Linking terrestrial P inputs to riverine export across the United States
Citation:
Metson, G., J. Lin, J. Harrison, AND J. Compton. Linking terrestrial P inputs to riverine export across the United States. American Society of Limnology and Oceanography, Honolulu, Hawaii, February 27 - March 03, 2017.
Impact/Purpose:
Human activities have greatly increased the movement of phosphorus (P) from land to aquatic ecosystems, often resulting in water quality problems that impacts human health, the economy and ecosystems. There has been a great deal of research conducted on phosphorus inputs and cycling, but there are a number of gaps in our understanding of how natural and anthropogenic landscape characteristics mediate losses of P from watersheds. National Research Council post-doctoral associates Genevieve Metson and Jiajia Lin tackle this question for the US, along with John Harrison of Washington State University and Jana Compton of EPA-WED. They produced maps of terrestrial P inputs and outputs (fertilizer, confined manure, crop harvest and sewage) across the continental U.S. for 2012, and then examined how these P inputs, along with climate, hydrology, and land use, influenced P exports from 72 watersheds across the US. Their analysis was able to explain more than 56% of the variance in any of the water quality variables (TP fractional export vs P manure inputs). The lack of clear and strong relationships between contemporary, high-resolution, anthropogenic, terrestrial P and riverine P export at the national scale highlights the fact that a complex suite of factors mediates P export and that further investigation, including the potential importance of soil P legacies, is needed. This presentation contributes to SHC 4.61.
Description:
Human beings have greatly accelerated phosphorus (P) flows from land to aquatic ecosystems, often resulting in eutrophication, harmful algal blooms, and hypoxia. Although a variety of statistical and mechanistic models have been used to explore the relationship between terrestrial nutrient management and losses to waterways, our understanding of how natural and anthropogenic landscape characteristics mediate losses of P from watersheds lags behind that of nitrogen. The need for higher resolution data is often identified as an important barrier that limits our capacity to predict P loading. In order to address this gap, we constructed spatially explicit datasets of terrestrial P inputs and outputs (fertilizer, confined manure, crop harvest and sewage) across the continental U.S. for 2012. We then examined how these P sources, along with climate, hydrology, and land use, influenced P exports from 72 watersheds as total P (TP) and dissolved inorganic P (DIP) concentrations and yields, and TP fractional export. TP and DIP concentrations and TP yields were best correlated with runoff, but using simple linear regression, we were not able to explain more than 56% of the variance in any of the water quality variables (TP fractional export vs P manure inputs). The lack of clear and strong relationships between contemporary, high-resolution, anthropogenic, terrestrial P and riverine P export at the national scale highlights the fact that a complex suite of factors mediates P export and that further investigation, including the potential importance of soil P legacies, is needed.