Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Proceedings
Publication Acceptance Date: 9/25/2001
Publication Date: 3/13/2002
Citation: Knight, S.S., Cullum, R.F., Welch, T.D., Cooper, C.M. 2002. Sediment-Chlorophyll Relationship in Oxbow Lakes in the Mississippi River Alluvial Plain. Proceedings of Total Maximum Daily Load (TMDL) Environmental Regulations, March 11-13, Fort Worth, TX, pp. 76-82. (Sponsored by the American Society of Agricultural and Biological Engineers International (ASABE)). Interpretive Summary: Farming activities have been implicated as the sources of such pollutants as sediments, pesticides and nutrients. The Clean Water Act requires states to improve impaired waters by establishing Total Maximum Daily Loads (TMDLs) of these pollutants that will be allowed in our rivers, lakes and streams. Research conducted as a part of the Mississippi Delta Management Systems Evaluation Area project (MSEA), showed that the amounts sediment and nutrient in oxbow lakes were related. Furthermore this research showed that reducing sediment using good conservation practice allowed the plankton in the lake water to more effectively use nutrients such as phosphorus. The results were increased productivity and improved fisheries. Since, most states attempt to establish TMDL for nutrient levels in such a way that a balance is achieve between nutrient and plankton so that fish productivity is maintained this information should prove quite valuable.
Technical Abstract: During of the past century, aquatic habitats have declined worldwide, primarily due to draining and clearing for agriculture and urban development. These activities often result in increased erosion and sedimentation with detrimental impacts on stream and lake water quality. Oxbow lakes are important components of riverine ecosystems often found in agricultural watersheds. If suspended sediment concentrations are low enough to provide suitable light penetration, oxbow lakes provide conditions conducive to photosynthesis, primarily via phytoplankton, and may support a sustainable sport fishery. However, agricultural practices often result in soil erosion that can lead to increased turbidity in the oxbow lakes and subsequent inhibition of photosynthesis. To establish reasonable Total Maximum Daily Loads for these types of systems, critical concentrations of total or suspended sediments, necessary to elicit a corresponding increase in chlorophyll, must be established. Oxbow lake water quality data collected from various research projects by the authors suggests that critical concentrations for suspended sediments may be established. This paper examines the relationship between suspended sediments, chlorophyll, and lake ecology and suggests a possible critical concentration for suspended sediment TMDL.