A Method For Security Assessment Of Centralized Surface Source Water Area

The thesis establishes an index system and a method for the security assessment of source water area, before analyzing and assessing the security conditions of Yuqiao Reservoir in Tianjin. At first, it reviews the status of researches at home and abroad into security assessment of source water area, introduces the current security conditions of source water area in China and existing problems. Then discusses the influencing factors and security connotation of source water area by analyzing the course of water cycle and the security connotation. After that, it establishes an index system for source water area security, determines the relevant assessment criteria and decides on AHP-based fuzzy assessment method as the primary assessment method. To test the method, an analysis is made into the assessment of Yuqiao Reservoir conducted in 2003.The index system contains two hierarchies: the first one contains five security indexes, including water quality, water quantity, ecology, engineering, and other objective effects; the second involves such indexes as water quality grade, eutrophication grade, water quality risk,water storage, the ratio between in-coming and outgoing water, vegetation density, flood control security, the quality of managerial stuff, funds input and so on, and takes the initiative to contain risk assessment into source water area security assessment. The establishment of assessment is achieved via extensive reference to currently available criteria, assessment conducted by experts, statistical analyses, and coordination of qualitative and quantitative methods.Analysis Hierarchy Process (AHP method) is adopted to determine the weight of each evaluating index. The rating criterion of each basic index is classified, each basic index is classified into five grades, the security status of each index was expressed by their degree of membership belonging to each security grade, and the fuzzy synthetic judgement model is chosed as the evaluation model. During the assessment, quantitative method is used for rating risk, water quantity security and other indexes. This is an unprecedented attempt in source water area security assessment in China. The advantages of the method lie in that it not only takes into consideration the fuzziness of the assessment process, but also reflects the overallsecurity statuses of the indicators at various hierarchies. The comprehensive assessment of Yuqiao reservoir shows that its overall security grade is 3.68, close to low grade, and that water quality security and ecological security are at a low level. Therefore, the security status of Yuqiao Reservoir is very discouraging. From the process and findings of the assessment of Yuqiao Reservoir we may conclude that the method established is practical, comprehensive, and accurate. The findings are significant for the management and protection of source water area.