HAPpy Hour Seminar - Modeling of riverine transport and reaction of anthropogenic nitrate in the Great Lakes Basin

Nitrogen (N) cycle has been transformed by agriculture and urban developments over the past decade, but has received less attention from the Earth system modeling community compared to carbon and water cycles. Anthropogenic disturbances of the N cycle include N leaching from agricultural drainage which ends up in rivers, disrupting downstream N balance. Since our knowledge of riverine nitrogen budgets is limited due to the paucity of in situ measurements, there is a pressing need for improved modeling of N transport and transformation using land surface models. This study presents first-order estimates of large-scale stream nitrate reaction and transport by implementing a nitrogen routing scheme in the Model for Scale Adaptive River Transport (MOSART) coupled with the Community Land Model (CLM5). The new scheme numerically solves the one-dimensional advection-diffusion-Reaction equation for explicitly resolving basin-scale nitrate concentration. Simulations are set up over the Great Lakes Basin (GLB) at 2 arc-min (∼3.5 km) land resolution and 1/8th degree (~12 km) river routing resolution, forced by the NLDAS-II meteorological data. Industrial and manure fertilizer applications are prescribed by crop functional types based on two datasets and four scenarios. The study opens up new opportunities for improved understanding of large-scale nitrogen transport modeling.