CRWA Baseline Water Quality Monitoring

Water Quality Is Improving

CRWA research indicates that water quality has steadily improved in the Charles River over the past ten years. In 2005, the Lower Basin (downstream of the Watertown Dam), represented by nine sampling sites, overall met the boating standard for bacteria limits 87 percent of the time and the swimming standard 33 percent of the time.  This compares favorably to 1995 when boating standards were met just 39 percent of the time and swimming standards just 19 percent of the time.  To view a complete report summarizing 2005 water quality sampling results throughout the entire watershed click here.

Improvement is reflected in the US EPA’s annual "report card" for the Charles River Basin. The river’s "D" rating in 1995 was upgraded to a "C-" in 1996, a "C" in 1997, a "B-" in 1998, and a "B" from 1999 to 2002.  In 2003, the river's grade decreased slightly to a   "B-", but has rebounded in 2004 and 2005 to a "B+". To view an Excel table of previous year's grades and percentages of times the Lower Basin was safe for swimming and boating, click here. The water quality of the river is very good during dry weather conditions, however, worsens after a rainstorm.  In dry weather during 2005, the river met the boating standard 89 percent of the time, but in wet weather only 76 percent of the time. The river met the swimming standard 41 percent of the time in dry weather, but only 12 percent of the time in wet weather. (Wet weather is when it rains more than a tenth of an inch in a 72-hour period.)  

Over the past couple of years, the apparent diminishing discrepancy between dry and wet weather bacteria counts may be attributed to sewerage infrastructure upgrades such as the separation of combined sewers, the removal of illicit connections to storm sewers, remediation of faulty sewer pipes and less combined sewage overflow discharges to the river.  Despite these infrastructure improvements, the grade for the Charles River has reached a plateau over the past three years signaling that the river is still impaired significantly by stormwater pollutants.  When it rains, oil, grease, gasoline, pet waste, cleaning agents, pesticides, fertilizers, and trash on streets, parking lots and other hard surfaces wash into storm drains. From there pollutants discharge into the Charles River. These pollutants can seriously degrade water quality for fish and wildlife habitat, and for recreation.  Click here to learn more about how you can protect the river.