Abstract: Spring water is the important drinking water source for the village of Tuguanpu to the Da’an Town on the west side of the Hanzhong basin. The Study on the hydrochemical characteristics and genetic mechanism is of great significance to guide the development and protection of local water resources. In this study, 13 spring water samples were collected for water quality analysis. Mathematical statistics, Piper trigram, Gibbs diagram, saturation index method  and major ion ratios were used to comprehensively analyze the hydrochemical characteristics and genetic mechanism of the spring water in the study area. The results show that the spring water in the mountainous area on the west side of Hanzhong basin is weakly alkaline and low salinity water. In the hydrochemical composition, the cation is dominated by Ca2+ and Mg2+, while the anion is dominated by HCO3-. The main hydrochemical type of the spring water is HCO3-Ca·Mg，which is mainly controlled by the weathering of rocks. The CO2(g) in all water samples is not saturated and could be redissolved in groundwater. The dolomite and calcite of most spring water are in an unsaturated state, and the dissolution of them can still occur. The calcite and dolomite of Taixingya spring (S06), Jinjiakan spring (S07), Shuimogou spring (S08) and Chenjiaying spring (S11), and the calcite of Nangoumen spring (S12) have been oversaturated and are about to precipitate. Human activities slightly influence on the hydrochemistry of spring water. The ions in the spring water samples in the study area are mainly from the dissolution of carbonate rocks, and partly from the dissolution of silicate rocks.

Key words: hydrochemical characteristics, spring water, saturation index, Hanzhong basin