What is Water Transparency?

Water transparency is important to the growth of water plants. The clearer the water the more sunlight can penetrate, and the greater the amount of photosynthesis that can take place, allowing for more prolific plant growth.

Determination of water transparency is usually done by using Secchi disc, a disc painted in black and white quadrant. The depth of a secchi disc to disappear into the water bodies was measured and the transparency of water is used to measure the penetration of light in water.


In order that the Secchi Disk measurement be done to provide the greatest accuracy, the following conditions should be met:

1.) The same person should be taking all readings since sharpness of vision varies from person to person.
2.) The reading should be taken on the same day of the week, or at least not more than one day before or after the same day of the week.
3.) It is preferable that the measurement be taken between 10:00 a.m. and 4:00 p.m. so that the light rays from the sky are at a similar angle each time the reading is taken.
4.) Avoid taking the measurement when the lake is choppy or rough.
5.) The Secchi disk measurement should be taken at the deepest part of the lake.
This may be determined by viewing a bathymetric map or using a depth gage.
6.) After anchoring the boat at the predetermined site, take the reading on the shady side of the boat.
7.) The reading should be taken at the same location each week. In order to guarantee a sampling at the same location in the lake, a buoy may be permanently set at the site. If it is not possible to place a buoy at the site, line up two objects on the shore some distance apart (one at the shoreline) and line up two other objects on the shore and at right angles to the plane of the first two, anchor your boat and take the reading. Mark the shoreline objects and the intersect points on your map of the lake so that you will be able to find the same site the following week. If it is necessary that a substitute take the reading later in the season, they will be able to find the same location.