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item Kuhnle, Roger

Submitted to: Federal Interagency Sedimentation Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 12/1/2005
Publication Date: 4/2/2006
Citation: Wilson, C., Kuhnle, R.A. 2006. Determination of sediment sources on the CEAP benchmark watersheds. In: Proceedings of the 8th Federal Interagency Sedimentation Conference, April 2-6, 2006, Reno, Nevada. CDROM.

Interpretive Summary: Sediment has been identified by the US Environmental Protection Agency as the most common constituent degrading the quality of the water of the nation’s streams and rivers. Physical, chemical, and biological sediment damage has been estimated to be 16 billion dollars annually in North America. Knowledge of the rate of sediment at a location is necessary to gauge the level of impairment while knowledge of the source of the sediment is critical for designing environmentally aware management plans to rectify the sediment problem in agricultural watersheds. Currently the source and rate of sediment to the channels of an agricultural watershed may be predicted using one of the available watershed erosion models. While measured data on the total sediment rate at a location in a watershed are available, measured information on the source of the sediment is very rare. In this study a technique is presented which uses naturally occurring substances to provide information on the sources of the sediment measured at a location of a watershed. When compared to predicted sources for a given watershed, this technique provides a powerful tool to evaluate the accuracy of watershed erosion models. This technique will be applied on USDA-Agricultural Research Service experimental watersheds to provide information on sediment sources. This information will be used to check and improve sediment source prediction routines on watershed erosion models.

Technical Abstract: As part of the Conservation Effects Assessment Program (CEAP), 12 watersheds across the country have been designated as CEAP benchmark watersheds. These watersheds were chosen to evaluate the effectiveness of the conservation practices applied under various landscape and agricultural conditions in different parts of the country. Goodwin Creek, located in the north central part of Mississippi, is one of the CEAP benchmark watersheds where the effects of land use and management practices on sediment transport have been studied since 1982. Recently, technology to differentiate the source of fine sediments in the suspended load of streams using naturally occurring radionuclides has been applied within this watershed. Preliminary data from Goodwin Creek show that fine sediment is predominantly derived from the land surface during the initial part of a runoff event. The latter parts of the same runoff event indicated that the sources of fine sediment shifted to predominantly channel bank sources. Further measurements will provide information on the variations of sediment sources of fine sediments during different parts of the year and for different magnitude flows. This technique will be applied to other CEAP benchmark watersheds with the cooperation of the researchers from these watersheds. Knowledge of the sources of sediment in the different benchmark watersheds will provide critical information regarding sediment problems and the types of management practices that will most likely be effective in rectifying these problems.