management is a global problem worldwide. In high-water years, it is advisable to control the volume of water in reservoirs, taking into account such factors as increased loads on them, due to siltation and sedimentation of soils. In particular, in years with hydrological security of more than 75%, it is necessary to direct the main part of floods and mudflows into the lower stream, for this it is recommended to keep the water level as close as possible to the level of useless volume in high water, and water pumps should operate at full capacity during the passage of floods and downpours. In years when the water consumption of the water source is above 75%, the months of April and May are considered sufficient to create water reserves in high streams. Also, in years when the water consumption of the water source is less than 50%, it is necessary to collect mudflows and floodwaters to create the necessary water supply. In such conditions, it is recommended to carry out the dynamics of stopping water discharge at high temperature as follows. It is advisable to distribute the useless volume of water between the precipitation zones of dense flow and the normal water level in the upper boeuf. Based on this, it is necessary to install “Hydraulic posts” on the upper reaches of reservoirs, with the help of which it is possible to control the transformation of water flows.

Phthalates in Surface Waters of the Selenga River (Main Tributary of Lake Baikal) and Its Delta: Spatial-Temporal Distribution and Environmental Risk Assessment

The Selenga River provides about half of the water and chemical runoff into Lake Baikal and plays an important role in the sustainability of the ecosystem of this large natural freshwater lake. Phthalate esters (PAEs) are organic compounds that can disrupt reproductive and endocrine systems. This study focused on investigating the distribution of six priority phthalates in the Selenga River and its delta utilizing SPE-GC/MS. The study found that the highest levels of Σ6PAE were observed during the high-water years, 2021 and 2023, and were evenly distributed along the river from the sampling sites upstream of Ulan-Ude to the delta channels. In contrast, the mean annual Σ6PAE content was relatively low in the low water period of 2022. Dibutyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP) are the two dominant phthalates found in the surface waters of the Selenga River and delta channels. In 2021, the average total concentration of six phthalates (Σ6PAE) ranged from 8.84 to 25.19 µg/L, while in 2022 it ranged from 0.45 to 4.01 µg/L, and in 2023 it ranged from 5.40 to 21.08 µg/L. The maximum level for the sum of phthalates was 61.64 µg/L in 2021, 13.57 µg/L in 2022, and 30.19 µg/L in 2023. The wastewater treatment facilities in Ulan-Ude were identified as a stable local source of phthalates. In some cases, PAE concentrations exceeded maximum allowable concentrations, particularly for DEHP. This could have adverse effects on aquatic organisms.

The effects of long-term drainage and wildfires on water table level and water chemistry of the Great Vasyugan Mire

In this paper, we assessed long-term changes in water table level of the Great Vasyugan Mire, water chemistry and the removal of mineral and organic substances in the mire-river system in the taiga zone of Western Siberia under the conditions of forest reclamation, pyrogenic factor and climate change. In the drained area of the Great Vasyugan Mire, a significant decrease in water table levels and an increase in the amplitude of their fluctuations by 1.6 times were noted. The effect of the pyrogenic factor is expressed, on the contrary, in an increase in water table levels due to surface burnout. In the water of the drained part of the Great Vasyugan Mire, an increase in the concentrations of Са2+, Mg2+, Fetotal, Cl-, К+, Na+, Cl-, SО42–, NO3-, DOC was noted. An increase in the content of NH+4, Feобщ, Cl-, SO42-, NO-3, and DOC is observed in river waters. An indicator of the effect of the pyrogenic factor on the chemical composition is an increase in the pH value and the content of K+, Na+, SО42–, NО–3, HCО3– ions, as well as Са2+, Mg2+, Feобщ. In connection with the overgrowth of the ditches, the process of self-healing of the mire is observed, and backwater zones are formed near the ditches and the amplitude of level fluctuations increases, as a result, the chemical composition of the waters of the drained and natural areas of the Great Vasyugan Mire in certain periods has minimal differences. Studies have shown that the removal of mineral and organic substances from the drained area of the great Vasyugan Mire prevailed in the high-water year 2018 and amounted to 2054 tons, of which the removal of DOC was equal to 47% or 969 tons. In the future, climate change, an increase in air temperature and precipitation in the region are likely, will contribute to the removal of biogenic elements and organic substances from mires and increase their concentration in river waters.

