Investigation of geochemistry of surface water is a fundamental study of the regional environment in ungauged areas. Also the study is helpful to determine the relationship between hydrological processes and environmental factors including the climate change and geologic structure. Sampling of the lake and river waters in the northern-central parts of Mongolia was carried out in 2013 and 2014. Then, using the measured chemical data of water solutes, the ion compositions and its controlling factors were anal...