Quantifying hydrologic pathway and source connectivity dynamics in tile drainage: Implications for phosphorus concentrations

Flowpathways and source water connectivity dynamics are widely recognized to affect tile-drainage quality. In this study, we developed evaluated a framework that couples event-based hydrograph recession specific conductance end-member mixing analysis (SC-EMMA) provide more robust for quantifying both flow pathway of drainage in tile-drained landscapes. High-frequency (30-min) conductivity data were collected from an edge-of-field tile main located northwestern Ohio, the newly was applied year 2019. Multiple linear regression (MLR) used evaluate impact pathway-connectivity on flow-weighted mean dissolved reactive P (DRP) concentrations, which as part USDA-ARS monitoring network. The SC-EMMA results highlighted intra- interevent differences between quick (preferential) new (precipitation) transported during events, challenging common assumption reflects through preferential paths. hydrologic pathways demonstrated matrix–macropore exchange (Qquick-old), (Qquick-new), slow old (Qslow-old), (Qslow-new) contributed 9, 39, 42, 10% discharge, average, with variability. Matrix is drains via macropore flowpaths found be activated throughout year, even under drier antecedent conditions, suggesting sensitive within-event hydrological processes compared conditions. MLR fractions improved prediction DRP although improvement may pronounced landscapes higher rates exchange.