Three-Dimensional Numerical Modeling of Flow, Sediment and Mercury Distribution in Enid Lake, Mississippi

摘要

Enid Lake is a large reservoir located in Yazoo River Basin, the largest basin in Mississippi. It was impounded by Enid Dam on the Yocona River in Yalobusha County and covers an area of 60 square kilometers. This lake provides significant natural and recreational resources. The soils in this region are highly erodible, resulting in a large amount of sediment discharged into the lake. Sediments are normally associated with many pollutants and greatly affect water quality and aquatic lives of the lake. It has been observed that Mercury concentrations in water, sediment and fish in Enid Lake are relatively high, and a fish consumption advisory has been issued by Mississippi Department of Environmental Quality since 1995. In this study, a 3D numerical model was developed to simulate the flow, sediment and mercury distributions in Enid Lake. Flow fields in the lake are generally induced by wind and upstream river discharge. Sediment are normally introduced by river discharge and resuspended from lake bottom. Total mercury in water and sediment were simulated, and the major processes, including advection, diffusion, adsorption/desorption, bed release, atmosphere deposition, settling, etc., were taken into account in the model. This model was calibrated and validated using field measurements and remote sensing data. The model results help us understand the processes of fate and transport of mercury in natural lakes, and provide useful information for fish consumption advisories and potential risk assessment.