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Fluxes of nutrients, carbon, sediment, and water in large watersheds and regions

Led largely by Dennis Swaney and Bongghi Hong, the lab has a major emphasis on modeling at the scale of large watersheds and regions, using both statistically based models such as NANI and mechanistically based models such as ReNuMa.


ReNuMa is a large-watershed-scale model based on the Generalized Watershed Loading Function model (Haith and Shoemaker, 1987) which allows planners and other stakeholders to explore scenarios for reducing nitrogen fluxes from the landscape. Unlike previous models, ReNuMa allows for biogeochemical parameters such as denitrification or within-soil, riparian-zone, and in-stream processes and explicitedly considers atmospheric nitrogen inputs NOx, NHx).


NANI, originally developed as part of the International Scientific Committee on Problems of the Environment (SCOPE) Nitrogen Project, is a mass balance approach used to analyze the relative contribution of various nitrogen(N) sources and sectors to riverine N fluxes. We have applied NANI at various spatial scale ranging from individual watersheds to large (to 4,000,000 km2) regions and found that NANI is well correlated to the average N flux in rivers. Our latest model, which considers precipitation and river discharge, estimates N fluxes with an 89% accuracy.

Other modeling efforts

The Howarth-Marino lab has also worked on other models, including a simulation model of how ecological and biogeochemical controls interact to control nitrogen fixation in aquatic ecosystems, empirical models of the exchange of oxygen between aquatic ecosystems and the atmosphere ecosystems, and a detailed hydrodynamic model of an estuary.