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1996 Citizens Report: Agawam River, Wareham

Embayment: Agawam River

Embayment and Watershed Characteristic

The Agawam River is part of the Wareham River estuary previously discussed. We examine it separately because the Agawam River is the major contributor of both nutrients and freshwater to the Wareham River estuary, and because we have monitored two brackish water sites which due to their freshwater nature, could not be included in the Eutrophication Index scores for the Wareham River estuary. The Agawam River is also noteworthy because it receives discharges from the Wareham Sewage Treatment plant which serves both the town of Wareham and selected areas of the Buttermilk Bay and Buzzards Bay sections of Bourne. This treatment plant, which discharges .76 million gallons per day of secondarily treated effluent will in the next few years be reviewed by state and federal agencies for possible facility improvements to better protect coastal water quality.

The Buzzards Bay NEP has not evaluated nitrogen loadings to the Agawam River estuary separately from the larger Wareham River estuary watershed, but a cursory examination of land use maps suggests that it contains less residential land than portions of the Wareham River estuary adjoining the center of Wareham Village. Clearly the sewage treatment plant, followed by upstream cranberry bogs are the largest sources of nitrogen in this subbasin. The Agawam River is closed to shellfishing due to high coliform levels.

Water Quality monitoring

Only oxygen, salinity, temperature, and secchi depth were monitored at station AG1 in all four years. Both stations have brackish water that fluctuates depending on weather the tide is ebbing or flooding. Down stream station AG2 is saltier and shows wider fluctuations in salinity than AG1 which often had salinities less than 3 ppt. Station AG2 was not monitored in 1992 and only in the latter half of the 1993 season. Nitrogen and phytoplankton pigments were not monitored. Oxygen concentrations were low in the Agawam compared to most Buzzards Bay embayments monitored, with the four year mean saturations being 64%, 53%, 61%, and 37% respectively. The big drop in oxygen concentrations in 1995 were largely the result of low readings observed at station AG2, the more saline station. Station AG1 saw better oxygen concentrations in 1992 and did not show an appreciable decline in saturations in 1995. The low oxygen saturations at AG2 were also observed in several other Buzzards Bay embayments in 1995 and may be due to weather related changes in biological activity. In 1995, water transparency declined, which suggests that more phytoplankton were in the water, which could account for the lowered oxygen concentrations that year.

Nitrogen Management needs

Like Marks Cove and Broadmarsh River, the Agawam River cannot be managed separately from the larger Wareham River estuary complex. It is likely that improvements in nitrogen removal efficiency of the Wareham Sewage Treatment Facility will eventually be required, particularly in light of continuing new connections to the town's sewer system and poor water quality observed in both the Wareham and Agawam Rivers. Because of low oxygen concentrations observed in the Agawam River, nitrogen loading limits for the plant should not only be protective of water quality in the Wareham River, but protective of the Agawam River as well. In light of these management decisions, nutrient monitoring of the Wareham River should be expanded into the Agawam River subestuary.

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