April 5, 2019

New map provides insight into water quality trends on the Presumpscot River

A new interactive map, available to view online, shows changes in water quality over the past 10 years. The map includes sites along the Presumpscot River from Sebago Lake through Standish, Windham, Gorham, Westbrook, Falmouth and Portland.

For Maine’s most urban river, the good news is that the majority of the top recreational spots along the Presumpscot River have been generally below the state threshold and stable for E. coli bacteria levels. The concerning news is that many of the tributaries to the Presumpscot River exceeded state standards for bacteria levels the majority of the time, and bacteria levels are increasing at many of these sites.

The Presumpscot River watershed covers much of Greater Portland and is the largest freshwater input into Casco Bay. As the region has quickly grown so has recreational use of the river; there are now over 20 water access points for paddling the river, several swimming holes, and numerous great fishing spots. Due to the recent removal of barriers, the river now hosts the largest fish migration from Casco Bay.

Clean water is critical to safe recreation and for healthy wildlife habitat in the watershed. The community-based nonprofit, the Presumpscot Regional Land Trust, works to conserve and steward land and clean water while also providing access for recreation throughout the watershed and beyond.

2019 will be the third year of the Presumpscot Regional Land Trust’s water stewards program, building on over a decade of work by the Presumpscot River Watch. The Land Trust uses the findings from the water stewards program to help identify important places to conserve land and work in collaboration with partners on restoration projects.

Over 150 volunteer citizen scientists have collected water samples at 40 sites throughout the Presumpscot River watershed over the past 10 years. The Land Trust tests for two important indicators of clean water:  E. coli bacteria (an indicator of potential fecal contamination) and dissolved oxygen (needed for most wildlife to survive in the water).  The results from the past 10 years, both averages and trends, can be viewed in an interactive map at www.prlt.org/water.

The Water Stewards program works in collaboration with the Maine Department of Environmental Protection’s Volunteer River Monitoring Program. The Land Trust volunteer citizen scientists collect water quality samples throughout the Presumpscot River watershed and Stroudwater River every other Saturday during the summer months for a total of ten sampling events per year. The state uses this data to identify rivers and streams that do not attain state standards and works with partners to develop restoration plans that address potential water quality problems in the watershed.   Mary Ellen Dennis, coordinator of the state Volunteer River Monitoring Program stated, “volunteer groups like the Presumpscot Regional Land Trust collect water quality samples from locations not regularly monitored by our staff. This allows us to have a better idea of water quality conditions for a broader geographic area.”

The Water Stewards program would not be possible without community volunteers. The Land Trust is now actively looking for volunteers for the 2019 season. Volunteers can sign up online by going to www.prlt.org.

Thank you to Casco Bay Estuary Partnership, USM’s Environmental Science and Policy Department, Town of Windham Watershed Protection Fund, IDDEX Laboratories and to the Land Trust Business Partners and Individual Members for supporting the water stewards program.


Making a clean water determination includes assessing water quality over long periods of time (to observe trends) and collecting several different types of data. Presumpscot River Watch (before merging with the Land Trust) collected data and provided it to the State of Maine for ten years. Starting in 2018 the Land Trust also began collecting water quality samples along the Stroudwater River. The annual water quality results can be viewed in an online map at www.prlt.org/water.

The Land Trust collects data on water temperature, dissolved oxygen and E. coli bacteria in its water sampling. Other factors affecting water quality are petroleum products, heavy metals and nutrients (such as nitrogen or phosphorus). Testing for these additional factors is not feasible for the Presumpscot Regional Land Trust’s water stewards program without significant program expansion. The Presumpscot Regional Land Trust would like to collaborate in the future with other organizations that have the equipment and capacity to expand the water quality monitoring program in the Presumpscot River and Stroudwater River.

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