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Identification of Suspended Sediment Sources Using Soil Characteristics in a Semiarid Watershed
Author(s) -
Rhoton F. E.,
Emmerich W. E.,
DiCarlo D. A.,
McChesney D. S.,
Nearing M. A.,
Ritchie J. C.
Publication year - 2008
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2007.0066
Subject(s) - sediment , transect , silt , hydrology (agriculture) , soil water , environmental science , watershed , loess , soil test , soil science , geology , geomorphology , oceanography , geotechnical engineering , machine learning , computer science
Identification of primary sediment source areas in watersheds is necessary to ensure that best management practices are installed in areas that maximize reductions in sediment and chemical loadings of receiving waters. Our objectives were to use a soil geomorphology–erodibility approach to locate sediment sources in the Walnut Gulch Experimental Watershed (WGEW). Major soil mapping units were sampled along transects in six subwatersheds (SWs). At each sampling point, latitude–longitude, slope gradient, slope aspect, and hillslope position were recorded. Samples collected from the surface 5.0 cm were characterized for a range of basic soil characterization properties. Additionally, 137 Cs, 40 K, 226 Ra, and stable C isotope distributions were quantified as potential source area indicators. Suspended sediment samples collected from WGEW and SW flumes were characterized for the same properties. Relative to the SW soils, the suspended sediments were generally enriched in silt, clay, organic C, inorganic C, total N, extractable cations, extractable Fe and Mn, 13 C from C3 plants, 40 K, and 226 Ra. The suspended sediment from three SWs was enriched in 137 Cs. Eleven characterization parameters were used in a multivariate mixing model to identify the SWs contributing the greatest sediment loads in the WGEW. The mixing model results indicated that three SWs were contributing approximately 86% of the sediment, and that the greatest amount originated in the three SWs with the lowest soil aggregation index (highest erodibility).These results were supported by the δ 13 C data, which indicated that approximately 65% of the stable C isotopes leaving the WGEW during this period were derived from C3 plants (shrubs), the dominant vegetation on the three SWs.