[Integrated fuzzy evaluation of water eutrophication based on GIS in the Taihu Lake]

Abstract

Supported by geographic information system and geostatistics, the application of fuzzy mathematics and analytic hierarchy process for water eutrophication evaluation was discussed. Taking Taihu Lake as an example, the research selected total phosphorus, total nitrogen, chlorophyll a, COD, BOD5, DO and transparence as evaluation index. After geostatistical analysis of the datum of monitoring site, the values of evaluation indices were estimated in the whole research area. Given that, the different dependence functions were developed for these indices and the function values were calculated. Furthermore, according to the principle of analytic hierarchy process, the weight of every index was calculated, then integrated evaluation value was obtained for the whole research area and the evaluation map for water eutrophication was drawn. The result shows that the level of nutrition is the highest in the north and north-west of lake, which is hypertrophic, that is meso-eutrophic in the middle and that is the lowest in the south-east of lake, which is mesotrophic.