This letter results of experiments conducted to assess the use of linear mixing models to unmix the reflectance spectra of water. The model was tested with 11 reflectance spectra measured at Tucurui reservoir, Brazilian Amazon. The results showed that fraction of chlorophyll reflectance accounting for the reflectance spectra of the various samples corrlate significantly withthe cholorophyll concentration in the 600 to 700 nm spectral region.