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Title: IDENTIFICATION OF SEDIMENT SOURCES IN A SEMIARID WATERSHED USING MULTIPLE DIAGNOSTIC PROPERTIES

Author
item Rhoton, Fred
item Emmerich, William
item Nearing, Mark
item Wilson, Christopher
item Dicarlo, David

Submitted to: Federal Interagency Sedimentation Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 1/5/2006
Publication Date: 4/2/2006
Citation: Rhoton, F.E., Emmerich, W.E., Nearing, M.A., Wilson, C.G., Dicarlo, D.A. 2006. Identification of sediment sources in a semiarid watershed using multiple diagnostic properties. Federal Interagency Sedimentation Conference Proceedings, April 2-6, 2006, Reno, Nevada. CDROM.

Interpretive Summary: Sediment source identification is a scientific approach used to locate the primary sources of sediment and chemical pollutants in watersheds. We characterized the watershed soils and their sediments for several physical and chemical properties commonly used for sediment sourcing purposes. The data were evaluated using a multivariate mixing model to determine which subwatershed was contributing the greatest amounts of sediment. Based on the data, only two of the six subwatersheds investigated were contributing approximately 75% of the sediment leaving the watershed, due to their unstable surface soils. Thus, these specific areas with the most highly erosive soils can be targeted for best management practices that will affect the greatest reduction of contaminant transport at the watershed scale.

Technical Abstract: The identification of sediment source areas in watersheds is important for the development of sediment budgets, and for the design of management practices to reduce sediment and chemical loadings in receiving streams. This study was conducted to determine the primary sources of sediment at a watershed scale using a weighted means soil geomorphology approach to the characterization of soil properties that influence erodibility and sediment transport. Each major soil mapping unit in six subwatersheds (SW) was sampled along transects positioned to include the normal soil geomorphological features associated with a given mapping unit. At each sampling point, latitude-longitude, slope class, topographic position, and aspect were recorded. Soil samples collected from the surface 5.0 cm were characterized for a range of physical and chemical properties used for fingerprinting purposes. Suspended sediment samples collected from supercritical flumes at the mouth of each SW were analyzed identically. An aggregation index (AI) was calculated for the soils in each SW as follows: 100 (1-water dispersible clay/total clay) served as a measure of soil erodibility. The physical and chemical signatures of the suspended sediment collected at the six flumes were used in a multivariate mixing model to identify the primary contributing source. The results suggested that the SWs with the lowest soil AI were contributing the greatest amounts of sediment.