CLEAN WATER 

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.

Clean water is critical to safe recreation and for healthy wildlife habitat in the watershed. The Land Trust uses the findings from the Water Quality Monitoring program to help identify important places to conserve land and work in collaboration with partners on restoration projects.

Water Quality Monitoring

The Presumpscot Regional Land Trust coordinates volunteer water quality sampling throughout the region.

We maintain an online map that shows 14-year averages and trends for water quality at our sample sites. Please click on the map to the right to explore a full-screen version.

What our monitoring measures

Samples are tested for E. coli bacteria. These bacteria come from animal feces and affect the suitability of water for people to drink and recreate in.

Dissolved oxygen readings are also taken at each site. Dissolved Oxygen reflects the habitat quality of water for wildlife. Levels are low when excessive nutrients in the water cause algal blooms.

Averages shown on the Historical Map reflect the percentage of total samples that met the Maine DEP Standards for bacteria or dissolved oxygen levels, respsectively.

Trends were calculated from abundance readings. First, all samples taken in a year were averaged. This resulted in 10 yearly average numbers for each site (n=10). Linear regression analysis was then performed to determine if there was a significant trend (p = 0.10) for the site and whether that trend was positive or negative. All sites that showed no statistically significant trend are shown in the map as diamonds. Sites with no trend symbology did not have enough samples to calculate a trend.

You can explore the results from last year's Water Quality Monitoring program below. Please click here to see a full-screen version.

2023 Water Quality Results

The water quality data from 2023 showed some decline in water quality compared to 2022. The long-term water quality trends on the Presumpscot River have remained stable, with the sites closest to Sebago Lake having the highest water quality. This analysis includes data from the Presumpscot River as well as the River’s eleven tributaries, with a focus on the Pleasant River, Little River, and Mill Brook. The analysis also incorporates historical data, from the last fourteen years.

The PRESUMPSCOT RIVER:

  • The "main stem" of the Presumpscot River almost always met dissolved oxygen and bacteria standards. Four sites met both standards 100% of the time, which was down from seven in 2022.

  • Historically, the main stem almost always meets both bacteria and dissolved oxygen standards, and raw scores (bacteria levels and dissolved oxygen amounts) are consistently the most favorable of any sites in the region.

  • Overall we have seen increased bacteria readings, with four sites showing higher bacteria levels over the past 15 years.

The Presumpscot River Tributaries:

  • In the eleven Presumpscot River tributaries, dissolved oxygen results met standards more frequently than in 2022. Just five  tributary sites met dissolved oxygen standards less than 50% of the time (declining results compared to 2022).

  • Most Presumpscot River tributary sites met bacteria standards more consistently than in 2022. No tributary sites met these standards 100% of the time, eight sites met the standard less than half of the time (compared to six in 2022).

  • The Pleasant River upstream and downstream sites mostly met bacteria standards while those in between did not. For dissolved oxygen, downstream sites mostly met standards while upstream sites did not.

  • Most tributaries of the Presumpscot have historically met dissolved oxygen standards most of the time. Two exceptions are Black Brook and Pleasant River in Windham, and efforts are being made to address this. 

  • The majority of tributary sites have rarely met bacteria state standards. Historical trends suggest that this is getting worse rather than better.

The Stroudwater River:

  • Sites on the Stroudwater River almost always met dissolved oxygen standards (an improvement from 2022) but mostly did not meet bacteria standards (with variable scores compared to 2022).

  • No meaningful historical trends are evident for the Stroudwater River yet as it has only been sampled for four years.

For a summary of these results click the button below.

 Additional Resources

Click here to access the interactive Presumpscot River Paddle Map to explore water access sites and portage routes all along the Presumpscot River.

Pleasant River Watershed Management Plan (Cumberland County Soil and Water Conservation District)