The hydraulic connection between Jinci and Pingquan in Taiyuan' Shanxi and its contribution to the reflow of Jinci spring

Jinci Spring,which is composed of Nanlao Spring,Shengmu Spring and Shanli Spring,is exposed at the foot of Xishan Mountain in Taiyuan. The average horizontal discharge of Jinci Spring was 1.94 m³/s from 1954 to 1958. Pingquan spring,located in the piedmont fault zone with Jinci spring,became the source of superlarge karst water self-flowing wells in 1978, with the maximum self-flowing rate reaching 1.56 m³/s. Because of the exploitation of these self-flowing wells,the flow of Jinci Spring dropped sharply and was cut off on April 30,1994. The study of the hydraulic connection between Jinci Spring and Pingquan Spring in Taiyuan,Shanxi Province,is of great significance for the formulation of Jinci Spring recharge plan. With Jinci spring and Pingquan spring as the research objects and through sample collection and water quality monitoring,hydrochemistry (ion ratio,sulfur isotope,hydrogen and oxygen isotope) methods were comprehensively applied. The result has revealed hydrogeochemical characteristics and environmental isotope characteristics of Jinci spring to Pingquan spring as well as the characteristics of groundwater flow system and hydraulic connection. From 1980 to 1992, the change of groundwater level in Jinci Spring showed a steady downward trend. The main reason was that a large number of karst groundwater was exploited in Taiyuan Chemical Industry Company,Kaihua Valley,Pingquan Village and Liangquan Village in Zhaoxu County,which resulted in the decline of groundwater level. The hydrogen and oxygen isotope values of karst groundwater in Jinci spring to Pingquan spring area were close to each other,indicating that the source of recharge and the way of recharge were quite similar. Water quality monitoring analysis shows that the change trend of each ion in Jinci spring and Pingquan spring is basically the same,suggesting that Jinci spring and Pingquan spring have close hydraulic connection,so Jinci spring and Pingquan spring must have a strong water channel. The water level of Jinci spring can be raised by curtain grouting on the downstream water channel of Jinci spring,so that Jinci spring can flow out.