О моделировании гидродинамического режима течений в системах речных русел в период прохождения волны половодья на примере участка р. Оби

Рассмотрен пример численного моделирования прохождения волны половодья на участке верхней и средней Оби ниже плотины Новосибирской ГЭС. Расчеты выполнены с использованием численной модели для описания распространения и трансформации волн половодий и паводков в системе русел (STREAM), разрабо танной в ИВЭП СО РАН. Модель основана на одномерных уравнениях Сен-Венана. Система русел моделируется в виде графа типа дерево, в вершинах которого за даются условия сопряжения основных гидродинамических параметров. Приведена приближенная численная оценка порядка точности метода решения. Результаты моделирования хорошо согласуются c данными наблюдений. The goal of the study is to analyze the possibility of using the numerical model STREAM for performing research on the passage of a flood wave in a system of channels. The model was developed at IWEP SB RAS on the basis of one-dimensional Saint-Venant equations. It allows describing the flow regimes in channels, represented as a directed graph of the tree type. In the nodes of the graph (channel gates), the conjugation conditions for the main hydrodynamic parameters flow rates and water levels are set. The finite difference method is used to solve the system of equations. The difference scheme has a second order of accuracy in space and a first order in time. An approximate numerical estimate of the order of accuracy of the model using the Runge method is obtained. Numerical simulation of the Ob river section under the conditions of a high-water year 2014 has been carried out. To construct the morphometric model of the graph, data from the pilot map of the river and data of the expedition studies of IWEP SB RAS were used. The hydrological information is taken from the open access source “Automated information System of State monitoring of water bodies”. As a simulated object, a section of the Ob river from the Novosibirsk hydroelectric power station to Alexandrovskoye village is taken. The length of the site is 1210 km. The flow rates of six tributaries are taken into account. The graph consists of 12 segments. In the closing section, a boundary condition is set for water flow in the form of a flow rate versus level. To estimate the influence of the boundary condition on the simulation results, two water flow curves were constructed according to the data of 2013 and 2014 years. Qualitative and quantitative estimates of the difference in levels using two different curves, as well as comparison with the measurement data, were obtained. It is shown that the calculation method provides an acceptable agreement between the calculated values of water levels and the observational data. The possibility of using the water flow curve according to the data of the previous year as a boundary condition in the closing gate is demonstrated.

PROSPECTS AND PROBLEMS OF USING LOCAL WATER RESOURCES FOR IRRIGATION IN THE BASINS OF SMALL RIVERS OF THE FOREST-STEPPE OF UKRAINE

On the example of a separate agricultural farm located in the basin of the small Manzhelia River within the Left Bank Forest Steppe, the approaches to the selection of potential sources of irrigation and the specifics of determining the volumes of local water resources intended to be used for irrigation, as well as the areas of possible irrigation in the absence of existing irrigation systems, are given. The results of the research indicate that the prospects for the development of land irrigation on farmland can be mainly provided subject to the combined use of surface runoff accumulated in ponds on the Manzhelia River and groundwater admissible for extraction, taking into account their quality. It was determined that influenced by a complex of anthropogenic factors, the river runoff sharply decreased compared to natural conditions, and the feeding of river course ponds during the entire low water period occurs only due to lateral inflow. Based on calculations it was determined that in average and low-water years, the volumes of surface and ground inflow to the cascade of ponds for the period from June to September are smaller than evaporation losses. Under such conditions, the use of the river runoff for irrigation is possible only due to the accumulation of flood and, partially, high water runoff. The calculations of flood runoff volume for March - April at the gate of the lower pond indicate the impossibility of using water from it for irrigation in very low-water years, as well as the dependence of runoff use for irrigation in low-water years on the pre-flood filling level of the ponds. It was determined that up to 0.8 million m3 of water can be used for irrigation in medium-water years, and up to 1.4 million m3 in high-water years, which will provide irrigation on an area of 400 and 700 hectares, respectively (having an irrigation rate of 2000 m3/ha). The possibility of installing at least 40 water intake wells within the territory of the farm with a total flow rate of 20-24 thousand m3/day and a total water intake during the irrigation period of about 1.5 million m3 has been substantiated. This will make it possible to irrigate 750 hectares of land having an irrigation rate of 2000 m3/ha, and at least 1000 hectares having an irrigation rate of 1500 m3/ha. It is focused on the mandatory preliminary investigation of water quality for irrigation, which for many small rivers and aquifers is a limiting factor when using local water resources for the construction of irrigation systems.

