Numerical Simulation Research Of Groundwater With FEFLOW In The West Of Jilin Province

The paper which is based on the project"the research on groundwater overexploitation and its surface ecological effect in the West of Jilin Province"of Land Mineral Resources Management in Jilin Province has appraised and forecasted for groundwater resources in Western Jilin Province. The water resources are scarce in the west of Jilin Province, per-capita quantity of water resource is 809m3/a, which is 53.2% of the hole province (1520m3/a) and only 36.4% of China(2220m3/a). Land desertification and salinization are very serious in the research area, natural calamity such as the sandstorm takes place occasionally, so this area is a typical farming grazing transitional belt and vulnerable ecological environment area. In recent years, with the development of urban construction and national economy, water demand, the discharge of waste water and waste residue increased year by year, the contradiction of supply and requirements about water resources and the problems of environmental pollution become outstanding day by day, and have produced the inestimable negative effect on the ecological environment and human health. Considering these questions, this paper utilized the existing dynamic observation data of groundwater of the western region, spatial distribution materials of groundwater quality and some relevant data, set up the reasonable modeling of groundwater quantity and quality, and get clear understanding of exploitable resources amount of groundwater and groundwater environmental quality in the research area. The paper offers scientific basis for protecting the groundwater resources and realizing the sustainable development of regional water resource.This text introduces numerical model, especially the current situation of domestic and international researches, development trends and existing main problems of the water quality model. On the basis of fully collecting and analyzing relative materials such as geology, hydrogeology and environment of the west of Jilin Province, the paper explaines systematically the cause, era and lithology of the main stratum in the research area, and analyzes the law of recharge, runoff, drainage and dynamic characteristics of the groundwater. After confirming the range of simulation district and object layer for calculation and generalizating hydraulic characteristics, vertical and lateral boundary, a groundwater mathematical model is set up, according to the hydrogeological conceptual model. And FEFLOW(Finite element subsurface flow system)which is based on finite element method is employed to solve the numerical equations.Before data input, overlap parameter subarea and administrative region, then divide the source sink data of each administrative region into the recharge of sub area. This simulation used the water level observed value of selecting January of 2000 - January of 2002 to identify and inspect the model, the fitting effect is all right, and it explains that the determination of aquifer structure and hydrogeological parameter, the generalization boundary condition are reasonable, so the model can be used in forecast. Based on the model, the paper predicts the groundwater flow field of the following 15 years in the research area. The prediction results demonstrate that exploiting according to the predicted enlargement exploiting amount, the water tables of the phreatic water and the artesian water have the tendency to decline continuously year by year, comparing to the water table of the artesian water, the water table of the phreatic water declines in evidence, especially the water table of the advancing edge of Tao-er River Fan and Taonan and Zhenlai has the largest change, is 5-8m, the water table of phreatic water of plot among Songla River appears obvious declining too, the average decreasing amplitude in year is about 0.5m. The water table of the artesian water declines obviously in the center of the basin whose recharge condition is worse and western plain in front of mountain and transitional belt of low plain that the penetrability of aquifer is worse and the exploitation quantity is large, decreasing amplitude is 2-4m.Based on the water quantity model, the groundwater solute transport model of the West Jilin is set up. Firstly, the Factor Analysis Method is used to analyze the main ion of groundwater chemical composition in the research area, the result shows that nitrate nitrogen is the main pollutant influenced by human activity. Ignoring the conversional mechanism between three nitrogen, we confirm the total nitrogen( NO3 ? ?N,NH 4+ ?N,NO 2? ?N) as simulation target of this research. Because the content of the total nitrogen in artesian water is low, and changes unconspicuously in many years, the simulation didn't have actual meaning, so this paper gives the simulation and the forecast in total nitrogen of the artesian water. It chooses the water- chemical materials which keep the same time with flow model to identification and inspection, from the fitting picture of groundwater calculation and actual measurement concentration field, we can know that the fitting curve reflected the variation tendency, the precision of model agrees with the standard, so the modelcan be used to predict. The forecast time is ten years. The prediction results demonstrate that under the condition of area shape pollution because of using of nitrogenous fertilizer, the nitrogen concentration of the research area assume up tendency, especially in Baicheng and Taonan, because domestic wastewater, industrial sewage and solid waste that are piled up at will, the change of the nitrogen concentration is very obvious. Qianguo takes second place. In the other place, with the flow of the groundwater, nitrogen is discharge outside the area, and the concentration of the nitrogen does not change much on the whole.The groundwater resources quantity of the research area is limited, and the intensity of development and utilization is high, so at the present time the water table drops obviously, which could not satisfy water need of long-term development of the whole area, so there are some suggestions that on the base of reasonable utilizing the groundwater resources, strengthen the building of hydraulic engineering of the river pass through, fully utilize surface water resource that pass through, and according to the allocation and management of surface water and groundwater, reach the long-range objective that can satisfy water demand and improve the fragile ecological environment of the research area. At the same time, reduce the artificial pollution of groundwater, control the discharge of waste water of industry and rural enterprise and the piling up of solid waste strictly, and reduce the pollution of the groundwater from industry and the continuation depravation of ecological environment. Improve the technology of digging well, especially the technology that agriculture well drilling, improve its close craft, reduce hydraulic interaction of the phreatic water and the artesian water, and control the pollution of the artesian water quality when the phreatic water is infiltrating. Then, satisfying growth in gear of crops as the precondition, improve the technology of the using of chemical fertilizer, and develop ecological agriculture and green agriculture to reduce the pollution to groundwater from pesticide and the using of chemical fertilizer.