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Mystic River Watershed
Contact Us

Mystic River Watershed Report Cards

EPA has been assigning a report card grade for the Mystic River Watershed since calendar year 2006. For the last six years, grades have been assigned to 14 individual stretches of the river and its tributaries. Prior to 2014, a single grade was assigned to the watershed as a whole.

Map identifying water quality grades and compliance rates in the Mystic River Watershed for the 2021 calendar year.
EPA produced a watershed map for 2021 (pdf) (2.7 MB) that identifies areas in the watershed where water quality is generally good and generally needs improvement.

Grading Criteria 2014-Present

Since calendar year 2014, EPA, in coordination with the Mystic River Watershed Association (MyRWA), has utilized an enhanced, more locally-specific analysis of water quality in the Mystic River Watershed to better illuminate environmental conditions for the public. Instead of one grade for the entire watershed, EPA and MyRWA now issue grades for each segment of the watershed, totaling 14 separate stretches of river and its tributaries. The same grading system applies (see below), but now an average between the overall percentages that water quality met the state criteria for swimming and boating (for the Aberjona in 2016, it was 61.8%) as well as qualitative criteria that are similar to those developed for the Charles River Initiative (see below) are calculated for each segment to produce the grades shown here.

Chart: Mystic River Compliance Rates and Grades for 2021
View a larger version of this image.
Figure 1 - Developed and provided by MyRWA.
Mystic River Water Quality Grades & Compliance Rates for Freshwater Sites
Sites 2021 2020 2019 2018 2017 2016 2015 2014
Grade Total Grade Totel Grade Total Grade Total Grade Total Grade Total Grade Total Grade Total
Aberjona River C 64.4% C- 58.8% C- 55.7% D+ 52.6% C- 59.4% C 61.8% C+ 66% C+ 65%
Alewife Brook D 46.7% D 46.5% D 45.6% D 50.0% D+ 53.8% D+ 54.2% D 50% D 46%
Little River D+ 52.6% D+ 51.0% D+ 50.7% D+ 52.6% D+ 54.2% D 49.4% D- 44% D- 40%
Malden River C- 59.4% C- 59.6% C 63.9% C 60.1% C 63.7% C+ 65.1% C 63% C- 59%
Meetinghouse Brook B- 72.5% C+ 70.0% B- 72.6% B- 71.9% B 78.4% C+ 66.5% C- 58% D 47%
Mill Brook D+ 54.7% D 48.6% D+ 50.5% D 49.4% C- 55.1% D+ 53.1% D 49% D- 46%
Mystic River (fresh) B+ 80.4% B+ 81.9% A- 85.5% A- 86.9% A- 87.6% A- 85.8% A- 85% B+ 85%
Upper Mystic Lake A+ 98.6% A 93.2% A 92.9% A 93.4% A+ 98.6% A+ 98.9% A+ 96% A+ 96%
Winns Brook D 45.3% D 45.7% F 36.3% D- 40.1% F 38.4% D- 42% F 33% F 33%
Mystic River Water Quality Grades & Compliance Rates for Saltwater Sites
Sites 2021 2020 2019 2018 2017 2016 2015 2014
Grade Total Grade Total Grade Total Grade Total Grade Total Grade Total Grade Total Grade Total
Belle Isle Inlet B- 70.3% B 78.1% B+ 83.8% A- 86.0% A- 89.3% A- 85.7% B 78% C 64%
Chelsea River B+ 83.3% A 90.9% A 90.4% A 95.0% A 94.6% A 91.2% A- 90% A- 87%
Island End River A 91.7% A+ 96.9% B 76.3% C+ 66.7% D- 42.5% F 36.3% F 25% F 33%
Mill Creek F 30.2% F 32.9% D- 41.3% F 36.1% F 31.3% F 33.5% F 34% F 32%
Mystic River (salt) B+ 81.4% B 79.8% B+ 83.7% A- 86.0% A- 88.3% A- 87.6% A- 89% A 90%

For more information on how the grades are assigned please read the Frequently Asked Questions and review the data on MyRWA's Website.

2021 Report Card
  • 2021 Report Card Grades by Segment
  • 2021 Water Quality Map (pdf) (2.7 MB)
2020 Report Card
  • 2020 Report Card Grades by Segment
  • 2020 Water Quality Map (pdf) (6.7 MB)
2019 Report Card
  • 2019 Report Card Grades by Segment
  • 2019 Water Quality Map (pdf) (6.5 MB)
2018 Report Card
  • 2018 Report Card Grades by Segment
  • 2018 Water Quality Map (pdf) (6.4 MB)
2017 Report Card
  • 2017 Report Card Grades by Segment
  • 2017 Water Quality Map (pdf) (6.2 MB)
2016 Report Card
  • 2016 Report Card Grades by Segment
  • 2016 Water Quality Map (pdf) (1.1 MB)
2015 Report Card
  • 2015 Report Card Grades by Segment
  • 2015 Water Quality Map (pdf) (950 K)
2014 Report Card
  • 2014 Report Card Grades by Segment
  • 2014 Water Quality Map (pdf) (1.2 MB)

