Projection pursuit model for comprehensive evaluation of water quality based on free search.

The method of projection pursuit(PP)was presented to evalute the water quality for solving the problems such as the incompatibility of water quality indexes and the rough grade levels evaluteed by other methods. Based on the grade division standard of water quality, the projection function which could reflect the variability of the water quality was constructed,and free search (FS) was introduced to optimize the function and seek the optimum projection vector, while the data of the vector were used to research the influential level of each water quality index. Take Fenhe River Basin for instance to evaluate the water quality, compared with the resules which evaluteed by RAGAPP and PSOPP. The achieved results suggested that the error precision of FSPP is superior to RAGAPP and PSOPP, the conclusion assessed by the model was accordant with the actual water quality condition, and the projection pursuit model could identify the grade of water quality, FSPP model is an effectivemethod for evaluating water quality. It is effective and general, which can be applied to comprehensive evaluation of other environmental quality.