Colour classification of coastal waters of the Ebro river plume from spectral reflectances

This paper presents a colour classification of coastal waters from features of spectral reflectance. Experimental data were collected in coastal water s of the Ebro river mouth area during two periods of non-bloom conditions a nd low suspended load. Examination of the reflectance spectra reveals a few significant shapes corresponding to different apparent colours and specifi c values of hydrological parameters. A colour classification is proposed. A n empirical method and a semi-analytical method are presented in order to r etrieve suspended particulate matter concentration, namely SPM, chlorophyll a concentration, chl, sediment refractive index, m(r), and absorption coef ficient of yellow substance at 440 nm, a,(440). The first method is a direc t application of the colour classification. It is based on correlations fou nd for each water type between spectral features of the first derivative of reflectance and SPM, chl, m(r), a(y)(440) values. A second method uses the inversion of a three component reflectance model. Measured reflectance spe ctra and typical values of m(r), deduced from the colour classification, ar e assimilated in the model. As a result, it appears that estimates of SPM a nd chi are more accurate by calculating chl from the correlation technique and SPM along with a(y)(440) from inversion of the reflectance model.