Новые данные о трансформации стока воды и наносов в дельте реки Лены по итогам экспедиционных измерений в августе 2022 г.

Field hydrological measurements were performed in the Lena River delta from the 10th to the 16th of August 2022. 25 values of water discharge and 58 suspended sediment concentrations (SSC) were measured, multiple chemical composition water samples were taken, along with samples of bottom and bank river sediments, and thermal abrasion coasts were highlighted. Particle size and chemical composition analyses of the sediment samples were carried out. The aim of the study was to estimate the water flow distribution in the delta and to determine the directional SSC, sediment particle size and chemical composition changes along the delta and inside the depth of the river flow, and define the roles of the local hydrological and morphological factors of river flow transformation. Moreover, field measurements are crucial for SSC estimation and monitoring based on satellite image data. The laboratory analyses included particle size definition in suspended and bottom sediment samples, organic matter and SSC definition. The August 2022 expedition results were compared to the previous surveys. It was established that the flow distribution around the Stolb island corresponds with that of 2016: the Bykovsky, Trophimovsky, Tumatsky and Oleneksky branches receive 24.9–25.5, 58–59.2, 6 and 6.6 % of the water discharge from the Kusur gauging station on the Lena River, respectively. However, the role of the Main channel was slightly overestimated. The new data includes water discharges in the branches around the Samoilovsky island and in the channel systems of the Oleneksky and Tumatsky branches. SSC was relatively low and amounted to around 12–24 mg/l, rising from the water surface to the bottom 1.2–2 times. SSC decreased along the course of the Oleneksky and Tumatsky branches (1.5 and 1.1 times, respectively) due to the ratio between SSC and the potential stream transport capacity. SSC rose along the course of the Bykovsky branch, even though it wasn’t shown by the Landsat-8 satellite image (16th of August 2022). A significant sediment source in the delta are eroded and thermo eroded shores of the edoma island systems. The average sediment size proved to be from 0.011 to 0.019 mm. SSC does not vary much around the main channel and the nearest branches. Important relations between SSC, optical turbidity and ADCP backscatter intensity were estimated. The coarse diameter of 30 bottom sediment samples was 0.46 mm. The largest sediments were discovered in the Bykovsky branch, while the smallest sediments were found in the smaller transverse branches. Along the Tumatsky and Oleneksky branches the bottom sediments alternate from fine to medium sands.Статья содержит важные итоги полевых и комплексных гидрологических исследований, проводившихся в дельте р. Лены с 10 по 16 августа 2022 г. Были измерены 25 расходов воды и концентрации взвесей вбречных водах, отобраны пробы воды, образцы донного и берегового грунтов на гранулометрический и химический состав, отмечены размываемые берега. Целью исследований было изучение распределениябстока воды и наносов Лены между дельтовыми рукавами, изменений мутности воды, гранулометрического и химического состава наносов от вершины к морскому краю дельты, по глубине и ширине потока, роли в них местных гидролого-морфологических и термоабразионных процессов. Полученные натурные данные необходимы для познания особенностей современного рассредоточения стока воды и наносов в огромной и многорукавной дельте Лены, его изменений с момента последних стационарных и экспедиционных измерений, для дешифрирования спутниковых снимков, разработки инструментария для пересчета поверхностных измерений в осредненные по сечению потока

A New Method for Calculating the Heat Flux of Rivers in the Absence of Gauging-Station Data

In the paper, a comparative analysis of previously developed methods for calculating the heat flux of rivers in the absence of gauging-station data are given, and a new method for such calculations is proposed. It is based on the Maps of specific annual heat flux of zonal rivers and empirical dependencies of heat flux on the average height of the catchment area. An example of such a map is the “Map of specific annual heat flux (MT, 109× kJ/km2) of rivers in the northeast of the Asian part of Russia” plotted on the data for the period from 1950/1955 to 2018 and on the basis of data from 112 gauging stations. General recommendations for calculating the annual heat flux of medium-sized rivers that do not have posts, the intra-annual distribution of heat flux, the values of heat flux at the mouths of large rivers are set out in the paper. The values of heat flux calculated for the marine mouths of region large rivers and the sections of seacoasts between these mouths are given as an example of the implementation of the new recommendations. The list of new materials that help calculations includes new maps of average monthly water temperatures (May-October), the dependence of water temperature and heat flux on the average height of the catchment area, the division of the territory of the Northeast Asian part of Russia into 10 altitude-thermal zones, the relationship between heat flux and water runoff, the catchment area of the river and other materials. In total, data from 34 weather stations, 231 posts with water temperatures and 145 posts with water discharges were used in the research.</jats:p

Current hydroecological state of the Ural River in the lower reaches

Abstract Climate and hydrological changes in the Ural River basin, together with water management activities determine the current hydroecological state of the river in its lower course. In comparison with the conventional natural background, the salinity of water in high water period increased by 2.5 times, in low water period- by 5-8 %. Contamination of the lower course of the river is caused by the inflow of pollutants from the upstream sections and the confluence of the polluted tributaries. In the area with no tributaries, the water is characterized as “standard-clean”. The saprobity indices, which characterize the content of organic substances in water, are located within the boundaries of the b-mesosaprobic zone, which characterize low level of water contamination. The content of dissolved oxygen indicates insufficient aeration of the river water during most of the year. The lowest oxygen content is observed during winter period.</jats:p

Causes and systematics of inundations of the Krasnodar territory on the Russian Black Sea coast