Water Flow Changes In The Don River (European Russia) During 1891–2019

The Don River Long near Razdorskaya Village had long phases (lasting 33–86 years) of increased/decreased naturalized annual and seasonal water flow, and their properties for 1891–2019 were identified. Long-term changes in the annual and snow-melt flood flow occurred in the opposite phase relative to changes in the winter and summer-autumn flow. Annual hydrographs in the phase of decreased flow were characterized by an increase in water discharge during the low-water seasons of the year, but a noticeable decrease in daily flood water discharge and maximum water discharge. The share of high-water years (years with a flow exceedance probability equal to or less than 25%) in the phase of increased flow is significantly higher than the share of low-water years (years with a flow exceedance probability equal to or more than 75%). And on the contrary. At the same time the cumulative share of low- and high-water years remains relatively stable. The total changes in the annual and seasonal flow, caused by both anthropogenic and climatic factors, throughout the entire period of modern global warming (since 1989) consisted in a decrease of the annual and snow-melt flood flow and an increase of flow values during low-water seasons.

HYDROCHEMISTRY OF THE ZEYA RESERVOIR IN HIGH-WATER YEARS

The results of studying the chemical composition of the waters of the Zeya reservoir in high-water years (2013, 2021) are presented. It is shown that a signifi cant infl ow of water into the reservoir during these years caused in its waters a uniform distribution of concentrations of dissolved substances in the water area and depth in the summer- autumn period and extremely uneven in winter. The maximum values of mineralization, concentrations of calcium, magnesium, bicarbonate and sulfate ions, ammonium nitrogen, organic substances and dissolved iron were established in winter in the estuarine areas of the Argi and Zey regions as a result of the infl uence of cryogenic processes and fl ooding of the marshes of the Upper Zey plain. In the dam and canyon parts of the reservoir in winter, there were no large diff erences in mineralization values (28,4–41,9 mg/dm3), low content of ammonium nitrogen (< 0,03 mg N/dm3), increased values of water color (62–87°), concentrations of dissolved iron (0,35–0,74 mg/dm3) and organic matter (10,0–13,3 mg O/dm3). An assumption is made about the receipt of large amounts of dissolved substances in the Amur River in winter due to increased water consumption of the Zeyskaya HPP

