Author
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Bennett, Sean |
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Submitted to: Laboratory Publication
Publication Type: Government Publication Publication Acceptance Date: 12/7/2001 Publication Date: 12/7/2001 Citation: Bennett, S.J. 2001. Sediment quality issues within a flood control reservoir, Little Tallahatchie County, MS. USDA-ARS National Sedimentation Laboratory Research Report. No. 23. 58 pp. Interpretive Summary: Since 1948, the USDA-NRCS has constructed nearly 11,000 upstream flood control dams in 2000 watersheds in 47 states. Because of population growth, land use changes, and time since construction, many sediment pools are nearly filled to capacity. Before any rehabilitation strategy can be designed and implemented, both the quantity and quality of the sediment impounded by these dams must be assessed. Moreover, since reservoirs represent a nearly 40-year record of continuous sedimentation, this record provides a number of opportunities to assess Total Maximum Daily Load (TMDL) criteria for sediment and its associated chemical and nutrient composition. To this end, a project was designed to collect continuous, undisturbed sediment cores from the reservoir of Hubbard-Murphree Dam Y- 17-73, near Charleston, MS, and to evaluate the sediment's physical and chemical characteristics. The sediment cores extracted are composed of alternating layers of silty clay, silty clay loam, and silt loam. Rates of sedimentation range from 20 to 42 mm/yr. The concentrations of 33 elements within the sediments do not vary significantly within each core or from core to core. A table provided herein summarizes average concentrations for 33 elements spanning a time period of nearly 40 years. Two depth-integrated sediment samples were analyzed for 53 agrichemicals and contaminants, and no compounds were found above their detectable limits. This work will assist the NRCS in their rehabilitation efforts at Hubbard-Murphree and provide the Mississippi Department of Environmental Quality with a nearly 40-year record of heavy metal concentrations associated with sediment. Technical Abstract: Since 1948, the USDA-NRCS has constructed nearly 11,000 upstream flood control dams in 2000 watersheds in 47 states. Because of population growth, land use changes, and time since construction, many sediment pools are nearly filled to capacity. Rehabilitation strategies must include an assessment of sedimentation issues. Moreover, since reservoirs represent a nearly 40-year record of continuous sedimentation, this record provides a number of opportunities to assess Total Maximum Daily Load (TMDL) criteria for sediment and its associated chemical and nutrient composition. To this end, a project was designed to collect continuous, undisturbed sediment cores from the reservoir of Hubbard-Murphree Dam Y- 17-73, near Charleston, MS, and to evaluate the sediment's physical and chemical characteristics. The sediment cores extracted are composed of alternating layers of silty clay, silty clay loam, and silt loam. Rates of sedimentation range from 20 to 42 mm/yr. The concentrations of 33 elements within the sediments do not vary significantly within each core or from core to core. A table provided herein summarizes average concentrations for 33 elements spanning a time period of nearly 40 years. Two depth-integrated sediment samples were analyzed for 53 agrichemicals and contaminants, and no compounds were found above their detectable limits. |
