Application of Watershed Scale Models to Predict Nitrogen Loading From Coastal Plain Watersheds
DRAINMOD-based watershed models have been developed and tested using data collected from an intensively instrumented research site on Kendricks Creek watershed near Plymouth. NC. These models were applied to simulate the hydrology and nitrate nitrogen (NO3-N) loading from two other watersheds in the Coastal Plain of North Carolina, the 11600 ha Chicod Creek watershed and the 8300 ha Upper Broad Creek watershed. GIS databases were compiled that include the existing land use/land cover, hydrography, soils series, digital elevation models, and digital orthophoto quarter quadrangles for each watershed. The resulting databases were used as input for process-based models (DRAINMOD-DUFLOW) that predicted the hydrology of the watersheds in their existing state of land use and management practices. These simulations characterized the hydraulics and hydrology of the watersheds, and generated inputs to a simpler GIS-based lumped parameter model that predict NO3-N loads at the outlets of the watersheds. The GIS-based lumped parameter models were then used to make long-term (30-35 year) simulations of the watersheds in their current states of land use and management practices. Predicted mean annual NO3-N load delivered at the watershed outlets and the delivery ratios of NO3-N from each field that arrived at the watershed outlets are analyzed and compared for the three watersheds.