The Three-dimensional Numerical Simulation For Groundwater System In Yancheng City

Groundwater is a valuable natural resource. And it is a basic element of environment. Population, resource, and environment, being the three major problems that nowadays world is confronting, are directly or indirectly relevant with groundwater. With the increase of population, the development of the urban size, industry and agriculture, the groundwater demand increases sharply. And a series of environmental geologic problems such as regional groundwater table fall, water quality worsening, subsidence and so on, have emerged in the course of exploiting groundwater due to uncontrolled extraction and poor management. So it can be said that for human being exact evaluation of groundwater resource is the premise and base of scientific management and rational utilizing groundwater.Yancheng city, located in the north of Jiangsu province, covers about 14893sq km. In this area, the groundwater mainly is pore water. Because the quality of the phreatic aquifer and the first confined aquifer is not good, the primary exploitation layers of the research area are the second, the third and the forth confined aquifers. The groundwater exploitation of the area has reach considerable scale at present. Regional cone of depression has come into being due to centralized exploitation and overexploitation in the important towns of each county/district.In this thesis the geological and hydrogeological conditions of the area are systematically analyzed, and, from top to bottom the primary exploitation layers are divided into five layers in order: the second confined aquifer, the second aquitard, the third confined aquifer, the third aquitard, and the forth confined aquifer. Based on fact data and partly insert method, the concept model of research zone is presented. Then the isoparametric finite-difference three-dimensional transient groundwater numerical model is presented. Visual Modflow, the most popular standard visualization software package approved by the hydraulic scientists and technicians on simulating the groundwater flow is used to simulate and calibrate the groundwater level and quantity of the research area. At last ,the changes of the hydraulic head and the produced quantity in the future were predicted according to the tested parameter and the modified model.This model reveals the characteristics of the system of the groundwater, reflect the pattern of change and transportation of groundwater, and it can give scientific support to the prediction of groundwater table, evaluation of resources and give scientific support to control the subsidence in Yancheng.