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Phosphorus Transport in Intensively Managed Watersheds
Dolph, Christine L. Boardman, Evelyn DaneshāYazdi, Mohammad Finlay, Jacques C. Hansen, Amy T. Baker, Anna C. Dalzell, Brent
Dolph, Christine L.
Boardman, Evelyn
DaneshāYazdi, Mohammad
Finlay, Jacques C.
Hansen, Amy T.
Baker, Anna C.
Dalzell, Brent
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Abstract
Understanding controls of P movement through watersheds are essential for improved landscape management in intensively managed regions. Here, we analyze observational data from 104 gaged river sites and 176 nongaged river sites within agriculturally dominated watersheds of Minnesota, USA, to understand the role of landscape features, land use practices, climate variability, and biogeochemical processes in total, dissolved and particulate P dynamics at daily to annual scales. Our analyses demonstrate that factors mediating P concentrationādischarge relationships varied greatly across watersheds and included nearāchannel sediment sources, lake and wetland interception, assimilation by algal P, and artificial land drainage. The majority of gaged sites exhibited mobilizing behavior for all forms of P at event (i.e., daily) timescales and chemostatic behavior at annual timescales. The large majority of watershed P export (>70%, on average) occurred during high flow conditions, suggesting that more frequent large storm events arising from climate change will drive increased P losses from agricultural watersheds without substantial management changes. We found that P export could be dominated by dissolved P, particulate P, or an even mix of the two forms, depending on watershed attributes. Implementation of management practices to control P losses must be guided by understanding of how local landscapes interact with current and future climate conditions. Managing for both dissolved and particulate P is required to reduce overall P load in many agricultural watersheds.
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An edited version of this paper was published by AGU. Copyright 2019 American Geophysical Union.
Date
2019-10-24
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American Geophysical Union
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Dolph, C. L., Boardman, E., DaneshāYazdi, M., Finlay, J. C., Hansen, A. T., Baker, A. C., & Dalzell, B. (2019). Phosphorus Transport in Intensively Managed Watersheds. Water Resources Research, 55, 9148ā 9172. https://doi.org/10.1029/2018WR024009