Comparing transport times through salinity zones in the Ogeechee and Altamaha River estuaries using squeezebox
Sheldon, Joan E.
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This study explored differences in the transit times of dissolved substances through salinity zones in the Altamaha and Ogeechee River estuaries under a range of flow conditions. Salinity distributions and transit times were estimated from box models generated using the SqueezeBox modeling framework. The estuaries were compared in spite of the large difference in their river flow ranges by using flow rates ranging from the 10th-90th percentile within each range. In each case, zone lengths and transit times were calculated for the tidal freshwater, oligo-mesohaline, and polyhaline zones. Although the two estuaries have similar lengths, the slower-flowing Ogeechee grades from a zone of tidal freshwater (except at very low flows) through oligo-mesohaline zones to a polyhaline zone inside the mouth whereas the Altamaha always has a fairly long (>25 km) extent of tidal freshwater but only a short (or non-existent) polyhaline zone. Transit times through the whole Ogeechee estuary are 3.3-4.7 times longer than those in the Altamaha, but the lengths of time water spends in the tidal freshwater reaches of the estuaries are comparable whereas there are large differences in the times spent in oligo-mesohaline and polyhaline reaches. These types of predictions may be useful in interpreting nutrient and pollutant dynamics in estuaries as well as in studies that compare the relative susceptibility of estuaries to perturbations.