While most of the Charles River's water is in good shape, a tributary that runs through Boston and Brookline has water that's far less satisfactory, according to the latest water quality grades.
The Charles River's 2019 report card, created by the Charles River Watershed Association and New England branch of the Environmental Protection Agency, was released Monday and gives the Muddy River, the tributary that trickles from Jamaica Pond into the Charles under Storrow Drive a D-.
This report card is the first since the first in 1995 to assign grades for six individual segments of the river's full run, along with its two tributaries, the association said in a news release. In years past, a single grade was assigned to the Lower Charles River (Watertown to Boston).
The report gave A grades to the river's Upper Middle (Sherborn to Dedham) and Lower Middle Watershed (Newton to Waltham) sections, while the Upper Watershed (Hopkinton to Medfield) and the Stop River tributary (Medfield) earned A- marks.
The Lower Basin of Charles River, the popular stretch from Watertown to Boston, received a B grade, as it did in 2018's report, while Muddy River took the only lower grade, the D-, according to the CRWA.
"Previous iterations of the report card obscured the very poor water quality in the Muddy River," said Karen Mauney-Brodek, president of the Emerald Necklace Conservancy, in a statement. "This highly impacted waterway faces challenges from untreated roadway runoff, urban challenges and aged infrastructure."
The new grading system also considers more pollutants -- sewage overflow and cyanobacteria-- than in previous versions, the association said.
According to the EPA, the Charles River Report Card is meant to evaluate if the water quality of the river meets Massachusetts' standards for swimming and boating as well as to determine the general health of the water.