Secchi Depth

How to measure secchi depth transparency

When taking the Secchi disk readings, be sure to follow the instructions. The data you collect is only valuable if carefully measured according to set procedures.

  1. Use the map of your lake and its marked sampling site and proceed to the site. Always take your Secchi disk measurements from this same general location.
  2. Anchor the boat at the sampling site. Remove your sunglasses and hat.
  3. Lean over the shady side of the boat and slowly lower the Secchi disk into the water until it can no longer be seen. Note the depth that the Secchi disk disappears from site.
  4. Lower the disk a few more feet into the water. Slowly raise the disk. When the disk reappears, note this depth. Record the mean depth between where the disk disappeared and reappeared as the Secchi disk transparency depth.
  5. Tape Measure: Carefully read the depth to the nearest tenth of a foot.
    Be sure to record the measurement on the datasheet (see below for an example)


Measuring Tape Markings

A line drawing illustration of a measuring tape.
  • Read the tape at the water line. In this example, the arrow denotes a water line of 1.5 feet, not 1 foot 5 inches. In this example, you would record a reading of 1.5 feet.
  • Note: the marks on the measuring tape are in tenths (1/10) of a foot, not inches.