GROUNDWATER LEVELS AND COASTAL STREAM SALINIZATION PROCESSES

In coastal watersheds, the migration of saltwater upstream is a major water quality concern. The dynamics of the saltwater-freshwater interface have been studied, as have the relationships between groundwater pumping and streamflow, but a link between these processes in coastal watersheds requires further investigation. It is possible that changes in groundwater level could affect streamflow, and therefore stream salinity, in these systems. Using data from USGS stream gages and groundwater wells and NOAA tidal stations, we explored two coastal watersheds in the Southeastern United States. In Florida, the Suwannee River shows spikes in specific conductance near the coast caused by fast salinization processes related to both storm events and decreased freshwater discharge. In Georgia, the Savannah River experiences periods of lower discharge and associated higher specific conductance. There has historically been extensive pumping of the Upper Floridan Aquifer in and around the city of Savannah. While there is no direct connection between this aquifer and the stream near the coast, it is possible that changes in the water level in this and other aquifers could be having an effect on this complex coastal system over a long time scale. Both the fast and slow salinization processes observed in these two sites have water resource implications that should be further investigated.