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Boston Harbor and Massachusetts Bay
Massachusetts Water Resources Authority

Management and use of a long-term
water quality monitoring database for
Boston Harbor and Massachusetts Bay

Suh Yuen Liang, Doug Hersh, Wendy Leo,
MWRA Environmental Quality Department

See our database management poster. (PDF)

The Massachusetts Water Resources Authority (MWRA) maintains an extensive environmental database, which consists of long-term monitoring data for Boston Harbor and Massachusetts Bay, and effluent testing data for MWRA treatment plants and combined sewer overflow treatment facilities. To increase the awareness and to encourage the use of the MWRA environmental database, in this presentation we highlight (1) data quality assurance and control, (2) data sources, database management, and application, (3) studies and sampling locations, and (4) examples of data use.

(Click on the thumbnails below to see larger images).
Most of the monitoring data have been collected by MWRA and its consultants during the past decade. These data are under stringent quality assurance (QA) and quality control (QC) following the Deming/Shewhart model for quality management (Figure 1).

Data checking takes place in many stages including laboratory data collection, data entry, QC check plots (Figure 2) and statistical summary of data, QA review of data, and loading to database.
Data from other agencies and organizations are included in the database only when the data are thoroughly documented.
All data are stored in an Oracle relational database management system. Sources and users of the data are diagrammed in Figure 3. (PDF)
Major categories of monitoring data in the database are: water quality, effluent chemistry, fish and shellfish chemistry and pathology, sediment contaminants, plankton abundance, and benthic infauna. Sampling locations in relation to each monitoring study are shown in Figure 4. (PDF)

Examples of data use by a broad range of clients are shown in Figures 5 through 10, below.
A time series (open symbols) from September 1997 to December 2001
(Figure 5a.) (PDF)
SeaWIFS-derived annual mean chlorophyll concentration in Massachusetts Bay. (Figure 5b). (PDF)
Receiver operating characteristic (ROC) curves of previous day Enterococcus density (a) and 48-Hour antecedent rainfall (b) for Constitution Beach.
(Figure 6.) (PDF)
Observed (black circles) and predicted (red line) Enterococcus counts between 1996 and 2003 at Deer Island (a) and Nut Island (b) outfalls regions. (Figure 7a and Figure 7b.)
Data from across studies are synthesized to improve our understanding of ecological processes in Mass. Bay.( Figure 8.) (PDF)
Surface temperature (color gradients) and current (arrows) in summer 1999 from Massachusetts Bay hydrodynamic model. (Figure 9.) (PDF)
A two-dimensional hydrodynamic and water quality model of the Lower Charles River in Boston.(Figure 10.) (PDF)


MWRA water quality database has been used intensively for management internally and for compliance with MWRA’s discharge permit and court orders. It also serves as a data warehouse for the public and the academic community interested in the health, ecology and physical characteristics of Boston Harbor and Massachusetts Bay. Water quality data and reports are available to the public upon request. For complete list of the reports about our water quality monitoring studies, please visit our website at