What's Monitored


Resources
Data Sheets
Methods (Fact Sheets)
Video Training

 

Transparency Tube Construction

Like the Secchi disk, the turbidity tube is a simple and easy way to estimate water clarity.

TubeEquipment (to make three tubes)

· 8 ft. fluorescent light sleeve
· 3- 1 9/16 to 1 5/8 inch Plexiglas discs
· 3- 1½ inch white Plexiglas discs
· Sharp knife (e.g., Exacto knife)
· Black permanent marker or electrical tape
· Plexiglas sealant
· Measuring tape or yard stick

Procedure

  1. Using the knife, cut the 8-foot fluorescent light sleeve into three equal lengths (about 31 inches).

  2. Insert the 1 9/16 to 1 5/8-inch Plexiglas disc into one end and seal with Plexiglas sealant. If disc has a center hole, plug it with sealant. (Note: this will likely have to be treated with sealant more than once to fill all spaces. After allowing it to dry, an easy way to check to see if more sealant is necessary, is to blow into the tube at the opposite end of the disc and feel if air escapes near the end with the disc inserted into it.)

  3. Using the black marker or electrical tape (and razor blade to cut edges smooth), color half of the white Plexiglas disc or color two opposite quadrants black, similar to a Secchi disc.

  4. Drop the white and black disc (target) into the tube.
  5. *Attach a measuring tape (inches or cm) along the length of the tube, with the tape's zero mark aligned with the top of the target. When assessing turbidity, convert to (approximately) NTUs using the chart included in the WAV monitoring fact and data sheets.

*Or, alternatively: From the top of the target, measure up the tube each "distance above target" indicated on the table below. Draw lines around the tube at the distances above the target and mark the NTU conversion for each line.

Note that turbidity unit labels are nonlinear, therefore it is difficult to estimate NTUs between lines on the turbidity tube.

Line Distance above target (inches) Turbidity Units (roughly NTUs)
1
2 7/8
200
2
4 1/2
100
3
7 1/2
50
4
12 1/4
20
5
17
15
6
20 3/4
10

 

These directions are based on information from Jim Peterson, UWEX Environmental Resources Center, UW-Madison.

 

© 2007 by the Board of Regents of the University of Wisconsin System, UW-Extension provides equal opportunities in employment and programming, including Title IX requirements. UW-Extension programs are open to all persons without regard to race, color, ethnic background, or economic circumstances. All rights reserved.
Citizen Water Monitoring Network Home l Contact l UWEX Water Resources l Wisconsin DNR | Citizen Monitoring Network