Abstract:

It is an efficient method of water environment survey to using remote sensing data for large area water quality monitoring.The Poyang Lake was selected as the research area in this research. The chlorophylla content which gives an important index to eutrophic state of water was chosen as the study object. The water reflectance spectra were acquired with an ASD FieldSpec HH (3501050nm) and the MODIS data collected during the same period. Based on MODIS data, the range of the Poyang Lake was extracted by a approach named Floating Algae Index (FAI).After the measured spectra were preprocessed with deleted abnormal data,normalization and Spectral derivative,the relation between the spectral reflectance of the Poyang Lake and the corresponding moment of the chlorophylla concentration were analyzed in spectral index method which was structured by band difference,ratio and the normalized [JP2]difference.The sensitive band scope
was harvested,including the band intervals of 673-680 nm and 650-665 nm,680-710 nm and 650-670nm,662-671 nm and 700-720 nm. Then the optimum bands combination [JP]was chosen. At last the inversion model of MODIS data for chlorophylla concentration of the Poyang Lake was achieved,and the correction coefficient was 0.67. Applying the model,the chlorophylla concentration distribution map of the Poyang Lake in the autumn of 2011 was given. The result showed that the chlorophylla concentration of the Poyang Lake was not high,and in spatial distribution the chlorophylla concentration was higher at the border of water and land than at the center of lake. The analysis supports that the spectrum of the Poyang Lake has been known by quantitative analysis of the measured spectra,and the long wave drift of spectral reflectance phenomena is revealed. A method of remote sensing to monitor chlorophylla concentration the for Poyang Lake which is of low eutrophication and unevenly distributed is established. Meanwhile it provides a forceful scientific guidance for water environment management of the Poyang Lake