Application Of Fuzzy Logic And Integrated Multilevel Theory In Assessment Of Water Quality

Water environment assessment is a basic important work for water resource protecting. Water environment assessment can be classfied into organic pollution assessment, eutrophication assessment, sediment assessment and hydro-ecosystem assessment by assessing object.It can also be classfied into single-factor method, multi-foctor method and others. The single-factor method is not accord with the inner oneness of water environment. So, a great deal research has been done on multifoctor methoed. In this paper an integrated cascade fuzzy method based on fuzzy theory for water quality assessment is developed.The integrated cascade fuzzy method was presented based on the analysis of present water quality. The key of this method is integrated fuzzy assessment method. Combined with cascade theory, the great amount of complicated phenomena in water quality assessment and the relations between different factors were quantified. Then, the grade of water quality was gained. When analyzing and applying the data, the weight of each factor was determined using main content - factor analysis weight assignment method which is based on the measured data of sample. This method avoided the subjective differences of expert analysis weight assignment method. Meanwhile, the results from integrated fuzzy analysis were analyzed using weight average method. This avoided information loss when using maximal subjection method, and the assessed results can be sorted.In the case study of Xuanwu Lake, the water quality and eutrophication status were assessed using the integrated cascade fuzzy method presented in this paper. The practicability was validated in this case.