Implementation of a hydrodynamic model for salinity in Nueces and Corpus Christi Bays

The purpose of this research was to implement and calibrate a hydrodynamic model for Nueces Bay, Texas and use said model to predict how salinity and circulation in the bay could be affected by sea level rise and changes in freshwater input. The Nueces Bay estuary is fed fresh water from the Nueces River and connects to Corpus Christi Bay, which connects to the Gulf of Mexico. Salinities in Nueces Bay range from near 0 PSU at times of high riverine flow to over 50 PSU during drought periods. The model selected is the Finite Volume Coastal Ocean Model (FVCOM), an unstructured grid, finite-volume, three-dimensional primitive equation ocean model developed for the study of coastal oceanic and estuarine circulation. An unstructured triangular mesh was created for the bay and bathymetry was interpolated to the mesh. Forcing inputs included water level, water temperature, salinity, wind speed and direction, and the flow rate of the Nueces River. Several software utilities were created to facilitate set-up and testing of the model. Predictions were compared with measured water levels and salinity at several locations in the study area for years 2008 & 2010. The model produced good results for water level predictions with a mean absolute error of 6.5 cm over the test period. The model also produced overall realistic currents and salinity variations in Corpus Christi Bay with a mean absolute error of 1.7 psu at Ingleside. However, the model predicted salinity poorly in Nueces Bay with a mean absolute error greater than 6 psu at all stations and a maximum absolute error of greater than 20 psu. While its initial goal was to investigate the impact of sea level rise on salinity levels, the study focused instead on model performance for salinity predictions in Nueces Bay. The investigation revealed that while freshwater from the Nueces River was entering the system at the correct rate, the model was not accurately reflecting salinity response in cells further down river and ultimately in Nueces Bay.