Relationship between nephelometric turbidity and scattering coefficients in certain Australian waters

Abstract

It has been shown for five water bodies in the southern tablelands of New South Wales that there is a linear relationship between the nephelometric turbidity measured on water samples, and the value of 2R_αK; where R_α is the asymptotic (maximum) value of underwater irradiance reflectance. and K is the vertical attenuation coefficient of irradiance, both measured in situ. An earlier theoretical analysis had shown that 2R_αK should be equal to b_b′, a new scattering parameter of the water, referred to as the asymptotic backscattering coefficient. The observed relationship between turbidity and 2R_αK supports the interpretation of this latter parameter in terms of the scattering properties of the water. It is here proposed that b_b′ (i.e. 2R_αK) provides a useful alternative measure of light scattering by different waters.

Theoretical calculations, using published data for underwater radiance distribution and volume scattering function for other water bodies, have been used to determine the ratios of the asymptotic backscattering coefficient, b_b′. to the normal backscattering and total scattering coefficients (b_b and b), for different types of water. The relationships which have been found may be used to obtain approximate values for these fundamental, but hard to measure. scattering coefficients.