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Identifying Riparian Buffer Effects on Stream 1 Nitrogen in Southeastern Coastal Plain Watersheds
Citation:
CHRISTENSEN, J., M. S. NASH, AND A. C. NEALE. Identifying Riparian Buffer Effects on Stream 1 Nitrogen in Southeastern Coastal Plain Watersheds. ENVIRONMENTAL MANAGEMENT. Springer-Verlag, New York, NY, 52(5):1161-1176, (2013).
Impact/Purpose:
Poor water quality due to nutrient enrichment is a major environmental concern across the United States. Increased levels of nitrate in drinking water can lead to human health problems including ethemoglobinemia (Blue Baby Syndrome; Ward et al. 2005). The eutrophication of lakes, rivers, and estuaries can produce harmful and nuisance algal blooms, increase hypoxia and fish kills, and shift species compositions (Turner and Rabalis, 1991; Vitousek et al., 1997; National Research Council, 2000).
Description:
Riparian areas have long demonstrated their ability to attenuate nutrients and sediments from agricultural runoff at the field scale; however, to inform effective nutrient management choices, the impact of riparian buffers on water quality services must be assessed at watershed scales. In this study, GIS derived flow-path riparian metrics are compared with general watershed land use/land cover (LULC) metrics and riparian LULC metrics in selected watersheds from the Southeastern Coastal Plain for their ability to predict average concentrations and annual yields of total nitrogen and total phosphorus. LULC metrics were calculated for entire watersheds as well as for headwater catchments. Metrics related to point sources, confined animal feeding operations (CAFOs), subsurface flows, atmospheric deposition, and artificial agricultural drainage were also included in the analysis. Multiple regression and partial least squares analyses were used to relate metrics to water quality parameters. Flow-path riparian metrics modestly increased explanatory power for nitrogen concentrations and yields and appear to better characterize spatial interactions and nitrogen processes across the landscape. Metrics for the headwater catchments generally outperformed entire-watershed metrics for nitrogen concentrations. Total phosphorus concentrations and yields were not explained by flow-path riparian metrics and were related only to percent agriculture and CAFOs. The proxy for artificial agricultural drainage was a significant predictor for nitrogen parameters which illustrates the need to better quantify artificial agricultural drainage at the watershed scale. Further efforts with flow-path riparian metrics could incorporate known influences such as subsurface flows or artificial drainage on riparian buffers.