The Great North American Secchi Dip-In Turns Ten

The Great North American Secchi Dip-In is 10 years old this year. The Dip-In began in 1994 as a pilot study in six Midwest states funding from the EPA’s Clean Lakes Program. Since then more than 375 programs and 10,000 volunteers in the U.S., Canada, and several other countries have generated 30,000 records. These data are used to map regional differences in transparency and to detect trends.

LMVP volunteers have been participating in this program since 1995. You can look at the data for all Missouri sites at their website by selecting “Missouri” and clicking "submit query" from the list at the Dip-In website:

LMVP volunteers are encouraged to participate in this program. All you have to do to participate is:
Visit your lake site sometime from June 26 through July 18. If this coincides with your regularly scheduled sampling, you’re already halfway there!
Record the date, time and sky conditions (sunny, partly cloudy, etc) and the Secchi transparency. If you’re on the lake sampling anyway, all of this information will be on your datasheet already!
Either enter your data at their website (, or send it to me and I’ll enter it for you. If you enter the data yourself, our program ID is 115.

Dip-In data shows that lakes in the northern parts of the U.S. and those in Canada have the clearest lakes, and that lakes in agricultural regions are the murkiest. One Nebraska lake had a Secchi value of one half of an inch. That means that the black and white disk 8 inches in diameter completely disappeared from view when only half an inch underwater. Some lakes in the northern portions of the continent (e.g. Alaska and Canada) can have Secchi values around 60 feet. LMVP Secchi values from Missouri lakes range from 3 inches at North Lake (near Harrisonville) to 33 feet at Table Rock.

The Dip-In has also collected data that measures the volunteers’ perception of water quality. According to the Dip-In press release, noise, boat congestion, rude boaters and trash are important problems to volunteers. A 2002 survey of LMVP volunteers confirms this, with 68% of those responding saying that “too many boaters” is a problem on their lakes.

A Secchi disk is a tool used to measure water clarity. The black and white Secchi is lowered into the water until it disappears from view. This depth is recorded as the “Secchi value”. Secchi values in Missouri range from 3 inches to 33 feet. Missouri water clarity can vary depending up on the amount of algae and sediment in the water.


Brought to you by the Lakes of Missouri Volunteer Program