Paper No. 00083 of the Journal of the American Water Resources Association.Discussions are open until June 1, 2002.
TURBIDITY SUSPENI)ED SEDIMENT, AND WATER CLARITY: A REVIEW1
Article first published online: 8 JUN 2007
JAWRA Journal of the American Water Resources Association
Volume 37, Issue 5, pages 1085–1101, October 2001
How to Cite
Davies-Colley, R. J. and Smith, D. G. (2001), TURBIDITY SUSPENI)ED SEDIMENT, AND WATER CLARITY: A REVIEW. JAWRA Journal of the American Water Resources Association, 37: 1085–1101. doi: 10.1111/j.1752-1688.2001.tb03624.x
- Issue published online: 8 JUN 2007
- Article first published online: 8 JUN 2007
- fish habitat;
- optical properties of water;
- Secchi disc;
- suspended sediment;
- water quality
ABSTRACT: Suspended sediment causes a range of environmental damage, including benthic smothering, irritation of fish gills, and transport of sorbed contaminants. Much of the impact, while sediment remains suspended, is related to its light attenuation, which reduces visual range in water and light availability for photosynthesis. Thus measurement of the optical attributes of suspended matter in many instances is more relevant than measurement of its mass concentration. Nephelometric turbidity, an index of light scattering by suspended particles, has been widely used as a simple, cheap, instrumental surrogate for suspended sediment, that also relates more directly than mass concentration to optical effects of suspended matter. However, turbidity is only a relative measure of scattering (versus arbitrary standards) that has no intrinsic environmental relevance until calibrated to a ‘proper’ scientific quantity. Visual clarity (measured as Secchi or black disc visibility) is a preferred optical quantity with immediate environmental relevance to aesthetics, contact recreation, and fish habitat. Contrary to common perception, visual clarity measurement is not particularly subjective and is more precise than turbidity measurement. Black disc visibility is inter-convertible with beam attenuation, a fundamental optical quantity that can be monitored continuously by beam transmissometry. Visual clarity or beam attenuation should supplant nephelometric turbidity in many water quality applications, including environmental standards.