Citation:

Sabo, R., B. Pickard, J. Lin, B. Washington, C. Clark, J. Compton, M. Pennino, B. Bierwagen, S. Leduc, J. Carleton, M. Weber, M. Fry, R. Hill, S. Paulsen, A. Herlihy, AND J. Stoddard. Comparing Drivers of Spatial Variability in U.S. Lake and Stream Phosphorus Concentrations. Journal of Geophysical Research: Biogeosciences. American Geophysical Union, Washington, DC, 128(8):1-17, (2023). https://doi.org/10.1029/2022JG007227

Impact/Purpose:

Multiple lines of statistical evidence highlight impacts of contemporary and historical agricultural practices on surface water total phosphorus concentrations across the United States as well as other emerging environmental threats to water quality. These statistical inferences and the spatially explicit maps of contemporary inputs, P surplus, weather, and watershed characteristics available in the publicly available datasets used in this effort can help guide watershed managers on where and how to implement watershed restoration plans and anticipate future challenges in the Anthropocene.

Description:

Decision makers need to know the drivers of surface water phosphorus (P) concentrations, the environmental factors that mediate P loading in freshwater systems, and where pollution sources and mediating factors are co-located. Publicly available spatial datasets of P pollution sources and relevant environmental variables, like temperature, precipitation, and agricultural soil erodibility, were matched with >7,000 stream and lake total P observations throughout the conterminous United States. Using an ensemble of statistical approaches, 1) correlation, 2) regression, and 3) machine learning, we identified likely drivers of P concentrations and provide a semi-quantitative summary our findings. Surface water concentrations in streams may be more immediately responsive to improvements in agricultural nutrient management, whereas lake concentrations may be more influenced by historic erosional inputs and environmental factors. Both stream and lake P concentrations will potentially increase because of warming temperatures and deacidification. The identified spatial datasets and relationships elucidated in this effort can inform the placement and development of watershed restoration strategies to reduce excess P in aquatic systems.

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