This study established the hydrochemistry and stable isotope variations in three lakes, namely brackish Zigetang Co, freshwater Cona and Ranwu lakes located in the central and southeastern Tibetan Plateau of China. Vertical profile fluctuations in the water column, such as temperature and dissolved oxygen (DO)concentration, displayed significant differences which were linked to the thermocline. The hydrochemistry of the three lakes showed that HCO−3 as the dominant anion, whereas Na+ is the main cation in Zigetang Co and Cona lake and Ca2+ is the prevailing cation in Ranwu lake. In Zigetang Co, K+ and Na+ concentrations
decreased by 42 % from 1999 to 2012, caused by the enlargement of the lake area, documented by field investigations carried out in 1998, 2002, 2006 and 2012. The δ13CDIC and δ18OH2O values analysed from the three lakes varied from −6.0 to 2.0 ‰, and from −14.8 to −6.4 ‰, respectively. The closed Zigetang lake showed higher δ13CDIC and δ18OH2O values compared to those of the rivers, the semi-closed Cona and open Ranwu lakes. The δ13CDIC values of lake water in Zigetang Co
were mainly controlled by CO2 exchange between lake water and
atmosphere; the δ18OH2O values were dominated by the
evaporation/freshwater input ratios.