Dnieper Water Research Articles

ОГЛЯД РЕЗУЛЬТАТІВ ДОСЛІДЖЕНЬ ЗАБРУДНЕННЯ КАХОВСЬКОГО ВОДОСХОВИЩА ЦЕЗІЄМ-137 І СТРОНЦІЄМ-90, ЯКІ ПРОВОДИЛИСЬ ПІСЛЯ АВАРІЇ НА ЧОРНОБИЛЬСЬКІЙ АЕС (1986-1921 РР.)

The available data on the state of radioactive contamination of water and bottom sediments of the Kakhovka Reservoir were analyzed in order to assess the possible deterioration of the quality of the environment based on the indicators of radioactive contamination in the zone of influence of the emergency discharge of water due to destruction of the Kakhovka NPP dam by the Russian military. Contamination of the Kakhovka Reservoir with 137Cs occurred mainly through the fallouts of this radionuclide with aerosols on the water surface in May 1986. A much smaller part of this radionuclide transported by water runoff directly from the headwaters of the Dnieper basin. Strontium-90 entered the reservoir exclusively by water pathway starting from October 1986. The steady trends of decreasing activity of both radionuclides in water has been observed since 1987. Approximately to 1996 137Cs activity concentrations had decreased to pre-accident level, 90Sr activity demonstrated a slow decrease and by 2022 remained slightly higher than pre-accidental level. The average levels of contamination of the Kakhovka reservoir bottom with 137Cs and 90Sr turned out to be the lowest compared to the other reservoirs of the Dnieper cascade. It was shown that in 1994 137Cs activity levels were 0.06 Ci/km2(2,2 kBq/m2) on 80% of the bottom surface (submerged former floodplain of the Dnieper) and were lower than on the territory adjacent to the reservoir. In the areas of silt accumulation (former channel of the Dnieper) 137Cs activity was on average three times higher. Balance calculations based on the data of radiation monitoring of water showed that the amount of 137Cs activity in the bottom sediments in the period 1987-2022 halved due to natural radioactive decay, the amount of 90Sr activity decreased by approximately 20%, since activity losses due to natural radioactive decay were partially compensated by the constant supply of this radionuclide with water runoff from the contaminated part of the catchment. After a catastrophic water leak from the reservoir, the Dnieper floodplain had exposed. According to the calculations, the average density of soil contamination of the ехposed areas with 137Cs does not exceed 0.03 Ci/km2 (1,1 kBq/m2), with 90Sr – less than 0.1 Ci/km2 (3,7 kBq/m2). Silt deposits of the former Dnieper channel, which had an increased level of 137Cs contamination, were re-suspended, probably, and carried out into the Dnipro-Bug estuary and further into the Black Sea. However, according to our assumptions, this should not have a negative effect on the radioecological state of the sea, because the 137Cs activity concentrations in the water of north-western part of the Black Sea were always 20-30 times higher than in the Dnieper water.

CHANGES IN THE KEY HYDROLOGICAL FACTORS OF THE LOWER REACHES OF THE DNIEPER WATER ECOSYSTEMS FUNCTIONING AFTER THE KAKHOVKA HYDROELECTRIC POWER STATION DAM WAS DESTROYED

CHANGES IN THE KEY HYDROLOGICAL FACTORS OF THE LOWER REACHES OF THE DNIEPER WATER ECOSYSTEMS FUNCTIONING AFTER THE KAKHOVKA HYDROELECTRIC POWER STATION DAM WAS DESTROYED

FEATURES OF THE FORMATION, INTAKE AND DISTRIBUTION OF THE IRON-CONTAINING COMPONENT IN THE WATER SUSPENSION OF THE DNIEPER RIVER WITHIN ZAPORIZHZHIA CITY

