Study On The Optimization Adjustment Of Karst Water Protection Zones In Xingtai

The study area is located in Xingtai City in the south of Hebei Province.There are 3centralized groundwater and drinking water sources in the urban area.They are also located in the runoff drainage area of the Baiquan Karst Water System.All of them are exploited in the Ordovician Middle System karst water,with a total designed mining capacity of16.0×10~4m~3/d.In recent years,with the water supply of the Middle Route of the South-to-North Water Diversion Project,water from the river has replaced groundwater and has become the main drinking water source in the urban area of Xingtai,which has transformed its water supply pattern from a single groundwater source to"one use and one reserve.In June 2020,the urban area of Xingtai officially completed the water source switching,the amount of groundwater source area extraction has been greatly reduced,and the scope of mining impact will also be significantly reduced.In this case,in order to protect the groundwater source more specifically,the original water source protection area needs to be re-divided.In this paper,based on the physical geography,geology and hydrogeology data of the study area,combined with the lithology and thickness of the overburden above the karst aquifer,this paper evaluates the antifouling performance of the vadose zone,and divides the areas with good antifouling performance,medium areas and poor areas.According to the regional karst water replenishment and drainage conditions at different stages in the past,the dynamic changes of karst water and the characteristics of flow field changes are discussed,and analyzed the trend of change.According to the regional hydrogeological conditions,the groundwater flow numerical model of the study area is established with the mining layer of the water source(karst aquifer)as the simulation layer.The simulation period is from November 2011 to June 2020.After the various parameters and conditions are given,the simulation will be carried out.The identification and verification of the model led to the conclusion of the water balance during the simulation period of the whole area.The replenishment amount was 17395.03×104m3/a,the excretion amount was 17174.29×10~4m~3/a,and the supplementary discharge difference was220.74×10~4m~3/a.The overall situation is in positive equilibrium.After the numerical model has been identified and verified,the particle reverse tracking method is used to calculate the range of solute migration in 25a under the 5 mining schemes,and compare the range of 5 solute migration in 1000d and the range of particle migration to the boundary delineation.After analysis,three optimization and adjustment plans for protection zones were put forward.The area of secondary protection zones was significantly smaller than the scope delineated in 2012.Finally,combining the division of water source protection areas and hydrogeological conditions,relevant suggestions for water source protection are put forward.