CHEMICAL MIXING PATTERN IN SCOUR POOLS ON THE COASTAL PLAIN IN GEORGIA

Fisheries biologists in Georgia have hypothesized that sturgeon congregate in deep scour pools in coastal rivers during the summer months due to the presence of artesian springs. It's believed that springs create zones of lower temperature or low salinity that the fish seek during periods of stress in the summer months. An investigation was carried out to determine whether a chemical or temperature signature could be found that would indicate the presence of artesian springs in two scour pools where sturgeon are known to congregate. Here, physical and general chemistry data were obtained from discrete samples collected along the streambed.

Early data showed strong chemical anomalies in the two scour pools that suggested artesian groundwater was mixing with surface water. However, the pools in question, located near the confluence of the Ogeechee and Canoochee rivers, are 56 river kilometers from the coast and remain tidally influenced. Therefore, additional samples were collected to test a second hypothesis that the anomalies are merely the result of tidal mixing at the confluence of the two rivers. The additional data supports this later hypothesis. However, the dataset at low tide still shows a chemical anomaly in one of the pools that is difficult to explain by tidal mixing, thus may still be explained by the presence of a groundwater spring. The location of this potential spring also happens to coincide with a lineament that runs through the forested wetlands adjacent to the river and where small tributaries exhibit a rectangular drainage pattern. A new investigation is currently underway to determine if the observed chemical anomaly in the scour pool is related to the lineament and rectangular drainage pattern.