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Relative Sensitivity of Simulated Nitrogen Discharge to Projected Changes in Climate and Land Cover for Two Watersheds in North Carolina, USA
Citation:
Gabriel, M., Chris Knightes, E. Cooter, AND R. Dennis. Relative Sensitivity of Simulated Nitrogen Discharge to Projected Changes in Climate and Land Cover for Two Watersheds in North Carolina, USA. Presented at AGU Fall Meeting 2013, San Francisco, CA, December 09 - 13, 2013.
Impact/Purpose:
Poster presented at the 2013 AGU Fall Conference
Description:
We investigated the effects of projected changes in land cover and climate (precipitation, temperature and atmospheric carbon dioxide [CO2] concentrations) on simulated nitrate (NO3) and organic nitrogen (ORGN) discharge for two watersheds within the Neuse River Basin, NC for years 2010 to 2070. We applied the Soil and Water Assessment Tool (SWAT) watershed model to predict future nitrogen discharge using (1) atmospheric CO2 concentrations from the International Panel on Climate Change (IPCC), (2) land cover change predictions from the Integrated Climate and Land Use Change (ICLUS) project and (3) estimates for precipitation and temperature from two statistically downscaled and bias-corrected Global Circulation Models (GCMs). Our primary intent was to determine the sensitivity of simulated nitrogen discharge to separate changes in each treatment ([1] land cover, [2] precipitation + temperature (P+T), and [3] CO2) by comparing each treatment to a reference condition. Results showed nitrogen discharges (NO3 and ORGN) were most sensitive to changes in P+T over the 60-year simulation. Nitrogen discharges had similar sensitivities to the CO2 and land cover treatments which were only one-tenth the influence of the P+T treatment. Under the CO2 treatment, NO3 and ORGN discharges increased with increasing ambient CO2. NO3 discharge decreased with increased urbanization; however, ORGN had a varied response. Under the P+T treatment, there was high spatio-temporal variability in nitrogen discharges because of P+T’s intense effect on nitrogen discharges. In a single year, certain sub-basins showed an 80% increase in nitrogen discharge relative to reference, while others showed a 400% decrease. With nitrogen discharge showing high sensitivity to P+T change, we suggest more emphasis should be placed on investigating impacts of climate change on nutrient transport compared to land cover change in the Neuse River Basin.
