Intensifying salinity intrusion in the Barataria Basin, 2010 to 2026: a coastward gradient in the rate of change

Aaron Wang 

The Barataria Basin, a shallow microtidal estuary in coastal Louisiana, has lost a substantial part of its wetland area and is exposed to increasing salinity intrusion as the Mississippi River remains leveed and relative sea level rises. Salinity conditions in this basin have been described, but whether the rate at which salinity changes varies spatially across the basin has not yet been established. In this study, we analyzed continuous salinity records of 54 stations from the Coastwide Reference Monitoring System across the basin between 2010 and 2026. We then expressed each station relative to a coastal reference station to remove basin-wide variability, estimated a trend for each station, and related those trends to distance from the Gulf shoreline and to potential candidate environmental drivers. The salinity ratio to the coastal reference increases at 46 of 54 stations, with the rate of increase declining with distance from the basin shoreline. The gradient was present before the basin-wide increase of the early 2020s and was amplified by it. Of potential drivers examined, only storm surge and changes in tidal amplitude remain associated with the saltening rates after adjustment for distance and multiple testing. These findings show where basin salinity exposure is concentrated and provide an observational constraint for process-based models of tidal exchange. Because exposure varies systematically with position across the basin, monitoring and restoration efforts can be targeted, and the same approach applies to other tidally influenced deltaic basins.