Simulation Study On Hydro-environment Of Chuanhu Waters In The Western Of Changchun City

This thesis is supported by the item for technology tackle key plan of Changchun Science and Technology Office"Study on the governing technology of artificial wetland pollution and zoology restoring effect of Chuanhu Lake in Changchun City". Based on the materials collection,field survey and the sample testing, the indoor hydrodynamics dispersion test and soil column leaching test have been done,the GMS and PHREEQC Software are applied to proceed solute transport simulation and hydrogeochemistry simulation,and study the incidence and variation trend of groundwater pollutant.In order to realize the actuality of water environment,the histogram of each ion concentration was drawed by water sample test data, integrating with the quality classification standards of surface water and groundwater , the concentration of calcium(Ca2+),magnesium(Mg2+),total hardness,COD,BOD5,ammonium(NH4+),nitrate(NO3-),nitrite(NO2-),total phosphorus and total alkalinity have been discussed. Integrating with the hydrogeologic background, the groundwater quality is appraised,the appraisement result shows that the concentration of nitrite and nitrite is the most serious and the groundwater samples quality are both greater than gradeⅢ.Based on the field survey and materials collection,porosity,permeability coefficient and coefficient of hydrodynamic dispersion are computed by the indoor hydrodynamics dispersion test. Forecasting the change trend of pollutant concentration in groundwater,around Xinyue reservoir,by soil column leaching test,the result shows that the peak value of pollutant concentration relate to the polluter position and pollutant concentration,the time, peak value appears, relates to the distance of the polluter.Building the mathematic model of groundwater flow system,simulated the groundwater flow by the MODFLOW module of GMS6.0 (Groundwater Modeling System). The area of the calculated zone is 18.8 km2,the software used the finite difference method to calculate, grid with rectangle. The simulation period was from 1998.10.1 to 2000.9.30,every time interval is 6 month and every 30 day is a time step. The main simulated aquifer is Quaternary water table aquifer in this simulation model of groundwater. The inflow from the groundwater system upper boundary included precipitation infiltration and river leakage inflow,the outflow included evaporation and river leakage outflow. Run the model,diagnose the model parameters by fitting the fact and the calculating groundwater flow field,run the diagnosed model,check the model again,portraying the characteristic of groundwater system factually.Based on the above researches,the path of pollutant moving from source to destination, simulated by the MODPATH module of GMS,using Cl- as tracer ion.and the time needed is computed.Selecting two observation wells G2,S3 from pollutant source to Yanming Lake, along the direction of groundwater flow,the minimum time is 120days from source to G2,and the minimum time is 1100days from source to S2,about 3 years.The MT3DMS part of GMS is applied to proceed solute transport simulation.The MT3DMS,coupled with Modflow as an independent part of GMS, can be used to build groundwater solute transport model expediently.Setting the pollution typeas point source pollution,and injecting the pollution into aquifer with injection well in the model on and after settings for parameter.By counting,when the simulated time is 120days,the capture zone passing G2, the maximum distance and range are about 900m and 1.9km2around the Xinyue reservoir. when the simulated time is 1100days,the capture zone passing S3, the maximum distance and range are about2250m and 6.5km2.The study shows that the movement of pollution accords with the direction of groundwater folw.PHREEQC is applied to simulate the transfer and conversion process of nitride in unsaturated zone,and forecast the pollution of unconfined aquifer by nitride.Based on the model diagnosed and error analysis,changing the character of unsaturated zone,forecasting by setting three project.The result shows,the concentration of NO2-come to the least while the temperature reaches at 28℃,pH value is 7.5,and soil horizon top is well-oxygenated environment,infrastructure is reducing environment,it accords with the III level standard of groundwater quality,meeting the the needs for life drinking water and industry,agricultural water.The author suggested strengthening the management and protection of Chuanhu Waters,decreasing groundwater pollution,improving the water environment of Chuanhu Waters by building the artificial wetland.