Along the middle reaches of the Dnieper River in central Ukraine, braided riverbeds with many islands have developed in alluvial valleys. In the 1970s, six dams were commissioned, and respective monitoring infrastructure was installed. Riverbanks and valley floors composed of unconsolidated material have much lower bank strengths and are susceptible to fluvial erosion and bank collapse, particularly during the release of high flow volumes from hydropower dams. The regulation of the Dnieper River along a cascade of storage reservoirs caused significant changes in its active river channel and hydrological regime. In order to estimate channel stability downstream of the Kaniv reservoir, we conducted an analysis of the hydraulic conditions in terms of changes in flow velocity and propagation of waves caused by intervention water discharges from the Kaniv Hydroelectric Power Plant (HPP). In this paper, we assess the hydromorphological parameters of the studied river reach as well as the characteristics of the related erosion and deposition zones. Therefore, a monitoring framework for channel processes (MCP) downstream of the Kaniv HPP was installed. The analysis of the intervention discharge parameters was conducted based on measurements from July 2015. Channel stability was expressed by the following factors: Lohtin’s number (L), Makkaveev’s (Kc) factor of stability, and a complex index of stability (Mx) by Grishanin. This study shows that the velocity of artificial wave propagation may reach a speed of up to 74.4 km·h−1. The wave propagates for a distance of approx. 45 km within 65 min at a mean velocity of 37.4 km·h−1. The L, Kc, and Mx indicators used in this work showed that when water discharge increased (e.g., during typical peak-capacity operation), the channel becomes unstable and sediments are subject to erosion processes. The riverbed stability indicators clearly illustrate that an increase in parameter values is not dependent on the distance to the dam. The results are valuable for sustainable sediment management at catchment scale and hence, directly applicable in water management.
Knowledge of the cyclicity features in the fluctuations of river runoff, duration and nature of the low-water and high-water period interchange in one or other river basins, and especially their prediction, provides invaluable assistance in the planning and sound management of water resources, improving the operational efficiency of hydropower, reclamation and other water facilities. Currently, the interest in the study of long-term cyclical fluctuations in river runoff, as well as patterns of fluctuations of its underlying factor, has highly increased due to their use in long-term forecasts. Time series of annual water runoff for basins of Tisza, Dniester and Prut rivers were estimated with the use of mathematical tools, methodological framework of which is based on a statistical means of summarizing, systemisation of the input data, evaluation methods of time random sets of runoff characteristics, methods of analysis of the time-series variability and manifestation of their structure.
У роботі представлено та обґрунтовано алгоритм та методику встановлення гідроенергетичного потенціалу річок. Апробація алгоритму та методики здійснювалась на водотоках Українських Карпат. За результатами апроба-ції запропоновано підхід визначення гідроенергетичного потенціалу через встановлення чотирьох його складових: загального, екологічного, технічно можливого та економічно ефективного гідроенергетичного потенціалу. Обґрун-товано доцільність встановлення та концепцію визначення екологічного та зокрема технічно можливого гідроенер-гетичного потенціалів. Запропоновано критерії експертної оцінки ризиків втрат технічно можливого гідроенерге-тичного потенціалу водотоків. Представлено та проаналізовано схему басейнового розподілу та прогнозу змін гід-роенергетичного потенціалу.Ключові слова: гідроенергетичний потенціал, річки Українських Карпат, встановлення гідроенергетичного поте-нціалу, середньорічний стік.
The transformations of river channels as a result of human activity may reflect the level of anthropogenic pressure. Recorded in macroscale, they are indicators of transformations for the larger part of the river basin, while in the microscale they usually refer to its fragment. The human activity that has the strongest influence on the fluvial processes, including suspended sediment transport, is the interference in the riverbed, such as hydrotechnical construction (create of water stages) or transformation of the river banks (concreting of the river banks). The aim of the research was to determine the impact of bridges on the process of water turbidity in the longitudinal profile of large lowland rivers. The research area was the lower reach of Vistula-bridge profiles: Torun, Bydgoszcz, Kiezmark (Poland) and bridge profile on Sukhona-a tributary of the Northern Dvina River near the city of Veliky Ustyug (Russia-Arkhangelsk Oblast). The research conducted in the years 2013-2017 included the measurements of water turbidity in the cross-sections of the above-mentioned rivers. The determinations of water turbidity were carried out using traditional (granulometry analysis) and nephelometric methods (devices: LISST-25X and turbidimeter). The impact of bridges on the variability of water turbidity was determined. The obtained results were related to the variability of depth conditions (bathymetric measurements) and hydrodynamics in the cross-section profile of the channel.
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