В статье приведены оценки влияния каскада вилюйских водохранилищ на трансформацию расходов воды и взвешенных наносов реки Вилюй. Оценки получены на основе данных многолетних сетевых наблюдений, а также экспедиционных измерений в августе – сентябре 2021 года и материалов спутниковой съемки. В ходе экспедиционных исследований оценено распределение мутности воды по акватории и глубине Вилюйского водохранилища, исследована продольная трансформация мутности воды – вдоль руслового Светлинского водохранилища и его нижнего бьефа вплоть до поселка Сунтар. Показано, что в результате подпора Вилюйским водохранилищем, бóльшая часть речных наносов откладывается в приустьевых зонах крупных притоков этого водоема. Здесь также наблюдается и наибольшая мутность воды по данным отбора проб воды и спутникового зондирования. По итогам георадарной съемки дна установлено, что осаждение значительной части речных наносов в верхних отсеках Вилюйского водохранилища объясняет практически отсутствие современных речных отложений в его приплотинной части. Составлен баланс наносов Вилюйского водохранилища с оценкой сбрасываемых в нижний бьеф наносов. По всем собранным данным описан характер продольной трансформации воздействий водохранилищ на расходы и уровни воды, расходы наносов и мутность воды по длине среднего и нижнего течения реки Вилюй. Показано, что не только на зарегулированной реке Вилюй, но и почти на всех ее притоках доминирует тенденция к снижению стока наносов. При этом обнаружены аномалии величин стока и гидрофизических показателей в некоторых притоках реки Вилюй, подверженных сильному антропогенному воздействию.

Publications on changes in river water regime in Russia under the conditions of current climate changes are reviewed. Most recent generalizations of such publications are presented in Roshydromet evaluation reports. The publication of these basic studies followed by many studies improving the conclusions of national reports. The objective of this review is to generalize the current concepts regarding the effect of climate changes in Russian Federation territory on the mean annual and maximal river runoff, primarily, based on most recent publications and the authors' own studies. New maps, developed by the authors, are given to characterize variations of the annual and maximal runoff, including the dates of the disturbance of the stationary character of the series based on data up to 2019. Considerable attention is paid to statistical analysis of the revealed changes. The annual runoff on the average for the Russian territory is shown to tend to increase in the recent decades because of an increase in the moistening of the territory. However, the changes in the majority of the analyzed basins are statistically insignificant. The average annual runoff of rivers into the Arctic seas from the territory of Siberia and Far East has also slightly increased. Changes in the maximal runoff are more pronounced and differently directed.

Significant degradation of the Agrakhan Bay on the eastern coast of the Terek River delta has occurred in the course of the 20th century as a result of the combined action of natural and anthropogenic factors. Comprehensive studies conducted by the authors in 2018–2020 have made it possible to describe the main causes of this degradation, characterize the current state of the reservoir, and establish scientific bases under recommendations for its improvement. It has been demonstrated that as a result of partial drying and reduction of water surface area the bay has lost its former importance as a spawning and rearing water body providing the West Caspian region with the younglings of valuable commercial fish species. By 2018, the catches decreased by ten times compared to the early 20th century with sturgeons having almost totally disappeared. The state of the northern part of the bay, which has transformed into a group of shallow water bodies almost entirely separated from each other and from the sea is particularly unfavourable. The study of hydrological and morphological, hydrobiological, fishery-related and hydrochemical parameters has shown that the improvement of the wetlands at the former bay site is possible. Detailed analysis of the water balance using multivariate limnological calculations has shown that there is enough water for watering and partial restoration of the water bodies of the Agrakhan Bay hydrographic system. Clearing of silted and overgrown canals, deepening and berming of the remaining water bodies, and directing the necessary amounts of river water into Northern and Southern Agrakhan Bay (in accordance with the calculated delivery schedule) will allow reduction of the overgrowing and siltation of water bodies, restore the water exchange between them, improve water quality, revive the fishery industry in the region, improve the habitats of many rare and protected animal species, and increase the recreational attractiveness of the region.

Inundatios on the Black Sea coast of Krasnodar krai between 1945 and 2013 have been analyzed. The main genetic types of inundations on the coast have been identified. The specific features and regularities of inundation wave transformation along the rivers and over time have been studied. Seasonal and maximal runoff of Black Sea rivers has been analyzed over a long-term period. Regularities in the variations of the number of inundatios and their characteristics over the coastal area have been revealed both at the annual and long-term scales. Quantitative estimates are given to the hazard and damage to the population and economic activity due to inundations in the valleys of Black Sea rivers.

Inundatios on the Black Sea coast of Krasnodar krai between 1945 and 2013 have been analyzed. The main genetic types of inundations on the coast have been identified. The specific features and regularities of inundation wave transformation along the rivers and over time have been studied. Seasonal and maximal runoff of Black Sea rivers has been analyzed over a long term period. Regularities in the variations of the number of inundatios and their characteristics over the coastal area have been revealed both at the annual and long term scales. Quantitative estimates are given to the hazard and damage to the population and economic activity due to inundations in the valleys of Black Sea rivers.