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Galen Richards Master’s Thesis Defense

Nitrate Dynamics and Source within Nested Watersheds of an Agricultural Stream, Nebraska, USA

Date: Time: 9:00 am ID: 986 4824 7626
Contact: Troy Gilmore, (402) 470-1741,
Bazile Creek lies within the Bazile Groundwater Management Area, characterized by high (>10 mg/L) groundwater nitrate concentrations originating from nonpoint sources. The purpose of the research was to determine how nitrate concentrations and source in Bazile Creek vary throughout the watershed and over time. Surface water nitrate samples were collected monthly from July 2018 through September 2019, and ?15N/?18O nitrate isotope samples were collected seasonally and after three summer rain events. Surface water nitrate concentrations varied seasonally in the main channel and most tributaries, with nitrate concentrations being highest in the winter. Analysis of soils and land use indicated that nitrate was leaching from fields into the underlying aquifer, eventually entering streams as groundwater discharge. Seasonal and rain event nitrate isotope sampling showed that the primary nitrate source was ammonium from fertilizer, and evidence of seasonal microbial denitrification was also detected. The results of this research showed that surface water nitrate concentrations in an agricultural watershed can vary substantially over small distances, and that sub-watershed scale factors such as land use play a role in dictating surface water nitrate concentrations. The collection of nitrate isotope samples was shown to be beneficial, providing insight on source and seasonal denitrification. This research will provide data for future projects in the area, and ultimately aid in the development of targeted best management practices tasked with reducing overall nitrate loading to Bazile Creek

Additional Public Info:
ID: 986 4824 7626

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This event originated in Biological Systems Engineering.