Abstract
Lake Issyk-Kul is one of the largest high-altitude and brackish lakes of continental origin. The long-term dynamics of the chemical composition of the water of its basin is evaluated and analyzed based on data from 1932, 1977, and 1986. The average long-term dynamics of water salinity is determined based on data from 1928, 1960, 1980, 2000, and 2014. The predominant ions of the lake water are sulfates, chlorides, sodium, and magnesium. The predominant cations are Na+ and Mg+ , and the predominant anions are Cl– and $${\text{SO}}_{4}^{{2 - }}$$ . Sulfates predominate in the chemical composition, so the water belongs to the sulfate class and the chloride–sulfate–sodium–magnesium mineralization type. The water in the lake is alkaline; its pH ranged from 7.95 to 8.82 in 2015. The salinity of Lake Issyk-Kul is 6.22 g/L. The study of the hydrochemistry of natural waters is of great practical importance for various sectors of the economy, since the chemical composition of water is taken into account for all types of water supply and use. Hydrochemical research is also of increasing interest due to increased water-reservoir pollution and anthropogenic activity.