Current Hydrological Regime of the Volga Reservoirs

The study is focused on variations of air temperature in the basin of the Volga reservoirs, the total inflow into the water bodies, their water exchange, water level and temperature, and the heat content of water mass in open-water period under various climate conditions. The object of the analysis is the long-term series of hydrometeorological data processed by statistical methods. It is shown that the present-day air temperature has increased by 1.3‒1.8°C compared with the period before 1976. The rate of warming was on the average 0.50°C/10 years. The volume of annual inflow increased by 12.4%. Three low-water and 4 high-water phases were identified in the reservoirs of the Upper Volga, including 29–31 low-water, 25–31 high-water, and 8–16 medium-water years. During the low-water phases, the volume of inflow into the reservoirs is 10–28% less than the long-term average, while in high-water years, it is 4–20% higher. The coefficient of water exchange in the reservoirs decreased or increased by 5–13% relative to the values obtained earlier. An increase in the winter and a decrease in the spring inflow were recorded in the reservoirs of the Upper Volga and in the Kuibyshev Reservoir. A tendency toward an increase in the normal annual water level was observed in the reservoirs in the upper part of the Volga and in the Kuibyshev Reservoir, while in the lower Volga, the normal annual level somewhat decreased. In low-water phases, the reservoir levels were on the average 17 cm below and in the high-water phases, 10 cm above the normal annual value. An increase in air temperature during the warm season in the reservoir water areas, on the average by 1.2°C, led to a synchronous increase in the temperature of the water mass by 1.1°C. At the same time, the heat content of the water mass of the reservoirs increased, on the average, by 24% in the upper part of the Volga and by as little as 2–11% in its lower part

Study of changes in soil-reclamation characteristics during collector-water irrigation

The paper considers land and water resources use and quality of return flow and its re-use for irrigation of salt tolerant crops in conditions of the Republic of Karakalpakstan. The article considers land and water resources use and quality of return water and its reuse for irrigation of salt-tolerant crops in the Republic of Karakalpakstan. The volume of the return (collector) flow and its quality in the Republic entirely depend on water availability, i.e. water availability in the Amu Darya River. In high-water years, such as 1992, 2005, 2010 and 2017, the return flow volume reached 3.0 billion m3, which constituted 35-38% of the total water withdrawal used for crop irrigation. In high-water years, almost 65% of the total water withdrawal has a salinity of 3.0 g/l, which is quite suitable for some food crops. Under conditions of fresh water deficit in the Republic of Karakalpakstan, multi-year (2000-2018) experimental-production research on collector-drainage water use for irrigation of salt-resistant forage, vegetable-gourd crops, pasture-hayfields, as well as for liman irrigation of wild forage crops (reed and others), was conducted. Based on the findings of the research, the article offers practical and scientific recommendations for solving these problems.

Transformation of the water runoff of the Volga River after the creation of the Zhiguli hydroelectric complex

For the Volga River, studies of interannual changes in water discharges in the period 1958-2021 were carried out. Systematic hydrological observations were carried out at the Zhiguli hydroelectric complex on the border of the Middle and Lower Volga. 97% of the water runoff of the entire Volga is regulated in this section in the seasonal, weekly and daily range. It was found that the average water flow was 7704 m3/s. The amplitude of interannual fluctuations was 5270-10431 m3/s. Temporal changes in the average annual water discharges were characterized by cyclicity, including the change of low-water and high-water phases. From 1958-1975 a low-water phase was observed, from 1976-1996 - high-water and since 1997-2021 - again shallow. A comparison of the historical (1877-1955) and modern (1958-2021) periods showed that over 144 years, the average water flow of the Volga River has not changed much. However, as a result of the regulation of water flow in the period 1958-2021 the value of water discharges in high-water years decreased, while in low-water years it increased.

Calculation of Total Erosion in the Lower Reaches of Mezhdurechensk Reservoir Using Empirical Morphometric Dependencies

The research aims are to develop a methodology and the choice of initial formulas for calculating channel deformations in the lower reaches of waterworks on rivers composed of easily eroded soils (like the Amu Darya river). To calculate the total erosion below the Mezhdurechensk reservoir, both theoretical equations of channel deformation (Saint-Venant equations) and empirical dependences of the transporting capacity of the flow (turbidity) and morphometric dependences of the connection of the width of the deformable channel from the average depth obtained for the lower reaches of the Takhiatash hydrounit, the stem of which is located slightly above the Mezhdurechensk hydrounit, were used. A hydrological series of years was formulated for the calculation (considering the actual frequency of low-water, medium-water, and high-water years). The results of calculating the total erosion of the bottom in the first ten years of the simulated hydrological series of years, provided that the width of the channel in the lower reaches is constant, is expected to be 0.17-0.41 m (with full flow clarification) and 0.16-0.38 m (with partial flow clarification ε = 0.8). The change in the cross-sectional area of the riverbed will be 304(292)m2. Provided that the width narrows to a stable width Bstable =kha : Δz = 0.41 m (with the concentration of the flow at a narrower width, the decrease will be correspondingly large). The proposed methodology can be applied to calculate the total erosion on rivers composed of easily eroded soils and having average slopes of the longitudinal profile of the river within 0.0001 (similar to the Amu Darya River).

