69 ISSN 2079-0961, Arid Ecosystems, 2019, Vol. 9, No. 1, pp. 69–76. © Pleiades Publishing, Ltd., 2019. Russian Text © T. Asankulov, J. Abuduwaili, G. Issanova, M. Long, E. Duulatov, 2019, published in Aridnye Ekosistemy, 2019, Vol. 25, No. 1(78), pp. 81–89. Long-Term Dynamics and Seasonal Changes in Hydrochemistry of the Issyk-Kul Lake Basin, Kyrgyzstan T. Asankulov a, b, c, * , ** , ***, J. Abuduwaili a, b , G. Issanova d, e, f , M. Long a, b , and E. Duulatov a, b a Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences and Research Center for Ecology and Environment of Central Asia (Urumqi), Urumqi, 830011 Xinjiang, China b University of Chinese Academy of Sciences, Shijingshan District, Beijing, 100049, China c Adyshev Institute of Geology, National Academy of Sciences, Bishkek, 720040 Kyrgyzstan d Research Center for Ecology and Environment of Central Asia, Almaty, 050060 Kazakhstan e Faculty of Geography and Environmental Sciences, Al-Farabi Kazakh National University, Almaty, 050040 Kazakhstan f Abai Kazakh National Pedagogical University, Institiute of Natural Sciences and Geography, Almaty, 050010 Kazakhstan *e-mail: asankulov12@yandex.ru **e-mail: agamprit@gmail.com ***e-mail: jilil@ms.xjb.ac.cn Received February 9, 2018; revised April 16, 2018; accepted May 16, 2018 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 . 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 nat- ural waters is of great practical importance for various sectors of the economy, since the chemical composi- tion 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. Keywords: Issyk-Kul, lake, hydrochemistry, ion, salinity, Kyrgyzstan DOI: 10.1134/S2079096119010025 INTRODUCTION Issyk-Kul is one of the largest high-altitude lakes of continental origin. Due to its depth, it contains a huge amount of water, more than the Aral Sea, but it is peculiar in the amazing uniformity of its water, both in its area and its depth, as indicated by the relative con- stancy of the specific density, salinity, and chemical composition (Kadyrov, 1986). The water resources of the Lake Issyk-Kul basin are represented by the drainless lake itself, with numerous inflow rivers and groundwater. Natural waters are a dynamic chemical system that contain in their composition a complex of gases, mineral and organic substances in the form of solutions, as well as suspensions and colloids. This system depends not only on the environmental conditions but also on var- ious processes occurring both outside and directly inside the water body. Knowledge of the chemical composition of water is of great practical importance for the development of various sectors of the econ- omy; the chemical composition must be considered in the use of natural waters for all types of water supply and water use (drinking, household, industrial, agri- cultural, and transportation). The study of the qualita- tive and quantitative chemical composition of natural waters (hydrochemistry) allows us to determine the possibility of their practical application to increase the productivity of organisms. Hydrochemical research is also of increasing interest due to increased waterbody pollution and anthropogenic activity. The study of the conditions of the formation of the chemical composition of water in the Lake Issyk-Kul basin was carried out by many scientists and research- ers, such as Schmidt (1882), Matveev (1930), and Kadyrov (1986). However, the results of hydrochemical studies differed from each other. The quality of water use of the lake and rivers of the Issyk-Kul basin was also stud- ied by such researchers as Kawabata et al. (2014), Alym- kulova et al. (2016), and Abdyzhapar et al. (2015). One should note the extreme insufficiency and limitation of work carried out earlier in the review of hydrochemical studies of the Lake Issyk-Kul basin. The goal of this study is to assess and analyze the main changes in the chemical composition of the lake 2 4 SO - WATER ECOSYSTEMS