Parameterization of Estuarine Mixing Processes in the San Francisco Estuary Based on Analysis of Three-Dimensional Hydrodynamic Simulations

The purpose of this analysis is to develop a dispersive mixing parameterization method and specific dispersion coefficients used to predict salinity in a one-dimensional tidally-averaged transport model. Longitudinal dispersive mixing is parameterized based on the analysis of three-dimensional simulations spanning a range of freshwater inflows in the San Francisco Estuary. The three-dimensional simulation results were analyzed at 28 cross-sections in the San Francisco Estuary to calculate salt fluxes, salinity gradients and other information required for the parameterization method. This method represents the spatial variability of dispersion and includes dependence on horizontal Richardson Number, Delta outflow and other environmental variability. These parameterizations are incorporated into a tidally-averaged one-dimensional model for predicting salinity in Central San Francisco Bay, San Pablo Bay, Suisun Bay and the Sacramento-San Joaquin Delta. This simplified model was developed for the Delta Risk Management Strategy (DRMS) project, funded by the California Department of Water Resources, in order to simulate thousands of levee failure scenarios. The dispersion coefficients are currently applied in the simplified model to represent all dispersive transport in most of the model domain. The resulting simplified model accurately predicts observed monthly-averaged salinity through the San Francisco Estuary for a 15 year simulation period.