Space–time analysis of the hydrochemical composition and pollution of water in the Northern Dvina basin

The dynamics of water quality along the Northern Dvina River is considered within the context of anthropogenic impact. In general, the waters of the river are characterized as very polluted. Cases of high and extremely high levels of water pollution in various locations have been considered. Organic substances, iron compounds, copper, and zinc are relatively common pollutants. Long-term average volumes of inflow of certain pollutants along the length of the river exceed the maximum permissible concentration by 2 to 5 times. A tendency toward slightly improved water quality downstream with decreasing amounts of petroleum products and zinc compounds was revealed also.

Multidimensional data analysis of jamming factors in river basins

The analysis and quantitative assessment of factors affecting the frequency of ice jams and the parameters of flood congestion is an important area for hydrophysical study. The influence on flood-congestion parameters of backwaters identified in the lower cross-sections on sections of rivers prone to jamming was estimated by applying discriminatory analysis to the data of long-term observations of the water regime of the rivers in the Northern Dvina basin. Additionally, methods of classification of characteristic areas were developed. In addition, models derived by multiple regression analysis made it possible to assess the influence of the morphometric features of the riverbed on the frequency of ice jams within the two large river basins in the European and Asian parts of Russia.

Evolution of groundwater chemistry in coastal aquifers of the Northern Dvina basin (NW Russia)

The specific objective of the study is to clarify the sources and characteristics of groundwater chemistry in coastal aquifers of the Northern Dvina basin. It has been established that the chemical composition of fresh water evolves in the direction (Ca-Mg-HCO3) - (Na-HCO3) - (Na-Cl). It is due to successive replacement of the process of calcite dissolution in the recharge area on the watershed i) by the process of hydrolysis of sodium aluminosilicates in the transit zone and ii) by the processes of mixing fresh water with salt water and brines, cation exchange of alkaline earth elements with alkaline elements and dissolution of gypsum near discharge areas at the seashore and in paleovalleys. In the brackish and salty waters the Na/Ca ratio is reduced to 1-4. This indicates that in the aquifers there are other sources of Ca, in addition to the dissolution of gypsum. The most probable process is the hydrolysis of Ca-aluminosilicates, which indicates a significant time of water-rock interaction. The “brackish1” water with TDS 5-6 g·L-1, is particularly distinguished by the degree of modification due to water-rock interaction.