Vol 50, No 1 (2023)

The long-term dynamics of the Northern Dvina delta was studied with the comparison of space images of 1977 and 2020. A map of delta dynamics, compiled by them, shows that the islands at the delta coastline keep increasing and join to the delta, channel islands in the main branches are increasing, and small watercourses in delta islands become narrower and disappear. However, this long-term tendency of the continuing increase in delta area is now accompanied by the processes of shore erosion in islands at delta coastline from the side of the Dvina Bay.

Soil loss rate, suspended load, and suspended sediment discharge were simulated for the drainage basin of the Komarovka R., located at the territory of the former Primorskaya Water Balance, Russian Far East. The study was based on an open-code SWAT model. The model was calibrated and verified using archive measurement data on sediment load and suspended sediment discharge at PWBS by data of Tsentral’nyi hydrological gage (157 km2). The simulation efficiency of the suspended load and suspended sediment discharge corresponds to categories satisfactory and higher. On the average for the drainage basin, the rate of soil washout is 11–12 t/ha per year. The washout rate is maximal in the period of active snow melting. The mean monthly value for April–May is 75 thous. t. The mean annual washout is 171 thous. t, and the maximal is 800 thous. t/year. The mean annual runoff of suspended sediments in the outlet section of the drainage basin is 2.6 thous. t. The highest monthly values of sediment runoff correspond to the period of summer floods in August, when with average of 1 thous. and maximum of 7.7 thous. t. The obtained data on the heterogeneity of the spatial distribution of the simulated values of washout rate are in good agreement with the landscape and climatic features of runoff formation in the drainage river basin. The major errors in the estimation of sediment load are due to the simulation quality of the hydrological regime and dynamics of runoff components that form flood hydrographs.

Specific features of water quality formation are considered for the Yauza R. flowing in an urbanized drainage basin containing Moscow City and nearest Moscow region. It has been found that the deep transformation of the natural hydrographic network along with diffused pollution from sources scattered over its basin have an adverse effect on water quality formation in the urban watercourse and its self-purification potential. The current ecological state of the river can be evaluated as unsatisfactory, notwithstanding the water protection measures taken in its basin. The existing system for managing the urban surface runoff has been analyzed. It is shown that monitoring the volumes and formation conditions of pollution runoff from the urban territory is not effective enough for an objective estimate of the environmental conditions of water bodies and reduces the efficiency of water protection measures.

The article gives the results of studies of the hydroecological characteristics (water temperature, dissolved oxygen, chemical characteristics, production, methane concentration and emission, and the abundance of phytoplankton and benthos) in the Ivankovo Reservoir in August 2020–2021. Data of integrated surveys were used to show that the specific weather conditions and flowage have led to difference in these closely interrelated characteristics. The hot weather and the low flowage in 2021 contributed to an increase in oxygen consumption by bed soil, intensification of exchange processes at the water–bottom sediment interface, an increase in mineral phosphorus flux, more active blooming of the water body, decay of dead organic matter at higher temperature of the bottom layer. The role of bioturbation in changes in the rate of exchange processes between bottom water layer and sediments is demonstrated. The changes in the combination of processes in the water body caused an increase in methane flux into the atmosphere in 2021 compared with the previous year.

Crimean salt lakes have a high resource potential used in various types of human activity, i.e., balneology, chemical industry, and therapy; now, they are attractive tourist sites. A combination of biotic and abiotic factors creates specific conditions for the development and functioning of biota and the formation of unique ionic composition of brine and bottom sediments, which are used in balneology and the production of spa-products. Sakskoe Lake is among the largest coastal salt lakes of Crimea, located on the southwestern coast of the Black Sea. The effect of climate conditions and biota caused the formation of a specific ecosystem in the lake, which has a peculiar ionic composition of brine, changing within the year, and a brine shrimp population. The concentrations of cations and anions in the brine increased in summer because of active evaporation and decreased in winter and spring because of dilution of atmospheric precipitation and snowmelt water. The dynamics of the brine population also showed characteristic seasonal features: the life cycle begins in April, the maximal number of various life stages is recorded in May–June, and the end, in November–December. The artificial regulation of the water–salt regime of the water body through addition of seawater in summer contributed to maintaining optimal conditions, thus ensuring a high vital activity of the biota. The obtained data can reflect the seasonal dynamics of processes in the salt lake, governed by climatic, seasonal, and anthropogenic factors.

It is well-known that the error of a measurement result can increase at each step of a laboratory procedure, as well as because of the sample character of partial measurements. To overcome these difficulties, close cooperation between hydrologists and analytical chemists is required in order to obtain reliable information about the composition and properties of natural waters, which are extremely unstable. The study focuses on details that are of importance for both the client-hydrologist and the performer—chemist-analyst. The article gives different variants of conclusions regarding the compliance or non-compliance with the established requirements. The cost of reliable measurements is calculated, and variants of optimization of enterprise’s payments for discharges are proposed. Recommendations are given to customers regarding the choice of a competent analytical laboratory.