Trends in Salinities and Flushing times of Georgia Estuaries

From 1973-1992, the Georgia EPD sponsored a monitoring program in which surface salinities were sampled regularly at fixed stations in many of Georgia’s estuaries. We used these data to examine changes in the salinities and flushing times of the Savannah, Ogeechee, Altamaha, Satilla, and St. Marys estuaries over the period of record. Water-year average salinities increased slightly over time in four of the five estuaries. When data were smoothed with a three-year moving average (based on fast Fourier analysis of river discharge), the increases in salinity were statistically significant in the Satilla and Savannah River estuaries. We used the measured salinity values to estimate flushing times (average transit time of river water through an estuary) over the period of record. Flushing times averaged 28 d in the Ogeechee, 7 d in the Altamaha, 63 d in the Satilla, and 65 d in the St. Marys, although there was considerable inter-annual variability in these estimates. These results are discussed in light of current proposals to increase surface water withdrawal from the Georgia rivers.