"Turbidity in water is caused by suspended matter, such as clay, silt, finely
divided organic and inorganic matter, soluble colored organic compounds, and
plankton and other microscopic organisms... Turbidity is an expression of the
optical property that causes light to be scattered and absorbed rather than
transmitted in straight lines through the sample."<sup>1</sup><br><br>
In streams, a major cause of elevated turbidity are disturbed and eroding soils
carried by storm run-off to streams. Once in the stream system, elevated
turbidity reduces the depth of photosynthesis and the feeding ability of aquatic
organisms. When soils settle out in downstream reaches with slower flow, bed
substrate becomes embedded, removing essential habitat for aquatic insects
and other organisms.<br><br>
Turbidity is expressed in NTU (Nephelometric Turbidity Units). <P>
<sup>1</sup> Standard Methods for the Examination of Water and
Wastewater, 18th Ed.,
1992, American Public Health Assoc.