Water Quality Data Table: CRWA analyzes river samples once per month at multiple locations for Escherichia coli (E. coli) bacteria, an indicator of human health risks. View the most recent bacteria data.
Monthly Water Quality Maps: View monthly color-coded maps representing the reaches of the river that meet or exceed state swimming and/or boating standards for E. coli bacteria:
Most Current Data - September 17, 2019:
Rainfall* At Logan International Airport (inches)
|5 days prior to sampling||0.00|
|4 days prior to sampling||0.07|
|3 days prior to sampling||0.00|
|2 days prior to sampling||0.21|
|1 day prior to sampling||0.00|
|Day of sampling||0.00|
What Does the Map Mean?
The blue color represents river reaches that met the E. coli swimming standard of 126 colony forming units per 100 milliliters (about a teacup of water) (#/100ml). Yellow represents the reaches of the river that exceeded the swimming standard yet met the boating standard of 630/100ml. A violation of the boating standard is represented by the red color. Finally, any reaches of the river colored gray represent non-sampled areas.
Standards are set by the Massachusetts Department of Environmental Protection (MassDEP) to indicate level of health risk in freshwaters. MassDEP recommends not swimming or fishing when the geometric mean of bacteria counts exceed 126/100ml, and not boating on days when the geometric mean of levels rise above 630/100ml.
View Data from Previous Months:
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Additional water quality testing results are available for download in Microsoft Excel below. New data will become available as it is checked for accuracy. For more information on the parameters CRWA tests for on a regular basis, read CRWA Water Quality Monitoring Parameters.
For questions regarding the following data, please contact Julie Wood.
Once per month, CRWA collects water samples from multiple sites along the entire length of the 80-mile Charles River. Prior to 2002, CRWA analyzed all samples for fecal coliform bacteria, however due to changes in water quality standards, CRWA now collects and analyzes samples for Escherichia coli , or E. coli, which serves as a better indicator of health risks. Previously, CRWA's laboratory analyzed samples for fecal coliform bacteria, which is one parameter used by the state for surface water quality standards.
According to the U.S. Environmental Protection Agency (EPA) and the Massachusetts Department of Environmental Protection (DEP), the swimming standard for E. coli is 126 colony forming units per 100 milliliters (cfu/100mL) and the boating standard is 630cfu/100mL.
The standards for fecal coliform are set by the Massachusetts Department of Environmental Protection to indicate level of health risk. The DEP recommends not swimming or fishing when bacteria counts exceed 200cfu/100mL, and not boating on days when levels rise above 1,000cfu/100mL.
In addition to collecting water samples which are analyzed for bacteria, CRWA measures temperature and depth on site on a monthly basis.
Every year in March, June, September, and December, CRWA takes a closer look at the water quality of the Charles River. In addition to testing for E. coli, CRWA tests for enterococci, nitrate plus nitrite, ammonia, total kjeldahl nitrogen, total nitrogen, phosphorus, orthophosphate, chlorophyll a, and phaeophytin. For more information the parameters CRWA tests for on a regular basis, read CRWA Water Quality Monitoring Parameters.
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