Transparency (or light transmission) of natural waters is due to their color and turbidity, i.e. The content of various colored and suspended organic and mineral substances in them.
Water, depending on the degree of transparency, is conventionally subdivided into :
Measure of transparency is the height of the water column at which a white plate of a certain size can be observed (Secchi disk) or a font of a certain size and type on white paper (usually a medium-fat font with a height of 3.5 mm).
Results are expressed in centimeters indicating the method of measurement. The attenuation of the intensity of light in the turbid water with depth leads to a greater absorption of solar energy near the surface. The appearance of warmer water near the surface reduces the transfer of oxygen from the air to the water, reduces the density of water, stabilizes stratification.
Reducing the flow of light also reduces the efficiency of photosynthesis and the biological productivity of the reservoir. The definition of water transparency is an obligatory component of programs for monitoring the state of water bodies. An increase in the amount of coarsely dispersed impurities and turbidity is characteristic of contaminated and eutrophic water bodies.