Results of the DCR/DWSP's 1998-2002 Monitoring Program, a Review of Plankton Data from Cosgrove Intake, and an Evaluation of Historical Records

A colonial chrysophyte of the genus Synura, this organism is one of several phytoplankton taxa that can cause unpleasant taste and odors in water supplied to consumers. The colony is about 120 microns in diameter.
A colonial chrysophyte of the genus Synura, this organism is one of several phytoplankton taxa that can cause unpleasant taste and odors in water supplied to consumers. The colony is about 120 microns in diameter.

This report details the scope, methods, and results of an intensive program of monthly sampling and analysis of nutrients and plankton in Wachusett Reservoir conducted from October 1998 through September 1999 and continued, with some modifications, on a quarterly schedule to the present day.

Laboratory measurement of nutrient concentrations was performed by Massachusetts Water Resources Authority (MWRA) staff of the Deer Island Central Laboratory at a higher level of precision and sensitivity than any previous study. The spatial coverage of the program (four stations each sampled at various depths) and frequency of sampling, combined with the efficacy of laboratory measurements provides the most comprehensive database currently available on nutrient and plankton dynamics in Wachusett Reservoir.

Also presented in this report is a review of plankton data generated independently from the following sources: (1) DWSP sampling conducted weekly (ice conditions permitting) at Cosgrove Intake since 1987; (2) historical reservoir sampling conducted in 1988, 1989, 1995, and 1996; and (3) historical data compiled by the MWRA. Additionally, a detailed characterization of the Quabbin "interflow," a hydrodynamic phenomenon resulting from the annual transfer of water from Quabbin Reservoir to Wachusett via the Quabbin Aqueduct is presented. Finally, this report integrates historical nutrient and plankton records and related information generated from numerous consultant studies of Wachusett Reservoir.

Major findings include the following: (1) marked seasonal and vertical variations in nutrient concentrations mediated by phytoplankton dynamics; (2) interannual shifts in nutrient concentrations and the intensities of other parameters corresponding to the divergent influences of the Quabbin transfer and the Wachusett watershed; (3) a phytoplankton community dominated by diatoms and chrysophytes typical of many oligotrophic, softwater systems located in the temperate zone; and (4) an annual cycle of phytoplankton succession and abundance also characteristic of this type of system, but with additional features unique to Wachusett Reservoir.

Please click on the following to view the entire report and appendices:

For more information , please contact Dave Worden at dave.worden@state.ma.us or (508) 792-7423 x316.