The Ordos Cretaceous Basin, located at western China, is an arid-semiarid area. Its south section and north section are covered by loess and desert, respectively. Chemical compositions of groundwater are prominently different regionally, with freshwater in the north and brackish water in the south. Based on chlorine concentrations and 36Cl composition of groundwater, this study discussed the influences of evaporation on the recharge of precipitation and the chlorine concentrations of groundwater. The results show that evaporation and enrichment of meteoric water and the dissolution of stratum chlorine have significant effects on the chlorine concentrations of groundwater. Compared with precipitation of meteoric water, the chlorine concentration of groundwater in the desert was evaporated by 29.9~63.0 times, and this provided more than 21.3~45.3 mg/L of Cl with the groundwater. In the loess area, the groundwater was evaporated by 266.0~523.7 times, with 191.5~377.0 mg/L of chlorine derived from evaporation.
