Water supply of the lakes depends mainly on the meltwater of alpine snow and ice during the warm season. Therefore, the change of the salinity of lake water is directly related to the distance from the supply source to the lake. With changing of the lake types from freshwater to saltwater to saline, the contents of HCO₃^- and Ca²⁺ are clearly decreasing, and Cl^- and Na⁺ increasing, In addition, in freshwater lakes, the absolute contents of HCO₃^-, and Ca²⁺ are obviously becoming higher with increase in the salinity of the lake. In saltwater and saline lakes, it is shown that the absolute contents of Cl^- and Na⁺ are clearly becoming higher with the increasing of salinity.

The evolution of the lakes during the Quaternary is the result of coaction of the tectonic uplift of the plateau and the global climatic changes. It can be divided to three main stages: viz., “Great Lake Period” before 46 000 a B.P.; “Lake-level Fluctuation Period” in the later stage of the Late Pleistocene, during this period, the great lake existing in the first stage disappeared and several small lakes were formed after 46 000 a B. P. Up to about 36 000 a B.P., a high lake-level appeared, which corresponded to the interstadial of the last glaciation. Another high lake-level appeared in the time from 21 000 a B.P. to 15 000 a B.P., about 40 m higher than the present day lake-level; and "Lake Shrinking Period” in the Holocene.