Lakes and Ponds Monitoring

The analysis of lake and pond water in Maine is conducted primarily by state and community groups to monitor changes in water quality and ecosystem health.  Lake and pond water in Maine is subject to a number of threats, from airborne pollutants like acid rain and mercury deposition to changes in water chemistry from land runoff  and other human inputs to changes in the physical characteristics of water bodies due to climate change (e.g. more storm events, higher temperatures).  This is not to mention the introduction of larger invasive species of plants and critters.

The biggest players in this arena are the Maine DEP's Lake Monitoring and Assessment Program and the Lake Stewards of Maine (formerly known as the Maine Volunteer Lake Monitoring Program).  Together with Maine's university scientists and students, and dozens of smaller lake stewardship groups, they have created one of the best data-sets for lake water quality in the country (links below).

Streams and Rivers

The Maine DEP created the Volunteer River Monitoring Program (VRMP) in 2009 to coordinate the efforts of existing volunteer monitoring groups.

Typical Water Quality Indicators Lakes and Ponds monitoring Streams monitoring Test performed in field MEL does this
alkalinity x x
ammonia-nitrogen x x
anions and cations x
bacteria - enterococcus x x
bacteria -E. coli, fecal coliform x x
chloride x x
chlorophyll a x
color x
conductivity x x
dissolved oxygen x x x
hardness x x
nitrate/nitrite-nitrogen x x
ortho-phosphorus x x
pH x x x x
phytoplankton x
specific conductance x x x
suspended sediment concentration x
temperature x x x
total alkalinity x x
total dissolved solids (TDS) x x
total Kjeldahl-nitrogen (TKN) x x
total phosphorus x x x
total suspended solids (TSS) x x
transparency (Secchi disk) x x
turbidity x x
zooplankton x
Source of data List from Lake Stewards of Maine Water Quality Indicators
Lake Stewards if Maine SOP

Fresh Water Swimming Safety & Bacteria

The State of Maine Dept. of Human Services determines if fresh water is clean enough for swimmer safety by testing for E. coli (enumerated). (Yes, we test for that). The safety limit for swimming has been set at 235 MPN/100 mL.  Enterococcus testing can also be used (we do that, too).


The Swim (website and App) helps you easily find your closest local beaches, and know at a glance which ones are safe for swimming. Includes some educational tidbits about bacterial water testing.

Maine DEP "Monitoring and Assessment of Lakes" (webpage):

Lakes of Maine (website) - comprehensive data on Maine's 5000+ lakes:

Lake Stewards of Maine  (website) - information-rich site dedicated to water quality monitoring and volunteer education:

Maine Lakes Society (website) - a consortium of dozens of Maine lakes groups:

Maine Volunteer River Monitoring Program:

Maine Water Resources (US Geological Survey, Maine Office) -

"Maine Lakes: Living on the Edge?" (61-minute video,2016), a George Mitchell Center panel presentation about the interdisciplinary project called "Engaging Citizen Scientists to Evaluate Water Quality Decline" 

Maine Waters Status Report

The Clean Water Act requires states to report on changes in their water quality every two years.* Data is collected from numerous public entities, including volunteer monitoring programs.

State of Maine Integrated Water Quality Monitoring and Assessment Reports (website)

2022 Maine Integrated Water Quality Report