Research On Groundwater Vulnerability In Tongyu Of Jilin Province

In recent years, with the ascendance of groundwater exploitation, there has emerged a number of environmental problems known as the decline of groundwater level and water quality which can be viewed as a response to the overdue exploitation. Therefore, the protection of groundwater resource is of great significance in order to maintain a sustaining utilization of the resource. The research on groundwater vulnerability will provide us with an effective measure of preventing groundwater pollution and protection of this resource, which finally solve the problems during groundwater utilization.Tongyu, which lies in the west of Jilin Province, is characterized by the semiarid and subhumid climate. During the last two decades, the global greenhouse effect has exerted a profound influence on Tongyu. The climate in this area is turning to an arid region, and as a consequence, the evaporating capacity is 2-3 times larger than precipitation, which leads to the sharp decrease in the surface water and sever land deterioration. The fragile natural environment is in great danger. Affected by the factors mentioned above, the groundwater environment is badly damaged and eventually this will involve some dreadful results, namely the decline of groundwater level, improper exploitation and redistribution, the expansion of alkaline soil and deterioration of swamped land. The issues of groundwater environment above in turn produce an undesirable influence on groundwater vulnerability. Based on these problems in Tongyu County, this article on groundwater vulnerability has a great practical significance and provides powerful support and scientific foundation to find out a solution.Based on the current situation and the progress of groundwater vulnerability research, this article has made a full study of the situation and issues in Tongyu. And with going deep into the mechanism of groundwater vulnerability, the article, according to the DRASTIC evaluating indicator system, successfully builds two vulnerability evaluating systems of phreatic water and confined water of Tongyu area respectively. 11 factors, including the depth of groundwater, the net aquifer recharge, aquifer media, the kinds of soil media, terrain slope, impact of the vadose zone, permeability coefficient, intensity of groundwater exploitation, intensity of phreatic water evaporation, phreatic water quality, and land use, are taken into consideration to build a MEQU-DRASTIC evaluating indicator system of the phreatic water in Tongyu. In the meantime, the DAADCQ vulnerability evaluating indicator system of confined aquifer is based on factors such as the depth of confined aquifer, aquifuge media, aquifer media, the extend of groundwater decline, permeability coefficient, the quality of confined water.On the base of the current groundwater quality analysis in Tongyu, this article, with the tested data of groundwater samples in 1998 and 2006, evaluates the groundwater quality in a fuzzy gathering classification method. Afterwards, an analysis is made based on the evaluation results to find out the tendency of groundwater quality variation and finally to attain the evaluating factors which can well reflect the groundwater quality vulnerability.A hydro-geological conceptual model is built on the analysis of hydro-geological conditions in the researching area. Then the groundwater numberical simulation model is built to simulate the groundwater number by Visual Modfolw and by this model, the net recharge of the aquifer and the coefficient of permeability are successfully acquired.The groundwater vulnerability evaluation in Tongyu, with the help of GIS technology, is completed on the ground of the system of groundwater vulnerability evaluating indicator and weight. The function of the management of attribute base and the special analysis of MapGIS software is applied to vectorize and partition the graphs of all evaluating factors involved. Every evaluating factor is attributed by different area, and saved in the form of files of different researching area. Then, all the files are superposed to generate new ones. All the attribute data are abstracted by the function of attribute base management, and according to the different integrative grade of vulnerability, the researching area is partitioned into different vulnerability areas. Besides, the comprehensive point-rating model and the fuzzy comprehensive evaluating model are introduced to visualize the groundwater vulnerability evaluation and the results in Tongyu. Therefore, the results are graded into four different kinds—higher, high, low, lower. All the causes of different vulnerability areas are carefully studied. At last, through the comparison of the results got from two models, the evaluating results are generally anastomosed, which powerfully proves the accuracy and the rationality of this evaluation.Partition of different vulnerability grades of the phreatic water and confined water of the researching area is generally based on the research of groundwater vulnerability in Tongyu, which provides important gist for the development and the establishment of various groundwater management and environment protection policies.This article builds a groundwater vulnerability evaluating indicator system on the basic situation in Tongyu area, which is of great value of reference to the similar area. In the meantime, the vulnerability evaluation of confined aquifer is achieved, which lies a firm foundation for the further research.