1996 Citizens Report: Broad Marsh River, Wareham
Embayment: Broad Marsh River
Embayment and Watershed Characteristic
The Broad Marsh River complex is actually a subestuary of the Wareham River. We discuss it separately in this section, but its water quality closely parallels that of the Wareham River. The Buzzards Bay NEP has not completed a separate subwatershed evaluation for the Broad Marsh estuary, and such an approach may not be warranted because of the overwhelming influence of the Wareham River on water quality conditions here.
Water Quality monitoring
The Broad Marsh River estuary is somewhat unusual in that the inner and outer embayment have very similar water quality, largely due to the "external" inputs from the Wareham River. In fact in one year total nitrogen was higher in the outer than it was in the inner. Overall total nitrogen concentrations parallel the pattern of the Wareham River, including the large spike of different forms of nitrogen in the water in 1994 (but at concentrations not quite as high as in the central portions of the Wareham River. Phytoplankton concentrations were less variable, with levels both above and below comparable years in the Wareham River. In other words, the Broad Marsh River parallels the Wareham River, but the patterns are somewhat "damped out". Oxygen saturation levels were better in Broad Marsh than the Wareham River, but showed a steady decline during the 4 years of study. The pattern shown in the graph of station BMR1 oxygen saturation is very apparent. The summertime highs, mean values, and summertime lows show a steady decline. During the same period, total organic nitrogen in the water showed large increases in concentration. These combined changes resulted in markedly lower Eutrophication Index Scores during 1994 and 1995.The results from the Broad Marsh River estuary support the general observations that waters in
the Wareham River complex are becoming more eutrophic, with water quality being particularly
poor in 1994.
Eutrophication Index scores
Nitrogen Management needs
In some respects the Broad Marsh River estuary acts somewhat isolated from the greater Wareham River estuary complex and could require some local nitrogen management. Clearly, water quality in this subestuary will improve only if nitrogen is managed both in the Wareham River and the Broad Marsh watershed.Back