Study of Sediment and Nutrients in Pelahatchie Bay and Upland Mill-Pelahatchie Creek- Watershed

Author(s): Chao, X.; Bingner, R.; Zhang, Y.; Yasarer, L.; Jia, Y.

Ross Barnett Reservoir is the largest drinking water source in the state of Mississippi. Pelahatchie Bay is a part of Ross Barnett Reservoir, and located in the southeast corner of the reservoir. The upland watershed of Pelahatchie Bay contains a high percentage of construction sites and developed area, causing a lot of sediment and associated pollutants to discharge into the bay through runoff. In addition, sediment, nutrients, and other pollutants may also flow into Pelahatchie Bay from the upstream Pelahatchie Creek.

The major water quality problem in Pelahatchie Bay is sedimentation, which causes high turbidity and limits boat navigation in the bay. The levels of nitrogen and phosphorus in the bay are relatively high and cause excessive growth of aquatic plants.

In this study, the AnnAGNPS watershed management model, developed at the USDA ARS, National Sedimentation Laboratory (NSL), are applied to simulate the loads of runoff, sediment and nutrients from the upland watershed. The simulated results are used as boundary conditions for CCHE, a free surface flow, sediment and water quality model developed at the National Center for Computational Hydroscience and Engineering (NCCHE), to simulate the flow, sediment transport and water quality processes in the Pelahatchie Bay. The concentration distributions of sediment and nutrients, and their variations in time due to the influence of loading, wind, and the operation of the Ross Barnett Reservoir are simulated.

This study provides a useful tool to evaluate the effectiveness of watershed BMPs on water quality in Pelahatchie Bay. Information obtained from the research can be used by decision makers to develop improved watershed management plans to achieve maximum water quality benefits to Pelahatchie Bay.

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