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MODELING THE DISTRIBUTION OF NONPOINT NITROGEN SOURCES AND SINKS IN THE NEUSE RIVER BASIN OF NORTH CAROLINA, USA
Citation:
Lunetta, R S., R. G. Greene, AND J G. Lyon. MODELING THE DISTRIBUTION OF NONPOINT NITROGEN SOURCES AND SINKS IN THE NEUSE RIVER BASIN OF NORTH CAROLINA, USA. SOIL AND SEDIMENT CONTAMINATION: AN INTERNATIONAL JOURNAL 41(5):1129-1147, (2005).
Impact/Purpose:
Our research objectives are to: (a) develop new methods using satellite remote sensor data for the rapid characterization of LC condition and change at regional to national scales; (b) evaluate the utility of the new NASA-EOS MODIS (Moderate Resolution Imaging Spectrometer) leaf area index (LAI) measurements for regional scale application with landscape process models (e.g., biogenic emissions and atmospheric deposition); (c) provide remote sensor derived measurement data to advance the development of the next generation of distributed landscape process-based models to provide a predictive modeling capability for important ecosystem processes (e.g., nutrients, sedimentation, pathogens, etc.); and (d) integrate in situ monitoring measurement networks with UAV and satellite based remote sensor data to provide a continuous environmental monitoring capability.
Description:
This study quantified nonpoint nitrogen (N) sources and sinks across the 14,582 km2 Neuse River Basin (NRB) located in North Carolina, to provide a tabular database to initialize in-stream N decay models and graphic overlay products for the development of management approaches to best achieve established N reduction goals. Modeling efforts included the development of a remote sensing derived land-cover classification to identify individual landscape modeling elements, followed by mass-balance modeling to quantify potential sources of excess N, and precipitation event driven hydrologic modeling to effectively transport N to individual stream reaches with subsequent labeling of transported N values corresponding to source origin. Results indicated that agricultural land contributed 55.3% of the total annual NPS-N loadings, followed by forested land at 23.0% (background), and urban areas at 20.9%. Average annual N source contributions were quantified for agricultural (1.4 kg/ha), urban (1.2 kg/ha) and forested cover types (0.5 kg/ha). NPS-N source contributions were greatest during the winter (39.8%), followed by spring (31.7%), summer (28.2%), and fall (0.3%).
Seasonal total N loadings shifted from urban and forest dominated sources during the winter, to agricultural sources in the spring and summer. A quantitative assessment of the significant NRB land-use activities indicated that high and medium density urban development (>35% 1 impervious) were the greatest contributor on NPS- N on a unit area basis (1.9 and 1.6 kg/ha/yr, respectively), followed by row crops and pasture and hay agricultural cover types (1.4 kg/ha/yr).