page 19 of the UWP Educator’s Guide to Teaching Students About the Upper Uncompahgre River Watershed (also see contents, introduction & pdf link)
Turbidity: What is It?
Turbidity is the measure of relative clarity of a liquid. It is a visual 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. The higher the intensity of scattered light, the higher the turbidity—or the murkier the darker the water looks.
Clay, silt, tiny organism, and organic matter, algae, dissolved colored organic compounds, and other microscopic organisms cause water to be turbid.
During high flows—such as spring run-off or after summer monsoons–water velocities are faster and water volumes are higher, which can more easily stir up and suspend material from the stream bed, causing higher turbidities.
Why Does it Matter?
High concentrations of particulate matter affect light penetration and habitat quality, recreational values, and cause lakes to fill in faster. In streams, increased sedimentation 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 heavy metals and bacteria. For this reason, high turbidity readings can be used as an indicator of potential pollution in a water body.
How is It Measured?
Turbidity is measured by collecting a water sample and visually comparing the water to a turbidy metric card used match clarity with the sample. Range and sensitivity is 0, 20, 40, 60, 80, 100 JTU.
Teachers: Students will work in pairs and take turns with other groups to “read” a water sample and determine the turbidity compared to a “scale” provided.
