Effect of suspended sediment and chlorophyll concentrations on water reflectance

Remote sensing can indicate water quality parameters such as turbidity and eutrophication. Surface water reflectance is affected by optically active constituents (OAC) and bathymetry. This research was undertaken to study the impact of suspended sediment (SS) and Chlorophyll-a concentrations on the reflectance property of water in the visible and near-infrared (VNIR) region. Two experiments were conducted with (a) seventeen levels of suspended sediment concentrations (SSC) varying from 0 to 1000 g/m3, and (b) five levels of Chlorophyll-a concentrations varying from 0 to 200 mg/m3. Water reflectance was measured with a spectro-radiometer. Both SS and chlorophyll-a increased water reflectance in the green to NIR wavebands. SSC produced scattering peaks at 580, 695 and 815 nm, while chlorophyll-a triggered reflectance or absorption peaks at 550, 675 and 695 nm. SSC explained over 90% of variability in turbidity index (TI) and the two new spectral indices SI and DSI. Both SI and DSI were highly accurate at very low to moderate SSCs (&le 600 g/m3) whereas TI was not very sensitive at very low (3) and very high (>950 g/m3) SSC. This study provided clear insight into how SSC and chlorophyll modifies water reflectance, and how these OACs affect different spectral indices. © 2006 AAAE.