Abstract: The groundwater supply in arid areas played a pivotal role in many fields. Firstly,it is closely related with some environmental problems such as desertification,storms and salinization. Secondly,it is a very important factor to control the economic development especially for the irrigation agriculture. The Dunhuang Basin,located in the Danghe River Basin,is facing serious groundwater problems. Additionally,tourism industry in this region is very developed but the ecological environment is rather fragile,therefore,to get an insight into the characteristics of groundwater in this region is the precondition for solving the groundwater problems. The groundwater water chemical type is a concentrated reflection of the groundwater chemical composition,and a system response of the whole water and groundwater circulation characteristics. Studies of the variation characteristics and the evolution of groundwater can better reveal the interaction mechanism of groundwater and environment. By using hydro-chemical and stable isotopic technology,this paper determined the evolution way of ground water hydro-chemical characteristics,the recharge environment of groundwater in the study area,and the physical and chemical properties of groundwater. Results show that the quality of groundwater and surface water was generally good with low salinity and unpolluted. The relationships between Na⁺ and SO₄^2-,Cl^- and Na⁺,as well as Ca²⁺ and SO₄^2- were quite good,indicating that the dissolution of rock salt,glauber's salt and gypsum had great influences on the concertration of Ca²⁺,Na⁺,SO₄^2- and Cl^-. Reverse cation exchange played an important role in the concentration of Ca²⁺ and Mg²⁺,and with the increase of Ca²⁺ and Mg²⁺ in groundwater,carbonate started to precipitation, leading to a reduction of HCO₃^-. This reaction was accelerated by the preceding hydro-geochemical evolution, especially the dissolution of the glauber's salt. The increase of Na⁺ can cause the cation exchange between Na⁺ of the groundwater and Ca²⁺ or Mg²⁺ of the aquifer. For stable isotope,δ¹⁸O ranged from -10.8‰ to -7.7‰, and δ²H from -74.4‰ to -52.5‰,indicating that the recharge environment had changed significantly in the recharge history. δ¹⁸O and δ²H values in unconfined groundwater increased along the groundwater flow path from SW to NE,reflecting the effect of evaporation and concentration. The stable isotope values in Nanhu group and southern of Dunhuang Basin were close to the surface water,indicating that the surface water had an important recharge for phreatic water. In contrast,stable isotopes in confined groundwater was relatively poor,revealing that the deep confined groundwater may be supplied under a cold climate conditions in the past. The results not only have important implications for water resources allocation and groundwater management,but also can help the further study about the regional groundwater circulation characteristics in the Dunhuang Basin.

Key words: groundwater, hydrogeochemistry, stable isotope, Dunhuang Basin