The article presents the results of research devoted to one of the aspects of environmental issues, namely: the determination of the distribution features of the solid component of the river suspension containing iron oxide; investigation of the morphological characteristics of iron-containing particles; and the discovering of their genetic affiliation to various technological processes of metallurgical production. The results of many years of continuous comprehensive research on the distribution of iron in the suspended matter of the Dnieper water within Zaporizhzhia city are presented. Field observations were carried out by scientists of the Institute of Geological Sciences of the National Academy of Sciences of Ukraine (IGS) in cooperation with specialists from the State Institution “Scientific Hydrophysical Center of the National Academy of Sciences of Ukraine” (SHC). Analytical studies of the solid phase of the suspended matter were done in the Center for Collective Use of Scientific Equipment of the National Academy of Sciences of Ukraine and the Educational and Scientific Institute “Institute of Geology” of Taras Shevchenko Kyiv National University. The publication considers the seasonal features of the distribution of the total iron content in suspension and the relationship of its monthly changes with the distribution of concentrations of such heavy metals as copper, chromium, nickel, zinc. Considerable attention is paid to the examination of iron-containing particles present in suspension, their chemical and trace element composition and the allocation of their individual categories in accordance with the technogenic processes during which they were formed. Comprehensive analysis of suspension samples made it possible to identify and classify a group of typical iron-bearing formations that are inherent in the territory of Zaporizhzhia city. Based on a set of characteristics, three main genetic categories have been identified: spherical mineral aggregates represented by iron oxide; clastic fragments of Fe2O3, and aluminosilicate spherules (formation, the main or essential component of which is aluminum oxide with an admixture of iron). The obtained data showed a significant influence of the metallurgical industry on the chemical composition of the Dnieper suspension within Zaporizhzhia. Comparison of iron-containing particles observed in the Dnieper suspended matter with the substance filtered out by gas purification systems of various parts of metallurgical production and slag deposits showed that the most active emission to the environment occurs during the preparation and smelting of iron ore.

Оценка качества воды и донных отложений Северо-Крымского канала перед запуском основного потока воды по содержанию углеводородов и некоторым микробиологическим показателям (весна 2022 г., полуостров Крым)

In the Spring 2014, the supply of Dnieper water to the North Crimean Canal (NCC) was stopped. The canal was previously used for centralized water supply and agriculture in the steppe part of Crimea. After 8 years, the active use of the Dnieper water in the Crimea requires comprehensive studies of its quality. Traditionally, microbiological studies are used to assess the ecological condition of water areas. In addition, it is important to monitor components of hydrocarbon origin such as aliphatic hydrocarbons. In general, the NCC waters by microbiological parameters (the number of heterotrophic, lipolytic and hydrocarbon-oxidizing bacteria) and the concentration of hydrocarbons can be attributed to the oligosapropic, low-polluted zone. According to the level of aliphatic hydrocarbons, the bottom sediments of the studied section of the NCC and the soil in the area adjacent to the canal are classified as naturally pure.

Analysis and mathematical modeling of chlorite formation and content in water treated with chlorine dioxide in the drinking water supply system

Today, at the present time, a study of methods of introduction of uncontaminated drinking water, which are characterized by high bactericidal ability and do not lead to the detection of toxic substances in drinking water in unsafe quantities, has been carried out. With the help of such methods, it is necessary to treat drinking water with chlorine dioxide. Through the use of this reagent in water treatment, toxic chlorites become the priority raw materials for drinking water. I have to conduct an analysis and apply mathematical modeling of the solution and amount of chlorites in water, which are developed from the water environment of the Dnieper at water supply stations with traditional technology of water purification by treatment with chlorine dioxide, to determine the optimal technological parameters for carrying out the technological process with the advantages of Ukrainian and European legislation. The developed mathematical models show the possibility of transferring the process of treatment of Dnieper water with chlorine dioxide and deeper purification at water supply stations, performing processes using the method of determining the characteristics of drinking water, as well as conveniently optimizing the process of preparing drinking water.

Небезпечні хлорити у питній воді: утворення та видалення з використанням діоксиду хлору У технології водопідготовки

