Salt composition of the waters of the Bureya reservoir

Significance. Significance of the work lies in the need to study the salt composition of the Bureya reservoir water from the beginning of filling, which is important for predicting the water quality of reservoirs in the Amur basin that are to be designed. The objective is to evaluate content of main ions in the water of the Bureya reservoir, and to identify factors determining their spatial and temporal variability. Methods. Hydro/chemical observations in the Bureya reservoir were made from 2003 to 2008 at five plots covering the major part of the water area. Water samples were taken from the surface, middle, and near-bottom horizons in winter, summer, and fall. Water samples were taken from the surface in January, July 2019 in the landslide area and in July 2020 at eight sites in the water body between the landslide and the hydropower dam. Analytical work was carried out according to the methods accepted in hydrochemistry. Materials of the Amur Basin Water Administration for 2005-2019 were used in the work. Results. The content of the main ions in the water of the reservoir during the filling period and the following years was assessed. The dominance of calcium ion among cations and hydrocarbonate ion among anions in the salt composition of water was shown. It is established that the emergence of oxygen deficit in water due to the increased area of flooded forests and reduced water inflow caused the absence of sulfate ion in the reservoir water in autumn and winter 2005. It is shown that staged filling of the reservoir contributed to gradual smoothing of differences in the content of major ions and stabilization of the salt composition of water in the sixth year of filling. In current conditions the content of sodium and potassium ions and chloride ions in the water area of the reservoir is relatively evenly distributed, the highest values of concentrations of calcium and magnesium hydrogen carbonates are observed near the mouth of the Tyrma River. The effect of a large landslide on the content of major ions in the water in 2019-2020 is considered.