Effect of Type of Forest Growth Conditions and Climate Elements on the Dynamics of Radial Growth in English Oak (Quercus robur L.) of Early and Late Phenological Forms

The pattern of annual radial growth is influenced by various factors: the local growth conditions, the age structure, and the ecotypes or provenances of trees. A more in-depth approach to the study of specific growth patterns of tree forms is needed to predict the further genesis of forests. This research was carried out on healthy English oak trees of early (EF) and late (LF) phenological forms in Shipov Forest, Voronezh Region. The dendroclimatic analysis was performed on permanent sample plots in wet, dry, and very dry oak stands grown on different soil types. The effect of precipitation on annual ring width was assessed using a one-way ANOVA. The LF showed higher radial growth rates on wet sites than the EF did on dry ones. Their annual radial growth was less stable and more variable compared with the LF. For both phenoforms, the most important radial growth factors are the composite indicators reflecting the ratio of temperature and moisture (Selyaninov’s hydrothermal coefficient and Lang’s rain factor). Generally, the radial growth minima coincided in time on dry and wet sites, and the periods of maximum growth were associated with high-water years.

Interannual variability of the functional state of bream (Abramis brama, L.) of the delta Volga in the pre-spawning period

Bream is an important fishing object of the Volga-Caspian region. Its catches here in the middle of the last century reached 60 thousand tons, while currently they do not exceed 14 thousand tons. The study of the functional state of bream in the pre-spawning period makes it possible to determine the success of spawning, predict the survival of offspring at the early stages of ontogenesis. During the spawning periods (2007–2017 and 2021), the functional state of female and male bream caught in the waters of the delta Volga was studied. To assess the physiological state, the following biochemical parameters of blood were analyzed: the amount of hemoglobin, total serum protein, β-lipoproteins, cholesterol, total lipids, triglycerides, inorganic phosphorus, glucose, activity of alkaline phosphatase and aspartate aminotransferase, generally accepted methods of hematological and biochemical studies of blood and blood serum were used. The work used generally accepted methods of hematological and biochemical studies of blood and blood serum. As a result, there were statistically significant differences in the values of such indicators as the level of hemoglobin in the blood, cholesterol and β-lipoproteins cholesterol, glucose between females and males were noted. Significant interannual differences in the values of the studied indicators were revealed. The flow regime and the volume of spring flood had a decisive influence on the functional state of bream in the prespawning period. Deviations from the values of these indicators from the limits of reference values characteristic of fish and bream, in particular, taken from literary sources, were usually observed in low-water years (hemoglobin, β-lipoproteins, total lipids). The average level of correlation (r = 0.50) between the value of total whey protein and cholesterol was established in bream, which indicates a close relationship between protein and lipid metabolism. Thus, the physiological state of the Lower Volga bream in the pre-spawning period of high-water years can be characterized as relatively favorable.

