Turbidity is a measure of the particle content of the water sample. Typical river water values range from 5 to 10. Values in excess of 10 indicate a soil erosion event. High particle concentrations are stressful to fish and filter feeding microorganisms because it clogs their gills. High particle concentrations also affect the bottom dwelling organisms as the particles settle out and blanket the river bottom. The turbidity meter used for the measurement detects the amount of light reflected by the particles. Results are reported as nephelometric turbidity units or NTU’s.