The Comprehensive Assessment Of Water Environmental Quality Based On The Set Pair Analysis

Water is the source of life and the foundation of the sustainable development of our society. Water environment is the precondition for human survival and society development. It is particular important to accurately understand the connotation of water environment and scientifically assessment of the water environmental quality. In general, water environment is narrowly defined as the quality of water body, that is to say water quality. On the basis of the previous researches, this paper proposes that water environment should contains the sediment and aquatic organisms, that is to say, water environment is a synthesis of water quality, sediment and aquatic organisms. Meanwhile, the thesis holds that water environmental quality assessment should be carried out from the following aspects:water quality, sediment quality and aquatic organism. It also means that water environmental quality assessment refers to the comprehensive assessment of water quality, sediment and aquatic organism.Many scholars has done a lot of researches and discussions on the evaluation method, especially since Mr.Keqin Zhao has proposed the Set Pair Analysis(SPA) method, the SPA method has been widely used in water quality evaluation. Considering the limitation of SPA, which can not accurately depict the connection degree between the standard level and the monitored data, especially when the data belongs to the same level, the expression of connection number has been optimized based on the basic concept of SPA and the characteristics of water environmental assessment, and then the developed set pair analysis model is established. We apply the model in the water quality evaluation, sediment evaluation and water environmental quality evaluation, and the model has been proved to be fairly effective. The author also hopes to provide a new way to appraisal work. Take Chang Lake for example, based on the monitored data establish the reasonable index system, and use entropy method to determine the weight of indexes, then the developed set pair analysis model was used to evaluate the water environment of Chang Lake, including water quality assessment, sediment quality assessment and the comprehensive assessment of water environmental quality. The results show that the water quality of Chang Lake are all worse than GradeⅣ, except Dahu with gradeⅢ. The sediment quality of every monitoring are great different from each other, individual with better result. The result of water environmental quality comprehensive assessment shows that the water environment quality of Qiaohekou and Xinyangqiao has reached the gradeⅤ, which could not meet the requirement. Meanwhile, the results also show that comprehensive assessment could better reflect the condition of Chang Lake.