Major chemical components of Lake Issyk-Kul and the river and ground water in its catchment area (Central Asia)

To elucidate the characteristics of the water quality of Lake Issyk-Kul, wherein the water level is rising but salinity is increasing as well, and those of the river and spring waters in its basin, a survey was conducted in the summers of 2012–2014. Based on the analysis results for the main chemical components and the dissolved organic carbon (DOC), the present conditions of the water quality characteristics of the river and spring water and the change in the salinity condensation of the lake are summarized. The chemical composition of the river and spring water is mostly Ca–HCO3 type; however, the river and spring water passing through urban areas and farmland contain many anthropogenic Na+, Cl−, SO42−, NO3−, and DOC components. The water composition of the lake is NaCl, SO4 type, and the condensation rate of each component can be divided into three groups of Na+, Cl−, Mg2+, SO42−, Ca2+, and HCO3−. As for the water quality of the lake as of 2014, the Na+, Mg2+, Cl−, and SO42− concentrations have continued to increase since 1986 and the increase in the Cl− concentration has been remarkable in recent years. The majority of the river water quality of the Lake Issyk-Kul catchment area consists of naturally-derived elements; however, in some river and spring waters, anthropogenic Na+, Cl−, and SO42− are introduced and the inflow of these components is one of the causes of the current increased salinity of Lake Issyk-Kul.