|Elliott, Herschel - Pennsylvania State University|
|Singha, Kamini - Colorado School Of Mines|
|Hamlett, James - Pennsylvania State University|
Submitted to: Journal of the American Water Resources Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2014
Publication Date: 7/14/2015
Citation: Williams, M.R., Buda, A.R., Elliott, H.A., Singha, K., Hamlett, J. 2015. Influence of riparian seepage zones on nitrate variability in two agricultural headwater streams. Journal of the American Water Resources Association. 51(4): 883-897. doi: 10.1111/1752-1688.12335.
Interpretive Summary: Groundwater seeps have long been suspected as an important source of nutrients to streams draining agricultural watersheds. We evaluated two small agricultural streams in central Pennsylvania to determine the effects of groundwater seeps on nitrate in stream water. Results showed that seeps exerted a strong influence on nitrate levels in streams, especially at lower flows. Findings indicate that groundwater seepage zones should receive priority consideration for best management practices that reduce nitrate pollution.
Technical Abstract: Riparian seepage zones are one of the primary pathways of groundwater transport to headwater streams. While seeps have been recognized for their contributions to streamflow, there is little information on how seeps affect stream water quality. The objective of this study was to examine the influence of seeps on stream nitrate-nitrogen (NO3-N) concentrations in FD36 and RS, two central Pennsylvania agricultural headwater catchments. From April 2009 to January 2012, stream water was sampled on 21 occasions (14 during base flow; 7 following storms) at 10-m intervals over stream reaches of 550 and 490 m in FD36 and RS, respectively. Nitrate concentrations in seep discharge were measured concurrent with stream water. Results showed NO3-N concentrations in stream segments with seeps increased, on average, by 0.25 mg L**-1, but declined by 0.02 mg L**-1 in stream segments with no seep inputs. The number of seep discharge locations was also positively correlated to spatial patterns observed in stream NO3-N concentration. Immediately following storm events, the influence of seeps on stream NO3-N concentration was less compared to base flow. One day after a summer storm in FD36, however, an increase in the number of seeps and decreasing stream discharge resulted in the greatest variability in stream NO3-N concentration recorded. Results showed that seeps are significant sources of NO3-N to the streams in FD36 and RS and play a key role in determining N fluxes from these catchments.