Flowpathways and source water connectivity dynamics are widely recognized to affect tile-drainage water quality. In this study, we developed and evaluated a framework that couples event-based hydrograph recession and specific conductance end-member mixing analysis (SC-EMMA) to provide a more robust framework for quantifying both flow pathway dynamics and source connectivity of drainage water in tile-drained landscapes. High-frequency (30-min) flow and conductivity data were collected from an edge-of-field tile main located in northwestern Ohio, and the newly developed framework was applied for data collected in water year 2019. Multiple linear regression (MLR) analysis was used to evaluate the impact of pathway-connectivity dynamics on flow-weighted mean dissolved reactive P (DRP) concentrations, which were collected as part of the USDA-ARS edge-of-field monitoring network. The hydrograph recession and SC-EMMA results highlighted intra- and interevent differences between quick (preferential) flow and new (precipitation) water transported during events, challenging a common assumption that new water reflects drainage through preferential flow paths. The analysis of hydrologic flow pathways demonstrated matrix–macropore exchange (Qquick-old), preferential flow of new water (Qquick-new), slow flow of old water (Qslow-old), and slow flow of new water (Qslow-new) contributed 9, 39, 42, and 10% to tile discharge, on average, with interevent variability. Matrix water that is transported to tile drains via macropore flowpaths was found to be activated throughout the year, even under drier antecedent conditions, suggesting that matrix–macropore exchange was more sensitive to within-event hydrological processes as compared with antecedent conditions. The MLR results highlighted that pathway-connectivity hydrograph fractions improved prediction of DRP concentrations, although improvement may be more pronounced in landscapes with higher rates of matrix–macropore exchange.
|Journal||Vadose Zone Journal|
|State||Published - Sep 1 2021|
Bibliographical noteFunding Information:
The authors would like to thank three anonymous reviewers for their comments and suggestions, which greatly improved the quality of the manuscript. The authors thank the landowners of the study sites who provided access to the field and management data; Jedediah Stinner, Katie Rumora, Marie Pollock, Phil Levison, Sara Henderson, and Christian Bower for help in data collection and site maintenance; and Eric Fischer, Katie Emmett, and Whitney Phelps for laboratory analysis of water samples. Current funding for the USDA‐ARS edge‐of‐field research network is in part through the NRCS Conservation Effects Assessment Project (CEAP).
© 2021 The Authors. Vadose Zone Journal published by Wiley Periodicals LLC on behalf of Soil Science Society of America
ASJC Scopus subject areas
- Soil Science