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Integration of National Coastal Assessment Data, Freshwater Nutrient (SPARROW) Modeling and Estuary Nutrient Mass Balance Calculations: An Example from Narragansett Bay

Richard B. Moore 1, Henry A. Walker 2 and Edward H. Dettmann 2

1 U.S. Geological Survey, NH-VT Water Science Center, Pembroke, New Hampshire
2 U.S. Environmental Protection Agency, ORD, National Health and Environmental Effects Research Laboratory, Atlantic Ecology Division, Narragansett, Rhode Island

A variety of data sources have been used to perform an assessment of water quality conditions in Narragansett Bay and support recent management decisions to reduce nutrient loadings to the Bay. These sources include probability survey data from estuaries, water and nutrient flux measurements from fixed stations in streams, measurements in estuaries from moored instrumentation, estuarine nitrogen mass balance calculations, and the New England SPARROW (SPAtially Referenced Regressions On Watershed Attributes) nitrogen model.

The National Coastal Assessment survey data document an area of poor biotic conditions in upper Narragansett Bay, while moored instrumentation in the upper Bay documents transient acute low DO levels. Estuarine nitrogen mass balance calculations identify nitrogen as the cause of the poor conditions, while the New England SPARROW model provides estimates of the sources of these nitrogen loadings to the Bay by upstream freshwater sources and from atmospheric deposition.

Updated SPARROW models are being developed by the National Water Quality Assessment (NAWQA) program of the USGS and will cover most areas of the U.S. These updated models and the integrated approach we describe for Narragansett Bay, should have utility in managing nutrient loadings in other estuaries, and serve as a prototype for how coastal assessments could be performed under the National Water Quality Monitoring Network (NWQMN) for U.S. Coastal waters and their tributaries.

Keywords: National Water Quality Monitoring Network, SPARROW Model, National Coastal Assessment, mass balance model, nutrients, Narragansett Bay

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