Hydrodynamic and Salinity Modeling of the Calcasieu-Sabine Basin

The Calcasieu-Sabine Basin is located in the southwest corner of the State of Louisiana and extends into Texas. Hydrodynamics of the Calcasieu-Sabine Basin involves a combination of estuarine processes such as saltwater intrusion and response to water level fluctuations at an open boundary, and lake dynamics such as strong response to wind forcing particularly water level setup and the development of high velocity currents in near-shore shallow regions. The basin is also affected by deep ship channels that are strongly salinity stratified, and therefore a three-dimensional model is more desirable for simulating the basin. A robust, flexible and efficient numerical model is required to incorporate all of these processes in an operational program. The three-dimensional finite-difference hydrodynamic model (H3D) was used to simulate the hydrodynamic characteristics of the Calcasieu-Sabine estuarine system. The model was calibrated and validated using a one-year record of data representing a full seasonal cycle of water level and salinity measurements at different measuring stations strategically located within the basin. Graphical comparisons and error analysis of the results illustrate the capability of the numerical model to produce accurate simulations of the complex flow patterns of the Calcasieu-Sabine Basin. Since H3D is based on solving the three dimensional mass, momentum and density conservation equations, it can be used to simulate flow and salinity patterns for the basin outside the range of the calibration field data for different hydrologic conditions. The model can also be used to simulate the effects of human induced hydrologic changes in the basin such as the addition of hydraulic structures, widening or deepening of navigation channels, or changing the volumes of freshwater inflow to the basin. Thus, the model provides a very useful planning and adaptive management tool.