Estimation and application of the water resources distribution using the Water Accounting Plus: A case study of the Kherlen River basin

It is crucial to assess water resources in a basin level to have observational data and measurements related to the water, its data processing and reporting. To present water resources in the spatial way is valuable information for the stakeholders including decision makers, water users and managers. However, not every river basin has adequate measurement network and spatially estimating water resources is challenging. Therefore, we applied the water accounting plus to estimate water resources as a spatial representation for the Kherlen river basin for the period of 2005-2020. Water Accounting Plus is a method to analyze water resources considering different land uses using the open-source remote sensing datasets. For this study, GPM and SSEBop datasets were used for the basin and validated with ground measurement data from six meteorological stations. Based on WA+ outputs, Sheet and Sheet 2 were developed for the Kherlen river basin in high and low water years. In high water year, the basin receives precipitated water as 35.3 km3 and its 23.3 km3 are lost by evapotranspiration and 1.9 km3 water is outflow as a runoff. For the low water year, 22.8 km3 water fall as a precipitation at the basin and only 0.7 km3 is outflow as a runoff of Kherlen river. In addition, we analyzed how spatial maps of water resources can be used for the water resources planning such as the Bag-level livestock water supply in Dornod province, which overlaps the Kherlen river basin. Of the 23 Bags in Dornod province, 11 have not enough water availability for the livestock. It noted that WA+ was a method of analyzing water resource and the. Further research is needed to validate remote sensing data with more ground data and will refine the groundwater resources estimation.

О НАХОЖДЕНИИ РЕДКОГО ВИДА OVALONA KARELICA (STENROOS, 1897) (BRANCHIOPODA: ANOMOPODA: CHYDORIDAE) В ПОЙМЕННЫХ ОЗЕРАХ ХОПЕРСКОГО ЗАПОВЕДНИКА

Ovalona karelica (Stenroose, 1897) was first discovered for the invertebrate fauna of the Voronezh region south of the main habitat. It is a rare benthic species of sladocerans crustaceans (Crustacea, Cladocera). The species was encountered among macrophytes in thickets Typha angustifolia (L.) and Potamogeton lucens (L.) in two floodplain lakes of the Khopersky Nature Reserve in summer. The explored small lakes, where the species was found, are distinguished by the peculiarity of the floodplain regime; they are flooded from the main river in medium and high water years and remain connected to each other for some time. Lake Bolshoe Podpesochnoe has an area of 2.7 hectares and a maximum depth of up to 6 m. It is characterized by a low degree of overgrowing – 25%, the distance to the river Khoper is 1.1 km, last flooding was noted in 2018. The area of the lake Maloe Podpesochnoe is 1.9 ha, the maximum depth is up to 5 m, the degree of overgrowth is 35–40%, the distance to the river is 0.9 km, the last flood was in 2018. The size of the individuals encountered was from 380 to 420 microns, the abundance varied from 90 to 550 ind./m3, the share in the total number of planktonic invertebrates was from 0.1 to 0.32%. The discovery of Ovalona karelica is associated with the specificity of its habitat conditions and small number, and this also indicates a poor study of the fauna of phytophilic and benthic invertebrates in small floodplain water bodies.

ИЗУЧЕНИЕ ПЕРЕФОРМИРОВАНИЯ БЬЕФОВ НИЗКОНАПОРНЫХ ГИДРОУЗЛОВ В НИЗОВЬЯХ РАВНИННЫХ РЕК

The article presents the results of long-term field studies of the re-formation of water courses in the zone of the Takhiatash hydroelectric complex. It was noted that due to low water, for a significant part of the year, the Takhiatash dam worked with fully closed gates in all spans. In these years, the role of regulating the level regime of the shield dam is almost lost, and the end regulators of the main channels are regulated.
 The data of comparison of actual expenses, turbidity and back-up at the Takhiatash hydroelectric power plant with the calculated ones are presented. It is proved that sharp fluctuations in the water level in front of the dam and water intake into the channels lead to changes in the hydraulic and alluvial regime of the shield dam and channels. As the analysis of the survey of the riverbed cross-sections in the headwaters of the Takhiatash hydroelectric complex showed, in the initial period of operation, the bottom marks in the upper stream are increasing and the bottom marks in the lower stream are decreasing. Further years of operation (after 1982) were characterized by the stability of the flowing riverbed processes, that each characteristic year has its own level and consumption regime. It is noted that in high-water years there were no difficulties with water intakes, and the main difficulties are associated with the passage of flood flows through the shield dam. In recent years, there has been a rapid rise in the water level in the upper reaches, despite all the open dam gates, shipping locks and water intake structures, which are explained by the influence of the drifted streams on the capacity of the shield dam. It is proved that without any damage to the water intake during the growing season, it is possible to effectively flush the upstream with a constant decrease in the water intake coefficient - Kv < 0.55. Practically, this means for the Takhiatash hydroelectric unit that the flushing flow rate should not be lower than Q ≥ 250 – 300 m3/s.

