1. Icings are sheet-like masses of layered ice that form on the ground surface or on top of river or lake ice in winter where water seeps out of the ground in springs, rivers and lakes (Van Everdin...

The basin of the transboundary Chikoy River is the largest in terms of area among the catchment areas of the main tributaries of the Selenga River. The Selenga basin as a whole is characterized by a wide distribution of icing. The paper presents the results of mapping icings and their distribution according to various physical and geographical characteristics. Based on the Landsat-8 satellite imagery for 2019, a cartographic database of icings was compiled for the first time for this territory. The database includes 6,319 objects on a total area of 140 km2. The largest icing is 671.13 thousand m2 in area. The mean value, median, and mode are 22.16, 12.86, and 10.24 thousand m2, respectively. Most of the icings are located at altitudes of 900–1,200 m and on the slopes of the eastern exposure. Icings were not found in the western part of the Chikoy River basin and in the near-top belt of the ridges. Fissure rocks are predominant in the study area, which indicates the leading role of groundwater in the formation of icing. The greatest icing coverage is found in areas with annual precipitation in the range of 350–460 mm and with an average annual temperature of –2.5 ... –3℃. In the landscape structure, icing is common in low- and mid-mountain taiga larch-dark coniferous landscapes. About 80% of the icings are located on the complexes of soddy podburs, podburs, soddy podzols, and other associated soils. The level of icing coverage was found to be not proportional to the natural resources of groundwater, which can be caused by both the imperfection of the original groundwater map and the uncharacteristic manifestation of icing in 2019. The resulting database will become the basis for retrospective and predictive assessments of the icing dynamics in the Chikoy and Selenga River basins.

The paper presents the results of the study on icings in the Selenga middle mountains (Western Transbaikalia). Current and retrospective maps of their distribution have been drawn up, relevant data on the main morphometric characteristics, interannual spatial dynamics, and area variability have been obtained. Comparison of vector data on the location of the icings in different years, together with the materials obtained during field expedition studies, allowed us to preliminary assess their belonging to different genetic types. It has been established that in the Selenga Middle Mountains, the predominant icings are formed as a result of groundwater rise to the surface during the seasonal freezing of rocks. About 30% of the icings are associated with groundwater sources coming from deep aquifers (key icings), river water icings are very rare. The interannual variability of the size of icings is in sync with the hydration cycles, at the same time, there is a tendency for an increase in the total number of icings. At the same time, the number of very large icings has decreased 2 times as compared to 1990, while the number of medium and small icings has increased. These trends are a consequence of changes in the state of the natural environment under the influence of climatic processes (increase in air temperature) and anthropogenic factors, which influence on the intensity of the icing formation processes in the Selenga Middle Mountains is significant.

Relevance. The increase in the intensity of icing formation in the territory of the Western Transbaikalia from 2019 to the present due to the beginning of the high-water climatic cycle. The volumes of icings increase annually, cases of flooding of settlements and infrastructure facilities are observed. This makes it advisable to conduct a modern detailed study of the icings using new technologies and approaches. In the Uda River basin, which was selected as the study area, icings have not been studied sufficiently, and there is little information about them in literature. At the same time, they are a valuable resource, since massive ice fields accumulate a significant part of the winter runoff of both surface and groundwater. Therefore, icings can be used for economic purposes as a source of water supply for agricultural production when they melt in the warm season. Aim. To assess the intensity of manifestation of icing formation within the Uda River basin with the identification of general patterns of modern distribution of the icings, the impact of various environmental factors on their dynamics, as well as the possibilities of their utilization. Subjects. Icings formed in the cold season in the Uda River basin in the conditions of dissected mid-mountainous relief and wide distribution of permafrost rocks (permafrost). Methods. Remote and field expeditionary methods of scientific research. Landsat-4-5, Landsat-8, Sentinel-2 space images and Resurs-P data were used as a source of information for remote sensing. Data on icings thickness were obtained using field methods in the course of icings surveys, and local digital terrain models of key sites in the areas of icings development were compiled using UAVs. Data processing was carried out using GIS methods. Results. Current and retrospective maps of icings location were obtained. On the territory with the total area of about 35 thousand km2 up to 3.2 thousand icings are formed in winter depending on the natural and climatic conditions. During low-water climatic cycles, the number of icings decreases by 1.5 times. The large number of icings with their relatively small size is a consequence of the discontinuity of the cryolithozone in the study area. Groundwater icings prevail, where ice fields contain most of their runoff during the cold period of the year. The Uda River basin icings characterize the groundwater reserves of the territory and can be used as sources of water supply for agricultural production in the dry period from April to June, when there is practically no precipitation.

The article presents the results of research on aufeis (icings) in the area where their concentration is maximal for the Selenga River basin. Landsat and Sentinel satellite imagery data were used to map the current location of aufeis in the valleys of permanent watercourses of the transboundary Dzhida River basin. It was found out that up to 3.5 thousand small aufeis with the area from 0.005 to 1 km² are formed in small watersheds of the territory. The total area of aufeis within the considered territory can reach up to 92.1 km², the aufeis coverage is 0.45%. It is revealed that in the total amount, small aufeis prevail, the area of which lies within 0.01 to 0.1 km². In addition, ecosystem and economic aspects of the processes of ice formation on the territory of Russia and neighbouring Mongolia are considered.