Abstract: Karst groundwater is one of the crucial water resources to karst area. Because of its sensitivity and vulnerability, the karst hydrology system is difficult to recover once it is polluted. In this study, by taking the Shuifang spring of Jinfo Moutanin in Chongqing as an example, the variation of hydro chemical parameters and its geochemical sensitivity in 2008 and 2016 were compared and analyzed. Results indicated that groundwater in study area was controlled by waterrock interaction and characterized by Ca-HCO₃ type. The sewage from tourism activities has been divided into accommodation and kitchen sewage since 2013. The former was discharged into underground after precipitation and degradation of septic tank, which made concentrations of K⁺, Na⁺, PO₄^3- reduced in 2016 compared with 2008. This reveals the effective regulation role of septic tank to contaminant. However, unprocessed sewage from accommodation was directly recharged the karst aquifer, increasing the concentrations of Cl^-, NO₃^- and deteriorating the groundwater quality. Meanwhile, the concentrations of HCO₃^-, Ca²⁺, Mg²⁺ elevated due to the dissolution of carbonate rock. In addition, because the tourist numbers in peak and offpeak was narrowing, the geochemical susceptivity indices of chemical parameters in 2016 were generally lower than 2008, and the time of groundwater influenced by tourism activities was longer. The geochemical susceptivity index of chemical parameters was largely consistent with normal concentration in 2008, but was disorderly in 2016. It maybe indicates that the groundwater system in study area gradually turned from order to disorder, with a destroyed stability and elevated entropy.

Key words: karst groundwater, hydrochemistry, geochemical susceptivity, tourism activities, Shuifang spring