Numerical Modeling of Sediment-Associated Water Quality Processes in Natural Lakes

Author(s): Chao, X.; Jia, Y.; Shields Jr., F.

Sediment is a major nonpoint source pollutant. It may be transported into surface water bodies from agricultural lands and watersheds through runoff. These sediments could be associated with nutrients, pesticides, and other pollutants, and greatly affect the surface water qualities. Therefore, sediment has been listed as the most common pollutant in rivers, streams, lakes, and reservoirs by the US Environmental Protection Agency (USEPA).

This paper presents the development and application of a three-dimensional water quality model for predicting the distributions of nutrients, phytoplankton, dissolved oxygen, etc., in natural lakes. Three major sediment-associated water quality processes were simulated, including the effect of sediment on the light intensity for the growth of phytoplankton, the adsorption-desorption of nutrients by sediment and the release of nutrients from bed sediment layer. This model was first verified using analytical solutions for the transport of non-conservative substances in open channel flow, and then calibrated and validated by the field measurements conducted in a natural oxbow lake in Mississippi. The simulated concentrations of water quality constituents were generally in good agreement with field observations. This study shows that there are strong interactions between sediment and water quality constituents.

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