Research On Layout Plan Of Monitoring Station Network In Groundwater Over-exploitation Area In Huaibei City

The development and utilization of groundwater resources in Huaibei City presents the characteristics of mixed exploitation of pore water and fissure karst water.Limited by recharge conditions and circulation conditions,coupled with the continuous over exploitation of karst water,the water level continues to decline,resulting in a large-scale depression funnel.For this reason,Anhui Province has designated the karst water Limited mining area in Huaibei and monitored it for a long time.The karst water in the limited mining area will be gradually pressed and mined in 2018-2019,2020-2024,2025 and later three stages in Huaibei City,and the water volume will be replaced by Xulou water source outside the limited mining area.The change of groundwater exploitation pattern will directly affect the regional groundwater flow field and change the spatial form and scope of groundwater depression funnel.The existing monitoring holes can no longer effectively monitor the overdraft area.Therefore,it is urgent to optimize the layout of monitoring station network in overdraft area under different pressure mining stages.This paper first analyzes the regional geological and hydrogeological conditions,establishes the mixed flow model of pore water and fissure karst water,and predicts the change trend of regional groundwater flow field in the next ten years;Secondly,based on the "pressure production scheme",the objective function and constraint conditions of cost minimization are proposed for 98 karst water exploitation wells in the study area.The genetic algorithm in Visual Modflow-MGO module is used to optimize the pumping scheme of three pressure production stages,and the optimal exploitation scheme of each stage is obtained;Then,based on the optimized karst water mining scheme,the new scheme of monitoring holes in overdraft area in each mining stage is put forward,and the sensitivity analysis method is used to test the new monitoring holes,change the same pumping volume,and reserve the monitoring holes with faster water level response,and finally the best layout scheme of monitoring station network in each stage is obtained.The conclusions are as follows:(1)The simulation results show that: at the end of the second mining year,the water level of the mining center in the limited mining area has a downward trend,while the water level outside the limited mining area is basically unchanged;at the end of the fifth year of mining,the water level of the central mining area rose,while the water level of Xulou water source outside the mining area decreased;at the end of the eighth mining year,the water level of the mining center in the restricted mining area rose rapidly,and the water level of Xulou mining point outside the restricted mining area continued to decline;at the end of the 10 th mining period,the water level in the mining area was basically restored to the initial water level state,and the water level of Xulou water source area outside the mining area decreased.(2)The genetic algorithm in Mg O module is used to optimize 98 karst mining wells,and the best mining scheme is obtained: in the first stage,28 wells are reserved in the limited mining area,8 wells are reserved outside the limited mining area,a total of 36wells;in the second stage,20 wells are reserved in the limited mining area,10 wells are reserved outside the limited mining area,a total of 30 wells;in the third stage,10 wells are reserved in the limited mining area,12 wells are reserved outside the limited mining area,a total of 22 wells There are two production wells.(3)The results are as follows: in the first stage,22 monitoring holes will be added,and 8 will be retained after the inspection;In the second stage,6 monitoring holes will be added and 2 will be retained after inspection;In the third stage,no monitoring holes will be added.On the basis of the current monitoring station network,a total of 10 monitoring holes are added in the three stages.With the existing monitoring holes added,the total number of monitoring holes is 28 after optimization,which realizes the optimization of the current monitoring station network in Huaibei City.