Community Scientists Track Water Quality in Vermont’s Lakes for Four Decades

By Shari Halik
April 10, 2023

Vermont is home to more than 800 lakes and ponds. Staff in the Vermont Lakes and Ponds Program of the Vermont Department of Environmental Conservation (DEC) monitor the water quality of these lakes and ponds, including Lake Champlain. But they have plenty of help from volunteer community scientists.

Since 1979, hundreds of volunteers, or lay monitors, have signed up to help track the health of Vermont’s lakes and ponds as part of the Vermont Lay Monitoring Program (LMP). With training and use of state equipment, volunteers collect water samples and take water quality measurements from Memorial Day to Labor Day. Using their own boats, they sample about every week to ten days for at least eight times throughout the summer.

Over the past 40 years, this dedicated group of community scientists have monitored more than 100 inland lakes and 40 Lake Champlain stations.

Monitoring lakes and ponds has helped to establish baseline conditions so that long-term changes in water quality and nutrient trends can be tracked,” said Mark Mitchell, Lake Monitoring and Community Outreach Coordinator with Lake Champlain Sea Grant and Lay Monitoring Program Lead with the Vermont DEC. “The lay monitoring program also helps to educate lakeshore homeowners and lake users about aquatic ecology and stewardship.”

Water Sampling and Testing to Monitor Lake Health

Each summer, volunteers collect water samples that Mitchell and other LMP staff pick up and deliver to the Vermont Agriculture and Environmental Laboratory, where lab staff test the samples for total phosphorus and chlorophyll-a, a green pigment which gives an indication of algae or cyanobacteria levels. Generally, lakes with higher phosphorus concentrations will have more algae and cyanobacteria growth.

Human activity along a lakeshore and throughout a lake watershed can accelerate the amount of phosphorus entering a lake. Sources of phosphorus include shoreline erosion, fertilizer run-off from agricultural land and residential lawns, failing septic systems, and erosion from construction and logging.

Lay monitors also measure water clarity with a Secchi disk, an eight-inch diameter disk with black and white quadrants. They lower the disk into the lake by a rope, marked in meters, until the disk disappears from sight, which is the Secchi depth. Sometimes volunteers use a special view tube to better see the Secchi disk in the water. The greater the Secchi depth, the greater the water clarity. Water clarity tends to decrease as chlorophyll-a concentration increases.

To complete the sampling process, volunteers fill out a lake sampling data form. They also complete a survey that includes their visual observations of cyanobacteria blooms.

In 2022, lay monitors visited 83 inland lakes and ponds and eight stations on Lake Champlain. They collected water for phosphorus and chlorophyll-a analyses from 66 of the lakes, ponds, and stations.

Over the course of years, I have had the good fortune to spend a lot of time at Lake Morey,” said Don Weaver, a lay monitor for 31 years in Fairlee, Vermont. “I have participated in numerous activities to preserve and protect the lake. Perhaps the most extensive is the Lay Monitoring Program. I like knowing that I am helping to keep the lake healthy for future generations.”

Mitchell trains lay monitors, provides them with collection supplies and Secchi disks, and visits each volunteer yearly to answer questions and provide updates on sampling protocol. He assesses lab results and water clarity data for compliance with Vermont Water Quality Standards and completes annual reports and a quality assurance project plan for the U.S. Environmental Protection Agency (EPA).

Findings Inform Management

Through this monitoring program and its many community volunteers, the state has collected more than four decades of data. Long-term trends indicate most lakes have relatively stable or improving nutrient conditions, though many lakes and stations show degrading conditions. The DEC prioritizes management of lakes that show increasing total phosphorus trends. For these lakes, staff recommend volunteer monitoring of lake tributaries through the LaRosa Partnership Program and Lake Watershed Action Plans to identify pollution sources and recommend restoration and protection projects.

Annual data and water sample analyses and reports for each lake and pond can be found on the Vermont Integrated Watershed Information System website and the LMP website reports section. The LMP reports section also posts Lake Score Cards, which give ratings that show how disturbed the lake watershed and shoreland are and how stressed the lake is based on water quality.

The LMP has documented an increase in phosphorus levels and a subsequent rise in algae and cyanobacteria in many of Vermont’s lakes and ponds. Even some of Vermont’s clearer lakes currently have high levels of phosphorus and chlorophyll-a, such as Great Hosmer Pond in Craftsbury and Albany, Lake Fairlee in Fairlee, and Valley Lake (or Dog Pond) in Woodbury.

“For these lakes, Secchi depth measurements meet Vermont clarity standards, but lake levels of phosphorus and chlorophyll are below standards,” said Mitchell.

He points out that volunteers take Secchi disk readings in the deepest water of the lakes, where clarity is usually better. Mitchell hopes to train lay monitors to test lake water at different depths to better understand what is happening in these lakes.

In worst-case scenarios, unnaturally high levels of phosphorus can result in excessive growth of algae, cyanobacteria, and aquatic plants which decreases water clarity. As the excessive growth dies back each year, it falls to the lake bottom, where it decomposes, depletes oxygen, and adds phosphorus to the bottom sediments. Once there is no oxygen left at the bottom of a lake or pond, a chemical process in the sediments releases phosphorus which can rise to the surface and cause an unhealthy increase in algae and cyanobacteria. This is called internal phosphorus loading. When the natural habitat of a lake is altered in this way, fish and wildlife populations using the lake may also change.

The DEC has listed Lake Carmi in Franklin, Ticklenaked Pond in Ryegate, and Lake Morey in Fairlee as impaired, partially due to internal phosphorus loading. Diagnostic sediment studies have been or will be conducted for these lakes, and Ticklenaked Pond received a successful alum treatment in 2014 to inactivate phosphorus in the sediment.

Thanks to the sampling efforts and activism of lay monitors, the DEC can more effectively assess, restore, and protect water quality in Vermont’s lakes,” said Mitchell.

Mitchell and Vermont DEC staff refine the sampling and testing methods each year. For the 2023 season, Mitchell plans to have lay monitors conduct sampling every two weeks. They will collect six surface and optional deep grab samples up to 20-meters deep or at least one meter off the lake bottom to analyze phosphorus and chlorophyll-a by depth. He will also request that the lab conduct caffeine testing of water samples to check for human wastewater sources of pollution from septic systems.

“If caffeine results show detectable concentrations, especially if some are higher, then we can present this data to municipalities, town health officers, lake associations, and other stakeholders to take action on inspecting and improving septic systems in partnership with the DEC,” said Mitchell.

Learn More

For more information on volunteering with the Vermont Lay Monitoring Program, email Mark.Mitchell [at] or call 802-490-6126.

Learn more about the Vermont Lay Monitoring Program and view a video recording of Mark Mitchell’s webinar about the program, part of the Lake Champlain Sea Grant webinar series.