Turbidity
Turbidity is a measure of the clarity of
a water body and is related to erosion
and sedimentation which impacts
streams and lakes. Turbidity can affect
the oxygen content and light
penetration of the water while
sedimentation can change the physical
structure of habitats, stress organisms
within the water body and smother
macroinvertebrates. Causes of high
turbidity include: soil erosion,
wastewater discharges, urban runoff,
farming and forestry practices, eroding
stream banks, and excessive algae
growth.
Suspended materials in a stream at Tuolumne Me-Wuk.
Understanding the Impact of Turbidity: A turbidity measurement is actually a
measurement of the amount of suspended particles in the water body. The suspended particles
absorb more heat which can raise water temperature and affect the oxygen content of water.
When the suspended materials settle at the bottom of a water body they can clog fish gills and
smother fish eggs, along with other organisms. Check tribal, state, or federal standards to
determine an acceptable range for turbidity in your water body of interest.
Monitoring Equipment: The following is a
list of the types of monitoring equipment
commonly used to measure turbidity in surface
water bodies. All options can be found in
laboratory supply stores. Contract laboratories
may also be used if necessary.
Lakes and Resevoirs:
• Secchi disc
• Kits
• Meters
• Multiparameter probes
Streams:
• Turbidity tube
• Kits
• Meters
• Multiparameter probes
for additional information:
www.epa.gov/owow/monitoring/volunteer/stream
Secchi Disk
For more information, please contact your CWA Project Officer or Kristin Gullatt, Manager of the Water Division, Tribal Office at (415) 972-3432.
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