Purpose. Study the spatial distribution of artificial reservoirs in the Dnipropetrovsk region and fragmentation impact of small riverbeds on changes in the quality of water resources. Methodology. Field studies on the current state of small river basins were carried out, rivers were selected on the principle of different geographical location and levels of anthropogenic impact. Analytical laboratory studies of water salt composition and methods of mathematical analysis were used to establish the dependence coefficients of water mineralization level and fragmentation of the river basin on the water flow regulation. Findings. The structure of the spatial distribution of artificial reservoirs in the administrative districts of the region and their hydrological characteristics are generalized. It is shown that small volumes of accumulated water in relation to the total area of reservoirs are the cause of intensive heating and evaporation of water. Due to this, the hydrochemical parameters of water are worsen, which affects the environmentally safe water use. It was found that the level of mineralization, the content of sulphates and chlorides exceed the maximum acceptable concentrations in all studied rivers. There is a tendency of deterioration of water quality in the salt block, especially in rivers with significant regulation of artificial reservoirs. In this case, water salinity exceeds the norm by 712 times. Indicators of water mineralization of rivers with fewer ponds and less fragmentation of the river basin exceed the standards by 25 times. Originality. It is determined that among the main factors of anthropogenic impact on the state of aquatic ecosystems is the fragmentation of riverbeds by artificial reservoirs, which turned rivers into cascades of water evaporating ponds. There is a close relationship between the factors of water flow regulation and the level of water mineralization (coefficient of determination R2 =0.62), as well as the coefficient of fragmentation of the river basin (R2 = 0.61). This proves the possibility, in the conditions of research of small rivers, to estimate the degree of change (increase) of water mineralization level by the coefficient of water flow regulation Kw and the coefficient of river fragmentation by the area Practical value. The main directions and ways to normalize the ecological status of watercourses are given. The necessity of systematic study of the current ecological condition of small rivers of Dnipropetrovsk region and their basins is determined.

In this work, we analyzed and studied the Ukrainian typical hydrotechnical structures of the ameliorative complex on soil materials. On the examples of such objects in Dnipropetrovsk oblast, we carried out research and determined the technical condition of the transporting (main irrigation canals) and regulating (retention ponds) hydrotechnical structures (HTS). The main factors and the reasons for the negative engineering-geological processes occurring in those structures and affecting the ecological balance of adjacent territories were determined. The study revealed that the long period of exploitation and absence of corresponding technical care have led to significant losses of irrigation water from the canals and retention ponds. Due to the systemic absence and low use of monitoring researchers, we have proposed the use of prompt and low-cost methods and means of technical diagnostics. The article presents the possibility of using a complex of geophysical methods of natural impulse magnetic field of the Earth and vertical electrical sounding for the purposes of technical diagnostics. The possibility of recording plots and parameters of zones of seepage deformations in the body and at the base of the structures was visually determined and instrumentally proven. This allows identifying the amounts of technical and material resources, stages and order of implementation of repair-restoration works. It was determined that share of the damaged zones accounts for 20 to 35% of the total length of the hydrotechnical structures dependingon their type and parameters of the constructions. In such conditions, the estimated losses of water equal 17-22% of the total amount of the delivery. The surveys showed that further operation of HC poses an ecological threat because of significant worsening of quality of water resources. The article presents disturbing dynamics of change in the irrigated areas involving the danger of secondary salinization, sodification, alkalinization, and toxification as a result of watering. We indicated threatening changes in the structures of the areas irrigated with low-quality water, which, according to various indicators of danger, increased by 1.4 times regarding threat of secondary salinization and by 2 times regarding threat of sodification. We proposed and substantiated approaches to improving the general technical and technological level of functioning of ameliorative structures in the context of maintaining ecological balance and economic practicability of their further use, based on the principles of systemic optimization of complex technical-natural ecosystems.

