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Partnerships | Long Island Sound Study

Connecticut River Nitrogen Project

Following the U.S. EPA’s 2001 approval of the Long Island Sound (LIS) dissolved oxygen TMDL, NEIWPCC established the Connecticut River Workgroup and the Connecticut River Nitrogen Project. This project is a cooperative effort involving staff from NEIWPCC, the states of Connecticut, Massachusetts, New Hampshire, and Vermont, and EPA's Region 1 and LIS offices. All are working together to develop scientifically-defensible nitrogen load allocations, as well as an implementation strategy, for the Connecticut River Basin in Massachusetts, New Hampshire, and Vermont, which are consistent with TMDL allocations established for LIS. Since its inception, the Connecticut River Workgroup has participated in a number of projects to better understand nitrogen loading, transport, and reductions in

New England SPARROW Project

A modeling effort using the New England SPARROW (Spatially Referenced Regressions On Watershed attributes) model was the first study completed by the CT River workgroup. The study had several goals, including predicting the ranges of nutrient levels in surface waters and identifying environmental factors that are statistically significant, as well as evaluating nutrient management options and monitoring efforts. The results of the study helped target needs for future monitoring and modeling efforts, concluding that point sources contribute 25 percent of the nitrogen load from the upper Connecticut River Watershed, and nonpoint sources, particularly atmospheric deposition, contribute the remaining 75 percent.

Monitoring the Connecticut River

The Connecticut River Workgroup worked with USGS to assess the total nitrogen in the Connecticut River north of the Connecticut border over a three year period (from 2002-2005). This study provided a baseline to compare with loading estimates from the LIS TMDL to actual measurements from the river during the same period. The monitoring effort looked at several factors, nitrogen loads in the upper basin and its tributaries, assessments of nitrogen loading from watersheds dominated by a variety of different land uses, and an analysis of water quality samples taken at treatment facilities in the upper Connecticut River Basin.

Nitrogen Attenuation Study

USGS and the workgroup worked to determine the rate of nitrogen loss in the upper Connecticut River during the last year of the monitoring. Earlier SPARROW models suggested that there was very little removal of nitrogen on an annual basis as the river flows toward the Sound. The nitrogen attenuation study confirmed this, as only no or small rates of attenuation occurred during the spring and summer of 2005. The highest recorded loss was 18 percent, detected during the low-flow period in the northern ten mile reach, suggesting that in-stream nitrogen loss is greatest at locations with low flow habitats.

Northeast AVGWLF

The Northeast AVGWLF (Arc View Generalized Watershed Loading Function) is a modeling tool that was used to utilize the monitoring and modeling done by the workgroup to develop nitrogen management measures. AVGWLF is a watershed scale model that uses a variety of critical watershed related characteristics to model sediment and nutrient transport within the watershed. The model was recalibrated for the Connecticut River watershed with the data collected by the USGS, and represents conditions from the 2002-2005 time period. The attenuation rates from SPARROW and USGS were used to determine the rate of nitrogen loss as water flows down the river to Long Island Sound. The effort is intended to estimate nutrients loads brought to LIS from the Connecticut River and estimate what costs and reductions are associated with implementing point source and non point source controls and best management practices in the region. This project resulted in an additional set of loading estimates and a set of cost curves for best management practices throughout the region. These curves will be used in the reassessment of the Long Island Sound TMDL by demonstrating what levels of reduction are economically feasible.

The LIS TMDL made a commitment to re-evaluate and revise the TMDL in the future. Beginning in 2008, the Connecticut River Workgroup began supporting and participating in the re-evaluation of the TMDL. The LIS TMDL Writing Team, a subset of the Connecticut River Workgroup, is conducting the technical and policy evaluation of work performed to support a revision to the LIS TMDL and will eventually be the group responsible for writing the revised TMDL. The Connecticut River Workgroup provides input to the LIS TMDL Writing Team as needed on issues that are relevant to the upper Connecticut River watershed.

Connecticut River Resources

Long Island Sound TMDL

Assessment of Total Nitrogen in the Upper Connecticut River Basin in New Hampshire, Vermont, and Massachusetts, December 2002-September 2005

Nitrogen Attenuation in the Connecticut River, northeastern USA; a comparison of mass balance and N2 production modeling approaches (abstract only)

An Evaluation of Potential Nitrogen Load Reductions to Long Island Sound from the Connecticut River Basin


For more information, contact Emily Bird, coordinator of our Long Island Sound TMDL workgroup.

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