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Tile Drainage as a Hydrologic Pathway for Phosphorus Export from an Agricultural Subwatershed
Author(s) -
Michaud Aubert R.,
Poirier SimonClaude,
Whalen Joann K.
Publication year - 2019
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2018.03.0104
Subject(s) - tile drainage , surface runoff , hydrology (agriculture) , environmental science , streamflow , hydrograph , surface water , tributary , groundwater , drainage basin , geology , soil water , soil science , environmental engineering , ecology , geography , geotechnical engineering , cartography , biology
Cyanobacteria growth in Missisquoi Bay of Lake Champlain is triggered by the P load carried by tributaries in surrounding watersheds where agriculture is a dominant land use. The objective of this study was to apportion the total P (TP) load in streamflow from an agricultural subwatershed into distinct hydrologic pathways: groundwater resurgence, surface runoff, and tile drainage components (matrix flow and preferential flow). Stream discharge during peak flow was separated into these four components using electrical conductivity (EC)–discharge relationships developed from the stream water EC at the subwatershed outlet and from EC values of surface runoff and tile drain water in 10 fields within the subwatershed. The four‐component hydrograph model revealed that 46 to 67% of the TP load at the outlet originated from surface runoff during peak flow. Preferential flow was responsible for most of the particulate P and dissolved reactive P loads lost through tile drainage. Groundwater resurgence was a minor source of TP, whereas other sources such as streambank erosion and resuspended sediments contributed up to 21% of the TP load and from 36 to 41% of the particulate P load at the subwatershed outlet. This work confirms that tile drainage contributes to the TP load in agricultural subwatersheds in the Missisquoi Bay region. Core Ideas Field water sources affected electrolytes and electrical conductivity in streamflow. Water yield from field hydrologic pathways was deduced from the stream hydrograph. Matrix and preferential flows to tile drainage, and surface runoff, were quantified. Preferential flow was an important source of sediment and P loads in streamflow. Stream water quality may be negatively affected by tile drainage outflows.