The article presents the results of the study on the current geoecological condi- tion of the basin of the Zhovtenka River. The study object corresponded to the criteria of a small river, having the length of 42 km and the area of the drainage basin of 293 km2. According to the geographic peculiarities and the level of anthropogenic impact it is a typical small river of the Ukrainian Steppe zone. At the current stage of water management, the river and its tributaries are significantly regulated by artificial aquatic objects – ponds and a water reservoir. The total number of hydrotechnical facilities that form the water bodies is 34 levees. On the river itself, average density of water bodies equals 1 pond per every 2 km of the river length. Such regula- tion contradicts the norms of the current water protection legislation of Ukraine. As a result of fragmentation, the river has turned into a cascade of evaporation ponds. Special ecological threat to water use is the quality of water in the ponds. We determined that due to absence of current and low water exchange, the saline content in water undergoes significant changes. During the field surveys, we collected samples and determined the parameters of mineralization, content of chlorides and sulfates in 10 water bodies. Sampling was carried out during the year in different seasons. We determined that the averaged parameters of mineralization level change within the range of 9.000 mg/dm 3 in spring to 13.000 mg/dm 3 in summer and autumn. The content of chlorides varies within 2.600-3.600 mg/dm 3, sulfates – 4.000-4.800 mg/dm 3 according to the similar seasonal dependence. Due to changes in the climatic conditions and current tendencies of warming and dry climate, decrease in the water resources heightens the risks of irreversible geoecological degradation of the river. Significant regulation and evaporation-caused loss of water leads to rapid shoaling of the water bodies and growth of aquatic-marsh vegetation. The authors suggest an approach to assessment of the level of geoecological transformation of the river basin based on determining quantitative parameters of the constituents of the elements of natural ecosystems and elements of negative anthropogenic impact. We proposed calculation of various coefficients (indicators) which alter the natural condition of water ecosystems, particularly: coefficients of fragmentation, coefficients of urbanization, coefficients of alienation, etc. We present a pos- sibility of using them in relation to the length of the river and hydrographic network, as well as the area of drainage. We determined that percentage parameter of geoecological impact was seen in 94.3% of the area of the drainage basin or 87.4% of the river length. We suggest approaches that would minimize the deleterious impact of economic activity and gradually restore the condition of aquatic ecosystem of the river. The article provides recommendations of using coefficients of geoecological transformation of river ecosystems.

This paper reports the results of studying soil hydraulic structures (SHS) of the CC1 class of consequences on small rivers. The representativeness of the results for the domestic and world practice of further operation of such structures is ensured by the typical technical and technological approaches to the construction, materials, and conditions of their work. Dams are built of soil materials and operated over significant time periods while their standard service life has been exhausted, which increases the environmental and technical danger of their further operation. Visual surveys were conducted and the technical condition was instrumentally diagnosed by the geophysical method of the earth's natural pulsed electromagnetic field (ENPEMF); observational data were mathematically treated. The possibility of arranging areas of increased water filtration through the SHS body was substantiated, as well as watering, loosening, and suffusion; potentially dangerous zones prone to landslides, cracks, and collapse were determined. The probability of risk of an accident on dams was estimated at their cascading arrangement as a result of filtration deformations of the body and the base of the structure. Under current operating conditions, the possibility of letting the normative and excess (forced) water volumes through water discharge facilities due to precipitation or a breakthrough of the structure located upstream was estimated. The proposed approach makes it possible to manage the cascade of hydraulic structures at different stages of operation: planned, operational decision-making, forecasting. This allows diagnostic examinations to be performed in order to identify structures that require priority in raising funds for repair and restoration work or demolition (dismantling)

Purpose. Development of simplified indicators for assessment of the effectiveness of local water flow management and use in reservoirs and ponds. Methodology. The methods of integral assessment by specific indicators that characterize the operational parameters of the reservoir are used. Analytical formulas for calculating specific indicators are applied, their values are in the range from -1.0 to +1.0, which greatly simplifies the perception of the received information. Findings. General characteristic of the artificial water objects of the study is given. Coefficients of operational parameters of reservoirs and regulation of local surface flow have been determined. Specific and integral indicators of the management effectiveness assessment of local surface water resources have been established. A formula for calculating the comparative total risk indicator and a conventional distribution scale are proposed, according to them the effectiveness of local water resources management within administrative units or river basins is evaluated for the elements of the sample taken for the study. The ratio of parameters of the total area of the territory occupied by ponds (44%) to the area occupied by reservoirs (56%) was determined, according to which the ponds will retain only 25% of the total volume of water resources. For almost all studied elements of the sample, the value of the average depth is less than 2 meters, and the volume is up to 1 × 106 m3. Thereby, most reservoirs act as evaporation ponds, which leads to the deterioration of the water resources quality. The determined coefficients of local surface flow regulation for 9 out of 11 administrative regions of the Steppe Zone of Ukraine range from 0.22 to 1.36, which is a significant excess of the permissible norms of modular coefficients for 95% coverage within 0.050.25. For Kherson (2.14) and Odesa (6.45) regions, this parameter exceeds the requirements of the Water Code of Ukraine by many times (with a norm of 0.05 and 0.2, respectively). Originality. Specific integral indicators of local water flow regulation and characteristics of operational parameters of reservoirs on the territory of the administrative regions of the Steppe Zone of Ukraine are proposed and determined. A point assessment of the impact of artificial water bodies on the surrounding natural environment is provided, which substantiates and emphasizes the conclusions regarding the irrationality of water use and the further exploitation of such a significant number of artificial water bodies, in particular small ponds. Practical value. Specific indicators of the effectiveness of the management and use of local water flow held in the ponds and reservoirs of the Steppe Zone of Ukraine simplify the perception of the received information and shorten the time of making management and water protection decisions.