| The karst groundwater system in Jinan spring area is relatively complex,and it is typical of karst distribution areas in northern my country.Based on the full analysis of regional geological and hydrogeological conditions in the study area,the monitoring data of borehole and stratum data,groundwater level,quality,temperature,isotope,conductivity and other data are collected.Combining the tracer test and the fixed-depth water quality sampling test of the existing boreholes,the groundwater flow system classification elements are identified from the groundwater dynamic field,temperature field,and chemical field angle,and the section is selected to classify the groundwater flow system,and different levels are analyzed Plane and profile characteristics of the flow system and its contribution and influence to spring water,which has a certain scientific basis and guiding significance for the work of Jinan spring protection.Through the above analysis and research,the following main research conclusions are drawn:(1)The groundwater of Ordovician Yeli-Liangjiashan formation,Cambrian Fengshan formation and Majiagou group in the study area has a unified groundwater surface.The groundwater of different water bearing formations can flow and exchange from south to North and from high to low.Most of the karst groundwater minerals in the study area belong to dissolution state,and the permeability characteristics of carbonate karst aquifer have certain correlation with the distribution of ionic strength and saturation index of karst water.(2)The groundwater flow system in the study area has multiple levels.The karst water in the study area with a shallower buried depth is greatly affected by the local flow system,and each aquifer is affected by different flow systems to different degrees.The fixed depth water quality and the vertical distribution of groundwater temperature are affected by different levels of groundwater flow systems,they can be used as important elements to identify the classification of groundwater flow systems.(3)Compared with Ordovician Fengshan formation aquifer,the groundwater age of Zhangxia formation aquifer is older,the tritium age of PFM model is generally higher than 15 years,the ages of Heihu Spring and Baotu Spring are 10-15 years,the ages of Zhenzhu spring and Wulongtan are 15-20 years,and the ages of Bianzhuang and Yingxian Spring are higher than 20 years.(4)The Cambrian Zhangxia Formation in the study area mainly participates in the regional flow system,the Cambrian Fengshan Formation and the Yeli-Liangjiashan Formation mainly participate in the intermediate flow system,and the local flow system mainly involves the Ordovician Majiagou Formation aquifer,Pore water,fissure water,and mountain descending springs formed by the influence of topography.The large area can be divided into three main flow systems:the 2.5 billion-year-old rock strata below the unconformity interface,the Cambrian Zhangxia Formation,and the Cambrian Fengshan Formation-Ordovician.The distribution of groundwater conductivity,temperature,and water chemistry type on the selected section of the study has vertical zoning,and there are also differences in the horizontal direction.There are two local flow systems in the selected section,and their temperature field and water chemical field are different from the deep intermediate and regional flow systems.(5)The local flow system has the variability of time and space and boundary,and it is easy to form a local flow system with the participation of karst water during the high water period.Epikarst springs also show different water chemistry characteristics.The spring water of the Fengshan Formation is HCO3—Ca·Mg,the Majiagou Formation is HCO3·SO4—Ca,and the Yeli-Liangjiashan Formation is HCO3—Ca Type and HCO3-Ca-Mg type.Different levels of groundwater flow systems contribute differently to the replenishment of spring water,and the local flow system replenishes spring water less.(6)Different intermediate flow systems in the low and high water periods exhibit different electrical conductivity characteristics at the location of the groundwater seepage channel,which also affects the local flow system and the regional flow system.The intermediate flow system in the study area mainly involves the Fengshan Formation to the spring,Yeli-Liangjiashan Formation to the spring runoff path,which makes a great contribution to spring replenishment.The temperature of groundwater shows different heating gradients with depth,and the main types of water chemistry are HCO3·SO4—Ca type and HCO3—Ca type.(7)During the dry and high seasons,there are certain differences in the distribution characteristics of the groundwater chemistry types in the study area.The groundwater chemistry types change from HCO3—Ca type to HCO3·SO4--Ca type from south to north.Based on the relationship between[Sr2+]/[Ca2+]values and TDS in the study area,the flow system of the study area is divided into three areas:the western suburbs runoff drainage area,the spring group runoff drainage area,and the recharge runoff area.The[Sr2+]/[Ca2+]value of the groundwater flow system is different in each region.During the dry season,the intensity of the karst water from the southwest of the spring group running to the southeast to the spring group increases. |
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