he aim of work was to study the features of the formation and removal of toxic chlorites at the treatment facilities of the Dnieper water pipeline in Kyiv, where chlorine dioxide is used in water treatment technology, and the influence of priority natural and technological factors on these processes. Materials and methods: The studies were carried out in 2021-2022. at the Dnieper waterworks in Kyiv, where chlorine dioxide is used instead of chlorine in water treatment technology. We have analyzed data from water studies for the content of dioxide and chlorites, carried out at treatment facilities by the laboratory of the Dnieper water pipeline in order to establish the features of the formation and efficiency of chlorite removal in water treatment technology. Also, selective studies of chlorine dioxide and chlorites in the water supply were carried out by titrimetric and photometric methods, the results of which coincide with the data obtained on the water supply using the ion chromatography method. Main results: A positive hygienic assessment of the modern new technology for the preparation of drinking water from surface sources using chlorine dioxide instead of chlorine gas is given. It is shown that with high purifying and disinfecting effects of water treatment with chlorine dioxide, its by-products, in particular, toxic chlorites, are constantly formed in it, the levels of which are directly dependent on the doses of chlorine dioxide used, which vary according to the seasons of the year. In general, the primary dose of chlorine dioxide and chlorites in the water after the clean water tank (CWT) entering the water supply networks is reduced by 89,3-92,0% for chlorine dioxide, and by 76,2-85,6% for chlorites. At the same time, the concentration of chlorine dioxide in disinfected drinking water is always within the normal range - not less than 0,1 mg/dm3, and chlorites - most often exceeds the national hygienic standard (0,2 mg/dm3), but does not exceed the standard recommended by the WHO ( 0,7 mg/dm3). The highest concentrations of chlorites are formed in water in summer (on average 0,35 mg/dm3) in accordance with the increased doses of chlorine dioxide during this period (on average 2,51 mg/dm3), and the lowest in winter (on average 0,17 mg/dm3). Conclusions: The studies carried out at the Dnieper water pipeline, where chlorine dioxide was introduced into the traditional water treatment technology, made it possible to establish the following. The process of treating natural water with chlorine dioxide is accompanied by the formation of its by-products in water, mainly toxic chlorites, the levels of which depend on the doses of chlorine dioxide used and are the lowest in winter and summer. After coagulation treatment of the source water with aluminum sulfate and ferric chloride (ratio 10:4-5), settling and filtration, the levels of chlorites in drinking water (CWT) decrease intensively, but do not always reach regulatory values. In the summer period, the maximum levels of chlorites in drinking water with RCHV can be higher than the national hygienic standard (0,2 mg/dm3) and range up to 0,7 mg/dm3, which corresponds to the WHO recommended standard for this substance in drinking water. The issue of revising the national standard for chlorites in water from 0,2 mg/dm3 to 0,7 mg/dm3 after appropriate scientific justification is being raised.

Использование орошаемых земель Республики Крым в условиях дефицита водных ресурсов

The need for irrigated agriculture in the Republic of Crimea is due to the natural and climatic conditions of the territory, which are characterized by a moisture defi cit with a high level of heat supply. The purpose of the research: an analytical assessment of the current state of irrigated agriculture in the Republic of Crimea and the success of its further development and reproduction, taking into account the natural resource potential of the territory and the existing experience of positive and negative approaches to the use of irrigated lands. The object of research is the crop production system of the agro-industrial complex, the subject of research is agricultural production on irrigated lands. The research material was the data of statistical reporting of agricultural and water management organizations of the republic; publications on the results of theoretical study and practice of the use of reclaimed lands, which are in the open press; as well as the author’s own work. The methodological basis of the research was: information-analytical, systematic and comparative approaches; analysis, generalization and synthesis of the obtained data; statistical, expert and heuristic evaluations. The analysis of the development and effi ciency of agricultural production on the irrigated lands of the republic revealed signifi cant shortcomings in their use. Of the total area of irrigated land, about 24 thousand hectares are irrigated, i.e. no more than 5%, which is associated both with limited water resources and with depreciation of 80% of fi xed assets, lack of necessary sprinkler equipment, understaffi ng of pumping stations, etc. It is shown that the natural resource potential of the territory is not fully realized. The average yield of cereals and leguminous crops under irrigation can exceed the actual one by 1.5-2 times. An increase in the area of irrigated lands with unsatisfactory indicators of alkalinization has been established. The priority measures for rational water use in the reclamation sector of the economy of the Republic of Crimea are presented, including a set of measures f or the effective use of water resources of the territory, taking into account economic, social and environmental components. Its implementation is necessary regardless of the renewed supply of Dnieper water to the North Crimean Canal.

