Study on the hydraulic connection between downtown and eastern and western suburbs in Jinan

YU Lingqin; LIN Guangqi; LIU Yuanyuan; QI Huan; MENG Qingzhai; MA Hekuan; JIANG Lulu; LIU Chunwei

doi:10.11932/karst20230505

Abstract：In order to identify the hydraulic connection between the spring water in Jinan city and the karst water in the western and eastern suburbs,we conducted a study to analyze the hydraulic connection between the three from the perspective of stratigraphic structure and hydrodynamic field,combining with the restults of pumping tests and tracer tests.Meanwhile,we also performed hydrochemical and correlation analyses. The results show that from the perspective of stratigraphic structure,there is no obvious water-blocking structure in the area of Huaiyuan Square-NO.9 Middle School-NO.14 Middle School near the rock contact zone on the north side of Liuchang mountain between downtown and western suburbs,and a continuous karst aquifer group is developed below the rock body at a burial depth of about 350 m.The Chaomidian fracture on the west side has good water conductivity and the urban spring water and karst water in western suburbs can be hydraulically connected through the aquifer of Sanshanzi Formation below the rock contact zone.The tongue-shaped intrusive rock body exists in the area of Yanchi mountain-the Qili river between downtown and the eastern suburbs,which plays a certain role in blocking the karst water of downtown springs and eastern suburbs,but the Wenhuaqiao fracture does not form a water blocking structure,and the aquifers on both sides are less misshapen,and the distribution of karst aquifers to the east of the Wenhuaqiao fracture and south of Yaojia is continuous and stable.The karst aquifers are exposed at a depth of 485 m north of the Honglou Campus of Shanda University.The urban spring water and karst water in eastern suburbs have a unified water system,which can be hydraulically connected through the aquifer of Sanshanzi Formation below the contact zone of rock mass. The western borehole pumping test shows that the top plate of the aquifer in the areas of Huaiyuan Square-NO.9 Middle School-NO.14 Middle School is gradually deepened from south to north.Both the horizontal and vertical fissures in the intrusive rock above are evenly developed.The fissured water can be recharged by the top-supply of the underlying karst water group.Due to the overall water-richness and smooth groundwater runoffs,the urban spring and the karst water in the western suburbs have hydraulic connection.The eastern borehole pumping test shows that the rock body in the area of Yanch mountain-the Qili river is gradually thickening from south to north with the depth increase of the top plate of the aquifer.The fissures in the rock body are developed with overall water-richness of the eastern Jinan strata and smooth groundwater runoffs. The water level map shows that there is no sudden change of water level on both sides of Liuchang mountain-Langmao mountain-Wanling mountaiin between urban area and western suburbs,and the water levels of the two areas are roughly the same with continuous and steady water level,indicating a connection between the two in the hydrodynamic field.Groundwater on the west side of the area of Yanchi mountain-the Qili river flows in the northwest direction,while groundwater on the east side of the same area flows in the northeast direction.However,both the urban area and the eastern suburbs are recharged by the same source.Therefore,if karst water in the eastern suburbs is exploited excessively,part of karst water flowing to the urban area from the southern mountainous area will be taken away,which will affect,to a certain extent,spring water in the urban area. The water chemistry analysis based on Piper's trilinear diagram and hydrogeological conditions shows that the chemical types of urban spring water are the same as those of karst water in the eastern and western suburbs,and the three areas have the same evolutionary environment.According to the correlation analysis between the urban spring water and the karst water in the western suburbs,the main chemical indexes of the fissure hole JZ and SSZ boreholes are correlated with those of the urban and western suburban boreholes,with all coefficients larger than 0.84,which indicates that the fissure water in JZ and SSZ boreholes is closely correlated with karst water.There is a vertical runoff channel in the area of Huaiyuan Square-NO.9 Middle School-NO.14 Middle School,and the intrusion above fracture water in the rock body can be recharged by the top-supply of the lower karst water rock group.The urban spring water and the karst water in the western suburbs are of the same source.According to the correlation analysis of urban spring water and karst water in eastern suburb,the correlation of the main chemical indexes between karst water collected from eastern suburban boreholes and urban spring water is larger than 0.95,an significant positive correlation,indicating the same source of karst water in both eastern suburban and urban area.According to the content distribution of the constant ion components in karst water in the study area,water chemical components of the urban spring and the karst water of the western and eastern suburbs are formed mainly by the dissolution of carbonate rocks.Karst water of the three areas is in a similar groundwater environment,and there is a certain hydraulic connection.