CHEN Xue-lian1,2, CHEN Xi1,2, ZHANG Zhi-cai1,2, ZHANG Yan-fang1,2, JI Zhong-hua3

(1.State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing 210098, China;
2.College of Hydrology and Water Resources, Hohai University, Nanjing 210098, China; 3.Nuclear and Radiation Safety Center, Beijing 100082, China)

Abstract: Surface water and groundwater transfer is very complex in the karst region due to strong heterogeneity of land surface conditions. In this study, a small karstic basin of Chenqi in Guizhou Province was selected for the analysis of runoff components based on stable isotopes and hydrochemical composition during rainfall and non- rainfall periods. According to the characteristics of various water source positions by field investigations in the basin, we collected water samples at these positions for analyzing isotopic and geochemical composition . Watershed outflow was separated into surface water (only existing during rainfall), epikarst water and groundwater. The results showed that the proportion of epikarst water increased and the proportion of underground runoff decreased during the rainfall period. After the rainfall ceased, the proportion of epikarst water decreased significantly and underground runoff increased. During the rainfall, the proportion of surface water is less than 10%, epikarst water is within the range of 28%-45% and underground water, 49%-62% of the total discharge. Underground runoff is a primary water resource of the entire basin during the non-rainfall periods, and the proportion is about 68%-88%.

Key words: karst basin; stable isotope; hydrochemical composition; epikarst; runoff component