Continental-scale Dissolved Inorganic Phosphorus Export by Rivers: Results from a Regional-Global Modeling Approach

In watersheds, spatial variation in nutrient sources and sinks results in spatial variability of nutrient export ratios and nutrient forms, with important implications for surface fresh water and estuarine ecosystem response. However, past attempts to model global and regional nutrient exports to the coastal zone in a spatially explicit manner have generally ignored within-basin spatial variation in nutrient sources and sinks. We describe, apply and evaluate a new continental-global scale model of dissolved inorganic phosphorus (DIP) transport by rivers called NEWS-DIP-0.5, based on a DIP export model developed by the Global NEWS (Global (N)utrient (E)xport from (W)ater(S)heds) work-group. This new model retains half-degree resolution of input variables in analysis and explicitly routes water and nutrients downstream through watersheds, accounting for both DIP sources and DIP sinks along major river systems. When NEWS-DIP-0.5-based predictions are compared to measurements from US rivers, the predictive capacity of this model is similar to previously developed, whole basin DIP export models, and does not exhibit detectable bias. Early results high rates of spatial variability with respect to DIP production and consumption and a significant role for reservoirs in storing and removing DIP as it flows across the landscape. In this poster we will focus on Global NEWS-0.5-based estimates of DIP sources and sinks and on how DIP dynamics vary by region and are influenced by human, edaphic, biotic, and climatic factors.