Lake Management Lake Depth Secchi Disk
A “Secchi Disk” is a tool for measuring the depth to which light penetrates liquid. Since sight, is based on light, then the distance at which you can still see an object in liquid, is the depth that the light can penetrate that liquid.
In order to have a standard measurement for this, the secchi disk is used. The disk is an 8 inch disk with 4 alternate triangles of black and white. It is attached to a string, or pole, and the distance at which it disappears from view in a pond or lake is the secchi depth. Ideally, that depth would be 18 to 24 inches. A secchi disk can be purchased from lake supply dealers, but it is easy to construct one of your own. Mine is an 8 inch steel disk, painted solid black, with the white triangles painted on top of the black, and a hole drilled in the center to attach a rod. I chose to attach a landscapers measuring rod to mine, in order to be able to use the disk and measure the depth in one operation.
This secchi disk is homemade, and has served me well for years. Note the alternating black and white triangles, the measuring rod, and the mud on the the disk.
This is the same secchi disk from a different perspective, and with the measurements visible.