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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Watershed Physical Processes Research » Research » Publications at this Location » Publication #195473
Title: DETERMINATION OF WATERSHED SEDIMENT SOURCES USING USDA WATERSHED AND CHANNEL MODELS

Author
item YUAN, YONGPING - UNIVERSITY OF MISSISSIPPI
item Bingner, Ronald - Ron
item Langendoen, Eddy
item Wells, Robert - Rob
item Simon, Andrew
item Alonso, Carlos

Submitted to: American Society of Agri Engineers Special Meetings and Conferences Papers
Publication Type: Proceedings
Publication Acceptance Date: 5/15/2006
Publication Date: 7/9/2006
Citation: Yuan, Y., Bingner, R.L., Langendoen, E.J., Wells, R.R., Simon, A., Alonso, C.V. 2006. Determination of watershed sediment sources using USDA watershed and channel models. American Society for Agricultural Engineers. Paper No. 062048, St. Joseph, Michigan, 17 pp.

Interpretive Summary: At the request and support of the Mississippi Department of Environmental Quality (MDEQ), sediment loadings in James Creek, Monroe County, Mississippi, were studied to determine sediment currently transported in the watershed (actual) and sediment for similar, but stable or unimpaired streams (reference) through which MDEQ could develop water-quality targets for sediment. Without historical sediment-transport data for James Creek, numerical simulations were performed to determine sediment loads transported in the watershed. The Annualized AGricultural Non-Point Source (AnnAGNPS) pollution model was used to estimate water and sediment contributions from upland areas; the CONservational Channel Evolution and Pollutant Transport System (CONCEPTS) computer model was used to determine the sediment contributions from the main channel of James Creek. Upland loadings from AnnAGNPS were supplied as the boundary conditions for CONCEPTS. The average sediment load at the mouth of James Creek over the 35-year period was about 253,170 T/y with about 70% of this material emanating from James Creek and its tributaries and only 30% derived from upland sources. The simulations showed that a significant portion of the sediment loading occurred from soybeans and corn production areas that are along the main channel. Therefore, areas along the main channel may be those that are first targeted for BMPs such as grass filter strips or riparian buffer implementation. In addition, stream channel erosion control structures would be beneficial in stabilizing eroding reaches and tributaries of James Creek since a significant proportion of the sediment emanates from stream channels. By identifying the sources of sediment production, action agencies such as NRCS can target the practices and sites within the watershed that would provide the most benefit from the effects of conservation practices.

Technical Abstract: James Creek, located in Monroe County, Mississippi, was impaired for not fully supporting the designated use of aquatic life due to sediment. Required by the USEPA, A Total Maximum Daily Load (TMDL) needed to be developed to limit the sediment loading to the creek so the water quality in the creek could be improved. However, there was no historical monitoring data available to show how much sediment entered the creek and what the sediment level should be to meet the requirements of aquatic life. In the absence of a numerical target for sediment, a percent reduction in the sediment loading was sought so that the James Creek watershed could produce sediment at rates commensurate with those in a biologically unimpaired stream. Therefore, determining sediment loads that are currently transported by the watershed, identifying sediment sources, and developing alternative management practices to achieve a percent of reduction (or meet water quality goals) are major tasks in the project of restoring the designated use of the James Creek. Since no historical monitoring data were available, the Annualized AGricultural Non-Point Source (AnnAGNPS) pollution model, which is a watershed pollutant loading model, was used to estimate water and sediment contributions from upland areas; the CONservational Channel Evolution and Pollutant Transport System (CONCEPTS) computer model, which is a channel-evolution model, was used to determine the sediment contributions from the main channel of James Creek. Upland loadings from AnnAGNPS were supplied as the boundary conditions for CONCEPTS. Peak-flow data simulated by AnnAGNPS using actual precipitation data was in very close agreement with the annual-maximum flow series obtained at a gaging station in James Creek. Flows generated by AnnAGNPS for 1967 and 1968 were also in close agreement with the measured data. AnnAGNPS simulation from each scenario showed that a significant amount of sediment was produced from AnnAGNPS cells, and the produced sediment from AnnAGNPS cells for different scenarios is fairly consistent. However, for the scenarios that had unstable tributaries, the sediment from tributaries was much more than from upland areas. Average sediment load at the mouth of James Creek over the 35-year period is about 253,170 T/y with about 89% of this material emanating from James Creek and its tributaries with only 11 % derived from upland sources. However, over last 10-year, the contribution from channels and uplands is 70% and 30%, respectively. AnnAGNPS simulation showed that a significant portion of the sediment loading seemed to occur from soybeans and corn production areas that are along the main channel. Therefore, areas along the main channel should be first targeted for BMPs such as grass filter strip or riparian buffer implementation. In addition, particular attention is also needed to stream-channel processes and stabilizing eroding reaches and tributaries of James Creek because a significant proportion of the sediment emanates from stream channels.