Air, Soil and Water Research

This study investigates changes in the nature, concentrations, and fluxes of dissolved organic carbon (DOC) in tile drains (aka subsurface drains), overland flow, and stream flow for 6 spring storms in an artificially drained agricultural watershed. For moderate size storms, DOC concentrations are primarily affected by variations in antecedent moisture conditions. Generally, DOC concentrations and aromaticity increase with flow, especially for storms associated with high antecedent moisture conditions. A shift in the source of DOC to the stream and tile drains from low aromaticity DOC at baseflow, to more aromatic DOC during storms was observed. Data indicates that increases in the frequency and intensity of large precipitation events as well as wetter conditions in spring would likely lead not only to an increase in DOC fluxes (simply because of higher discharge) but also to an increase in the amount of DOC exported for every unit of flow.