Water Quality Assessment Model Based on Index Subset Weights and Its Application

A fuzzy pattern recognition model is applied to the water-quality assessment on the basis of the fact that there exist no clear and absolute boundaries between different grades of water-quality. The model is constructed based on the relative membership degrees in fuzzy sets and it has some superior characteristics compared with the assessment methods applied at present. Furthermore, there are two criteria on how to decide the weights of different objectives, one is the effect of single index on environment pollution, and the other is the mutual-function and the relationship between different indexes. So based on the idea of hierarchical analysis, all indexes are classified into several subsets to take consideration of the interrelation of the indexes of water environment pollution and then the index subset weights are determined qualitatively and quantitatively. A case study is given to show how to use the fuzzy pattern recognition model based on the index subset weights.