Riparian Buffer Landscape Effects on Groundwater Flow Paths and Nitrate Occurrences in Groundwater near Streams of the Eastern Shore of Virginia

Abstract

Elevated concentrations of nitrate occur in groundwater throughout the United States due to the widespread application of nitrogenous fertilizers associated with agricultural land uses. Forested stream buffers, which separate upland agricultural areas from stream channels, are recognized for their importance as locations of groundwater nitrate removal through plant uptake and denitrification. An understanding of the groundwater hydrology of the buffer subsurface is important in being able to predict where denitrification can occur, since the groundwater hydrology determines the locations in which groundwater with elevated nitrate will intercept available supplies of organic matter. Previous studies have identified differences in the pattern of groundwater flow through riparian floodplains within stream buffers, which was related to differences in their ability to remove nitrate by denitrification. In this study, the effect of forested

Streambed Sediments of Virginia Eastern Shore Streams Are Poised for Pore-Water Denitrification

“…The homogeneity of grain--size analysis results was reflected in the narrow range of K values among streams, which only spanned three orders of magnitude. In this study, the mean K of Coal Kiln sediments was 6.23 x 10 --4 cm s --1 , which falls between the results of two slug tests at Coal Kiln by Probasco [2010] of of 7.4 x 10 --5 and 2.6 x 10 --3 cm s --1 . A mean K of 1.7 x 10 --3 cm s --1 from falling head measurements on an intact core extracted from Cobb Mill Creek on the VAES [Gu, 2007], was one order of magnitude greater than the mean K of 8.39 x 10 --4 cm s --1 from all samples of the four streams sampled here.…”