Hyperspectral remote sensing of chlorophyll-a in the Xuanwu Lake

The concentration of chlorophyll-a can reflect water quality to some extent. An approach for the determination of chlorophyll-a from field reflectance spectra was presented in the Xuanwu Lake. The reflectance spectra was measured from April to May in 2009 with FieldSpec 3 portable spectrometer, and water samples were collected directly from the lake to be analyzed in lab. Using correlations between the ground-truth data and combinations of spectral bands from the field spectral data, spectral indices including single band, band ratios, and the first-derivative models were developed which could be used to estimate chlorophyll-a. The results show that single band, band ratios and the first-derivative models have a better correlation with chlorophyll-a. But the model validation results show that coefficient of determination of the band ratios and the first-derivative models are higher (R2=0.7835 and R2=0.5913 with significance level P<0.01), and the single band model is the lowest (R2=0.4748). Therefore, band ratios and the first-derivative models can be used to indicate chlorophyll-a concentration of Xuanwu Lake, and the band ratios model is better than first-derivative model.