turbidity

the measure of relative clarity of a liquid. It is an optical characteristic of water and is a measurement of the amount of light that is scattered by material in the water when a light is shined through the water sample. Turbidity makes water cloudy or opaque. The higher the intensity of scattered light, the higher the turbidity. Material that causes higher levels of turbidity include clay, silt, algae, plankton, and other microscopic organisms.