The Secchi Dip-In

What is the Secchi Dip-in?

The Secchi Dip-in is an event held during July each year that helps volunteers like you collect water transparency data. Dip-in volunteers monitor all types of waterbodies including lakes, streams, and estuaries. Since 1994 the Dip-in has grown to include more than 375 partner programs and 6,000 volunteers. With their input, Dip-In data now includes more than 41,000 records on more than 7,000 waterbodies.

What does the Secchi Dip-In do?

The Dip-in shows that volunteers can collect quality data. And this data can help you map regional differences and detect trends in water transparency. Input from volunteers can also help you see that water quality problems go beyond algae and weeds to include human-related problems such as noise, rude boaters, and trash. And finally, the Dip-in can help you compare the difference between transparency data and perceptions of water quality. For example, one person views a lake with transparency of six feet as degraded. Meanwhile another person feels that a lake with transparency of only one foot is beautiful.

Why keep track of water transparency?

The color of water, bits of silt or clay, and algae can affect transparency. As such, Dip-in data is a simple measure of some forms of pollution. Keeping track of changes in transparency can help you understand the use of the land around your waterbody. And these changes may also point to the success of your efforts to restore your waterbody.

What is a Secchi disk?

A Secchi disk is a flat, normally black and white, round piece of metal attached to a rope or chain. The Jesuit priest Pietro Angelo Secchi, who used the disk more than 150 years ago, is the namesake of the Secchi disk. To determine water transparency you simply lower the disk into the water and take a measurement when you can no longer see the disk. Most Dip-In volunteers use a Secchi disk to take water transparency readings. Though, you are also welcome to use a turbidity tube or meter, or black disk.

What is the history of the Secchi Dip-in?

Dr. Robert Carlson started the Dip-In in 1994 and it has continued each year since. NALMS joined as a sponsor of the Dip-in shortly after it began. In April 2015 Dr. Carlson agreed to transfer the Dip-in and its related copyrights, trademarks, and website to the care of NALMS. In turn NALMS agreed to fund the Dip-in and appoint a committee to manage the program.

You can find more information on the Secchi Dip-In, including partner programs and results, at