SPECIFIC ABSORPTION AND BACKSCATTERING SPECTRA FOR SUSPENDED MINERALS AND CHLOROPHYLL-A IN CHILKO LAKE, BRITISH-COLUMBIA

Theoretical optical water quality models used in remote sensing require the specific absorption and specific backscattering spectra for each of the colored water components in order to model reflectance (R) or to use measured reflectance to find the component concentrations. The specific absorption and backscattering spectra for suspended minerals (SM), the specific absorption spectra for chlorophyll-a (C), and the absorption spectrum for water were determined solely from irradiance measurements collected simultaneously with the concentration of SM, C, and yellow substance (YS). The glacial SM in Chilko Lake have backscattering properties similar to SM found in Lake Ontario, but only about one-third the absorption. The absorption properties of C remain uncertain with two analysis techniques giving different results at shorter wavelengths and failing to find significant values at red wavelengths. The measured absorption of water closely matches reported laboratory results of Smith and Baker (1981). Tests showed that the calibrated R-model was slightly biased (less than 10%) with a standard deviation of +/- 6-16% depending on wavelength. When the model was used to solve for component concentrations, SM were found with a standard deviation of +/- 20%, C +/- 40%, and YS +/- 30%.