Projection pursuit grade evaluation model based on maximum information entropy principle for river health system

In order to rationally determine each index weight and effectively deal with fiazziness and randomness existing in evaluation process, projection pursuit grade evaluation model based on maximum information entropy principle, named PPE for short, is proposed as a new evaluation approach. Optimal projection direction of PPE using accelerating genetic algorithm reflects the objective weights of evaluation indexes, hereby the rationality of original evaluation criterion can be verified and the major indexes of influencing river health can be identified. The results of PPE applied to evaluating a river health in the South of China show that the calculated membership degree value of the river health fuzzy set is 0.6115, so the river belongs to the grade of ldquohealthrdquo and approaches the grade of ldquoinferior healthrdquo; there is only objective weight relatively small value of the index ldquoriver blanking probabilityrdquo in the 25 evaluation indexes, and the objective weight value of other indexes approaches 0.04; the major indexes of influencing the river health are ldquothe collecting rate of the fee of water resourcerdquo, ldquoself-purification rate of water bodyrdquo, ldquothe index of regulating abilityrdquo, ldquochange rate of sediment transport capacityrdquo, ldquoGDP of per cubic meter waterrdquo, ldquochange rate of fish kindrdquo, ldquoperfect rate of nonstructural measures of flood controlrdquo and ldquosewage handling raterdquo, respectively; it is the important working content of the water security management of this river at present to improve the river health degrees of these indexes.