The inundation situations on the Black Sea coast of the Krasnodar territory for the period from 1945 until 2013 were analysed and the main types of inundations at the coast are described. Synoptic factors of the formation of extreme precipitation and rainfall floods, features and regularities of the downstream flood wave transformation in the rivers are also studied. Therefore, assessments of seasonal and maximum flow of the Black Sea coast rivers for the period of hydrometric measurements were done. Regularities of change of the occurrence of inundations and their characteristics on the coastal terrain were analysed, for a year and on a perennial timescale. <br><br> Most catastrophic and exceptional inundations arise in the summer and in early autumn. Small inundations during the remaining year reflect the seasonal distribution of river flow and floods in the Black Sea rivers. Extensive and sometimes extreme precipitation dominates the river flow regimes. The seasonal distribution of small and moderately dangerous inundations reflects, on average, a water regime of two groups of rivers of the coast &ndash; to the north and to the south of the Tuapse River. To the north of the Tuapse River, floods prevail from November until March (up to 70 % of observed floods took place in this period) as a result of precipitation and winter snowmelt during frequent thaw periods. In winter, high waters often overlap to form a multi-peak high water of 2&ndash;3 weeks' duration. In the summer and in early autumn we observe a steady low flow. The total amount of runoff increases both in a southeast direction, and with the altitude of the river basins. Interannual variability of mean annual runoff, as well as maximum runoff, on the contrary decreases in the southern direction and with an increasing area of the river basins. The coastal high waters of the rivers of the Sochi part of the coast are typical at any time of the year, but more often floods in the cold season result from incessant rain, and thawing snow. Annually up to 25 floods have been observed. The principal reason of such distribution is the increase of extreme rainfall in the warm season. <br><br> Orographic features of the coast and detailed features of rainfall only cover a small number of local river basins and a limited area. The geographical correlation of individual rainfall and subsequent floods ceases to be statistically significant for distances over 40&ndash;60 km. <br><br> The annual flow cycle is mainly determined by two seasons, winter/spring and summer, with strong and weak flows, respectively; almost 71 % of all catastrophic and exceptional inundations took place in July&ndash;August (71 %) and in October&ndash;November (29 %). The characteristic features of dangerous floods are their rapid formation and propagation, a significant increase of water level (up to 5&ndash;7 m and more) and the multiple increase of water discharges in comparison with low flow period. <br><br> Analysis of the interannual changes of the number of inundations at the Black Sea coast of the Krasnodar territory has shown some increase of the number of inundations in the period from the early 1970s until the early years of the twenty-first century. <br><br> Quantitative assessments of risk, hazard and damage for the population and economic activities from accidental inundations in the valleys of the Black Sea coast rivers show that economic and social losses from inundations at the Black Sea coast of the Krasnodar territory are some of the highest in the Russian Federation. The basic conclusion from recent inundations is the need to consider not only the lower reaches and mouths of the Black Sea coast rivers where the main part of the social and economic development of the coast is concentrated, but also whole river basins and catchments. Further, an analysis of the efficiency of the measures applied at the coast to mitigate inundations and their after-effects is provided

Modern hydrological and morphological state of the Agrakhan Bay and its adverse changes

Abstract The study was based, firstly, on the diverse data collected during field work in 2018 – 2020 in the eastern part of the Terek River delta and long-term hydrological monitoring data on the Roshydromet gauges. Secondly, on a profound comparative analysis of multi-temporal cartographic materials and multiple satellite images, laboratory analysis of water and sediment samples and other research groups’ field data. The performed analysis resulted in unprecedented complex and profound assessment of the contemporary hydrological, morphological and ecological state of the former Agrakhan Bay of the Caspian Sea. The drivers, dependencies and parameters of hydrological and morphological degradation were described; a multi-layer large-scale GIS was created to design multiple illustrations. The performed assessment allowed for development of measures for partial restoration of the hydrological and ecological potential of the former Agrakhan Bay.</jats:p

What and where are periglacial landscapes?

Uncertainties about landscape evolution under cold, nonglacial conditions raise a question fundamental to periglacial geomorphology: what and where are periglacial landscapes? To answer this, with an emphasis on lowland periglacial areas, the present study distinguishes between characteristic and polygenetic periglacial landscapes, and considers how complete is the footprint of periglaciation? Using a conceptual framework of landscape sensitivity and change, the study applies four geological criteria (periglacial persistence, extraglacial regions, ice‐rich substrates, and aggradation of sediment and permafrost) through the last 3.5 million years of the late Cenozoic to identify permafrost regions in the Northern Hemisphere. In limited areas of unglaciated permafrost regions are characteristic periglacial landscapes whose morphology has been adjusted essentially to present (i.e., Holocene interglacial) process conditions, namely thermokarst landscapes, and mixed periglacial–alluvial and periglacial–deltaic landscapes. More widespread in past and present permafrost regions are polygenetic periglacial landscapes, which inherit ancient landsurfaces on which periglacial landforms are superimposed to varying degrees, presently or previously. Such landscapes comprise relict accumulation plains and aprons, frost‐susceptible and nonfrost‐susceptible terrains, cryopediments, and glacial–periglacial landscapes. Periglaciation can produce topographic fingerprints at mesospatial scales (103–105 m): (1) relict accumulation plains and aprons form where long‐term sedimentation buried landsurfaces; and (2) plateaux with convexo–concave hillslopes and inset with valleys, formed by bedrock brecciation, mass wasting, and stream incision in frost‐susceptible terrain