Ecological restoration pattern and quantitative evaluation of recirculation measures for northern discontinuous karst spring: A case study of Jinci Spring in Taiyuan City, Shanxi Province

Karst spring is the main natural discharge form of karst groundwater in northern China and is an important natural resource with the functions of water supply,tourism and ecological environment. Nearly 30% of karst springs have been dried up,influenced by natural factors,coal mining,especially by human beings'large-scale development and utilization of karst groundwater since the last century. The dried-up springs also include some world-famous karst springs. Since the 17th National Congress of the Communist Party of China (CPC),local governments have actively responded to the call of the CPC Central Committee and the State Council to strengthen ecological civilization construction,and hence ecological restoration projects have been initiated for the reflow of some important karst springs. Based on the structural mode and genesis of the karst springs in northern China,this paper proposes the spring reflow pattern,which includes the following measures:regulating the water flow of the leakage section by using the water storage of the upstream reservoir,implementing artificial supplementary projects in the seepage section of the river,closing the wells in karst groundwater strong runoff zones and drainage areas,blocking artesian wells downstream of the spring water outlet,monitoring drainage in coal mines under pressure,and conducting afforestation measures in recharge zones. Taking Jinci spring in Taiyuan of Shanxi Province as an example and based on the quantitative optimization evaluation of the effects of these reflow measures,it is concluded that raising the storage level of the Fenhe Second Reservoir to the design elevation,closing the drainage well of Baijiazhuang coal mine in the strong runoff zone of karst groundwater to reduce water pressure,and plugging and disposing of artesian well downstream of spring outlet seem to be economically feasible and effective measures in the near future. Finally,by using the numerical model of spring groundwater,it is predicted that,after the implementation of these measures,Jinci spring water is expected to reflow in about two years. The results can provide demonstration and reference for other karst springs of the same type in northern China.