Fluxed of fixed nitrogen species contributed by two adjacent wetland streams with different flow-source terms in Watkinsville, GA

Authors: SCHROER, K - UGA; Endale, Dinku; TEBES-STEVENS, C - USEPA; WASHINGTON, J - USEPA; NZENGUNG, V - UGA

Submitted to: Georgia Water Resources Conference
Publication Type: Proceedings
Publication Acceptance Date: 2/28/2007
Publication Date: 3/27/2007
Citation: Schroer, K.L., Endale, D.M., Tebes-Stevens, C., Washington, J.W., Nzengung, V. 2007. Fluxed of fixed nitrogen species contributed by two adjacent wetland streams with different flow-source terms in Watkinsville, GA. Georgia Water Resources Conference 2007, March 27-29, 2007, University of Georgia, Athens, Georgia.

Interpretive Summary: Agriculture is the largest single releaser of various forms of nitrogen into surface and subsurface waters. Nitrogen over-enrichment has been implicated as causing eutrophication in 60% of U.S. coastal rivers and bays. The hypoxia problem in the Gulf of Mexico that negatively impacts marine environment disrupting the fishing industry can extend to as large as 7700 square miles, and is fueled by discharge each year of about 1.8 million tons of nitrogen, mostly from agriculture, from the lower Mississippi/Atchafalaya River Basin. Most of the excess nitrogen flows from head waters and small streams draining agricultural catchments. To develop and/or refine management practices that mitigate the problem, we need to understand nitrogen processes in these small streams close to agricultural catchments. A collaborative study by scientists from the USDA-Agricultural Research Service, University of Georgia, and USEPA is studying this process in a small wetland serving as outlet for a 20-acre pasture near Watkinsville, GA. The scientists found that the concentrations of some forms of nitrogen, including nitrate (which is of concern in drinking water), were higher in a stream originating from a weak spring than from another nearby stream whose source was a large spring with a greater discharge rate. Local, state, federal and civic organizations responsible for monitoring and improving water quality can use this information to better design and manage improved wetlands that reduce nitrogen in ground and surface waters nationwide.

Technical Abstract: Inorganic, fixed nitrogen from agricultural settings often is introduced to first-order streams via surface runoff and shallow ground-water flow. Best management practices for limiting the flux of fixed N to surface waters often include buffers such as wetlands. However, the efficiency of wetlands to immobilize or reduce nitrate depends on several interacting local conditions that are not well understood. This research is part of a larger study in which in-stream processes are being evaluated to account for N loss along each of two adjacent spring-fed channels traversing through a small wetland at the outlet of a 10-ha pasture near Watkinsville, GA. Quantifying the individual nitrogen species and total N loadings contributed by each of the two channels will shade light on the importance of specific wetland hydrological and geochemical conditions to delivery of fixed N from agricultural settings to receiving waters.