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Sediment - Chlorophyll relationship in oxbow Lakes in the Mississippi River Alluvial Plain

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Pp. 76-82 in Total Maximum Daily Load (TMDL) Environmental Regulations: Proceedings of the March 11-13, 2002 Conference, (Fort Worth, Texas, USA)  701P0102.(doi:10.13031/2013.7532)
Authors:   S. S. Knight, R. F. Cullum, T. D. Welch, C. M. Cooper
Keywords:   Total Maximum Daily Loads, Water Quality, Sediment, Chlorophyll, Oxbow Lakes

Over the course 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. It is estimated that 60% of the approximately 3 billion tons of sediment per year deposited in the waterways originates from agricultural lands. Oxbow lakes are remnants of meandering floodplain rivers that have been cut off and physically isolated from their respective main river channels. Long known for their productivity and recreational value, these naturally formed lakes have not escaped the detrimental effects of soil erosion. Consequently, their popularity as recreational resources has decreased as water quality and fisheries have declined. 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. Turbidity in oxbow lakes can be persistent in areas having soils with high clay content. Although nutrients such as phosphorus are typically associated with alluvial soils and tend to load in oxbow lakes, these systems may become energy starved and very unproductive due to lack of light penetration. In order 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.

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