The USGS Water Science School
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Turbidity![]() Sediment-data collection in the Little Colorado River a kilometer upstream from the Colorado River, Grand Canyon, Arizona Credit: USGS Turbidity is the measure of relative clarity of a liquid. It is an optical characteristic of water and is an expression of the amount of light that is scattered by material in the water when a light is shined through the water sample. The higher the intensity of scattered light, the higher the turbidity. Material that causes water to be turbid include clay, silt, finely divided inorganic and organic matter, algae, soluble colored organic compounds, and plankton and other microscopic organisms.
Turbidity and water quality![]() Sediment-laden water from a inflow stream entering a much clearer Lake Tuscaloosa, Alabama, USA (Credit: City of Tuscaloosa, Alabama) Credit: City of Tuscaloosa, Alabama High concentrations of particulate matter affect light penetration and productivity, recreational values, and habitat quality, and cause lakes to fill in faster. In streams, increased sedimentation and siltation can occur, which can result in harm to habitat areas for fish and other aquatic life. Particles also provide attachment places for other pollutants, notably metals and bacteria. For this reason, turbidity readings can be used as an indicator of potential pollution in a water body. Turbidity and human healthExcessive turbidity, or cloudiness, in drinking water is aesthetically unappealing, and may also represent a health concern. Turbidity can provide food and shelter for pathogens. If not removed, turbidity can promote regrowth of pathogens in the distribution system, leading to waterborne disease outbreaks, which have caused significant cases of gastroenteritis throughout the United States and the world. Although turbidity is not a direct indicator of health risk, numerous studies show a strong relationship between removal of turbidity and removal of protozoa. The particles of turbidity provide "shelter" for microbes by reducing their exposure to attack by disinfectants. Microbial attachment to particulate material has been considered to aid in microbe survival. Fortunately, traditional water treatment processes have the ability to effectively remove turbidity when operated properly. (Source: EPA) Measuring turbidity
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World Water Monitoring Challenge is an international education and outreach program that builds public awareness and involvement in protecting water resources around the world. Some information on this page is from "A Primer on Water Quality", by Swanson, H.A., and Baldwin, H.L., U.S. Geological Survey, 1965 |
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