Application of fuzzy theory to satellite data for determining eutrophic status

Generally, eutrophic status of a water body is determined by a limited number of water samples. Statistically, we have not sufficient confidence with the overall eutrophic status by using point-basis water sampling which is usually executed under a physical and financial limitation. Also, a crisp determination of traditional eutrophic indices often causes debated argument. This paper proposed to apply fuzzy set theory to describe the classification of eutrophication. Multi-spectral satellite images were converted into water quality variables, such as phosphorus, Secchi depth, and chlorophyll that are the major affecting factors of eutrophication. Fuzzy synthetic evaluation for the eutrophication status was developed for OECD index and applied to satellite-derived two-dimensional water variables. The approach was experimented on the Feitsui Reservoir which is the most important water supply for the great Taipei area, Taiwan