Groundwater Vulnerability Assessment Of Jixi City Based On GIS

Jixi, which lies in the southeast of Heilongjiang Province, is characterized by the continental monsoon climate in mid temperate zone. During the last two decades, the global greenhouse effect has exerted a profound influence on Jixi. The evaporating capacity is 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. And wth the rapid development of economics of Jixi, the degree of exploitation and utilization increased continuously. 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 issues of groundwater environment above in turn produce an undesirable influence on groundwater vulnerability. Based on these problems in Jixi 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 methods of vulnerability assessment of groundwater. and choose comprehensive assessment method based on parameter system method and fuzzy mathematics theory as the basic methods of the groundwater vulnerability assessment of Jixi. And with going deep into the mechanism of groundwater vulnerability, the article, according to the DRASTIC evaluating indicator system, successfully builds a vulnerability evaluating system of Jixi. 10 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, groundwater quality, and land use, are taken into consideration to build a MQL-DRASTIC evaluating indicator system of the groundwater in Jixi. This system cause DRASTIC to assess the groundwater vulnerability of study area more exactly.Traditional DRASTIC method take the principle of"evaluation after division"to assess the groundwater vulnerability. According to the result of application of the DRASTIC method in the groundwater vulnerability, the article uses five grades to measure the degree of vulnerability. And the result accord with the basic rules of distribution of groundwater vulnerability of Jixi. Because traditional DRASTIC method do not involve human activity and the features of pollution sources as its indicators and divide the study area before the assessment, this system only can not precisely assess the groundwater vulnerability of Jixi.The function of the management of attribute base and the special analysis of ArcGIS software is applied to vectorize and partition the graphs of all evaluating factors involved. Every evaluating factor is attributed by different area, and being saved in the form of files of different researching area. Then, all the files are superposed to generate new ones. All attribute datas 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.The groundwater vulnerability evaluation in Jixi, with the help of GIS technology, is completed on the ground of the system of groundwater vulnerability evaluating indicator and weight. The comprehensive point- rating model and the fuzzy comprehensive evaluating model are introduced to visualize the groundwater vulnerability evaluation. The two models divide the study area before finishing the evaluation,and partition of different vulnerability grades of the groundwater of the researching area is generally based on the research of groundwater vulnerability in Jixi. The comprehensive point-rating model is one of parameter system methods, this method multiplys weights with scores of each indicator and then add the scores of ten indicators as the basis of the division of gradesof groundwater vulnerability. the fuzzy comprehensive evaluating model use the datas of attribute table from ArcGIS to calculate the matrix of membership, and use the multiplication of matrix and weights after normalization as the foundation of dividing vulnerability degree.The article graded equally the finial results of groundwater vulnerability using the comprehensive point-rating model and the fuzzy comprehensive evaluating model into five different kinds—higher, high, middle, low, lower, and compare the results with that of DRASTIC model. The distribution laws of three different models are similar and accurate. But the comprehensive point-rating model and the fuzzy comprehensive evaluating model as a useful tool in the assessment of groundwater vulnerability are more scientific and precise. The article proposes groundwater environmental problems and protection measures in Jixi on the ground of the result of assessment of groundwater and provides important gist for the development and the establishment of various groundwater management and environment protection policies.The result of research shows that only we consider the hydrogeology factor and the exterior factor can we evaluate the groundwater environment vulnerability objectively. Fuzzy comprehensive evaluating model has the preferably application effect. Groundwater environment vulnerability is intimately related with the pollution state. Groundwater system is intimately related with human society and economic.