Vodnye resursy

Approaches to regional hydroecological analysis are proposed, taking into account the relationship between surface and groundwater. Using the example of the Belgorod region, the features of the formation of surface and underground runoff resources in changing climatic and economic conditions in the forest-steppe zone of the Russian Plain are revealed. Trends in the use of water resources have been established. The impact of wastewater, runoff from urbanized territories and arable lands on them is estimated. It is shown that a very important hydrological and ecological role is played by changing climatic conditions, primarily an increase in air temperature. The changes in recent years (from 2008 to 2021) of river flow, its surface and underground components have been established, their positive and negative consequences have been revealed. Groundwater resources, which have not been fully developed, serve as an important reserve for providing high-quality water to the population. To improve the ecological condition of water bodies, it is very important to improve the wastewater treatment system, create monitoring of pollution of water bodies from diffuse sources and reduce irretrievable water losses during its use.

This paper presents an analysis of the factors contributing to the longitudinal increase in suspended sediment along the Lena River delta branches. Satellite images (Landsat 5-9) from 2000 to 2022 during the open channel period from June to September were captured for the suspended sediment concentration modeling. This period coincides with the water discharge in the Lena River ranging from 17,400 to 78,100 m³/s. The ERA5-Land reanalysis, monitoring observations at the Samoilovsky Island research station and remote sensing data were employed to estimate the factors influencing suspended sediment concentration changes. These factors included air temperature, precipitation, wind speed, solar radiation flux, permafrost temperature, water discharge and suspended sediment concentration in the top of the delta top, and the intensity of bank retreat. The results of the correlation analysis indicated that the observed increase in suspended sediment concentration was attributable to a combination of meteorological factors (temperature, precipitation, wind speed, and solar radiation flux) and the intensity of riverbank erosion associated with thermal processes. The longitudinal increase in in suspended sediment concentration (on average for the study period by 2-4% along the delta length) can be explained by an average daily air temperature and permafrost temperature increase. The analysis demonstrated that temperature factors exert a predominant influence on riverbanks comprising the Ice Complex. here was a significant correlation between the rates of riverbank degradation and the concentration of suspended sediment.

The Chulyshman River influence on the formation of density stratification of Lake Teletskoye in summer is considered. The relevance of this problem is determined by the importance of studying the specific features of the processes of impurity and pollutant transfer under the conditions of thermocline and thermal bar formation and water renewal in the lake. The above-mentioned problems are solved using the mathematical modeling methods and field data. To consider thermohydrodynamic processes in deep Lake Teletskoye and the Chulyshman River, the computer models have been built based on the open Delft3D package. For the lake, it is an improved 3D model and for the flow of the Chulyshman River in its mouth - a planned (2DH) model. The conjugation of 3D and 2DH models was implemented at the inlet of Lake Teletskoye. Field observations of the spatial thermal structure of the reservoir were carried out in the summer-autumn months of 2010–2023. The main results of the work performed are as follows: the revealed complex picture of density stratification and density currents in Lake Teletskoye during the period of summer heating of the reservoir and driving factors of its formation, distribution features of the Chulyshman River waters within the lake in summer.

Based on data from expeditionary studies of the Southern Scientific Center of the Russian Academy of Sciences, using statistical modeling, new quantitative estimates of the runoff of dissolved organic carbon, chlorophyll-a, total suspended solids, particulate organic carbon with the waters of the Don River into the Sea of Azov during the low water period 2007–2020 were obtained. Statistical models were constructed using Weighted Regressions on Time, Discharge, and Season (WRTDS), which provides some of the most accurate quantitative estimates of concentrations and fluxes to date. Seasonal and interannual features of the relevant substances’ concentrations in the river are considered, and their relationship with water discharges is shown. A comparison was made of the runoff of organic matter and suspended solids of the Don in the modern low water period and other periods of the 20th century.

The results of the study of the relationship between hydrochemical composition and water discharge based on measurements at the posts of the Crimean rivers according to hydrological yearbooks are presented. The Spearman rank correlation coefficient was used to calculate the closeness of the relationship. Three groups of rivers with peculiarities of flow formation were identified according to the nature of the relationship between changes in discharge and water composition: rivers with no relationship between discharge and the sum of ions, hardness and organic matter content, rivers with a relationship with the sum of ions, hardness and organic matter content, and rivers with a relationship only with the sum of ions. Spatial differences in water composition were investigated by cluster analysis using survey materials during the low-water period in July 2022 in the rivers of the southwestern part of Crimea. The analysis does not include elements whose concentration can be determined by anthropogenic factor (nitrates, phosphates). Inter-basin and intra-basin differences in water composition due to the different geological structure of the territory are revealed.

Measurements of pH, total alkalinity, humic substances were carried out in June 2005, 2006 in the waters of the downstream Amur River along distance 489 km on the 13 hydrochemical stations between the cities of Komsomolsk-on-Amur and the Nikolaevsk-on-Amur. In August 2016, hydrochemical observations were carried out at the mouth Amur River, which included measurements of pH, total alkalinity, humic substances, concentrations of major ions of river water (Na⁺, K⁺K⁺, Ca²⁺, Mg²⁺, Cl^–Cl^–) and dissolved organic carbon. The average annual rate of chemical weathering in the Amur River basin has been established which equal to 10.7 t/(km² year). Weathering of rocks and producing of organic matter by photosynthesis lead to the consumption of the atmospheric CO₂ in the river basin. Amur River annually exports this atmospheric CO₂ into the marine environment equaled to . It has been established that the Amur River waters annually emit  of carbon dioxide to the atmosphere. The balance of opposite processes (CO₂ export and CO₂ emission) showed that the ecosystem of the Amur River is a weak source of carbon dioxide to the atmosphere. The annual export of total alkalinity by the Amur into the marine environment (mol/year) increases normalized total alkalinity in the surface layer off the eastern shores of the Sakhalin Island (Sea of Okhotsk) and in the northern part of the Sea of Japan.