Numerical Simulation And Vulnerability Assessment Of The Groundwater In Zhangji Wells Field In Xuzhou City

Water is an important resource in the survival and development of human being. A series of environmental problems have appeared because of the long-time excessively extraction of groundwater: declining of the groundwater level,exhaustion of water sources, land subsidence, deterioration of groundwater quality and inbreaking of sea water. The main reason is the shortage of scientific evaluation and administration. The research was supported by the National Natural Science Foundation of China (No.40202027), and Fok Ting Tung Education Foundation (No. 91079). According to the pumping test in exploitation stage and after surveying the physical geography and collecting the hydrogeology data, the numerical simulation and the sensitivity analysis of the groundwater are conducted, and the groundwater vulnerability is assessed. The main conclusions are as follows:(1) The physical geography and the hydrogeology data are collected, and according to the pumping test in 2005 in Zhangji wells field, the groundwater simulation is completed, and the fitting of hydrogeology parameters has been done.(2) Based on the numerical simulation, the feasible pumping volume of the wells field in the next ten years is forecasted. The conclusion is: in the three schemes provided, the scheme I can be adopted, that is to say, in order to protect the wells field and avoid the declining of the groundwater level; the better pumping volume is 8×10~4m~3/d.(3) According to the numerical simulation, the sensitivity evaluation is completed using FORTRAN language. Two kinds of factors are utilized: the hydrogeology parameter and the source sink term. The results show: the pumping volume within the source sink term has the most obvious impact on the groundwater level and infiltration coefficient a has the most obvious impact on the groundwater level.(4) After obtaining the hydrogeology data of the wells field, the DRASTIC index which is widely used at home and abroad is used to assess the groundwater vulnerability of the wells field. Results show: the index ranges from 56 to 165, the highest score appears in the deposed yellow river fault zone, ranging from 150 to 165; and the score of the mountain area in south and north is lower. The southern plain has a better capability to avoiding pollutants, and the index is from 81 to 90.(5) According to the assessment results, protection area should be plotted out in the study area. First-grade protection area should be found in the deposed yellow river fault zone, the mountain area in the south and north zone should be second-grade protection area, and the southern plain should get vice protection. Item with much pollutant can not be constructed in the protection area, and domestic garbage, waste water, animal and human excreta must be arranged well.The conclusion of the paper can be a guidance of the administration of the wells field in Zhangji.