A spectral analysis of bottom-induced variation in the colour of Sand Hills lakes, Nebraska, USA
Colour yields information about the bio-optical properties, as well as the general quality, of surface waters. It allows inferences to be made about components of the water column, including transparency, type and concentrations of both suspended and dissolved substances. Where water transparency and depth permit electromagnetic radiation to reach to the bottom, the upwelling composite signal can include reflectance not only from the surface and from the water column but also from the bottom. The intensity of the 'bottom effect' on the optical properties such as colour depends on the composition of the bottom and on the type of water column constituents. The spectral data from five Nebraska lakes were analysed for the bottom-induced variation in the colour. The data indicated that the bottom significantly affects the apparent colour of water bodies.