Title: Development and testing of an in-stream phosphorus cycling model for the Soil and Water Assessment Tool Authors
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 2, 2012
Publication Date: December 5, 2011
Citation: White, M.J., Storm, D.E., Mittelstet, A., Busteed, P.R., Haggard, B.E., Rossi, C.G. 2011. Development and testing of an in-stream phosphorus cycling model for the Soil and Water Assessment Tool. Journal of Environmental Quality. doi:10.2134/jeq2011.0348. Interpretive Summary: The Soil and Water Assessment Tool (SWAT) is widely used to predict the phosphorus concentration in streams and rivers. However, the current instream P model may not be suitable for many stream systems. We developed an alternative model and applied it to the Illinois River Watershed in Oklahoma. The model predicted the gradual storage of phosphorus in streambed sediments and flushing of this phosphorus during periodic flooding events. Waste water treatment plants were predicted to have a profound effect on phosphorus dynamics in the Illinois River due to their constant contribution even under low flow conditions.
Technical Abstract: The Soil and Water Assessment Tool (SWAT) is widely used to predict the fate and transport of phosphorus (P) from the landscape through streams and rivers. However, the current instream P model may not be suitable for many stream systems, particularly those dominated by attached algae and impacted by point sources. In this research, we developed an alternative model based on the Equilibrium P Concentration (EPC) concept coupled with a particulate scour and deposition model. This model was applied to the Illinois River Watershed in Oklahoma, a basin influenced by waste water treatment plant (WWTP) discharges and extensive poultry litter application. The model was calibrated and validated using measured data. Highly variable instream P concentrations and EPC values were predicted both spatially and temporally. The model also predicted the gradual storage of P in streambed sediments and the resuspension of this P during periodic high flow flushing events. WWTPs were predicted to have a profound effect on P dynamics in the Illinois River due to their constant discharge even under base flow conditions. A better understanding of P dynamics in stream systems using the revised model may lead to the development of more effective mitigation strategies to control the impact of P from both point and nonpoint sources.