Secchi Disk

    Secchi Disk

    We use Secchi Disks to measure the turbidity of lakes, ponds or wetlands.  The black and white disk is lowered into the water, and the maximum distance at which the disk can be seen is recorded.


    This is best to do when the sun is near its apex, generally between 10 AM and 2 PM.  Also, you need to remove sunglasses before measuring.

    On the shady side of a boat or dock, begin to lower the disk into the water.

    Kid with a Secchi Disk

    Lower the Secchi Disk until it completely disappears.  Then slowly retrieve the disk.  As soon as you can make out the faint black and white markings stop.

    Lowering the Secchi Disk

    Mark the tape at the surface of the water to record the depth to the nearest centimeter.

    If you are on a dock and out of arm's reach of the water, use a clothespin to mark the height of the dock and then measure to the surface of the water.  Subtract this from your final measurement.

    Rasing the Secchi Disk back up and marking the tape