Science

Vermont’s Lakes Are Among the Clearest in the Nation

Volunteer monitor obtaining a Secchi disk measurement.

Volunteer monitor obtaining a Secchi disk measurement.

Vermont ranks among the highest states in the nation for clear lakes according to research published in February 2015 in the journal Lake and Reservoir Management. Dr. Dana Bigham Stephens at the University of Florida and her colleagues gathered Secchi disk transparency measurements from over 14,000 lakes and reservoirs across the United States to compare regional differences in lake water clarity. A Secchi disk is a black and white device about the size of a dinner plate that is lowered into a lake until it disappears from sight. Used by professional scientists and citizen monitors alike, the Secchi disk provides a simple but scientifically valid measurement of water clarity. Volunteers with the Vermont Lay Monitoring Program have been recording the depths of Secchi disk disappearance in Vermont lakes for decades and their data were used in this research.

Lake Willoughby is one of Vermont’s clearest lakes, with a Secchi disk transparency of 7.9 meters.

Lake Willoughby is one of Vermont’s clearest lakes, with a Secchi disk transparency of 7.9 meters.

Vermont’s lakes, with a median water clarity of 4.0 meters (13 feet), ranked fourth among all 50 states, behind only Alaska (5.9 m), Montana (4.8 m), and Maine (4.6 m), and just ahead of New Hampshire (3.8 m). At the other end of the scale, Louisiana, Mississippi, Oklahoma, Delaware, and South Dakota had the lowest median Secchi disk values at 0.8 meters or less.

At a time when water quality problems in Lake Champlain and some other Vermont lakes are receiving much-needed political and governmental attention, it is good to remember that the majority of our lakes have water clarity that is the envy of most other parts of the country.