Boundary condition, water cycle and water environment changes in the Jinan spring region

The Jinan spring region is the area in Jinan City with spring flow and subterranean water storage. Four spring groups, namely, Baotu, Heihu, Wulongtan and Zhenzhu, are identified in the center of the northern city area. Protection of karst groundwater in the Jinan spring region is critical for sustainable utilization. In this paper, several sensitive aspects of the karst area, including boundary conditions, underground channels in karst, water cycle characteristics and changes in water quality are discussed using spring flow analysis, analysis of the flow field characteristics, artificial groundwater recharge estimation and investigation of self-drilled wells. The boundary conditions in the Jinan spring region were re-defined. The eastern boundary was extended 4 km eastward in the northern permeable section of the original boundary. Using karst stratified statistics and buffer analysis of drilling it was concluded that there is a 100 to 150 m deep groundwater flow zone in the direction of Dangjiazhuang, Shiliuli river and Qianfoshan fault (Quancheng park section). Additionally, the water cycle of Wulongtan and Zhenzhu springs is dominated by deep circulation, while Baotu spring and Heihu spring are affected by both shallow and deep circulation. Baotu spring is mainly recharged by karst groundwater and surface water in west and south Jinan, while Heihu spring receives a certain amount of karst water from the southeast region. It is notable that the karst water quality is deteriorating. Therefore, the ecological environment of the karst area in the southern Jinan spring region, and particularly the surrounding rivers and reservoirs, needs to be addressed urgently.