Effect of suspended sediment and chlorophyll concentrations on water reflectance.

摘要

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 region. Two experiments were conducted with 17 levels of suspended sediment concentrations varying from 0 to 1000 g/m3, and 5 levels of Chlorophyll-a concentrations varying from 0 to 200 mg/m3. Experiments were conducted a the Arkansas Agricultural Research and Extension Centre at Fayetteville, Arkansas, USA. Water reflectance was measured with a spectro-radiometer. Both SS and chlorophyll-a increased water reflectance in the green to NIR wavebands. SS concentration produced scattering peaks at 580, 695 and 815 nm, while chlorophyll-a triggered reflectance or absorption peaks at 550, 675 and 695 nm. The SS concentration explained over 90% of variability in turbidity index (TI) and the 2 new spectral indices SI and DSI. Both spectral index (SI) and derivative spectral index (DSI) were highly accurate at very low to moderate SSCs (<=600 g/m3) whereas TI was not very sensitive at very low (<25 g/m3) 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..