Groundwater Resources Vulnerability Assessment And Mapping To Qianjiang County Of Chongqing Based On GIS

Groundwater is a very important natural source for human being. The research of groundwater vulnerability is the basis of groundwater protection. The groundwater environmental problem is getting more serious with the rapid development of economic and increasing human activities. And groundwater vulnerability assessment and mapping is more and more recognized by researchers and decision-makers. Many countries used many methods to assess the groundwater vulnerability and completed many groundwater maps to protect the groundwater resources.Qianjiang County is the southeast economic center of Chongqing. The groundwater environmental problem is getting more serious with the development of economic. The main measures of groundwater protection are groundwater vulnerability assessment and aquifer protection area delineation. Qianjiang County of Chongqing was chosen as the typical study area to assess groundwater vulnerability and delineate the groundwater protection area in this paper.In 1968, Margat (French) first raised the term "groundwater vulnerability" in his article, and he and Albinet successively made descriptions through pictures of vulnerability degree of groundwater on pollution, so as to arouse the human society attention to the danger of groundwater pollution. In 1993, the American State Committee of Scientific Research gave groundwater vulnerability a definition: It is the tendency and possibility of pollutants reaching a certain position above the highest water-containing level.GIS, which has the functions of the input, store, management, search, disposal, and synthetic analysis of geographical spatial data and information, has been widely used in every field. Since GIS is becoming more and more practical, which has the ability of synthetic analysis as well as spatial module construction, and to change and renew the data base at any time, the evaluation process is facilitated, strong support is given to groundwater vulnerability, and the development of the research on groundwater vulnerability is promoted, thus GIS has been widely applied in the evaluation and cartography of groundwater vulnerability.After field work in Qianjiang, Consulting the hydrogeological background, from the result of the analysis of the groundwater chemical characteristics, and the landform of Qianjiang, the author regionalizes 22 subareas. And some subarea's boundaries are the same as geological structure lines. In conclusion, these subareas can show the real difference in groundwater vulnerability.Based on ArcGIS platform and large amount of data of groundwater in Qianjiang of Chongqing, the author makes evaluation of its vulnerability using DRASTIC method. In the essay, the author introduces the current situations at home and abroad of groundwater vulnerability, describes the groundwater formation conditions and hydrogeological features in Qianjiang of Chongqing, details the DRASTIC method adopted in European and American countries to evaluate groundwater vulnerability, and illustrates the scoring of 7 parameters: depth to the underground water-table, net Recharge, aquifer material, soil media, topography, impact of the vadose zone hydraulic Conductivity of aquifer and the subarea which should be noticed in evaluation. And also calculates the 7 parameters to get the divide sections pictures using ArcGIS, a painting tool, gets parameter score through weight, and finally pictures synthetic evaluation chart. Through the research of groundwater vulnerability, the division of vulnerable extent of different section groundwater, the evaluation of potential pollution of groundwater and the fix of vulnerability scope of groundwater, people can apply practical measures when exploring and utilizing the groundwater in Qianjiang County of Chongqing to ensure the sustainable use of groundwater.And because of the alternation of topography and geological background, when doing a single parameter assessment, such as "the depth of water-table", we find the result look the same as difference of the topography. The depth of water-table on the mountain is deeper than in valley, so the groundwater under mountain is harder to be wasted than in valley.