Transport and Transformations of Nitrogen in Groundwater Seeps along the Stream Corridor of an Agricultural Watershed

Track 1C: Insights into Groundwater
Thursday, October 12, 2017, 12:40 pm – 1:50 pm

Brian Redder
Ph.D. Candidate in Soil Science and Biogeochemistry
Penn State University

Nitrogen (N) pollution is a growing environmental concern due to potential health effects, contributions to climate change, and negative impacts on aquatic ecosystems. Areas of the northeastern United States have elevated N levels in groundwater that migrate to surface waters. Here, we quantify nitrogen inputs via groundwater seeps to an agricultural watershed in headwaters of the Chesapeake Bay. We estimated the amount of nitrogen entering a 175 m stream reach during recharge periods via streambed diffuse seepage and point-source seeps. Seeps where groundwater emerges were located using thermal imaging. In-stream piezometers provided streambed water samples and head gradient measurements to determine gains and losses of N. Preliminary results show that at the start of the recharge period, the stream lost 0.2 m3 water/day and 0.0042 kg N/day; and as much as 116 m3/day and 2.05 kg N/day enters via riparian seeps. Further observations provided information on how the stream reacts as it recovers from an uncharacteristic drought. Groundwater seeps, which can deliver disproportionate loads of N to streamflow, should be targeted in restoration of nutrient polluted stream corridors.