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Use of Output From the New England Sparrow Model to Estimate Concentrations of Total Nitrogen in Estuaries

Edward H. Dettmann 1, Richard B. Moore 2, Keith W. Robinson 2, Henry A. Walker 1, and Jaime B. Palter 3

1 U.S. Environmental Protection Agency (USEPA), ORD, National Health and Environmental Effects Research Laboratory, Atlantic Ecology Division, 27 Tarzwell Dr. Narragansett, Rhode Island 02882
2 U.S. Geological Survey (USGS), New Hampshire/Vermont District, 361 Commerce Way, Pembroke, New Hampshire 03275
3 Duke University, School of Environment and Earth Sciences, Division of Earth and Ocean Sciences
Durham, North Carolina 27705

The USGS's SPARROW Model is a statistical model with mechanistic features that has been used to calculate annual nutrient fluxes in nontidal streams nationally on the basis of nitrogen sources, landscape characteristics, and stream properties. This model has been useful for assessment of water quality in stream networks. In this study, we explore use of output from an application of this model to New England watersheds, with higher spatial resolution than in the national model, for assessment of concentrations of total nitrogen in estuaries receiving these stream fluxes. Output from the New England SPARROW Model, calibrated using estimates of nitrogen sources and measured river fluxes in the early 1990s, was used with supplemental data on discharges by wastewater treatment plants into tidal areas, estuary flushing times, and nitrogen concentrations at the seaward boundaries, as input to a USEPA model to calculate annual average concentrations of total nitrogen in three New England estuaries: Narragansett Bay, Boston Harbor, and the Piscataqua Estuary. This USEPA model calculates annual spatially-averaged concentrations of nitrogen in an estuary using the nitrogen loading rate from the watershed and atmosphere, estuary flushing time, and concentration of nitrogen at the seaward boundary. We describe previous tests of the EPA model, perform a limited validation of the results of this application with nitrogen fluxes calculated by the SPARROW model, and explore the utility of this methodology in wider assessment of estuarine water quality.

Keywords: land-estuary interaction, New England estuaries, total nitrogen, water quality assessment, watershed model

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