Relationships Between Freshwater Discharge, Salinity, and Large-Scale Climate Patterns in Galveston Bay, Texas

Abstract

Freshwater input into an estuary is one of the most important factors that affect various aspects of the estuarine ecosystem. The goal of this study was to develop a correlation of the variations of climatic patterns to annual river discharge levels and salinity regimes, and to denote the differences in dry versus wet years in Galveston Bay. This was accomplished through a time-series analysis developed in R-studio of freshwater discharge data from the US Geological Survey (USGS), the salinity data from the Texas Water Development Board’s (TWDB’s) Water Data for Texas, and National Oceanic and Atmospheric Administration’s (NOAA’s) climate indices. Data was collected and run through a series of regressions to develop the average salinity, freshwater discharge, and El Niño/La Niña Southern Oscillation (ENSO) and Atlantic Multidecadal Oscillation (AMO) index values that were then denoted as “normal conditions” during our analysis from which comparisons could be made. We hypothesized the following: 1) higher rainfall and thus more freshwater discharge into Galveston Bay will be seen in times of El Niño and opposite trends will be shown in La Niña, and 2) positive AMO conditions to correspond to trends of higher precipitation, and the reverse shown for negative trends in AMO. This understanding will aid in the prediction of ecological and biophysical responses of the Galveston Bay estuary due to climate change. Our current analysis indicates that significant correlation exists between freshwater discharge and salinity values around regionally around the bay. A similar correlation between discharge and the climate indices has been found, leading us to conclude that, climate regimes are important factors in predicting the ecological and biophysical responses in Galveston Bay. However, local factors have larger impacts on the observed scale. We hope that further analysis will be carried out to finalize the relationship between the three factors and develop a model of Galveston Bay.