Charles River Basin Flagging Program
Testing
the Waters
From July through October, the Charles River Watershed Association
forecasts daily water quality conditions at four sites in the Charles
River Basin. The water quality models estimate the probability of
the river sites exceeding the State secondary contact recreation (boating) standard for fecal coliform bacteria
using recent rainfall conditions and results of water quality testing.
The State boating standard for fecal coliform bacteria is 1,000 colony forming units per
100 milliliters (cfu/100 mL); for e.coli bacteria, the State
boating standard is 630 cfm/100 mL. Historical bacteria data from this flagging program, and
rainfall data collected by the United States Geological Survey, were used
by CRWA and Tufts University to create the models.
A blue flag is posted
when it is estimated that the probability of bacteria exceeding the
boating standard is less than 50%. A red flag is hoisted when the
probability of the river exceeding boating standards is equal to or
greater than 50%. A yellow flag is hoisted when probability is uncertain, or if there are other factors (such as blue-green algae) potentially impacting boater safety. The presence
of fecal bacteria in water suggests contamination by sewage or feces,
which in turn could mean that disease-causing bacteria or viruses are
present. Most red flag days occur after heavy rainfall when storm
drains
and sewer system overflows flush pollutants into the river. CRWA research
shows that the Basin does not meet state boating standards over 13% of
the time after a heavy rain.
While it is always a good idea
to wash after being on the river, it is particularly important on red
flag days. Some boaters choose to stay off the river on red flag days
because of elevated bacterial levels.
In addition, CRWA will collect river samples once a
week, analyze them for fecal contamination, and present the results on
our website.
If you would like further information about CRWA's methodology for
predicting bacteria, read the article
"Predicting Fecal Coliform Bacteria Levels in the Charles River"
published in the Journal of the American Water Resources Association; or contact David Kaplan at 781-788-0007 x224.
For The Gulf of Maine Times Autumn 2002 article, click here.
Supporters of the Charles River Flagging Program
Partner Includes:
United States Geological Survey
Volunteers from: Access
Sport America, Charles
River Canoe & Kayak, Charles River Yacht
Club, Community
Boating, Community
Rowing Inc., Henderson Boathouse (Northeastern University), Newton Yacht
Club, Riverside
Boat Club, Union Boat Club,
Weld Boathouse (Harvard University).
(Click on participating program name for their
website.)
Funders and
In-Kind Donations: Monetary support is provided by the U.S. Environmental Protection
Agency and Boston Water and Sewer
Commission. Community Rowing, Inc. provides a motorboat for
collection of river samples. |