Field Notes: How Measure Water Clarity With a Secchi Disk

Ever wondered how scientists measure lake water clarity? One of the simplest and most enduring tools for the job is the Secchi disk.

Long before it became a formal scientific tool, sailors and scientists were already using simple methods to estimate water clarity, like lowering white objects into the water to gauge visibility and depth. In 1865, Italian astronomer Father Pietro Angelo Secchi built on these early techniques by developing a uniform white disk and standardized utilization method. His published findings helped establish the Secchi disk as a practical tool for water quality assessment.

The design was later improved by George C. Whipple, who added alternating black and white quadrants to enhance visibility. Today, this version of the Secchi disk remains a staple in the field kits of aquatic scientists and limnologists worldwide.

As part of our Field Notes blog series, which spotlights essential tools and techniques used by our team, Senior Aquatics Manager Christopher L. Mikolajczyk, CLM, demonstrates how to properly use a Secchi disk and explains how this simple method helps inform lake and pond management strategies. Watch now:

As Chris explains in the video, water clarity is a key indicator of overall lake health, and monitoring it provides valuable insight into the condition and functioning of aquatic ecosystems. Regular monitoring helps lake managers understand whether conditions are within a healthy range, identify potential indicators of future algal blooms, and make informed decisions to maintain ecological balance.

Interested in getting involved? With a few simple materials, you can build your own Secchi disk and participate in the Secchi Dip-In, a community science initiative where volunteers measure and report water clarity data. While the Dip-In is traditionally celebrated in July during Lakes Appreciation Month, data collection is welcomed and encouraged year-round.

Chris has dedicated over 25 years to advancing the science and practice of aquatic ecology and water resource management. His expertise spans the management, oversight, and coordination of projects in three key areas: aquatic resource restoration and management, aquatic ecosystem sampling and investigations, and stormwater quality modeling and management. Chris has an Associate’s, Bachelor’s, and Master’s degree in Water and Watershed Resource Management. In addition to his work with Princeton Hydro, Chris currently serves as the President-Elect of the Colorado Lake and Reservoir Management Association’s 2025 Board of Directors and has also served as President of North American Lake Management Society. These leadership roles highlight his dedication to advancing aquatic resource conservation.

• Environmental Education
• Lake and Pond Management
• Lake Restoration
• Natural Resource Management