Suitability Of Emergency Groundwater Source And Division Of Protection Area In Karst Area

With the development of society and the improvement of people's living standards,water resources,especially groundwater resources,become more and more important.In recent years,due to climate change and groundwater exploitation,the groundwater level in Zibo mountain area is decreasing year by year,which is difficult to meet the demand of water supply.At the same time,excessive pumping of groundwater will bring great threat to the local ecological environment.Therefore,it is urgent to find and build new emergency water sources to meet the coordinated development of social economy and ecological environment protection.Taking XJD emergency water source in Shandong Province as an example,based on groundwater resources investigation,geological environment investigation and source protection area division theory,Karst groundwater resources was studied in the study area by using numerical simulation method,pumping test method,compensation drainage method,water balance method and comprehensive index method,and quantitatively calculates exploitable resources of XJD water source.The author also analyzed the suitability conditions from the aspects of exploitable resources,water environment,and environmental geological problems that may be caused by the construction of water source area,and made a reasonable division of the protection area.The main achievements were as follows:(1)The geological and hydrogeological conditions of the study area were identified.It was recognized that the main water rich strata in the study area are carbonate Karst fissure water bearing rock group,and the underground water bearing rock group was relatively independent.It was mainly recharged by atmospheric rainfall infiltration,and there was no other lateral runoff supply.Therefore,the groundwater dynamic state presentd the characteristics of seasonal variation.The direction of groundwater flow was controlled by topography and fault.The rainfall infiltrates into the mountain area and forms groundwater flowed to the direction of Zihe River Valley,and finally flowed northeastward along the Zihe graben.(2)The feasibility of constructing new water sources in the study area was analyzed from three aspects of exploitable resources,water supply conditions and aquifer permeability.According to the calculation of compensation drainage method,the exploitable resources of the water source field is 17074m~3/d,which can meet the water supply gap of 15000m~3/d in Boshan city.By calculating the remaining water resources of balanced area and key balanced area are 97200 m~3/d and 98000 m~3/d respectively,it is proved that the calculated recoverable resources have sufficient supply sources.Numerical simulation method was used to predict the water level performance of the main pumping well in XJD water rich area in the next 26 years under the mining condition of 17000m~3/d.The results showed that the maximum water level drawdown of the main pumping well met the constraint conditions,which proved that the rock permeability and single hole water inflow of the water source can meet the requirements.(3)The feasibility of water source construction was analyzed from the aspects of water quality and environmental geological conditions in the study area.The comprehensive index method was used to evaluate the water environment quality.The results showed that the regional water environment quality was good and meets the requirements of water source construction.Based on the analysis of the factors causing Karst collapse,it is considered that Karst development is better in the south side of the syncline of the penquan Beiboshan fault,and Karst collapse may occur when a large amount of groundwater was extracted after the completion of the water source field.Based on the analysis of the formation conditions of the water rich sections in the three water sources,the observation data of the relevant pumping holes in this pumping test,the obvious difference of water level in different water sources and the reasons for the formation of XJD spring group,it was considered that there was a water blocking zone between XJD water source.The two groups of water sources were relatively independent in groundwater relationship.The relationship between surface water was upstream and downstream.The exploitation of Karst water in XJD area will reduce the recharge of surface water in downstream water source field.(4)In order to avoid the pollution of the water source,the protection area is divided around the pumping well.The formula method and numerical simulation method are used to divide the protection area.Comparing the shape and size of the two kinds of reserves,it is considered that the numerical simulation method is more comprehensive and the results are more accurate.