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Source‐Pathway Separation of Multiple Contaminants during a Rainfall‐Runoff Event in an Artificially Drained Agricultural Watershed
Author(s) -
Tomer M. D.,
Wilson C. G.,
Moorman T. B.,
Cole K. J.,
Heer D.,
Isenhart T.M.
Publication year - 2010
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/jeq2009.0289
Subject(s) - tile drainage , surface runoff , environmental science , hydrology (agriculture) , watershed , nonpoint source pollution , water quality , erosion , outfall , sediment , surface water , drainage , environmental engineering , soil water , geology , soil science , ecology , paleontology , geotechnical engineering , machine learning , computer science , biology
A watershed's water quality is influenced by contaminant‐transport pathways unique to each landscape. Accurate information on contaminant‐pathways could provide a basis for mitigation through well‐targeted approaches. This study determined dynamics of nitrate‐N, total P, Escherichia coli , and sediment during a runoff event in Tipton Creek, Iowa. The watershed, under crop and livestock production, has extensive tile drainage discharging through an alluvial valley. A September 2006 storm yielded 5.9 mm of discharge during the ensuing 7 d, which was monitored at the outlet (19,850 ha), two tile‐drainage outfalls (total 1856 ha), and a runoff flume (11 ha) within the sloped valley. Hydrograph separations indicated 13% of tile discharge was from surface intakes. Tile and outlet nitrate‐N loads were similar, verifying subsurface tiles dominate nitrate delivery. On a unit‐area basis, tile total P and E. coli loads, respectively, were about half and 30% of the outlet's; their rapid, synchronous timing showed surface intakes are an important pathway for both contaminants. Flume results indicated field runoff was a significant source of total P and E. coli loads, but not the dominant one. At the outlet, sediment, P, and E. coli were reasonably synchronous. Radionuclide activities of 7 Be and 210 Pb in suspended sediments showed sheet‐and‐rill erosion sourced only 22% of sediment contributions; therefore, channel sources dominated and were an important source of P and E. coli The contaminants followed unique pathways, necessitating separate mitigation strategies. To comprehensively address water quality, erosion‐control and nitrogen‐management practices currently encouraged could be complemented by buffering surface intakes and stabilizing stream banks.