Date Awarded

2018

Document Type

Thesis

Degree Name

Master of Science (M.Sc.)

Department

Virginia Institute of Marine Science

Advisor

Mark J Brush

Committee Member

Iris C Anderson

Committee Member

Deborah A Bronk

Committee Member

Michael F Piehler

Abstract

Freshwater inflow influences numerous physical, chemical, and biological characteristics of estuaries. The influx of freshwater to an estuary typically serves as an important source of allochthonous material from which primary producers derive their energy and transfer this energy to higher trophic levels. Any changes to freshwater flow subsequently impacts nutrient delivery and indirectly impacts organisms across multiple trophic levels. Anthropogenic changes to coastal land use and climate both act to threaten the integrity of estuarine systems by influencing freshwater inflow and dissolved nutrient input. Watershed loading models such as the Regional Nutrient Management (ReNuMa) model offer the ability to estimate freshwater inputs and dissolved nutrient loads to estuaries under current and future conditions. This tracking is important because it allows scientists to better understand how watershed delivery is currently impacted by anthropogenic activities and natural environmental variability, which allows for a better understanding of how watershed delivery is likely to be affected by anthropogenic changes in land use and climate. This research aims to assess how changes in climate and coastal land cover will impact streamflow and loads of total dissolved nitrogen (TDN) and total dissolved phosphorus (TDP) to the New River Estuary (NRE), NC. We applied the ReNuMa model to the NRE watershed to estimate streamflow, TDN, and TDP loads. We used in situ data to calibrate (2009-2011) and validate (2012-2014) modeled streamflow and dissolved nutrient loads within 10 subwatersheds located on Marine Corps Base Camp Lejeune (MCBCL), which surrounds the estuary, and one subwatershed in the off-base portion of the NRE watershed. Following model calibration and validation, model parameters were scaled up from these subwatersheds to estimate loads from the entire NRE watershed. Model results confirm the ability of ReNuMa to capture seasonal variability in streamflow, TDN, and TDP for >50% of the subwatersheds. Under current conditions, most (71-98%) streamflow and dissolved nutrient loads are sourced from the off-base portion of the NRE watershed, while a smaller percentage of loads (2-29%) are sourced from MCBCL. Projected changes in climate revealed that changes in precipitation, even when compounded with changes in temperature, will have the greatest impact on resulting streamflow, TDN, and TDP. Streamflow and dissolved nutrient loads generally increased under anticipated climate projections through the year 2100 and such increases were further amplified under hypothetical increases in land use, especially agricultural land. Watershed delivery patterns for the NRE may therefore be substantially altered under projected changes in climate and land use. The potential impacts of changes in these loads on estuarine physical, chemical, and biological processes highlights the necessity for research assessing the impacts of land use and climate changes on watershed delivery.

DOI

http://dx.doi.org/10.25773/v5-3thg-cv39

Rights

© The Author

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