Controls on carbon dioxide and methane fluxes from a low-center polygonal peatland in the Mackenzie River Delta, Northwest Territories

Growing season surface–atmosphere exchange of carbon dioxide and methane were quantified at Fish Island, a wetland site in the lower northeast Mackenzie River Delta, Northwest Territories, Canada. The terrain consists of low-center polygonal tundra and is subject to infrequent flooding in high water years. Carbon dioxide and methane fluxes were continuously measured using eddy covariance and the relevance of different environmental controls were identified using neural networks. Net daily carbon dioxide uptake peaked in mid-July before gradually decreasing and transitioning to net daily emissions by September. Variations in light level and temperature were the main controls over diurnal net carbon dioxide uptake, whereas thaw depth and phenology were the main seasonal controls. Methane emissions measured at Fish Island were higher than comparable studies on river delta sites in the Arctic and were influenced by the interaction of a large number of factors including thaw and water table depth, soil temperatures, and net radiation. Spikes in methane emissions were associated with strong winds and turbulence. The Fish Island tundra was a net sink for carbon during the growing season and methane emissions only slightly reduced the overall sink strength.

СОДЕРЖАНИЕ БИОГЕННЫХ ВЕЩЕСТВ В ВОДЕ БУРЕЙСКОГО ВОДОХРАНИЛИЩА В МНОГОВОДНОМ 2021 ГОДУ

The paper presents the research results on the content of nitrogen mineral forms and phosphorus in water of the Bureysky reservoir in the high-water year of 2021. The highest content of ammonium nitrogen was determined at the Tuyun site bottom water layer, and of nitrate nitrogen – at the Priplotinny site. The average concentration of ammonium nitrogen was found to be 0.026 mg N/l, of nitrate nitrogen – 0.077 mg N/l, and of mineral phosphorus – 0.0013 mg R/l.

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.

Long-Term Dynamics of Chlorophyll in Plankton of Different Sites in a Large Plain Reservoir

On the basis of field observations in 2009–2019, the seasonal and long-term dynamics of chlorophyll at six standard stations of the Rybinsk Reservoir is considered. The fluorescence method is used to determine chlorophyll. The average chlorophyll content at stations varies from the minimum 3.5–10.8 to the maximum 16.9–40.5 μg/L in different years and from 12.0 at station 5 (Sredny Dvor) up to 21.6 μg/L at station 2 (Mologa) on average for the entire period. The seasonal dynamics of chlorophyll is characterized by spring; summer; and, in some years, autumn maxima. With the same type of seasonal dynamics, the change in chlorophyll at the stations is to varying degrees coupled in the years of observation and is most often correlated in neighboring areas. Significant differences in the amount of chlorophyll at the stations are observed during surveys carried out within one day and are determined by the complex hydrological structure of the reservoir; active dynamic processes; and, in the spring, by the thermal regime. The presence of stable large circulation zones smoothes out the spatial differences of chlorophyll, the average seasonal concentrations of which do not differ significantly at all six stations in years with an average water level, and at four stations of the Main Reach in extremely high-water years. A close correlation in long-term dynamics is revealed for the average chlorophyll concentrations for the growing season at six stations, as well as at each station and the reservoir as a whole. The results of the work confirm the reliability of the data obtained for assessing the ecological state of the Rybinsk Reservoir.