46 Years of Secchi Disk Measurements

Kelsie French and I got out on the lake today to start Water Quality Monitoring for the 2021 season, a spring ritual that has been taking place on Clary Lake since 1975. All the data we collect is periodically sent to the Lake Stewards of Maine (formerly the Volunteer Lake Monitor Program) where it is checked for validity and accuracy. My father Stuart Fergusson was the first person to submit secchi disk readings for Clary Lake in 1975. David Hodsdon started accompanying him at about the same time and according to DEP’s Linda Bacon, David took over completely in 1991. For many years David worked solo until Jack Holland joined him around 2001. I got involved in 2013 and Kelsie French, our newest water quality monitor, started in 2018. After 44 years on the lake, David retired after completing the 2019 season and Jack Holland has taken a hiatus from water level monitoring. We hope he resumes sometime soon! Becoming a water quality monitor requires certification by the Lake Stewards of Maine, and periodic recertification.

Total Phosphorus

The plan is to collect data every two weeks throughout the boating season which typically  is from early May through September. Sometimes we get a start in April and usually we continue into early October. Each time out we anchor at the “deep hole” (at right) and collect secchi disk (transparency) readings and Dissolved Oxygen (DO) readings at the surface and every meter down to 7 or 8 meters, depending on the lake level. We use a standard 8″ secchi disk and a YSI Pro 20 Dissolved Oxygen meter that the Association purchased in 2009. The DO meter is calibrated by DEP every year. About 3 times a year we also take a core water sample for Phosphorus testing. The water sample is dropped off at the State’s Health and Environmental Testing Laboratory.

We post a subset of the data we collect on the Clary Lake Water Monitoring Data page. You’ll also find it (and more!) on the Lake Stewards of Maine’s Lakes of Maine page and also on the Near Real Time Lake Data site. The two charts shown on this page are all the secchi disk readings from 1975 through today and all the Phosphorus tests through last season. HIGHER secchi disk readings are better and LOWER Phosphorus readings are better. Both are currently trending in the right direction, and with your support, the Clary Lake Association is working to see to it that they continue to trend in the right directi0n.