Abstract:

With the development of social economy and the expansion of human activities,water quality has gradually deteriorated in many areas.Water pollution is a serious problem threatening the survival of human beings,plants and animals.Water quality comprehensive assessment,as a important reference for water environment treatment，is increasingly being valued by the people.Large amounts of information and complex situations are the radical character of water quality comprehensive assessment.How to effectively extract useful information and set weight of water quality index objectively,has long been a main problem of water quality assessment.With the ability to deal with both numeric and nominal information,and express knowledge in a rulebased form,the Rough Set Theory (RST) has been successfully employed in many fields such as image segmentation,location services,travel modeling,medicine and so on.However,the application of RST has not been widely investigated in water quality analysis.As a mathematical tool to deal with uncertainty information,RST can effectively exploit information from complex water quality data.Information entropy has an important application in RST,and it can solve the problem in information loss and resultant sort for RST,thanks to the characteristic which can reflect the importance of properties accurately.Based on roughinformation entropy theory,a new method for assessing water quality is put forward in this paper.This method inherits the features of RST that can effectively exploit information from the raw data directly.For this reason,it can reduce the influence of the subjective factors which have a very large impact on the traditional water quality assessment methods.In addition,the method based on roughinformation entropy theory can further make water classification for monitoring sections which are the same pollution levels,and it has important meaning to the estimation of input in funds and technology for water pollution control.By comparing the evaluation results with the ones obtained from comprehensive index method,fuzzy synthetic evaluation method and principal component analysis method,it was proved that the method established in this paper is not only simple and clear,but also rich and objective in the content .What’s more,it can refine classification and make the evaluate results more exact and more reliable.The research can not only provide some certain references for water quality evaluation,but also can offer guidance and recommendation to the measures for water pollution control