Spectral reflectance with varying suspended sediment concentrations in clear and algae-laden waters.

Abstract

The objective of the study was to characterize and compare the relationship between suspended sediment concentration (SSC) and reflectance in clear and algae-laden waters. A controlled experiment was conducted outdoors in a 7510-litre water tank using natural sunlight. A red loam soil was added and suspended in the tank filled with clear and algae-laden waters, respectively. A total of 20 levels of SSC (from 25 to 500 mg I-*) were created for each type of treatment. Reflectance was recorded using an ASD spectroradiometer, and the bi-directional reflectance factor was computed and analyzed. The same amount of suspended sediment generated higher reflectance between 400 and 700 nm in clear water than in algae-laden water due to the blue and red absorption of chlorophyll. The effect of chlorophyll on the SSC-reflectance relationship was minimum at wavelengths between 700 and 900 nm. For both clear and algae-laden waters, the linearity in the SSC-reflectance relationship increased with wavelength between 400 and 900 nm. A near-linear relationship between ssc and reflectance was found between 720 and 900 nm.