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Title: Goodwin Creek Experimental Watershed - Effect of Conservation Practices on Sediment Load

item Kuhnle, Roger
item Bingner, Ronald - Ron
item Alonso, Carlos

Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Proceedings
Publication Acceptance Date: 9/15/2006
Publication Date: 9/30/2006
Citation: Kuhnle, R.A., Bingner, R.L., Alonso, C.V., Wilson, C.G. 2006. Goodwin Creek Experimental Watershed - Effect of Conservation Practices on Sediment Load. In: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE) Meeting, July 9-12, 2006, Portland, Oregon. Paper No. 062069, 11 pp.

Interpretive Summary: Conservation practices on agricultural lands are important tools used to protect the long term productively of the land as well as protecting offsite areas from sediment and other substances that may be removed from the land as a result from agricultural practices. Yet the effectiveness of many conservation practices has not been adequately evaluated. The Conservation Effects Assessment Project (CEAP), a cooperative effort of the Agricultural Research Service (ARS) and the National Resources Conservation Service (NRCS), was initiated to quantitatively determine the effectiveness of conservation practices in use on agricultural lands. The Goodwin Creek Experimental Watershed (GCEW) was identified as one of twelve benchmark CEAP watersheds to study the effectiveness of conservation practices in a detailed manner. This study presents an updated summary of the measured record of land use, rainfall, movement of water, and movement of sediment that has been collected on the GCEW since 1982. A watershed simulation model was used to generate similar information for the period of record of the watershed and produced similar trends to the measured data. This study has yielded confidence in the use of this watershed model to adequately represent the important processes acting on the GCEW. Through the use of measured data and model simulations, the effect of conservation practices will be evaluated in future studies and will yield improved information for land use managers for the responsible management of agricultural and other lands.

Technical Abstract: The Goodwin Creek Experimental Watershed, a benchmark watershed in the USDA-ARS Conservation Effects Assessment Project (CEAP), drains 2132 ha in the north central part of the state of Mississippi, USA. The watershed is characterized as having high sediment yield (13.2 t/ha/yr) and unstable channel substrate and banks. The effectiveness of management practices applied to the watershed will be evaluated as part of CEAP, and new practices and strategies for continued reduction in sediment loading will be explored using watershed computational models. Land use on the watershed has changed from 26 to 6 percent cultivated with corresponding increases in timber (26-38%) and pasture (48-55%) lands over the period of record. Annual concentrations of sediment have decreased from about 5000 ppmw in 1982 to about 2000 ppmw at the present. Sediment source tracking using naturally occurring radionuclides has indicated that channel processes are one of the main sources of sediment to the streams of the watershed. In addition to the reduction in sediment, a significant reduction has occurred in the relation between runoff and precipitation in the first part (April-July) of the land use year. Simulations using AnnAGNPS have been shown to favorably compare to the relative trends of the measured rates of runoff and sediment concentration except for periods of cultivation on agricultural lands. Enhancements or applications with advanced channel erosion models are needed to better reflect ephemeral gully and channel erosion.