CYCLES OF SOLAR ACTIVITY AS A BASIS FOR FORECASTING THE QUALITY OF DNIEPER WATER

One of the main features of the quality of the Dnieper water is the content of natural organic substances which determine the water oxidizability and color indexes. A special problem is that organic substances are poorly removed by water treatment plants. A significant problem in the operation of water treatment plants is the unpredictability of annual changes in the quality of Dnieper water, which complicates logistics management, for example, the supply of reagents. Many years of experience related to the Dnieper water supply station in Kyiv (DnWS) have led to the hypothesis that these changes are in some way related to the cycles of solar activity.
 The purpose of this work is to test this hypothesis to substantiate the possibility of predicting the quality of Dnieper water depending on the action of such a global factor as solar activity. The work was performed by statistical methods using 60-year results of Dnieper water analyzes provided by the DnWS laboratory, as well as Wolf numbers (Sunspot Numbers) provided for free use by the Royal Observatory of Belgium. The influence of solar activity on the quality indicators of Dnieper water, especially in its peak and post-peak periods, has been statistically confirmed. The interaction of biological and physicochemical parameters as factors influencing water quality is shown.
 Conclusions. As a result of the construction of six reservoirs in 1931-1976, the Dnieper from the river actually turned into a network of water bodies. Now these reservoirs are a kind of reactors in which water is treated by electromagnetic solar radiation, which leads to the cyclic transformation of phytoplankton and natural organic matter. Taking into account the cycles of solar activity, the logistical planning of the operation of water treatment facilities receives an independent "base", changes in which can be predicted with some reliability for years to come.

Capabilities of Ultra- and Nanofiltration in the Purification of Dnieper Water from Natural Organic Compounds

Capabilities of Ultra- and Nanofiltration in the Purification of Dnieper Water from Natural Organic Compounds

RELIABILITY OF WATER TREATMENT FACILITIES ACCORDING TO OPERATING DATA

The centralized water supply system from the water source to the consumer includes 3 main complexes: water intake, water treatment and supply and distribution. The reliability of water supply in the area depends on the reliability of each of these complexes, which, in turn, consist of a number of structures. The paper develops the developed principle of assessing the reliability of water treatment plants (WPP) by quantitative indicators of the quality of treated water. The assessment of the reliability of the current WPP was performed to reflect its work, which implements the "black box" model. That is, some process parameters have one value at the input and other values at the output. The disadvantage of this method is that it is impossible to assess the reliability if the process does not occur. In addition, it is impossible to assess the reliability of the BOC for another set of individual structures. And the advantage is the sufficient simplicity of calculating the reliability indicator. Data on the purification of the Dnieper water at the Kremenchug WPP in terms of turbidity and chromaticity are used. Graphs of average variable indicators of turbidity and chromaticity of Dnieper water at the entrance of the WPP and graphs of exceedances of maximum permissible concentrations of treated water are constructed. The main indicator of reliability for municipal water supply facilities is the coefficient of readiness of KD, and the basic indicators of reliability are the average operating time for failure T and the average recovery time of the TR. The possibility of calculating the coefficients KD downtime and KR readiness in case of exceeding the MPC treated water is shown. After analyzing the graphs of water quality indicators, it was determined that the greatest turbidity and chromaticity of the Dnieper water is observed in the autumn.

Менеджмент окружающей среды и экология водоемов в поисках ответов на вызовы времени

Currently, the destruction of landscapes is taking place with a decrease in the sustainability and productivity of natural ecosystems. One of the main reasons for this is inadequate environmental management, which, as a rule, is based on inadequate outdated theoretical ecological concepts. The totality of accumulated data shows that real ecosystems can be in several alternative states and demonstrate relatively rapid changes in the regime of existence with significant, abrupt and permanent changes in structure and functioning. In this regard, the main ecosystem paradigm is currently being revised. From the theoretical concept of the unicity of the ecosystem stable state, ecology moves to the concept of the multiplicity of stable states in the ecosystem. The dynamics of ecosystems can be represented, according to K. Holling, in the form of an adaptation cycle with the alternation of four phases, the features of which are considered. The importance of no return points and possible uncertainty in the dynamics of ecosystems are shown. Ecosystems, in a certain sense, have memory, which is the reason for the hysteresis effect during multidirectional changes in systems. The necessity of developing approaches of adaptive ecosystem management based on this concept is shown. Which is especially important in cases of rapid transformation of natural ecosystems, such, as an example, in the Crimea after the cessation of the supply of Dnieper water to the North Crimean canal. The difficulties of transition to adaptive environmental management in modern conditions are analyzed.

