MODELING FUTURE NITROGEN DYNAMICS IN CHESAPEAKE BAY HEADWATERS

Widespread agricultural growth has altered global nutrient cycles and may continue to do so over coming centuries, as agricultural practices are projected to increase to meet population demands into the 21^st century. To understand the potential impacts of agricultural expansion in the Eastern U.S., we simulate nitrogen fluxes using the INtegrated CAtchment (INCA) model in the Tioughnioga River in upstate New York, a headwater catchment to the Upper Susquehanna River Basin and Chesapeake Bay. As a headwater system, this catchment provides a unique opportunity to model the potential impacts that future changes in agricultural practices may have on nutrient fluxes, and thus the eutrophication of Chesapeake Bay. Nitrogen inputs to the model included fertilizer application, animal waste, treated effluent, and atmospheric wet/dry deposition. The model was calibrated from 2012-2016 to simulate streamflow and nitrate (NO₃-N) concentrations. Model scenarios were run over a baseline period (1961-1990), and three future periods (2010-2039, 2040-2069, and 2070-2099). We incorporated several global climate models and fertilizer application scenarios to simulate a range of plausible future outcomes. Our results indicate that changing climate may significantly alter nutrient cycles in northern headwater catchments. This information is relevant to land use managers and state and municipal regulatory agencies when considering the expansion of agricultural operations in headwater catchments that drain to affected waters.