Numerical Simulation And Application Of Groundwater In The Eastern Part Of Tumochuan Plain,Inner Mongolia,China

The groundwater resources in the TuMoChuan plain are very rich.With the continuous exploitation of groundwater in recent years,there have many problems,such as descending funnel formed in some areas;The salty soils caused by saline groundwater;Being ill caused by drinking groundwater which containing fluorine and arsenic;Industrial facility and leakage of landfill site caused groundwater pollution,etc.These problems seriously affect our production and health,so it is very important to study the evolution of groundwater environment in the TuMoChuan region.Based on the theory of groundwater flow system,this paper makes use of GMS（Groundwater Model System）groundwater simulation software to simulate groundwater flow and apply to the eastern region of TuMoChuan plain.In the early stage of the work,a lot of geological and hydrogeological conditions of TuMoChuan plain have been collected,understanding the landform,stratum lithology,boundary conditions,structure characteristics,the groundwater level of aquifer,the source and discharge characteristics of groundwater,etc.On this basis,using the MODFLOW module of GMS software to establish hydrogeological conceptual model and groundwater flow model,simulating the actual circumstances of the groundwater flowing in the region.After constructed,the model is calibrated with the method of flow field test and water balance test to improve the precision of the model.After the model is corrected,the MT3D module will be used to simulate the migration of the solute and groundwater in the landfill site in the research area HeLinGeEr county,and to understand the flowing characteristics of the groundwater in the landfill site.The main conclusions of this paper:1.By simulating the changes of groundwater flow field for 10 years,it is found that the variation of groundwater level in the study area is small.The variation range of groundwater level in the eastern,southeastern and southern regions are between1-3m,and the variation range of groundwater level in the western and northern regions are between 3-5m.2.During the 10 years of the simulation period,the total recharge of the groundwater in the study area was 7.491×10⁹m³,the total excretion was 7.002×10⁹m³,and the balance difference was 4.837×10⁸m³.We found the balance difference was small,indicating that the groundwater recharge relationship in the study area was more balanced.3.From the conclusions of the simulated transport of landfill leachate,the pollutants mainly spread to the downstream following time,and after the end of the simulation period,the first layer of chloride diffused to the downstream 8290m,the highest concentration of the pollutant in the landfill center is 4010 mg·L^-1,the downstream direction exceeded the standard distance of 4134m,and the second layer chloride expanded downstream 5503m,the highest concentration of pollutants is2124mg·L^-1,the downstream direction exceeding the standard distance is 2901m,and the concentration of third layer chloride is always 0 during the simulation period,indicating that the pollutant does not move down to the third layer.In view of the simulation results,it is suggested that we should Strengthen management and supervision of landfill and other production enterprises in the study area.the real-time monitoring system of groundwater can be set up to monitor the characteristics of the groundwater quality around the landfill.We can find out and take corresponding measures to reduce environmental risks at the first time.