Groundwater Protection And Reflow Of Numerical Simulation In Jiyuan Basin

Jiyuan city is located in the northwest of Henan province,it is named Jiyuan because it is the birthplace of Ji river.In the northwest of Jiyuan basin,near the mountain front,there is a groundwater overflow zone.Historically,there have been such springs as Jidu spring,Pearl spring and Laolongtan spring,with the maximum total flow of 3.5m/s.In recent years,due to the unreasonable exploitation and utilization of groundwater,the groundwater level in Jiyuan basin has been falling continuously,and the flow rate of spring water has been sharply reduced,even cut off,The flow rate of pearl spring is only 0.3m/s.Therefore,Jiyuan city has put forward the goal of reflow of famous springs,recovery of groundwater level and construction of landscape garden city.It is urgent to find out the hydrogeological conditions and determine the reflow scheme.On the basis of the detailed analysis of the hydrogeological conditions of Jiyuan basin,the groundwater extraction,output and water quality were investigated comprehensively,and the groundwater resources were calculated and the groundwater quality was evaluated by the method of water balance.On this basis,using the international general Visual MODFLOW groundwater simulation software,build the three layers of three-dimensional unsteady seepage Jiyuan basin groundwater numerical model,and combining the Jiyuan basin groundwater exploitation and utilization present situation and the complex flow requirements,design seven springs flow scheme,add the conditions of each scheme corresponding to the model,operating model,predict the effect of various complex flow scheme of complex flow.The achievements of the thesis mainly include:（1）The groundwater resources in Jiyuan basin show a negative equilibrium state.From 2015 to 2017,the groundwater recharge of Jiyuan basin was calculated to be175.7402 million cubic metres,177.8699 million cubic metres and 171.1122 million cubic metres.The total groundwater excretion in the Jiyuan basin from 2015 to 2017 was183.7228 million cubic metres,175.2589 million cubic metres and 184.9538 million cubic metres.The equilibrium difference of groundwater water amount is-7.9826million cubic metres,2.602 million cubic metres and-13.8426 million cubic metres.（2）The groundwater chemical types in Jiyuan basin can be summarized into five types,namely HCO₃·SO₄-Ca,HCO₃·SO₄-Ca·Mg,（HCO₃·SO₄-Mg·Ca）,HCO₃-Ca·Mg,HCO₃-Ca·Mg,HCO₃-Ca,and complex type.Jiyuan basin,according to the results of the groundwater water quality factor of Jiyuan basin groundwater existⅢclass standard.（3）In this paper,a three-dimensional numerical model of unsteady seepage in three layers of groundwater in Jiyuan basin is established.The simulation results show that,under the current conditions,the spring level in laolongtan presents a declining trend year by year,with a decreasing range of 0.20m/a in dry years,0.17m/a in flat years and0.13m/a in wet years.In the reflow effect of a single measure,the best is to close the Qingduo water source,the second is to close the industrial Wells,and the worst is to reduce the discharge of Longquan lake.By comparing the re-flow results of various schemes,the optimal re-flow scheme was finally determined as the comprehensive re-flow scheme combining the closure of the industrial-owned well and the closure of the Qingduo-water source.