Grading Criteria Prior to 2014

When assessing water quality to assign a grade to the Mystic River Watershed prior to 2014, EPA used an average between the overall percentages that water quality met the state criteria for swimming and boating (for 2013, it was 66%) as well as qualitative criteria that are similar to those developed for the Charles River Initiative, as follows:

A - met swimming and boating standards nearly all of the time
B - met swimming and boating standards most of the time
C - met swimming standards some of the time, and boating standards most of the time
D - met swimming and boating standards some of the time
F - fail swimming and boating standards most of the time

Mystic River Report Cards: 2003 - 2013
Year Grade Overall* Dry* Wet*
Boating Swimming Boating Swimming Boating Swimming
2013 D 83% 49% 88% 51% 67% 42%
2012 D 75% 47% 84% 58% 45% 14%
2011 D 87% 46% 93% 54% 69% 25%
2010 D- 70% 28% 72% 26% 63% 33%
2009 C- 93% 57% 93% 51% 90% 75%
2008 C- 90% 59% 93% 64% 81% 43%
2007 D 68% 46% 63% 45% 83% 50%
2006 D 80% 52% 93% 59% 41% 30%
2005**   85% 56% 90% 64% 69% 31%
2004**   79% 52% 85% 59% 61% 59%
2003**   81% 55% 81% 53% 81% 62%
*Figures represent the percentage of time that state bacterial standards are met.
**The Mystic River Watershed did not receive formal grades for the years 2003 - 2005.

Mystic River in the News

  • 07/14/2021
    Boston River Report Cards Show Widespread Improvements in Bacteria Concentrations and Remaining Localized Challenges
  • 08/13/2020
    Annual Report Card Indicates Improving Bacterial Water Quality in the Mystic River in 2019
  • 06/26/2019
    Annual Report Card Shows Good Water Quality in Main Stem of the Mystic River in 2018
  • 06/13/2018
    Annual Report Card Shows Water Quality Improvements in Parts of the Mystic River Watershed in 2017
  • 06/29/2017
    Annual Report Card Shows Water Quality Improvements in Parts of the Mystic River Watershed
  • 05/31/2016
    Localized Mystic River Report Card Shows Specific Information about Water Quality
  • 07/18/2015
    New Grading System for Mystic River Watershed Gives Public Better Localized Information
  • 12/18/2014
    EPA Announces 2013 Report Card Grade for the Mystic River Watershed
  • 08/19/2014
    EPA Awards $120,000 in Urban Waters grants to Revitalize Mystic River Watershed
  • 08/07/2013
    EPA Announces 2012 Report Card grades for the lower Charles River and the Mystic River Watershed
  • 05/10/2013
    Federal Agencies Expand Urban Waterway Revitalization Efforts in Communities Across the Nation
  • 08/23/2012
    Settlement Requires Boston Water and Sewer Commission to Remedy Sewer and Stormwater Discharges
  • 08/22/2012
    Clean Water Act Settlement Ensures That Boston Racetrack Addresses Wastewater and Stormwater Discharges
  • 05/20/2012
    Mystic River Water Quality Receives a "D" - Ongoing efforts, analysis highlight problem areas
  • 10/14/2011
    ExxonMobil Addresses Stormwater at Everett Terminal – Better Water Quality in Mystic and Island End Rivers Will Result
  • 05/15/2011
    Mystic River Water Quality Score Downgraded to D- Despite ongoing efforts, analysis shows more work needed
  • 05/16/2010
    Mystic River Scores C- : Good Progress Underway
  • 05/02/2009
    Report Card for Mystic River: "C-" with Notable Improvement
  • 10/17/2008
    Equipment Loans Help New England Volunteers Collect Water Quality Info
  • 5/15/2008
    Suffolk Downs Race Course Ordered to Reduce Bacterial Waste in Stormwater
  • 04/10/2008
    EPA Mystic River Report Card: "D" – Room for Improvement – Help Is On the Way
  • 04/17/2007
    EPA Kicks Off Major Effort to Improve Conditions of Mystic River Watershed
  • 02/26/2007
    Everett, Mass. Metal Finisher Fined and Settles Environmental Violations
  • 10/30/2006
    Massachusetts Celebrates World Water Monitoring Day
  • 07/12/2006
    Mass. Recycling Facility Facing Fines for Clean Water Violations
  • 03/10/2004
    $1.4 Million Environmental Settlement With MBTA Brings Clean Air and Water Benefits to Boston: Settlement Stems from Bus Idling and Water Pollution Violations
  • 12/03/2001
    EPA Awards $363,257 Grant to Somerville for Mystic River Project
Contact Us to ask a question, provide feedback, or report a problem.
Last updated on July 15, 2022
United States Environmental Protection Agency

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