Two-Dimensional Simulations of Contaminant Currents in Stratified Reservoir

Abstract

An unsteady two-dimensional (2D) reservoir hydrodynamics and transport model is employed to simulate contaminated density currents in the Shasta Reservoir after a chemical spill into the Sacramento River, Calif. Three flow regimes (plunging flow, underflow, and interflow) and their occurrence are captured by the laterally averaged model. Transport and mixing processes in the temperature-stratified reservoir are analyzed through simulations of flow velocities, water temperature, and contaminant concentration. Flow behavior of the contaminant plume is described by plunge distance, separation depth, intruding thickness, and the spatial and temporal dilution of chemicals. Simulation results are compared with field data for water temperature and contaminant concentration collected in the reservoir during the emergency response to the spill. Relatively good agreement between field measurements and predicted reservoir stratification and chemical dilution is obtained. It is shown that the aeration system installed in the reservoir contributed to the downstream reduction of chemical concentration to a nondetectable level shortly after the spill. The 2D simulations and analyses improve understanding and predictions of the movement of a conservative contaminant plume in a stratified reservoir. The results can assist in contamination control and remediation after a toxic chemical spill, guide field sampling during the spill, and provide information useful for water quality management.