Characteristics Of The Circulation And Renewability Of The Karst Water System In Xishan Area,beijing

The karst water system in Xishan has important regulating function to surface water and Quaternary pore water in Beijing plain area.The karst water has the characteristics of good water quality and high development potential.In the case of over-exploitation of groundwater resources,the function of Xishan karst water system is weakening.In recent years,there are many different opinions about the karst water circulation in Xishan,but the study on renewability of karst water is relatively small.Therefore,this paper will use isotope technique,as well as hydrochemistry and traditional hydrogeological methods to study the characteristics of circulation and renewability of the karst water system in Xishan area based on field investigation,which will provide the basis for the reasonable utilization and scientific management of karst water.Through in-deep analysis,I obtained the following conclusions:Quaternary groundwater in Yongfengtun area has the characteristics of low TDS,pH and ion concentration and simple hydrochemical type,while the TDS,pH,ion concentration and hydrochemical type of Shijingshan area are on the contrary.The Sr2+ concentration of Karst water increases along the the flow direction,and the hydrochemical types become singular from complex.The karst water hydrochemical types of Tanzhe Temple and Junzhuang recharge area are relatively complex.Finally,they changed into the single type of HCO3-Ca·Mg in Sijiqing and Yuquanshan area along karst water flow direction.Surface water,Quaternary groundwater and karst water in the study area are mainly recharged by precipitation,and the surface water as well as Quaternary groundwater are strongly affected by evaporation.Karst water in Tanzhe Temple area receives precipitation infiltration recharge and which in Junzhuang area receives the double recharge of river water leakage and atmospheric precipitation.The proportion of river water recharge for karst water is greater than 50% accounting for 68% of the total karst water,which resulted in severe accumulation of karst water 18 O.This paper reveals the circulation characteristics of the karst water system in Xishan area by isotope,hydrochemistry and water hydrogeological data.The Karst water is recharged in Tanzhe Tample and Junzhuang area and then flows along the Babaoshan fault,Yongding River fault and Baijiatuan fault respectively.Finally,the karst water is discharged in Haidian anticline and Sijiqing area.In addition,the runoff velocities of groundwater in different recharge areas are different from fast to slow as: Tanzhesi recharge runoff velocity > Yongding river?leakage?runoff velocity > Junzhuang recharge area?recharge?runoff velocity.The ages of ³H,CFCs and ¹⁴ C indicate that karst water in Xishan area is a mixture of new water and old water.The age of karst water is between 3 and 2945 years and is mainly less than 30 years old,which reflects that the renewability of the karst water system in Xishan area is strong.The renewability of karst water in mountain area is stronger than that in plain area,and the age of karst water increases from the recharge area to the discharge area.In addition,The average age of karst water in the recharge area of Tanzhe Tample is less than that of Junzhuang,and it has the best circulation conditions and the strongest renewability.