EUTROPHICATION IN THE IPSWICH RIVER, ESSEX COUNTY, MASSACHUSETTS

Modern watersheds face increasing strain due to anthropogenic impact like eutrophication degrading biotic processes and water quality. Present conditions may be creating a eutrophic zone between dams along a segment of the Ipswich River. Isotopic ratios of particulate matter showing a bias toward freshwater algae impacted by low oxygen conditions are expected. This study abides an integrated approach to hydrological research including evaluation of riverine discharge hydrographs, in-situ hydrochemical measurements, and carbon, nitrogen, and sulfur isotopic ratios. Four data collection sites have been established along the Ipswich River in Essex County, Massachusetts, upstream to downstream: South Middleton at Boston Street Bridge, and Ipswich at Willowdale Mills Dam, Ipswich Mills Dam, and Choate Bridge.

Bivariate hydrographs of the Boston Street Bridge sub-watershed and the Choate Bridge watershed created using USGS data show no discrepancies in volume. The Boston Street Bridge sub-watershed displays a steeper curve demarking recharge events whereas a gentler recharge curve is observed for Choate Bridge. For all locations pH and specific conductance rates were within expected ranges for healthy river water. However, dissolved oxygen saturation was lower than the desired 80% at both dam sites. Isotopic results are pending.

Hydrographs show a steeper curve for the Boston Street Bridge sub-watershed, likely due to an increased percentage of urbanized surface area. Since this ground is impenetrable, runoff goes directly to lower elevations sans percolation through soil. A lower percentage of urbanized surface area is recorded for the Choate Bridge watershed, meaning the water may percolate into lowlands more slowly. Dissolved oxygen levels at the dam sites may be indicative of biotic overload and a eutrophic subzone at these microenvironments. Eutrophic conditions would provide isotopic data of particulate matter at these sites showing a heavy presence of riverine algae.

Presently, this study does not definitively find whether there are eutrophic zones within the Ipswich River. It does point to likely zones of biotic imbalance due to human made dams. On a municipal scale this research presents important information regarding deterioration of surface water quality due to dams.