Algae blooming in the Kamianske Reservoir

According to observation data obtained at the drinking water intake in the Kamyanske reservoir in the village of Auly, the basic patterns of water blooming were specified. Water abstraction in here is performed from the depth of 8-9 m, which roughly corresponds to a mid-point of the maximum depths. It was determined that the number of algae per unit volume is very large - significantly higher than at the water intake of the Dnieper Water Supply Station (DWSS), which is located in the downstream of the Kyivska HPP. In some cases, it may exceed 1000 million in 1 dm3. During the study period, a decrease in algae amount was recorded, mainly, starting from 2018. The largest algae amount per a volume unit is usually observed in September, i.e. later than in the surface layer of water. The largest algae amount was recorded in September of 2010 and 2014.
 The factors that contributed to the development of algae at this time are given. Such factors were primarily high air and water temperatures, as well as low cloud cover. There is some delay in changing weather conditions. From June to November, blue-green algae are dominant in the water intake in the village of Auly, the share of which in August-October reaches 95-99%. From December to April, diatomic algae are dominant. The share of green algae is the highest in summer, but it does not usually exceed 2-3% of the total. The significant development of algae in the Kamyanske Reservoir is confirmed by remote sensing data. According to satellite data, it was found out that in this reservoir the largest blooming is observed in the place of water intake location. The dependence of water blooming on hydrometeorological conditions, in particular the direction of wind currents is also shown. The dominance of the northeast wind over the Kamyanske Reservoir in the summer causes a wind setup to the water intake, which results in the increase in the number of algae cells per volume unit.

VARIATION OF THE DNIEPER BASIN HYDRONYMY
 ON THE TERRITORY OF THE SMOLENSK REGION

The article is devoted to the analysis of the Dnieper water bodies nominations on the territory of the Smolensk region. The research is aimed at consideration of the most important onomastic problem at present – variation in the sphere of the proper names, particularly in the hydronymy. Amidst the regional onomastic development, the research in the sphere
 of toponymy and hydronymy is being actively carried out, toponymic dictionaries are being published. In these dictionaries the variants of the geographical objects are often only marked down. However, more focused attention to the revealing
 and describing the reasons and methods of their variation allows the researchers to carry out more detailed diachronic analysis of the onyms existence in the different historical periods and define the invariants formation. The most interesting field of research is the toponymy and hydronymy study of the Smolensk region – western border region of Russia. The material of
 the research is based on the military-topographical map of Smolensk Governorate, large scale maps and an atlas of the Smolensk region, as well as written information sources. The author has analyzed the examples of the orthographical,
 phonetical, morphological and lexical variants of hydronyms and has tried to reveal the linguistic and extralinguistic reasons of the water bodies nominations variation in this region.
 It is proved that the hydronyms variants origin is typical for small water currents; it is linked with their shallowing and the loss of their significance in the economic life of the population. The predominance of the phonetical variants is explained by the influence of the general-linguistic process, a local dialect lect, a living colloquial language. The variation on the word formation level is widely represented by diminutive forms as a result of the changes in the water currents physico-geographical parameters.
 Lexical variation of the hydronyms in the region depends on the nominations de-etymologisation. Moreover, in the analyzed region the author has found out a lot of variants of hydronyms with changes at different language levels. Linguistic
 and extralinguistic reasons of variation in hydronymy are closely linked. This fact can make it more difficult to determine the method of the new variant creation. The analyzed factual material will be practically used in the «Hydronym’s Dictionary of the Smolensk Region», which will be published soon.

ФРАКТАЛЬНІ ДОСЛІДЖЕННЯ РІЧКИ ДНІПРО

Розглядаються питання дослідження фрактальності стока р. Дніпро у 1818-1872 роках.

Features of Application of Aluminum–Iron Composite Coagulants in Purification of Water with High Content of Natural Organic Substances

Disposal of red mud from aluminum production is a worldwide problem and is of great importance in protecting the environment. In previous studies, the authors determined the possibility of obtaining a composite coagulant for the treatment of natural water and wastewaters. The effectiveness of purification of colored Dnieper water by such a reagent due to the presence of iron and aluminum compounds in its composition was shown. On the other hand, there were difficulties associated with an increase in the content of residual iron in purified water. Obviously, for this reason, iron coagulants (in “pure” form and mixed with aluminum sulfate) have not been used in the purification of Dnieper water. In continuation of these works, we have studied the use of composite coagulants and mixtures obtained from red mud using hydrochloric and sulfuric acids, sulfates of iron and aluminum in different proportions. The article presents the results of seasonal studies on the treatment of Dnieper water using jar tests, simulating the real parameters of the existing water treatment plant. It has been found that the best effect of purifying Dnieper water is achieved by using composite mixtures with a ratio of Fe2O3/Al2O3 not exceeding 1/1. A significant effect of pH on the residual concentrations of iron and aluminum in water has been noted. The results of the work are in good agreement with modern ideas about the coagulation of such waters, explain the failures in the use of iron-containing coagulants, and determine the possible ways of this application in the purification of Dnieper colored water containing a significant amount of natural organic compounds.

