Impact of flow pathway and source water connectivity on subsurface sediment and particulate phosphorus dynamics in tile-drained agroecosystems

Authors: NAZARI, SAEID - University Of Kentucky; FORD, W - University Of Kentucky; King, Kevin

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2022
Publication Date: 4/14/2022
Citation: Nazari, S., Ford, W.L., King, K.W. 2022. Impact of flow pathway and source water connectivity on subsurface sediment and particulate phosphorus dynamics in tile-drained agroecosystems. Agricultural Water Management. 269. Article #107641. https://doi.org/10.1016/j.agwat.2022.107641.
DOI: https://doi.org/10.1016/j.agwat.2022.107641

Interpretive Summary: Tile drainage is required for viable production agriculture in poorly-drained humid regions of the world, but has been identified as a significant transport pathway for sediment and sediment bound phosphorus. A newly developed hydrograph analyses technique and fifteen months of high resolution data from a tile-drained edge-of-field site located in northwest Ohio was used to show that quick-flow of rainfall event water had the greatest sediment concentrations in tile discharge and was the primary source connectivity throughout the period of record; the exception being quick-old water following tillage and cover crop planting. These findings will help to improve prediction technologies and highlight the need to reduce preferential flow as a means to reduce sediment and sediment bound phosphorus transport in tile drainage.

Technical Abstract: Tile drainage is recognized as a significant transport pathway for sediment and particulate phosphorus (P) in the midwestern U.S. However, the role of subsurface flow pathway and source connectivity dynamics on sediment transport is poorly understood. In this study, we used a recently developed framework that couples event-based hydrograph recession and specific conductance-end-member mixing analysis (SCEMMA) to assess governing drivers of sediment transport through tile. We collected high-frequency specific conductance, turbidity, and tile discharge data from an edge-of-field (EOF) tile main located in northwestern Ohio for 15 months. Multiple linear regression (MLR) analysis and hysteresis analysis was employed to evaluate the impact of pathway-connectivity dynamics on flow-weighted mean Total suspended solid (TSS) concentrations. The MLR analysis showed that quickflow of new water (Quick-new) had the highest flow-weighted mean sediment concentrations, and that concentrations associated with quickflow of old water (i.e., matrix-macropore exchange) were variable. Analysis using the hysteresis index (HI) showed that hysteresis characteristics (magnitude and direction) for separated hydrographs using the pathway-connectivity framework deviated from HI values of total tile discharge (Qtile) and highlighted the importance of Quick-new through much of the monitoring period. However, Qquick-old was found to be the primary driver of sediment loadings immediately following tillage and cover crop applications, resulting in reduced sediment loadings. The findings suggest that reducing preferential transport of new water may be an effective strategy for reducing sediment and particulate P loadings at the edge-of-field.