What's Monitored


Tips for Trainers Teaching Transparency Measurement

Pre-training thoughts:

  • Note: In 2006 we opted to change terminology for this parameter. Traditionally, we used the term turbidity to describe what was being monitored, but we opted to begin using the term transparency, since it seems to better describe what we are able to monitor (both color and cloudiness of the water) with the tubes. The fact sheet pdf (1.1 mb) has been updated to reflect this change.
  • Read through the transparency fact sheet in the Volunteer Stream Monitoring Factsheet Series.

  • It might be of interest to you and your trainees to learn the history of transparency/turbidity tubes. Check out the Fall 1994 version of The Volunteer Monitor (Volume 6 No. 2) for some information about the tubes' Australian history. http://www.epa.gov/volunteer/fall94/wtrshd19.htm

  • WAV's transparency tubes have been calibrated in a similar fashion to Morgan's (see the Aussie history in the Volunteer Monitor) and the conversion to turbidity units (approximately equal to NTUs) from inches is found on the back of both the turbidity data sheets and the fact sheet. (The conversion from cm to NTUs is found on the fact sheet pdf (1.1 mb))

Teaching Tips:

  • Discuss the importance of measuring transparency and what concerns exist when water is increased in turbidity due to sediments. (Sediment and organic matter can block the light needed for aquatic plant growth, reduce the visibility for fish that are sight feeders, irritate gills of aquatic organisms that are not adapted to such conditions, and smother bottom-dwelling aquatic life or and eliminate habitat spaces. Turbid water may also have higher oxygen demand.)

  • You should point out that the transparency tube method of assessment does not differentiate between water coloration due to tannic acids from leaves and needles entering the stream or to cloudiness due to algal growth (hence our reasoning for changing terminology in 2006).

  • Each stream has a baseline level of turbidity. Organisms within the stream are generally adapted to the level of turbidity (and resulting temperature regime) that is "normal" in the stream. Turbidity and transparency assessments can help pinpoint problems during storm events if a baseline is known.

  • When collecting the sample, be sure to enter the stream downstream from where the sample will be collected so as not to disturb the bottom sediment and thus the transparency.

  • Please point out to monitors that WAV protocols direct that transparency be assessed twice on each visit and that both of these scores AND the average transparency are reported on the data sheet. Monitors should also convert their measurement into transparency units (approximately NTUs) using the conversion chart on the back of the data sheet.
  • Be sure to give monitors a copy of the data sheet for use at the training as well as for use at their own sites. All data sheets can be printed from the WAV website: here


  • Transparency samples can also be collected (and often are) by simply using the tube and plunging it into the stream as the directions state for collecting a sample with a bucket. It is usually necessary to splash some water into the top of the tube, or use a cup to top off the sample in the tube. When using this method of collection, monitors should read the level of water immediately following collection because stirring the sample will be impossible.

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