Quantifying Nitrogen Transport form Groundwater to a River in a Large Agricultural Watershed in NC Grant uri icon

abstract

  • As human population has grown and agricultural, commercial, and industrial activities have expanded in coastal watersheds, loading of anthropogenic wastes from localized (e.g., sewage, industrial effluent) and diffuse (e.g., agricultural run-off) sources to surface waters and groundwater have increased. Ultimately, these materials end up in coastal waters, where they cause eutrophication, the increase in labile organic matter supply to an ecosystem. Today, increases in the frequency of harmful algal blooms, water column hypoxia/anoxia, fish kills, and reduced water quality are clear signs of eutrophication in the coastal zone. Understanding the response of the coastal ecosystem to eutrophication is one of the most important research challenges facing marine scientists today. Many factors, including land use (natural vs. developed, e.g., residential, agricultural or commercial), soil type and erosion rate, influence water quality. To date, the scientific effort has focused largely on documenting the composition and, flow of surface waters (e.g., rivers, streams), the most conspicuous component of the hydrologic cycle. However, predicting the response of coastal ecosystems to land use change and eutrophication requires robust models that include all relevant sources of nutrients and organic materials. Among these, groundwater is an important, but poorly understood, source of nutrients and organics to coastal waters. Groundwater-derived fluxes need to be quantified, particularly in Southeastern U.S., coastal systems where such data are rare. The lack of information regarding groundwater flux and groundwater quality in coastal systems makes it impossible to predict how the quality (chemistry) or quantity (freshwater flux) of this "input" or "source term" will respond to increased development pressures in coastal regions. This study will quantify the groundwater and groundwater-borne nitrogen input to the Neuse River associated with land-use variations. We will address several research questions including: 1. What are spatial/temporal dynamics of gw discharge, and gw-based N discharge, to Neuse river and estuary? 2. What proportion of N inflow to the Neuse estuary is derived from gw discharge in agricultural areas of the watershed (i.e., the Coastal Plain)? 3. What are the proportions of N flux accounted for by different species (nitrate, ammonia, DON)? 4. How does the gw-based N flux compare to that from atmospheric deposition?

date/time interval

  • September 2003 - August 2007