Date of Award
Master of Science (MS)
Laura K. Lautz
Hydrology, Nitrogen, Urban Streams
Physical Sciences and Mathematics
Urbanization negatively impacts water quality in streams by reducing stream-groundwater interactions, which reduces the stream’s ability to naturally attenuate nitrate. Meadowbrook Creek, a first order urban stream in Syracuse, New York, has a negative urbanization gradient that results in urbanized headwaters that are disconnected from the floodplain, and downstream reaches that have intact riparian floodplains and connection to riparian aquifers. This system allows us to assess how stream-aquifer interactions in urban streams impact the net sources and sinks of nitrate at the reach scale. We used continuous (15-minute) streamflow measurements, along with weekly grab samples at three gauging stations positioned longitudinally along the creek to develop continuous nitrate load estimates at the inlet and outlet of two contrasting reaches. Nitrate load estimates were determined using a USGS linear regression model, RLOADEST, and differences between loads at the inlet and outlet of contrasting reaches were used to quantify nitrate sink and source behavior year-round. In water year 2018, the outlet of the disconnected reach exported 13.1 x 105 kg NO3-, while nitrate export at the outlet of the connected reach in the same year was 9.8 x 105 kg NO3-. We found the hydrologically disconnected reach was a net source of nitrate regardless of season and stream-groundwater exchange allowed the hydrologically connected reach to be both a source and sink. Both reaches alter nitrate source and sink behavior at various spatiotemporal scales. Groundwater connection in urban streams reduces annual nitrate loads and provides more opportunities for sources and sinks of nitrate year-round than hydrologically disconnected streams, including groundwater discharge into the stream with variable nitrate concentrations, surface-water groundwater interactions that foster denitrification, and stream load loss to surrounding near-stream aquifers. This study empathizes how loads are important in understanding how stream-groundwater interactions impact reach scale nitrate export in urban streams.
Beltran, Julio I., "The impact of stream-groundwater exchange on seasonal nitrate loads in an urban stream" (2020). Theses - ALL. 424.