How to interpret the data

First...have the right amount of coffee available

OARS' water quality and streamflow data is assessed in several ways. We can ask:

• Does the river or stream meet the state's water quality standards for Class B waters? (below)
• Do the nutrient concentrations exceed EPA's recommendations for unimpaired waters? (below)
• Is there enough streamflow to support fish?
• Using OAR's Stream Health Index, do the overall conditions provide healthy habitat for fish?

Massachusetts Standards
Parameter  Standard
Dissolved oxygen* >= 5.0 mg/l and 60% saturation for warm water fisheries >= 6.0 mg/l and 75% saturation for cold water fisheries
pH* 6.5-8.3 for inland waters
Nutrients* "control cultural eutrophication"
Temperature* <= 28.3 C and less than 2.8 C deviation for warm water fisheries <= 20.0 C and less than 1.7 C deviation for cold water fisheries
Suspended Solids** Aquatic life: 25 mg/L maximum and <= 10 mg/l increase due to a discharge
Primary or secondarily contact recreational use: no nuisance organisms that render the water aesthetically objectionable or unusable, "best professional judgment"; cover of macrophytes < 50% within any portion of the lake area at maximum extent of growth.
Fecal coliforms** Primary contact recreational use -- Dry weather guidance: (<5 samples taken) <= 400 cfu/100ml. Wet weather guidance: dry weather samples meet and wet samples <=2000 cfu/100ml.
Secondary contact recreational use -- Dry weather guidance (< 5 samples taken) <=2000 cfu/100ml. Wet weather guidance: dry weather samples meet and wet samples <= 4000 cfu/100ml.
*MADEP 1997 Massachusetts Surface Water Quality Standards - 314 CMR 4.00 1997.
** MADEP 2002 Massachusetts Year 2002 Integrated List of Waters, Part 1.
Reference Conditions for Ecoregion XIV Subregion 59 Streams*
Parameter  Reference condition
(25th percentile of June - September data)
Reference condition
(50th percentile of June - September data)
Total Phosphorus (mg/L) 0.025 0.050
Total Nitrogen (calculated) (mg/L) 0.44 0.74
NO2 + NO3 (mg/L) 0.34 0.43
chlorophyll-a (micrograms/L) 2.00 4.00
* adapted from USEPA. 2000. Ambient Water Quality Criteria Recommendations: Rivers and Streams in Nutrient Ecoregion XVI. EPA 822-B-00-022. United States Environmental Protection Agency: Office of Water, Office of Science and Technology, Health and Ecological Criteria Division. Washington, D.C. December 2000.

Useful references: