Concentrations and Estimated Loads of Nitrogen Contributed by Two Adjacent Wetland Streams with Different Flow-Source Terms in Watkinsville, Ga.

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 efficacy of wetlands to immobilize or reduce nitrate depends on several interacting local conditions that are not well understood. Two adjacent streams (14 m apart at source) draining a wetland depression have partly different flow-source terms. One has a flowing spring at its head-cut, and is protected by surface runoff by a man-made berm. The other accepts run-off from the upland pasture and does not have a conspicuous spring. The lower discharge and higher organic substrate, residence times and water/sediment contact all apparently contribute to the lower nitrate loads from the runoff stream.