Abstract: There are a series of lakes in Taerhu, Wuyuan of Inner Mongolia in the Hetao Plain, which is an obvious comparison to the local arid climate. Researching on the mechanism of lakes is important to hydrogeology and climate changes in Quaternary period. By carrying out chemical tests on the samples along the way from Serteng Mountain to Taerhu lakes and to Yellow River, the results show that Gibbs model projection indicates lakewater samples lie in the transition of evaporation and rock weathering effects, which is far away from the effect of precipitation while groundwater is mainly controlled by rock weathering effects, showing groundwater recharges lake water that suffers extremely evaporation; Piper trilinear diagram reveals hydrochemical types are mainly HCO3—Ca for springs in front of mountains, HCO3—Na and Cl—Na for groundwater, HCO3—Na for Yellow River water and Cl—Na for lake water, which also shows there exists hydraulic relationship between groundwater and lake water that contains great concentration of the salt during the process of being recharged; TDS of the groundwater rapidly increases from the north to the south, varying from 262 mg/l to 2,296 mg/l. The lakes TDS, however, after reaching the maximum value of 1,213 mg/l in the north of Taerhu, decreases and is finally lower than that of groundwater, which shows lake water is recharged by present Yellow River and the change of groundwater conforms to hydrogeology model. The results of Quaternary geological survey show lakes can not only develop upon the riverbed subfacies, but also upon the dam facies in Taerhu. In addition, the distribution features of scattered lakes are not similar to those of oxbow lakes. The two arguments above basically eliminate the possibility that lakes are left by the ancient Yellow River. Alluvial deposit was ever eroded by the wind, which led in occurrence of underlain groundwater. In conclusion, the basins of lakes were formed by wind erosion.

Key words: Quaternary, Hetao Plain, Taerhu, mechanism of lakes, hydrochemistry, recharge