Aerial shot of Passaic River Institute.

Why Measure Turbidity?

The Main Points

  1. Low turbidity levels insure that sunlight will reach submerged aquatic plants.
  2. Turbidity is related to the overall health of a waterbody.
  3. Changes in turbidity can be linked to a number of sources but most commonly to erosion or algal blooms.

The Details

Turbidity is a measure of water clarity or how much matter is suspended in water. Suspended matter decreases the passage of light through the water. Suspended materials include soil particles (clay, silt and sand), algae, plankton, microbes and other substances. Turbidity can affect the color of the water.

Turbidity has a direct effect on the amount of sunlight available to aquatic plants. High levels of suspended materials can clog fish gills and, if they settle on the bottom of the waterbody, can smother fish eggs along with the bottom-dwelling insects, worms, snails and shellfish. Certain species of fish and invertebrates are adapted to high levels of turbidity. Among the most famous of these fish are the humpback chub that thrived in the Grand Canyon.

Common sources of turbidity include soil erosion and excessive algae growth. Stormwater runoff can also contribute to high turbidity. In lakes and rivers where there are large populations of bottom dwelling fish such as catfish and carp, they can stir up the bottom sediments and increase turbidity.