Cesium-137 in Crimean Salt Waters

The concentration of the technogenic radionuclide ¹³⁷Cs was studied in different groups of salt lakes of Crimean Peninsula. It was established that one of the major sources of ¹³⁷Cs input in them is the North Crimean Canal, which, up to 2014, had been delivering the Dnieper water with a high concentration of radionuclides of Chernobyl origin. Another source of ¹³⁷Cs inflow is Black Sea water through its drainage and direct interaction with the coastal salt lakes of Crimea, in which a positive correlation was observed between ¹³⁷Cs concentration and water salinity.

Do separated taxa react differently to a long-term salinity increase? The meiobenthos changes in Bay Sivash, largest hypersaline lagoon worldwide

In the world's largest hypersaline lagoon Bay Sivash, its ecosystem twice transformed from a previous state to a new one due to human intervention. Before the North Crimean Canal construction, it was hypersaline (average salinity of 140 g l−1). The canal was built between 1963 and 1975, which resulted in intensive development of irrigated agriculture discharging drainage water into the bay. Between 1988 and 2013, salinity gradually dropped to average of 18–23 g l−1; a new ecosystem with a different biotic composition formed. In April 2014, the supply of Dnieper water into the North Crimean Canal ceased. This resulted in a gradual salinity increase in the bay to an average of 52 g l−1in 2015. The start of second ecosystem shift was observed in 2015. In 2018, TSS, DOM and meiobenthos were studied in a salinity gradient from 30 to 88 g l−1. There was an increase in TSS and DOM with increasing salinity. The meiobenthos structure was significantly different in the bottom community and floating mats of filamentous green algae. No correlation was recorded between the number of meiobenthic macrotaxa in the sample and salinity. From 2013 to 2018, changes were seen in the taxocene structure of Nematoda and Harpacticoida. Changes in Nematoda were more dramatic and prolonged than in Harpacticoida. The structure of the Harpacticoida and Ostracoda taxocenes are less variable and more stable than that of the Nematoda taxocene. One of the reasons may be more mobility of Harpacticoida/Ostracoda than Nematoda and/or better osmoadaptation mechanisms.

Актуальність нових правил експлуатації каскаду дніпровських водосховищ

Актуальність нових правил експлуатації каскаду дніпровських водосховищ

The Use of Products of Recycling Waste of Aluminum Manufacturing as a Coagulant when Purifying Highly Colored Natural Water

Results of test coagulation of highly colored Dnieper water by a composite coagulant (CC) obtained by acidizing red mud are presented. It is shown that CC ensures a decrease of basic quality indexes of Dnieper water by 10–20% more effectively than aluminum sulfate (AS). In this case water is contaminated with iron compounds. To lower its concentration it is proposed additionally treat water with ozone, chlorine dioxide or sodium hypochlorite being fed to mixers or flocculation chambers. An alternative way is the use of composition mixture in the form of addition CC to AS in the ratio 1/2–1/1 (in terms of Fe2O3/Al2O3).

The political decision caused the drastic ecosystem shift of the Sivash Bay (the Sea of Azov)

Political and economic decisions have led to more drastic changes of aquatic ecosystems, than those caused by hydrological extremes (drought, floods). Examples of this are two transformations of the Sivash Bay (Sea of Azov); a review and analyses of them are given in the paper. Sivash Bay was a hypersaline lagoon before 1963. The North Crimean Canal was built to improve water supply to the Crimean peninsula by using the waters of the Dnieper River. After the initiation of Dnieper water via the North Crimean Canal and the subsequent development of irrigated agriculture, runoff waters from the fields began draining into Bay Sivash. The salinity began to drop. Pre 1997 the average salinity in Sivash Bay was 140 g L−1; in 1997 it had dropped to 17 g L−1. A fundamentally new brackish water ecosystem gradually formed in Sivash Bay. In April 2014, Ukraine made a political decision to stop supplying Dnieper water via the North Crimean Canal. Discharge of fresh water to the bay almost ceased. Salinity began to increase, and a new transformation of the Sivash ecosystem started. Six complex expeditions were conducted in the Sivash region; their results are described and analyzed in the article. The salinity of the lagoon has now risen to 55–75 g L−1, and drastic changes have occurred in the plankton, benthos, and aquatic vegetation.